制作一个简单的照片查看器(支持缩放手势)

本文主要实现的功能是制作一个照片查看器，点击照片能进入大图模式，支持左右滑动，支持手势缩放，

本文只演示1张图和3张图的效果，其他的效果分为为：

2张图的时候按照1行2列展示，

3张图的时候按照1行3列展示，

4张图的时候按照2行2列展示，

这样依次排列，

首先上能实现这个功能的控件，自定义的imglayout；

代码如下

package com.demo.swt.mystudyappshop.Wight;import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Build;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.Animation;
import android.view.animation.ScaleAnimation;
import android.widget.ImageView;
import android.widget.RelativeLayout;import com.demo.swt.mystudyappshop.R;
import com.demo.swt.mystudyappshop.Util.DisplayUtils;
import com.squareup.picasso.Picasso;import java.util.ArrayList;
import java.util.List;/*** Created by pc on 2016/12/6.*/public class CstImage extends RelativeLayout {private final int MAX_NUM = 9;private final int SPECIFIC_NUM_1 = 1;private final int SPECIFIC_NUM_2 = 2;private final int SPECIFIC_NUM_4 = 4;private int rowNum;private int margin;private int leftMargin, rightMargin, topMargin, bottomMargin;private ScaleAnimation downAnim;private ScaleAnimation upAnim;private Handler handler = new Handler();private OnChlidItemClickListener onChlidItemClickListener;private boolean isFour; //是否4张private int imgMargin;private int imgMarginDp = 1;private float onRatio = 0.67f;private float twoRatio = 1f;private float fourRatio = 0.67f;private float otherRation = 1f;private int MAX_WIDTH;//图片下方是否需要添加介绍private boolean isNeedIntro;private int oneWidth, twoWidth, fourWidth, otherWidth;public CstImage(Context context) {super(context);init();}public CstImage(Context context, AttributeSet attrs) {super(context, attrs);TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CstImgLayout);margin = a.getDimensionPixelSize(R.styleable.CstImgLayout_all_margin, 0);final int dp2px15 = dip2px(15);if (margin > 0) {leftMargin = rightMargin = bottomMargin = topMargin = margin;} else {isNeedIntro = a.getBoolean(R.styleable.CstImgLayout_need_intro, false);leftMargin = a.getDimensionPixelSize(R.styleable.CstImgLayout_left_margin, dp2px15);rightMargin = a.getDimensionPixelSize(R.styleable.CstImgLayout_right_margin, dp2px15);bottomMargin = a.getDimensionPixelSize(R.styleable.CstImgLayout_bottom_margin, dp2px15);topMargin = a.getDimensionPixelSize(R.styleable.CstImgLayout_top_margin, dp2px15);}rowNum = a.getInteger(R.styleable.CstImgLayout_row_num, 3);realWidth = a.getDimensionPixelOffset(R.styleable.CstImgLayout_real_width, 0);a.recycle();init();}public CstImage(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);init();}@TargetApi(Build.VERSION_CODES.LOLLIPOP)public CstImage(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {super(context, attrs, defStyleAttr, defStyleRes);init();}private int dip2px(float dpValue) {final float scale = getResources().getDisplayMetrics().density;return (int) (dpValue * scale + 0.5f);}private int realWidth;private void init() {int sw = realWidth <= 0 ? getResources().getDisplayMetrics().widthPixels : realWidth;imgMargin = DisplayUtils.dip2px(imgMarginDp);MAX_WIDTH = oneWidth = sw - leftMargin - rightMargin;twoWidth = (sw - leftMargin - rightMargin - imgMargin) / 2;fourWidth = twoWidth;otherWidth = (sw - leftMargin - rightMargin - 2 * imgMargin) / 3;initView();downAnim = new ScaleAnimation(1f, 0.98f, 1f, 0.98f, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);upAnim = new ScaleAnimation(0.98f, 1f, 0.98f, 1f, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);downAnim.setFillAfter(true);downAnim.setDuration(100);downAnim.setInterpolator(new AccelerateInterpolator());upAnim.setFillAfter(true);upAnim.setDuration(100);upAnim.setInterpolator(new AccelerateInterpolator());}private void initView() {if (isNeedIntro) {for (int i = 0; i < MAX_NUM; i++) {RelativeLayout layout = new RelativeLayout(getContext());layout.setVisibility(GONE);ImageView imageView = new ImageView(getContext());imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);imageView.setId(i);RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);layout.addView(imageView, lp);addView(layout);}} else {for (int i = 0; i < MAX_NUM; i++) {ImageView imageView = new ImageView(getContext());imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);imageView.setVisibility(GONE);imageView.setId(i);addView(imageView);}}}public void setOnChildItemClickListener(OnChlidItemClickListener l) {onChlidItemClickListener = l;}public interface OnChlidItemClickListener {void onClick(int position, List<String> imgs);}public void setImgs(List<String> imgs) {if (null != imgs && !imgs.isEmpty()) {if (imgs.size() > MAX_NUM) {imgs = new ArrayList<>(imgs.subList(0, MAX_NUM));}setVisibility(View.VISIBLE);int size = imgs.size();if (size == SPECIFIC_NUM_1) {setOne(imgs);} else if (size == SPECIFIC_NUM_2) {setTwo(imgs);} else if (size == SPECIFIC_NUM_4) {setFour(imgs);} else {setOther(imgs);}} else {setVisibility(View.GONE);}requestLayout();}//一张图private void setOne(List<String> imgs) {for (int i = 0; i < MAX_NUM; i++) {if (0 == i) {getChildAt(i).setVisibility(VISIBLE);} else {getChildAt(i).setVisibility(GONE);}}RelativeLayout.LayoutParams lp = (LayoutParams) getChildAt(0).getLayoutParams();lp.width = oneWidth;lp.height = (int) (lp.width * onRatio);lp.rightMargin = 0;setImg(imgs, 0, getChildAt(0));}//两张图private void setTwo(List<String> imgs) {for (int i = 0; i < MAX_NUM; i++) {if (0 == i || 1 == i) {getChildAt(i).setVisibility(VISIBLE);RelativeLayout.LayoutParams lp = (LayoutParams) getChildAt(i).getLayoutParams();lp.width = twoWidth;lp.height = (int) (lp.width * twoRatio);if (1 == i) {lp.leftMargin = imgMargin + twoWidth;}setImg(imgs, i, getChildAt(i));} else {getChildAt(i).setVisibility(GONE);}}}//四张图private void setFour(List<String> imgs) {isFour = true;for (int i = 0; i < MAX_NUM; i++) {if (0 == i || 1 == i || 3 == i || 4 == i) {getChildAt(i).setVisibility(VISIBLE);RelativeLayout.LayoutParams lp = (LayoutParams) getChildAt(i).getLayoutParams();lp.width = fourWidth;lp.height = (int) (fourWidth * fourRatio);lp.rightMargin = imgMargin;int topId = i - rowNum;if (topId >= 0) {lp.leftMargin = 0;lp.topMargin = (imgMargin + lp.height) * (i / rowNum);lp.leftMargin = (fourWidth + imgMargin) * (i % rowNum);} else if (i > 0) {int leftId = getChildAt(i - 1).getId();lp.leftMargin = (fourWidth + imgMargin) * (i % rowNum);lp.addRule(RelativeLayout.ALIGN_TOP, leftId);lp.addRule(RelativeLayout.ALIGN_BOTTOM, leftId);}int position = i;if (position > 1) {position--;}setImg(imgs, position, getChildAt(i));} else {getChildAt(i).setVisibility(GONE);}}}//其他private void setOther(List<String> imgs) {int size = imgs.size();for (int i = 0; i < MAX_NUM; i++) {if (i < size) {getChildAt(i).setVisibility(VISIBLE);RelativeLayout.LayoutParams lp = (LayoutParams) getChildAt(i).getLayoutParams();lp.width = otherWidth;lp.height = (int) (otherWidth * otherRation);if (i % rowNum == (rowNum - 1)) {lp.rightMargin = 0;} else {lp.rightMargin = imgMargin;}int topId = i - rowNum;if (topId >= 0) {lp.leftMargin = 0;lp.topMargin = (imgMargin + lp.height) * (i / rowNum);lp.leftMargin = (otherWidth + imgMargin) * (i % rowNum);} else if (i > 0) {int leftId = getChildAt(i - 1).getId();lp.leftMargin = (otherWidth + imgMargin) * (i % rowNum);lp.addRule(RelativeLayout.ALIGN_TOP, leftId);lp.addRule(RelativeLayout.ALIGN_BOTTOM, leftId);}setImg(imgs, i, getChildAt(i));} else {getChildAt(i).setVisibility(GONE);}}}private void setImg(final List<String> imgs, final int position, final View view) {ImageView imageView = null;ViewGroup viewGroup;if (!isNeedIntro && view instanceof ImageView) {imageView = (ImageView) view;} else if (view instanceof ViewGroup && (viewGroup = (ViewGroup) view).getChildCount() > 0 && viewGroup.getChildAt(0) instanceof ImageView) {imageView = (ImageView) viewGroup.getChildAt(0);}final ImageView img = imageView;if (null != img) {Picasso.with(getContext()).load(imgs.get(position)).into(img);//add by zhangxutong end ,feature :按尺寸加载图片img.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {view.startAnimation(downAnim);handler.postDelayed(new Runnable() {@Overridepublic void run() {view.startAnimation(upAnim);}}, 100);view.postDelayed(new Runnable() {@Overridepublic void run() {view.clearAnimation();if (null != onChlidItemClickListener) {onChlidItemClickListener.onClick(position, imgs);}}}, 120);}});}}}

