原文：http://tryenough.com/android-layoutparams

LayoutParams是什么？

LayoutParams是View用来告诉它的父控件如何放置自己的，LayoutParams是ViewGroup类里的一个静态内部类。

ViewGroup.LayoutParams仅仅描述了这个View想要的宽度和高度。可以理解成LayoutParams是子View告诉父View自身宽高的桥梁。

可取的值：

• fill_parent 强制性使子视图的大小扩展至与父视图大小相等（不含 padding )
• match_parent 与fill_parent相同，用于Android 2.3 & 之后版本
• wrap_content 自适应大小，强制性地使视图扩展以便显示其全部内容(含 padding )

不同ViewGroup的继承类对应着不同的ViewGroup.LayoutParams的子类，例如：ViewGroup.MarginLayoutParams, WindowManager.LayoutParams等。

原文：http://tryenough.com/android-layoutparams

实际使用的一个例子

Activity:

public class MoveActivity extends AppCompatActivity {private ImageView mIv;private TextView mTvBlue;private TextView mTvGreen;private ViewGroup.LayoutParams mVgLp;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_move);mIv = (ImageView) findViewById(R.id.mIv);mTvBlue = (TextView) findViewById(R.id.mTvBlue);mTvGreen = (TextView) findViewById(R.id.mTvGreen);mVgLp = mIv.getLayoutParams();findViewById(R.id.mTvMoveRight).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {ViewGroup.LayoutParams vg_lp = mIv.getLayoutParams();// RelativeLayout.LayoutParams 不可抽取为成员变量RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(vg_lp);params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT, R.id.mIv