会调有几个地方报错，一个一个来，首先在valus目录下新建一个attrs文件，代码如下

<?xml version="1.0" encoding="utf-8"?>
<resources><declare-styleable name="CstImgLayout"><attr name="bottom_margin" format="dimension" /><attr name="left_margin" format="dimension" /><attr name="right_margin" format="dimension" /><attr name="top_margin" format="dimension" /><attr name="all_margin" format="dimension" /><attr name="child_margin" format="dimension" /><attr name="row_num" format="integer" /><attr name="need_intro" format="boolean" /><attr name="real_width" format="dimension" /></declare-styleable>
</resources>

然后加一个小工具类

代码如下

package com.demo.swt.mystudyappshop.Util;import android.content.Context;
import android.graphics.drawable.Drawable;
import android.support.v4.content.ContextCompat;public class DisplayUtils {private static Context context;public static void setContext(Context Context) {DisplayUtils.context = Context;}/*** 根据手机的分辨率从 dp 的单位 转成为 px(像素)*/public static int dip2px(float dpValue) {if (null == context) return (int) dpValue;final float scale = context.getResources().getDisplayMetrics().density;return (int) (dpValue * scale + 0.5f);}/*** 根据手机的分辨率从 px(像素) 的单位 转成为 dp*/public static int px2dip(float pxValue) {if (null == context) return (int) pxValue;final float scale = context.getResources().getDisplayMetrics().density;return (int) (pxValue / scale + 0.5f);}/*** sp转px（正常字体下，1sp=1dp）** @param spValue* @return*/public static int sp2px(float spValue) {if (null == context) return (int) spValue;final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;return (int) (spValue * fontScale + 0.5f);}/*** sp转dp** @param spValue* @return*/public static int sp2dp(float spValue) {int sp2Px = sp2px(spValue);return px2dip(sp2Px);}public static int getQToPx(int rid) {return (int) context.getResources().getDimension(rid);}public static Drawable getDrawable(int drawable) {return ContextCompat.getDrawable(context, drawable);}
}

最后还有一个错误，因为这个控件用的是pisso加载图片的所以在gradle里面配置上pisso

compile 'com.squareup.picasso:picasso:2.3.2'

同步后，就没错误了，自定义的view就弄好了，我们这样使用

在xml文件中直接加上

 <com.anlaiye.swt.bigphoto.CstImageandroid:id="@+id/cstimage"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginLeft="30dp"android:layout_marginRight="20dp"android:layout_marginTop="10dp"></com.anlaiye.swt.bigphoto.CstImage>

这个控件，然后findviewbyid找到控件，

通过

 image= (CstImage) findViewById(R.id.cstimage);image.setImgs();

通过setimgs来设置图片，里面的参数是list<string>

一般这个list<string>后台会返回给我们，我们这里只是一个demo就不写网络请求框架了，我们直接自己放一个进去

我们初始化一个数组，和一个网络图片地址，把这个地址放入mlist中，然后在放置在setimgs(mlist)中，

 private String img = "http://pic.anlaiye.com.cn/16b840dfab614965acb07562801fceee_748x750.png";private List<String> mlist = new ArrayList<>();

这里只有一张图片所以看到的是一张图片的效果

因为要方便左右滑动，想了一下还是放俩涨图片吧，

然后加上点击事件，所以完整代码如下

package com.anlaiye.swt.bigphoto;import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.widget.ImageView;
import android.widget.Toast;import java.util.ArrayList;
import java.util.List;public class MainActivity extends FragmentActivity {private String img = "http://pic.anlaiye.com.cn/6a143da5964749ab990343091ce3a0be_799x1066.png";private String img1 = "http://pic.anlaiye.com.cn/6a143da5964749ab990343091ce3a0be_799x1066.png";private List<String> mlist = new ArrayList<>();private CstImage image;private ImageView imageView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);image = (CstImage) findViewById(R.id.cstimage);mlist.add(img);mlist.add(img1);image.setImgs(mlist);image.setOnChildItemClickListener(new CstImage.OnChlidItemClickListener() {@Overridepublic void onClick(int position, List<String> imgs) {Toast.makeText(getApplicationContext(), position + "被点击了",Toast.LENGTH_SHORT).show();}});}
}

运行看下效果 (不要忘记加网络权限，因为是加载网络图片)

<uses-permission android:name="android.permission.INTERNET" />

现在的这个是俩张图的效果，其他的效果，小伙伴可以自行尝试，

好了，接下来制作大图模式，首先分析思路是点击进入另外一个activity或者(fragment)都可以，然后使用一个viewpager铺满屏幕,里面放置一个imageview，好了大概的思路有了开始写：

首先写一个新的activity：

接下来我直接把注释写代码里面，直接贴代码了，(突然发现写的在详细，也没人看，还是简单点，直接拿代码好了)

package com.anlaiye.swt.bigphoto;import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;import java.util.ArrayList;
import java.util.List;import uk.co.senab.photoview.PhotoViewAttacher;/*** Created by pc on 2016/12/5.*/public class BigImageActivity extends FragmentActivity {private ArrayList<String> tulist = new ArrayList<>();private NoPreloadViewPager noPreloadViewPager;private int pos;private List<MyPhotoView> mSimplelist = new ArrayList<>();@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);requestWindowFeature(Window.FEATURE_NO_TITLE);setContentView(R.layout.bigimagee);noPreloadViewPager = (NoPreloadViewPager) findViewById(R.id.nopreload);Intent intent = getIntent();Bundle bundle = intent.getExtras();tulist = bundle.getStringArrayList("tulist");pos = bundle.getInt("pos");getSimpleList();noPreloadViewPager.setAdapter(new PagerAdapter() {@Overridepublic int getCount() {return tulist.size();}@Overridepublic boolean isViewFromObject(View view, Object object) {return view == object;}@Overridepublic void destroyItem(ViewGroup container, int position, Object object) {container.removeView(mSimplelist.get(position));}@Overridepublic Object instantiateItem(ViewGroup container, final int position) {container.addView(mSimplelist.get(position));return mSimplelist.get(position);}});noPreloadViewPager.setCurrentItem(pos);}protected List<MyPhotoView> getSimpleList() {for (int i = 0; i < tulist.size(); i++) {MyPhotoView photoDraweeView = new MyPhotoView(getApplicationContext());photoDraweeView.setImageUri(tulist.get(i));mSimplelist.add(photoDraweeView);photoDraweeView.setOnPhotoTapListener(new PhotoViewAttacher.OnPhotoTapListener() {@Overridepublic void onPhotoTap(View view, float x, float y) {finish();}});}return mSimplelist;}}

可以看到我们在这个界面接收了上一个界面传过来的list<string> ，所以我们的MainActivity的最终代码是，把list<string>传过去

package com.anlaiye.swt.bigphoto;import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;import java.util.ArrayList;
import java.util.List;public class MainActivity extends FragmentActivity {private String img = "http://pic.anlaiye.com.cn/6a143da5964749ab990343091ce3a0be_799x1066.png";private String img1 = "http://pic.anlaiye.com.cn/7e6f898d8ed14d00a7b2b844c7dccfe0_799x1422.png";private List<String> mlist = new ArrayList<>();private CstImage image;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);image = (CstImage) findViewById(R.id.cstimage);mlist.add(img);mlist.add(img1);image.setImgs(mlist);image.setOnChildItemClickListener(new CstImage.OnChlidItemClickListener() {@Overridepublic void onClick(int position, List<String> imgs) {Intent intent = new Intent(MainActivity.this, BigImageActivity.class);Bundle bundle = new Bundle();bundle.putStringArrayList("tulist", (ArrayList<String>) mlist);bundle.putInt("pos", position);intent.putExtras(bundle);startActivity(intent);}});}
}

同时BigImageActivity还会有几个报错，

几个报错，一个一个的修补一下

NoPreloadViewPager 这是一个viewpager不过他不会预加载，为什么要这样呢，因为我们viewpager里面是根据position设置图片的，如果预加载，翻到最后一张就会出现空指针，闪退

下面是不会预加载的viewpager的源码，只修改了

private static final int DEFAULT_OFFSCREEN_PAGES = 0;//默认是1

其他的没动，直接copy就好了

package com.anlaiye.swt.bigphoto;import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Parcel;
import android.os.Parcelable;
import android.os.SystemClock;
import android.support.v4.os.ParcelableCompat;
import android.support.v4.os.ParcelableCompatCreatorCallbacks;
import android.support.v4.view.KeyEventCompat;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.VelocityTrackerCompat;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewConfigurationCompat;
import android.support.v4.widget.EdgeEffectCompat;
import android.util.AttributeSet;
import android.util.Log;
import android.view.FocusFinder;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.SoundEffectConstants;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.view.accessibility.AccessibilityEvent;
import android.view.animation.Interpolator;
import android.widget.Scroller;import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;/*** Created by pc on 2016/12/6.*/public class NoPreloadViewPager extends ViewGroup {private static final String TAG = "NoPreloadViewPager";private static final boolean DEBUG = false;private static final boolean USE_CACHE = false;private static final int DEFAULT_OFFSCREEN_PAGES = 0;//默认是1private static final int MAX_SETTLE_DURATION = 600; // msstatic class ItemInfo {Object object;int position;boolean scrolling;}private static final Comparator<ItemInfo> COMPARATOR = new Comparator<ItemInfo>() {@Overridepublic int compare(ItemInfo lhs, ItemInfo rhs) {return lhs.position - rhs.position;}};private static final Interpolator sInterpolator = new Interpolator() {public float getInterpolation(float t) {// _o(t) = t * t * ((tension + 1) * t + tension)// o(t) = _o(t - 1) + 1t -= 1.0f;return t * t * t + 1.0f;}};private final ArrayList<ItemInfo> mItems = new ArrayList<ItemInfo>();private PagerAdapter mAdapter;private int mCurItem;   // Index of currently displayed page.private int mRestoredCurItem = -1;private Parcelable mRestoredAdapterState = null;private ClassLoader mRestoredClassLoader = null;private Scroller mScroller;private PagerObserver mObserver;private int mPageMargin;private Drawable mMarginDrawable;private int mChildWidthMeasureSpec;private int mChildHeightMeasureSpec;private boolean mInLayout;private boolean mScrollingCacheEnabled;private boolean mPopulatePending;private boolean mScrolling;private int mOffscreenPageLimit = DEFAULT_OFFSCREEN_PAGES;private boolean mIsBeingDragged;private boolean mIsUnableToDrag;private int mTouchSlop;private float mInitialMotionX;/*** Position of the last motion event.*/private float mLastMotionX;private float mLastMotionY;/*** ID of the active pointer. This is used to retain consistency during* drags/flings if multiple pointers are used.*/private int mActivePointerId = INVALID_POINTER;/*** Sentinel value for no current active pointer.* Used by {@link #mActivePointerId}.*/private static final int INVALID_POINTER = -1;/*** Determines speed during touch scrolling*/private VelocityTracker mVelocityTracker;private int mMinimumVelocity;private int mMaximumVelocity;private float mBaseLineFlingVelocity;private float mFlingVelocityInfluence;private boolean mFakeDragging;private long mFakeDragBeginTime;private EdgeEffectCompat mLeftEdge;private EdgeEffectCompat mRightEdge;private boolean mFirstLayout = true;private OnPageChangeListener mOnPageChangeListener;/*** Indicates that the pager is in an idle, settled state. The current page* is fully in view and no animation is in progress.*/public static final int SCROLL_STATE_IDLE = 0;/*** Indicates that the pager is currently being dragged by the user.*/public static final int SCROLL_STATE_DRAGGING = 1;/*** Indicates that the pager is in the process of settling to a final position.*/public static final int SCROLL_STATE_SETTLING = 2;private int mScrollState = SCROLL_STATE_IDLE;/*** Callback interface for responding to changing state of the selected page.*/public interface OnPageChangeListener {/*** This method will be invoked when the current page is scrolled, either as part* of a programmatically initiated smooth scroll or a user initiated touch scroll.** @param position             Position index of the first page currently being displayed.*                             Page position+1 will be visible if positionOffset is nonzero.* @param positionOffset       Value from [0, 1) indicating the offset from the page at position.* @param positionOffsetPixels Value in pixels indicating the offset from position.*/public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels);/*** This method will be invoked when a new page becomes selected. Animation is not* necessarily complete.** @param position Position index of the new selected page.*/public void onPageSelected(int position);/*** Called when the scroll state changes. Useful for discovering when the user* begins dragging, when the pager is automatically settling to the current page,* or when it is fully stopped/idle.** @param state The new scroll state.* @see android.support.v4.view.ViewPager#SCROLL_STATE_IDLE* @see android.support.v4.view.ViewPager#SCROLL_STATE_DRAGGING* @see android.support.v4.view.ViewPager#SCROLL_STATE_SETTLING*/public void onPageScrollStateChanged(int state);}/*** Simple implementation of the {@link android.support.v4.view.LazyViewPager.OnPageChangeListener} interface with stub* implementations of each method. Extend this if you do not intend to override* every method of {@link android.support.v4.view.LazyViewPager.OnPageChangeListener}.*/public static class SimpleOnPageChangeListener implements OnPageChangeListener {@Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {// This space for rent}@Overridepublic void onPageSelected(int position) {// This space for rent}@Overridepublic void onPageScrollStateChanged(int state) {// This space for rent}}public NoPreloadViewPager(Context context) {super(context);initViewPager();}public NoPreloadViewPager(Context context, AttributeSet attrs) {super(context, attrs);initViewPager();}void initViewPager() {setWillNotDraw(false);setDescendantFocusability(FOCUS_AFTER_DESCENDANTS);setFocusable(true);final Context context = getContext();mScroller = new Scroller(context, sInterpolator);final ViewConfiguration configuration = ViewConfiguration.get(context);mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();mLeftEdge = new EdgeEffectCompat(context);mRightEdge = new EdgeEffectCompat(context);float density = context.getResources().getDisplayMetrics().density;mBaseLineFlingVelocity = 2500.0f * density;mFlingVelocityInfluence = 0.4f;}private void setScrollState(int newState) {if (mScrollState == newState) {return;}mScrollState = newState;if (mOnPageChangeListener != null) {mOnPageChangeListener.onPageScrollStateChanged(newState);}}public void setAdapter(PagerAdapter adapter) {if (mAdapter != null) {
//            mAdapter.unregisterDataSetObserver(mObserver);mAdapter.startUpdate(this);for (int i = 0; i < mItems.size(); i++) {final ItemInfo ii = mItems.get(i);mAdapter.destroyItem(this, ii.position, ii.object);}mAdapter.finishUpdate(this);mItems.clear();removeAllViews();mCurItem = 0;scrollTo(0, 0);}mAdapter = adapter;if (mAdapter != null) {if (mObserver == null) {mObserver = new PagerObserver();}
//            mAdapter.registerDataSetObserver(mObserver);mPopulatePending = false;if (mRestoredCurItem >= 0) {mAdapter.restoreState(mRestoredAdapterState, mRestoredClassLoader);setCurrentItemInternal(mRestoredCurItem, false, true);mRestoredCurItem = -1;mRestoredAdapterState = null;mRestoredClassLoader = null;} else {populate();}}}public PagerAdapter getAdapter() {return mAdapter;}/*** Set the currently selected page. If the ViewPager has already been through its first* layout there will be a smooth animated transition between the current item and the* specified item.** @param item Item index to select*/public void setCurrentItem(int item) {mPopulatePending = false;setCurrentItemInternal(item, !mFirstLayout, false);}/*** Set the currently selected page.** @param item         Item index to select* @param smoothScroll True to smoothly scroll to the new item, false to transition immediately*/public void setCurrentItem(int item, boolean smoothScroll) {mPopulatePending = false;setCurrentItemInternal(item, smoothScroll, false);}public int getCurrentItem() {return mCurItem;}void setCurrentItemInternal(int item, boolean smoothScroll, boolean always) {setCurrentItemInternal(item, smoothScroll, always, 0);}void setCurrentItemInternal(int item, boolean smoothScroll, boolean always, int velocity) {if (mAdapter == null || mAdapter.getCount() <= 0) {setScrollingCacheEnabled(false);return;}if (!always && mCurItem == item && mItems.size() != 0) {setScrollingCacheEnabled(false);return;}if (item < 0) {item = 0;} else if (item >= mAdapter.getCount()) {item = mAdapter.getCount() - 1;}final int pageLimit = mOffscreenPageLimit;if (item > (mCurItem + pageLimit) || item < (mCurItem - pageLimit)) {// We are doing a jump by more than one page.  To avoid// glitches, we want to keep all current pages in the view// until the scroll ends.for (int i = 0; i < mItems.size(); i++) {mItems.get(i).scrolling = true;}}final boolean dispatchSelected = mCurItem != item;mCurItem = item;populate();final int destX = (getWidth() + mPageMargin) * item;if (smoothScroll) {smoothScrollTo(destX, 0, velocity);if (dispatchSelected && mOnPageChangeListener != null) {mOnPageChangeListener.onPageSelected(item);}} else {if (dispatchSelected && mOnPageChangeListener != null) {mOnPageChangeListener.onPageSelected(item);}completeScroll();scrollTo(destX, 0);}}public void setOnPageChangeListener(OnPageChangeListener listener) {mOnPageChangeListener = listener;}/*** Returns the number of pages that will be retained to either side of the* current page in the view hierarchy in an idle state. Defaults to 1.** @return How many pages will be kept offscreen on either side* @see #setOffscreenPageLimit(int)*/public int getOffscreenPageLimit() {return mOffscreenPageLimit;}/*** Set the number of pages that should be retained to either side of the* current page in the view hierarchy in an idle state. Pages beyond this* limit will be recreated from the adapter when needed.* <p>* <p>This is offered as an optimization. If you know in advance the number* of pages you will need to support or have lazy-loading mechanisms in place* on your pages, tweaking this setting can have benefits in perceived smoothness* of paging animations and interaction. If you have a small number of pages (3-4)* that you can keep active all at once, less time will be spent in layout for* newly created view subtrees as the user pages back and forth.</p>* <p>* <p>You should keep this limit low, especially if your pages have complex layouts.* This setting defaults to 1.</p>** @param limit How many pages will be kept offscreen in an idle state.*/public void setOffscreenPageLimit(int limit) {if (limit < DEFAULT_OFFSCREEN_PAGES) {Log.w(TAG, "Requested offscreen page limit " + limit + " too small; defaulting to " +DEFAULT_OFFSCREEN_PAGES);limit = DEFAULT_OFFSCREEN_PAGES;}if (limit != mOffscreenPageLimit) {mOffscreenPageLimit = limit;populate();}}/*** Set the margin between pages.** @param marginPixels Distance between adjacent pages in pixels* @see #getPageMargin()* @see #setPageMarginDrawable(android.graphics.drawable.Drawable)* @see #setPageMarginDrawable(int)*/public void setPageMargin(int marginPixels) {final int oldMargin = mPageMargin;mPageMargin = marginPixels;final int width = getWidth();recomputeScrollPosition(width, width, marginPixels, oldMargin);requestLayout();}/*** Return the margin between pages.** @return The size of the margin in pixels*/public int getPageMargin() {return mPageMargin;}/*** Set a drawable that will be used to fill the margin between pages.** @param d Drawable to display between pages*/public void setPageMarginDrawable(Drawable d) {mMarginDrawable = d;if (d != null) refreshDrawableState();setWillNotDraw(d == null);invalidate();}/*** Set a drawable that will be used to fill the margin between pages.** @param resId Resource ID of a drawable to display between pages*/public void setPageMarginDrawable(int resId) {setPageMarginDrawable(getContext().getResources().getDrawable(resId));}@Overrideprotected boolean verifyDrawable(Drawable who) {return super.verifyDrawable(who) || who == mMarginDrawable;}@Overrideprotected void drawableStateChanged() {super.drawableStateChanged();final Drawable d = mMarginDrawable;if (d != null && d.isStateful()) {d.setState(getDrawableState());}}// We want the duration of the page snap animation to be influenced by the distance that// the screen has to travel, however, we don't want this duration to be effected in a// purely linear fashion. Instead, we use this method to moderate the effect that the distance// of travel has on the overall snap duration.float distanceInfluenceForSnapDuration(float f) {f -= 0.5f; // center the values about 0.f *= 0.3f * Math.PI / 2.0f;return (float) Math.sin(f);}/*** Like {@link android.view.View#scrollBy}, but scroll smoothly instead of immediately.** @param x the number of pixels to scroll by on the X axis* @param y the number of pixels to scroll by on the Y axis*/void smoothScrollTo(int x, int y) {smoothScrollTo(x, y, 0);}/*** Like {@link android.view.View#scrollBy}, but scroll smoothly instead of immediately.** @param x        the number of pixels to scroll by on the X axis* @param y        the number of pixels to scroll by on the Y axis* @param velocity the velocity associated with a fling, if applicable. (0 otherwise)*/void smoothScrollTo(int x, int y, int velocity) {if (getChildCount() == 0) {// Nothing to do.setScrollingCacheEnabled(false);return;}int sx = getScrollX();int sy = getScrollY();int dx = x - sx;int dy = y - sy;if (dx == 0 && dy == 0) {completeScroll();setScrollState(SCROLL_STATE_IDLE);return;}setScrollingCacheEnabled(true);mScrolling = true;setScrollState(SCROLL_STATE_SETTLING);final float pageDelta = (float) Math.abs(dx) / (getWidth() + mPageMargin);int duration = (int) (pageDelta * 100);velocity = Math.abs(velocity);if (velocity > 0) {duration += (duration / (velocity / mBaseLineFlingVelocity)) * mFlingVelocityInfluence;} else {duration += 100;}duration = Math.min(duration, MAX_SETTLE_DURATION);mScroller.startScroll(sx, sy, dx, dy, duration);invalidate();}void addNewItem(int position, int index) {ItemInfo ii = new ItemInfo();ii.position = position;ii.object = mAdapter.instantiateItem(this, position);if (index < 0) {mItems.add(ii);} else {mItems.add(index, ii);}}void dataSetChanged() {// This method only gets called if our observer is attached, so mAdapter is non-null.boolean needPopulate = mItems.size() < 3 && mItems.size() < mAdapter.getCount();int newCurrItem = -1;for (int i = 0; i < mItems.size(); i++) {final ItemInfo ii = mItems.get(i);final int newPos = mAdapter.getItemPosition(ii.object);if (newPos == PagerAdapter.POSITION_UNCHANGED) {continue;}if (newPos == PagerAdapter.POSITION_NONE) {mItems.remove(i);i--;mAdapter.destroyItem(this, ii.position, ii.object);needPopulate = true;if (mCurItem == ii.position) {// Keep the current item in the valid rangenewCurrItem = Math.max(0, Math.min(mCurItem, mAdapter.getCount() - 1));}continue;}if (ii.position != newPos) {if (ii.position == mCurItem) {// Our current item changed position. Follow it.newCurrItem = newPos;}ii.position = newPos;needPopulate = true;}}Collections.sort(mItems, COMPARATOR);if (newCurrItem >= 0) {// TODO This currently causes a jump.setCurrentItemInternal(newCurrItem, false, true);needPopulate = true;}if (needPopulate) {populate();requestLayout();}}void populate() {if (mAdapter == null) {return;}// Bail now if we are waiting to populate.  This is to hold off// on creating views from the time the user releases their finger to// fling to a new position until we have finished the scroll to// that position, avoiding glitches from happening at that point.if (mPopulatePending) {if (DEBUG) Log.i(TAG, "populate is pending, skipping for now...");return;}// Also, don't populate until we are attached to a window.  This is to// avoid trying to populate before we have restored our view hierarchy// state and conflicting with what is restored.if (getWindowToken() == null) {return;}mAdapter.startUpdate(this);final int pageLimit = mOffscreenPageLimit;final int startPos = Math.max(0, mCurItem - pageLimit);final int N = mAdapter.getCount();final int endPos = Math.min(N - 1, mCurItem + pageLimit);if (DEBUG) Log.v(TAG, "populating: startPos=" + startPos + " endPos=" + endPos);// Add and remove pages in the existing list.int lastPos = -1;for (int i = 0; i < mItems.size(); i++) {ItemInfo ii = mItems.get(i);if ((ii.position < startPos || ii.position > endPos) && !ii.scrolling) {if (DEBUG) Log.i(TAG, "removing: " + ii.position + " @ " + i);mItems.remove(i);i--;mAdapter.destroyItem(this, ii.position, ii.object);} else if (lastPos < endPos && ii.position > startPos) {// The next item is outside of our range, but we have a gap// between it and the last item where we want to have a page// shown.  Fill in the gap.lastPos++;if (lastPos < startPos) {lastPos = startPos;}while (lastPos <= endPos && lastPos < ii.position) {if (DEBUG) Log.i(TAG, "inserting: " + lastPos + " @ " + i);addNewItem(lastPos, i);lastPos++;i++;}}lastPos = ii.position;}// Add any new pages we need at the end.lastPos = mItems.size() > 0 ? mItems.get(mItems.size() - 1).position : -1;if (lastPos < endPos) {lastPos++;lastPos = lastPos > startPos ? lastPos : startPos;while (lastPos <= endPos) {if (DEBUG) Log.i(TAG, "appending: " + lastPos);addNewItem(lastPos, -1);lastPos++;}}if (DEBUG) {Log.i(TAG, "Current page list:");for (int i = 0; i < mItems.size(); i++) {Log.i(TAG, "#" + i + ": page " + mItems.get(i).position);}}ItemInfo curItem = null;for (int i = 0; i < mItems.size(); i++) {if (mItems.get(i).position == mCurItem) {curItem = mItems.get(i);break;}}mAdapter.setPrimaryItem(this, mCurItem, curItem != null ? curItem.object : null);mAdapter.finishUpdate(this);if (hasFocus()) {View currentFocused = findFocus();ItemInfo ii = currentFocused != null ? infoForAnyChild(currentFocused) : null;if (ii == null || ii.position != mCurItem) {for (int i = 0; i < getChildCount(); i++) {View child = getChildAt(i);ii = infoForChild(child);if (ii != null && ii.position == mCurItem) {if (child.requestFocus(FOCUS_FORWARD)) {break;}}}}}}public static class SavedState extends BaseSavedState {int position;Parcelable adapterState;ClassLoader loader;public SavedState(Parcelable superState) {super(superState);}@Overridepublic void writeToParcel(Parcel out, int flags) {super.writeToParcel(out, flags);out.writeInt(position);out.writeParcelable(adapterState, flags);}@Overridepublic String toString() {return "FragmentPager.SavedState{"+ Integer.toHexString(System.identityHashCode(this))+ " position=" + position + "}";}public static final Creator<SavedState> CREATOR= ParcelableCompat.newCreator(new ParcelableCompatCreatorCallbacks<SavedState>() {@Overridepublic SavedState createFromParcel(Parcel in, ClassLoader loader) {return new SavedState(in, loader);}@Overridepublic SavedState[] newArray(int size) {return new SavedState[size];}});SavedState(Parcel in, ClassLoader loader) {super(in);if (loader == null) {loader = getClass().getClassLoader();}position = in.readInt();adapterState = in.readParcelable(loader);this.loader = loader;}}@Overridepublic Parcelable onSaveInstanceState() {Parcelable superState = super.onSaveInstanceState();SavedState ss = new SavedState(superState);ss.position = mCurItem;if (mAdapter != null) {ss.adapterState = mAdapter.saveState();}return ss;}@Overridepublic void onRestoreInstanceState(Parcelable state) {if (!(state instanceof SavedState)) {super.onRestoreInstanceState(state);return;}SavedState ss = (SavedState) state;super.onRestoreInstanceState(ss.getSuperState());if (mAdapter != null) {mAdapter.restoreState(ss.adapterState, ss.loader);setCurrentItemInternal(ss.position, false, true);} else {mRestoredCurItem = ss.position;mRestoredAdapterState = ss.adapterState;mRestoredClassLoader = ss.loader;}}@Overridepublic void addView(View child, int index, LayoutParams params) {if (mInLayout) {addViewInLayout(child, index, params);child.measure(mChildWidthMeasureSpec, mChildHeightMeasureSpec);} else {super.addView(child, index, params);}if (USE_CACHE) {if (child.getVisibility() != GONE) {child.setDrawingCacheEnabled(mScrollingCacheEnabled);} else {child.setDrawingCacheEnabled(false);}}}ItemInfo infoForChild(View child) {for (int i = 0; i < mItems.size(); i++) {ItemInfo ii = mItems.get(i);if (mAdapter.isViewFromObject(child, ii.object)) {return ii;}}return null;}ItemInfo infoForAnyChild(View child) {ViewParent parent;while ((parent = child.getParent()) != this) {if (parent == null || !(parent instanceof View)) {return null;}child = (View) parent;}return infoForChild(child);}@Overrideprotected void onAttachedToWindow() {super.onAttachedToWindow();mFirstLayout = true;}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {// For simple implementation, or internal size is always 0.// We depend on the container to specify the layout size of// our view.  We can't really know what it is since we will be// adding and removing different arbitrary views and do not// want the layout to change as this happens.setMeasuredDimension(getDefaultSize(0, widthMeasureSpec),getDefaultSize(0, heightMeasureSpec));// Children are just made to fill our space.mChildWidthMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredWidth() -getPaddingLeft() - getPaddingRight(), MeasureSpec.EXACTLY);mChildHeightMeasureSpec = MeasureSpec.makeMeasureSpec(getMeasuredHeight() -getPaddingTop() - getPaddingBottom(), MeasureSpec.EXACTLY);// Make sure we have created all fragments that we need to have shown.mInLayout = true;populate();mInLayout = false;// Make sure all children have been properly measured.final int size = getChildCount();for (int i = 0; i < size; ++i) {final View child = getChildAt(i);if (child.getVisibility() != GONE) {if (DEBUG) Log.v(TAG, "Measuring #" + i + " " + child+ ": " + mChildWidthMeasureSpec);child.measure(mChildWidthMeasureSpec, mChildHeightMeasureSpec);}}}@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);// Make sure scroll position is set correctly.if (w != oldw) {recomputeScrollPosition(w, oldw, mPageMargin, mPageMargin);}}private void recomputeScrollPosition(int width, int oldWidth, int margin, int oldMargin) {final int widthWithMargin = width + margin;if (oldWidth > 0) {final int oldScrollPos = getScrollX();final int oldwwm = oldWidth + oldMargin;final int oldScrollItem = oldScrollPos / oldwwm;final float scrollOffset = (float) (oldScrollPos % oldwwm) / oldwwm;final int scrollPos = (int) ((oldScrollItem + scrollOffset) * widthWithMargin);scrollTo(scrollPos, getScrollY());if (!mScroller.isFinished()) {// We now return to your regularly scheduled scroll, already in progress.final int newDuration = mScroller.getDuration() - mScroller.timePassed();mScroller.startScroll(scrollPos, 0, mCurItem * widthWithMargin, 0, newDuration);}} else {int scrollPos = mCurItem * widthWithMargin;if (scrollPos != getScrollX()) {completeScroll();scrollTo(scrollPos, getScrollY());}}}@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {mInLayout = true;populate();mInLayout = false;final int count = getChildCount();final int width = r - l;for (int i = 0; i < count; i++) {View child = getChildAt(i);ItemInfo ii;if (child.getVisibility() != GONE && (ii = infoForChild(child)) != null) {int loff = (width + mPageMargin) * ii.position;int childLeft = getPaddingLeft() + loff;int childTop = getPaddingTop();if (DEBUG) Log.v(TAG, "Positioning #" + i + " " + child + " f=" + ii.object+ ":" + childLeft + "," + childTop + " " + child.getMeasuredWidth()+ "x" + child.getMeasuredHeight());child.layout(childLeft, childTop,childLeft + child.getMeasuredWidth(),childTop + child.getMeasuredHeight());}}mFirstLayout = false;}@Overridepublic void computeScroll() {if (DEBUG) Log.i(TAG, "computeScroll: finished=" + mScroller.isFinished());if (!mScroller.isFinished()) {if (mScroller.computeScrollOffset()) {if (DEBUG) Log.i(TAG, "computeScroll: still scrolling");int oldX = getScrollX();int oldY = getScrollY();int x = mScroller.getCurrX();int y = mScroller.getCurrY();if (oldX != x || oldY != y) {scrollTo(x, y);}if (mOnPageChangeListener != null) {final int widthWithMargin = getWidth() + mPageMargin;final int position = x / widthWithMargin;final int offsetPixels = x % widthWithMargin;final float offset = (float) offsetPixels / widthWithMargin;mOnPageChangeListener.onPageScrolled(position, offset, offsetPixels);}// Keep on drawing until the animation has finished.invalidate();return;}}// Done with scroll, clean up state.completeScroll();}private void completeScroll() {boolean needPopulate = mScrolling;if (needPopulate) {// Done with scroll, no longer want to cache view drawing.setScrollingCacheEnabled(false);mScroller.abortAnimation();int oldX = getScrollX();int oldY = getScrollY();int x = mScroller.getCurrX();int y = mScroller.getCurrY();if (oldX != x || oldY != y) {scrollTo(x, y);}setScrollState(SCROLL_STATE_IDLE);}mPopulatePending = false;mScrolling = false;for (int i = 0; i < mItems.size(); i++) {ItemInfo ii = mItems.get(i);if (ii.scrolling) {needPopulate = true;ii.scrolling = false;}}if (needPopulate) {populate();}}@Overridepublic boolean onInterceptTouchEvent(MotionEvent ev) {/** This method JUST determines whether we want to intercept the motion.* If we return true, onMotionEvent will be called and we do the actual* scrolling there.*/final int action = ev.getAction() & MotionEventCompat.ACTION_MASK;// Always take care of the touch gesture being complete.if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) {// Release the drag.if (DEBUG) Log.v(TAG, "Intercept done!");mIsBeingDragged = false;mIsUnableToDrag = false;mActivePointerId = INVALID_POINTER;return false;}// Nothing more to do here if we have decided whether or not we// are dragging.if (action != MotionEvent.ACTION_DOWN) {if (mIsBeingDragged) {if (DEBUG) Log.v(TAG, "Intercept returning true!");return true;}if (mIsUnableToDrag) {if (DEBUG) Log.v(TAG, "Intercept returning false!");return false;}}switch (action) {case MotionEvent.ACTION_MOVE: {/** mIsBeingDragged == false, otherwise the shortcut would have caught it. Check* whether the user has moved far enough from his original down touch.*//** Locally do absolute value. mLastMotionY is set to the y value* of the down event.*/final int activePointerId = mActivePointerId;if (activePointerId == INVALID_POINTER) {// If we don't have a valid id, the touch down wasn't on content.break;}final int pointerIndex = MotionEventCompat.findPointerIndex(ev, activePointerId);final float x = MotionEventCompat.getX(ev, pointerIndex);final float dx = x - mLastMotionX;final float xDiff = Math.abs(dx);final float y = MotionEventCompat.getY(ev, pointerIndex);final float yDiff = Math.abs(y - mLastMotionY);final int scrollX = getScrollX();final boolean atEdge = (dx > 0 && scrollX == 0) || (dx < 0 && mAdapter != null &&scrollX >= (mAdapter.getCount() - 1) * getWidth() - 1);if (DEBUG) Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);if (canScroll(this, false, (int) dx, (int) x, (int) y)) {// Nested view has scrollable area under this point. Let it be handled there.mInitialMotionX = mLastMotionX = x;mLastMotionY = y;return false;}if (xDiff > mTouchSlop && xDiff > yDiff) {if (DEBUG) Log.v(TAG, "Starting drag!");mIsBeingDragged = true;setScrollState(SCROLL_STATE_DRAGGING);mLastMotionX = x;setScrollingCacheEnabled(true);} else {if (yDiff > mTouchSlop) {// The finger has moved enough in the vertical// direction to be counted as a drag...  abort// any attempt to drag horizontally, to work correctly// with children that have scrolling containers.if (DEBUG) Log.v(TAG, "Starting unable to drag!");mIsUnableToDrag = true;}}break;}case MotionEvent.ACTION_DOWN: {/** Remember location of down touch.* ACTION_DOWN always refers to pointer index 0.*/mLastMotionX = mInitialMotionX = ev.getX();mLastMotionY = ev.getY();mActivePointerId = MotionEventCompat.getPointerId(ev, 0);if (mScrollState == SCROLL_STATE_SETTLING) {// Let the user 'catch' the pager as it animates.mIsBeingDragged = true;mIsUnableToDrag = false;setScrollState(SCROLL_STATE_DRAGGING);} else {completeScroll();mIsBeingDragged = false;mIsUnableToDrag = false;}if (DEBUG) Log.v(TAG, "Down at " + mLastMotionX + "," + mLastMotionY+ " mIsBeingDragged=" + mIsBeingDragged+ "mIsUnableToDrag=" + mIsUnableToDrag);break;}case MotionEventCompat.ACTION_POINTER_UP:onSecondaryPointerUp(ev);break;}/** The only time we want to intercept motion events is if we are in the* drag mode.*/return mIsBeingDragged;}@Overridepublic boolean onTouchEvent(MotionEvent ev) {if (mFakeDragging) {// A fake drag is in progress already, ignore this real one// but still eat the touch events.// (It is likely that the user is multi-touching the screen.)return true;}if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) {// Don't handle edge touches immediately -- they may actually belong to one of our// descendants.return false;}if (mAdapter == null || mAdapter.getCount() == 0) {// Nothing to present or scroll; nothing to touch.return false;}if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();}mVelocityTracker.addMovement(ev);final int action = ev.getAction();boolean needsInvalidate = false;switch (action & MotionEventCompat.ACTION_MASK) {case MotionEvent.ACTION_DOWN: {/** If being flinged and user touches, stop the fling. isFinished* will be false if being flinged.*/completeScroll();// Remember where the motion event startedmLastMotionX = mInitialMotionX = ev.getX();mActivePointerId = MotionEventCompat.getPointerId(ev, 0);break;}case MotionEvent.ACTION_MOVE:if (!mIsBeingDragged) {final int pointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);final float x = MotionEventCompat.getX(ev, pointerIndex);final float xDiff = Math.abs(x - mLastMotionX);final float y = MotionEventCompat.getY(ev, pointerIndex);final float yDiff = Math.abs(y - mLastMotionY);if (DEBUG)Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);if (xDiff > mTouchSlop && xDiff > yDiff) {if (DEBUG) Log.v(TAG, "Starting drag!");mIsBeingDragged = true;mLastMotionX = x;setScrollState(SCROLL_STATE_DRAGGING);setScrollingCacheEnabled(true);}}if (mIsBeingDragged) {// Scroll to follow the motion eventfinal int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);final float x = MotionEventCompat.getX(ev, activePointerIndex);final float deltaX = mLastMotionX - x;mLastMotionX = x;float oldScrollX = getScrollX();float scrollX = oldScrollX + deltaX;final int width = getWidth();final int widthWithMargin = width + mPageMargin;final int lastItemIndex = mAdapter.getCount() - 1;final float leftBound = Math.max(0, (mCurItem - 1) * widthWithMargin);final float rightBound =Math.min(mCurItem + 1, lastItemIndex) * widthWithMargin;if (scrollX < leftBound) {if (leftBound == 0) {float over = -scrollX;needsInvalidate = mLeftEdge.onPull(over / width);}scrollX = leftBound;} else if (scrollX > rightBound) {if (rightBound == lastItemIndex * widthWithMargin) {float over = scrollX - rightBound;needsInvalidate = mRightEdge.onPull(over / width);}scrollX = rightBound;}// Don't lose the rounded componentmLastMotionX += scrollX - (int) scrollX;scrollTo((int) scrollX, getScrollY());if (mOnPageChangeListener != null) {final int position = (int) scrollX / widthWithMargin;final int positionOffsetPixels = (int) scrollX % widthWithMargin;final float positionOffset = (float) positionOffsetPixels / widthWithMargin;mOnPageChangeListener.onPageScrolled(position, positionOffset,positionOffsetPixels);}}break;case MotionEvent.ACTION_UP:if (mIsBeingDragged) {final VelocityTracker velocityTracker = mVelocityTracker;velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);int initialVelocity = (int) VelocityTrackerCompat.getXVelocity(velocityTracker, mActivePointerId);mPopulatePending = true;final int widthWithMargin = getWidth() + mPageMargin;final int scrollX = getScrollX();final int currentPage = scrollX / widthWithMargin;int nextPage = initialVelocity > 0 ? currentPage : currentPage + 1;setCurrentItemInternal(nextPage, true, true, initialVelocity);mActivePointerId = INVALID_POINTER;endDrag();needsInvalidate = mLeftEdge.onRelease() | mRightEdge.onRelease();}break;case MotionEvent.ACTION_CANCEL:if (mIsBeingDragged) {setCurrentItemInternal(mCurItem, true, true);mActivePointerId = INVALID_POINTER;endDrag();needsInvalidate = mLeftEdge.onRelease() | mRightEdge.onRelease();}break;case MotionEventCompat.ACTION_POINTER_DOWN: {final int index = MotionEventCompat.getActionIndex(ev);final float x = MotionEventCompat.getX(ev, index);mLastMotionX = x;mActivePointerId = MotionEventCompat.getPointerId(ev, index);break;}case MotionEventCompat.ACTION_POINTER_UP:onSecondaryPointerUp(ev);mLastMotionX = MotionEventCompat.getX(ev,MotionEventCompat.findPointerIndex(ev, mActivePointerId));break;}if (needsInvalidate) {invalidate();}return true;}@Overridepublic void draw(Canvas canvas) {super.draw(canvas);boolean needsInvalidate = false;final int overScrollMode = ViewCompat.getOverScrollMode(this);if (overScrollMode == ViewCompat.OVER_SCROLL_ALWAYS ||(overScrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS &&mAdapter != null && mAdapter.getCount() > 1)) {if (!mLeftEdge.isFinished()) {final int restoreCount = canvas.save();final int height = getHeight() - getPaddingTop() - getPaddingBottom();canvas.rotate(270);canvas.translate(-height + getPaddingTop(), 0);mLeftEdge.setSize(height, getWidth());needsInvalidate |= mLeftEdge.draw(canvas);canvas.restoreToCount(restoreCount);}if (!mRightEdge.isFinished()) {final int restoreCount = canvas.save();final int width = getWidth();final int height = getHeight() - getPaddingTop() - getPaddingBottom();final int itemCount = mAdapter != null ? mAdapter.getCount() : 1;canvas.rotate(90);canvas.translate(-getPaddingTop(),-itemCount * (width + mPageMargin) + mPageMargin);mRightEdge.setSize(height, width);needsInvalidate |= mRightEdge.draw(canvas);canvas.restoreToCount(restoreCount);}} else {mLeftEdge.finish();mRightEdge.finish();}if (needsInvalidate) {// Keep animatinginvalidate();}}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);// Draw the margin drawable if needed.if (mPageMargin > 0 && mMarginDrawable != null) {final int scrollX = getScrollX();final int width = getWidth();final int offset = scrollX % (width + mPageMargin);if (offset != 0) {// Pages fit completely when settled; we only need to draw when in betweenfinal int left = scrollX - offset + width;mMarginDrawable.setBounds(left, 0, left + mPageMargin, getHeight());mMarginDrawable.draw(canvas);}}}/*** Start a fake drag of the pager.* <p>* <p>A fake drag can be useful if you want to synchronize the motion of the ViewPager* with the touch scrolling of another view, while still letting the ViewPager* control the snapping motion and fling behavior. (e.g. parallax-scrolling tabs.)* Call {@link #fakeDragBy(float)} to simulate the actual drag motion. Call* {@link #endFakeDrag()} to complete the fake drag and fling as necessary.* <p>* <p>During a fake drag the ViewPager will ignore all touch events. If a real drag* is already in progress, this method will return false.** @return true if the fake drag began successfully, false if it could not be started.* @see #fakeDragBy(float)* @see #endFakeDrag()*/public boolean beginFakeDrag() {if (mIsBeingDragged) {return false;}mFakeDragging = true;setScrollState(SCROLL_STATE_DRAGGING);mInitialMotionX = mLastMotionX = 0;if (mVelocityTracker == null) {mVelocityTracker = VelocityTracker.obtain();} else {mVelocityTracker.clear();}final long time = SystemClock.uptimeMillis();final MotionEvent ev = MotionEvent.obtain(time, time, MotionEvent.ACTION_DOWN, 0, 0, 0);mVelocityTracker.addMovement(ev);ev.recycle();mFakeDragBeginTime = time;return true;}/*** End a fake drag of the pager.** @see #beginFakeDrag()* @see #fakeDragBy(float)*/public void endFakeDrag() {if (!mFakeDragging) {throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");}final VelocityTracker velocityTracker = mVelocityTracker;velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);int initialVelocity = (int) VelocityTrackerCompat.getYVelocity(velocityTracker, mActivePointerId);mPopulatePending = true;if ((Math.abs(initialVelocity) > mMinimumVelocity)|| Math.abs(mInitialMotionX - mLastMotionX) >= (getWidth() / 3)) {if (mLastMotionX > mInitialMotionX) {setCurrentItemInternal(mCurItem - 1, true, true);} else {setCurrentItemInternal(mCurItem + 1, true, true);}} else {setCurrentItemInternal(mCurItem, true, true);}endDrag();mFakeDragging = false;}/*** Fake drag by an offset in pixels. You must have called {@link #beginFakeDrag()} first.** @param xOffset Offset in pixels to drag by.* @see #beginFakeDrag()* @see #endFakeDrag()*/public void fakeDragBy(float xOffset) {if (!mFakeDragging) {throw new IllegalStateException("No fake drag in progress. Call beginFakeDrag first.");}mLastMotionX += xOffset;float scrollX = getScrollX() - xOffset;final int width = getWidth();final int widthWithMargin = width + mPageMargin;final float leftBound = Math.max(0, (mCurItem - 1) * widthWithMargin);final float rightBound =Math.min(mCurItem + 1, mAdapter.getCount() - 1) * widthWithMargin;if (scrollX < leftBound) {scrollX = leftBound;} else if (scrollX > rightBound) {scrollX = rightBound;}// Don't lose the rounded componentmLastMotionX += scrollX - (int) scrollX;scrollTo((int) scrollX, getScrollY());if (mOnPageChangeListener != null) {final int position = (int) scrollX / widthWithMargin;final int positionOffsetPixels = (int) scrollX % widthWithMargin;final float positionOffset = (float) positionOffsetPixels / widthWithMargin;mOnPageChangeListener.onPageScrolled(position, positionOffset,positionOffsetPixels);}// Synthesize an event for the VelocityTracker.final long time = SystemClock.uptimeMillis();final MotionEvent ev = MotionEvent.obtain(mFakeDragBeginTime, time, MotionEvent.ACTION_MOVE,mLastMotionX, 0, 0);mVelocityTracker.addMovement(ev);ev.recycle();}/*** Returns true if a fake drag is in progress.** @return true if currently in a fake drag, false otherwise.* @see #beginFakeDrag()* @see #fakeDragBy(float)* @see #endFakeDrag()*/public boolean isFakeDragging() {return mFakeDragging;}private void onSecondaryPointerUp(MotionEvent ev) {final int pointerIndex = MotionEventCompat.getActionIndex(ev);final int pointerId = MotionEventCompat.getPointerId(ev, pointerIndex);if (pointerId == mActivePointerId) {// This was our active pointer going up. Choose a new// active pointer and adjust accordingly.final int newPointerIndex = pointerIndex == 0 ? 1 : 0;mLastMotionX = MotionEventCompat.getX(ev, newPointerIndex);mActivePointerId = MotionEventCompat.getPointerId(ev, newPointerIndex);if (mVelocityTracker != null) {mVelocityTracker.clear();}}}private void endDrag() {mIsBeingDragged = false;mIsUnableToDrag = false;if (mVelocityTracker != null) {mVelocityTracker.recycle();mVelocityTracker = null;}}private void setScrollingCacheEnabled(boolean enabled) {if (mScrollingCacheEnabled != enabled) {mScrollingCacheEnabled = enabled;if (USE_CACHE) {final int size = getChildCount();for (int i = 0; i < size; ++i) {final View child = getChildAt(i);if (child.getVisibility() != GONE) {child.setDrawingCacheEnabled(enabled);}}}}}/*** Tests scrollability within child views of v given a delta of dx.** @param v      View to test for horizontal scrollability* @param checkV Whether the view v passed should itself be checked for scrollability (true),*               or just its children (false).* @param dx     Delta scrolled in pixels* @param x      X coordinate of the active touch point* @param y      Y coordinate of the active touch point* @return true if child views of v can be scrolled by delta of dx.*/protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {if (v instanceof ViewGroup) {final ViewGroup group = (ViewGroup) v;final int scrollX = v.getScrollX();final int scrollY = v.getScrollY();final int count = group.getChildCount();// Count backwards - let topmost views consume scroll distance first.for (int i = count - 1; i >= 0; i--) {// TODO: Add versioned support here for transformed views.// This will not work for transformed views in Honeycomb+final View child = group.getChildAt(i);if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() &&y + scrollY >= child.getTop() && y + scrollY < child.getBottom() &&canScroll(child, true, dx, x + scrollX - child.getLeft(),y + scrollY - child.getTop())) {return true;}}}return checkV && ViewCompat.canScrollHorizontally(v, -dx);}@Overridepublic boolean dispatchKeyEvent(KeyEvent event) {// Let the focused view and/or our descendants get the key firstreturn super.dispatchKeyEvent(event) || executeKeyEvent(event);}/*** You can call this function yourself to have the scroll view perform* scrolling from a key event, just as if the event had been dispatched to* it by the view hierarchy.** @param event The key event to execute.* @return Return true if the event was handled, else false.*/public boolean executeKeyEvent(KeyEvent event) {boolean handled = false;if (event.getAction() == KeyEvent.ACTION_DOWN) {switch (event.getKeyCode()) {case KeyEvent.KEYCODE_DPAD_LEFT:handled = arrowScroll(FOCUS_LEFT);break;case KeyEvent.KEYCODE_DPAD_RIGHT:handled = arrowScroll(FOCUS_RIGHT);break;case KeyEvent.KEYCODE_TAB:if (KeyEventCompat.hasNoModifiers(event)) {handled = arrowScroll(FOCUS_FORWARD);} else if (KeyEventCompat.hasModifiers(event, KeyEvent.META_SHIFT_ON)) {handled = arrowScroll(FOCUS_BACKWARD);}break;}}return handled;}public boolean arrowScroll(int direction) {View currentFocused = findFocus();if (currentFocused == this) currentFocused = null;boolean handled = false;View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused,direction);if (nextFocused != null && nextFocused != currentFocused) {if (direction == View.FOCUS_LEFT) {// If there is nothing to the left, or this is causing us to// jump to the right, then what we really want to do is page left.if (currentFocused != null && nextFocused.getLeft() >= currentFocused.getLeft()) {handled = pageLeft();} else {handled = nextFocused.requestFocus();}} else if (direction == View.FOCUS_RIGHT) {// If there is nothing to the right, or this is causing us to// jump to the left, then what we really want to do is page right.if (currentFocused != null && nextFocused.getLeft() <= currentFocused.getLeft()) {handled = pageRight();} else {handled = nextFocused.requestFocus();}}} else if (direction == FOCUS_LEFT || direction == FOCUS_BACKWARD) {// Trying to move left and nothing there; try to page.handled = pageLeft();} else if (direction == FOCUS_RIGHT || direction == FOCUS_FORWARD) {// Trying to move right and nothing there; try to page.handled = pageRight();}if (handled) {playSoundEffect(SoundEffectConstants.getContantForFocusDirection(direction));}return handled;}boolean pageLeft() {if (mCurItem > 0) {setCurrentItem(mCurItem - 1, true);return true;}return false;}boolean pageRight() {if (mAdapter != null && mCurItem < (mAdapter.getCount() - 1)) {setCurrentItem(mCurItem + 1, true);return true;}return false;}/*** We only want the current page that is being shown to be focusable.*/@Overridepublic void addFocusables(ArrayList<View> views, int direction, int focusableMode) {final int focusableCount = views.size();final int descendantFocusability = getDescendantFocusability();if (descendantFocusability != FOCUS_BLOCK_DESCENDANTS) {for (int i = 0; i < getChildCount(); i++) {final View child = getChildAt(i);if (child.getVisibility() == VISIBLE) {ItemInfo ii = infoForChild(child);if (ii != null && ii.position == mCurItem) {child.addFocusables(views, direction, focusableMode);}}}}// we add ourselves (if focusable) in all cases except for when we are// FOCUS_AFTER_DESCENDANTS and there are some descendants focusable.  this is// to avoid the focus search finding layouts when a more precise search// among the focusable children would be more interesting.if (descendantFocusability != FOCUS_AFTER_DESCENDANTS ||// No focusable descendants(focusableCount == views.size())) {// Note that we can't call the superclass here, because it will// add all views in.  So we need to do the same thing View does.if (!isFocusable()) {return;}if ((focusableMode & FOCUSABLES_TOUCH_MODE) == FOCUSABLES_TOUCH_MODE &&isInTouchMode() && !isFocusableInTouchMode()) {return;}if (views != null) {views.add(this);}}}/*** We only want the current page that is being shown to be touchable.*/@Overridepublic void addTouchables(ArrayList<View> views) {// Note that we don't call super.addTouchables(), which means that// we don't call View.addTouchables().  This is okay because a ViewPager// is itself not touchable.for (int i = 0; i < getChildCount(); i++) {final View child = getChildAt(i);if (child.getVisibility() == VISIBLE) {ItemInfo ii = infoForChild(child);if (ii != null && ii.position == mCurItem) {child.addTouchables(views);}}}}/*** We only want the current page that is being shown to be focusable.*/@Overrideprotected boolean onRequestFocusInDescendants(int direction,Rect previouslyFocusedRect) {int index;int increment;int end;int count = getChildCount();if ((direction & FOCUS_FORWARD) != 0) {index = 0;increment = 1;end = count;} else {index = count - 1;increment = -1;end = -1;}for (int i = index; i != end; i += increment) {View child = getChildAt(i);if (child.getVisibility() == VISIBLE) {ItemInfo ii = infoForChild(child);if (ii != null && ii.position == mCurItem) {if (child.requestFocus(direction, previouslyFocusedRect)) {return true;}}}}return false;}@Overridepublic boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event) {// ViewPagers should only report accessibility info for the current page,// otherwise things get very confusing.// TODO: Should this note something about the paging container?final int childCount = getChildCount();for (int i = 0; i < childCount; i++) {final View child = getChildAt(i);if (child.getVisibility() == VISIBLE) {final ItemInfo ii = infoForChild(child);if (ii != null && ii.position == mCurItem &&child.dispatchPopulateAccessibilityEvent(event)) {return true;}}}return false;}private class PagerObserver extends DataSetObserver {@Overridepublic void onChanged() {dataSetChanged();}@Overridepublic void onInvalidated() {dataSetChanged();}}
}

myphotoview是支持手势的一个自定义的view，

想要研究这个源码的可以参考这个链接https://github.com/biezhihua/MySimpleDraweeView

代码

package com.anlaiye.swt.bigphoto;import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.drawable.Animatable;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.util.AttributeSet;
import android.view.MotionEvent;import com.facebook.common.references.CloseableReference;
import com.facebook.datasource.DataSource;
import com.facebook.drawee.backends.pipeline.Fresco;
import com.facebook.drawee.controller.AbstractDraweeController;
import com.facebook.drawee.controller.BaseControllerListener;
import com.facebook.drawee.generic.GenericDraweeHierarchy;
import com.facebook.drawee.generic.GenericDraweeHierarchyBuilder;
import com.facebook.drawee.view.DraweeHolder;
import com.facebook.imagepipeline.core.ImagePipeline;
import com.facebook.imagepipeline.image.CloseableImage;
import com.facebook.imagepipeline.image.CloseableStaticBitmap;
import com.facebook.imagepipeline.image.ImageInfo;
import com.facebook.imagepipeline.request.ImageRequest;
import com.facebook.imagepipeline.request.ImageRequestBuilder;import uk.co.senab.photoview.PhotoView;/*** Created by pc on 2016/12/13.*/public class MyPhotoView extends PhotoView {protected DraweeHolder<GenericDraweeHierarchy> mDraweeHolder;public MyPhotoView(Context context) {this(context, null);}public MyPhotoView(Context context, AttributeSet attr) {this(context, attr, 0);}public MyPhotoView(Context context, AttributeSet attr, int defStyle) {super(context, attr, defStyle);selfInit();}private void selfInit() {if (mDraweeHolder == null) {final GenericDraweeHierarchy hierarchy = new GenericDraweeHierarchyBuilder(getResources()).setProgressBarImage(new LoadingProgressDrawable(getContext())).build();mDraweeHolder = DraweeHolder.create(hierarchy, getContext());}}@Overrideprotected void onDetachedFromWindow() {super.onDetachedFromWindow();mDraweeHolder.onDetach();}@Overrideprotected void onAttachedToWindow() {super.onAttachedToWindow();mDraweeHolder.onAttach();}@Overrideprotected boolean verifyDrawable(Drawable dr) {super.verifyDrawable(dr);return dr == mDraweeHolder.getHierarchy().getTopLevelDrawable();}@Overridepublic void onStartTemporaryDetach() {super.onStartTemporaryDetach();mDraweeHolder.onDetach();}@Overridepublic void onFinishTemporaryDetach() {super.onFinishTemporaryDetach();mDraweeHolder.onAttach();}@Overridepublic boolean onTouchEvent(MotionEvent event) {return mDraweeHolder.onTouchEvent(event) || super.onTouchEvent(event);}public void setImageUri(String uri) {final ImageRequest imageRequest = ImageRequestBuilder.newBuilderWithSource(Uri.parse(uri)).setAutoRotateEnabled(true).build();final ImagePipeline imagePipeline = Fresco.getImagePipeline();final DataSource<CloseableReference<CloseableImage>> dataSource = imagePipeline.fetchDecodedImage(imageRequest, this);final AbstractDraweeController controller = Fresco.newDraweeControllerBuilder().setOldController(mDraweeHolder.getController()).setImageRequest(imageRequest).setControllerListener(new BaseControllerListener<ImageInfo>() {@Overridepublic void onFinalImageSet(String id, ImageInfo imageInfo, Animatable animatable) {super.onFinalImageSet(id, imageInfo, animatable);CloseableReference<CloseableImage> imageCloseableReference = null;try {imageCloseableReference = dataSource.getResult();if (imageCloseableReference != null) {final CloseableImage image = imageCloseableReference.get();if (image != null && image instanceof CloseableStaticBitmap) {CloseableStaticBitmap closeableStaticBitmap = (CloseableStaticBitmap) image;final Bitmap bitmap = closeableStaticBitmap.getUnderlyingBitmap();if (bitmap != null) {setImageBitmap(bitmap);// 如果是长图，让其宽度放大至与屏幕等宽//setScaleType(ScaleType.CENTER_INSIDE);}}}} finally {dataSource.close();CloseableReference.closeSafely(imageCloseableReference);}}}).build();mDraweeHolder.setController(controller);setImageDrawable(mDraweeHolder.getTopLevelDrawable());}}

下面这个是一个loding的界面，在图片还没加载完成的时候会出现，

LoadingProgressDrawable

代码

package com.anlaiye.swt.bigphoto;import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.drawable.Drawable;public class LoadingProgressDrawable extends Drawable {private static final String TAG = "LoadingProgressDrawable";private static int[] Loadings = {R.mipmap.load_progress_1,R.mipmap.load_progress_3,R.mipmap.load_progress_4,R.mipmap.load_progress_6,R.mipmap.load_progress_7,R.mipmap.load_progress_8,R.mipmap.load_progress_9,R.mipmap.load_progress_10,R.mipmap.load_progress_11,R.mipmap.load_progress_12};private Paint mPaint;private int mLevel;private Context context;public LoadingProgressDrawable(Context context) {this.context = context;mPaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.DITHER_FLAG);}BitmapFactory.Options options = new BitmapFactory.Options();@Overridepublic void draw(Canvas canvas) {Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), Loadings[getIndex()], options);int left = getBounds().right / 2 - options.outWidth / 2;int top = getBounds().bottom / 2 - options.outHeight / 2;canvas.drawBitmap(bitmap, left, top, mPaint);}private int getIndex() {int index = mLevel / 1000;if (index < 0) {index = 0;} else if (index >= Loadings.length) {index = Loadings.length - 1;}return index;}@Overridepublic void setAlpha(int alpha) {mPaint.setAlpha(alpha);}@Overridepublic void setColorFilter(ColorFilter cf) {mPaint.setColorFilter(cf);}@Overridepublic int getOpacity() {return Color.TRANSPARENT;}@Overrideprotected boolean onLevelChange(int level) {this.mLevel = level;this.invalidateSelf();return true;}
}

然后看下我们的最终效果图，缩放类型可以自己在MyPhotot的源码里面去修改，不过我觉得inside类型看起来是最舒服的，

下图就是最终的效果图，有其他的功能需要扩展的可以在上面继续扩展，文末有完整的源代码的链接，

直接用android studio打开就好了，下载相应的api 和tool就可以运行了,

完整代码在这里http://download.csdn.net/detail/qq_15527709/9711091

(我是小白，不要喷我)

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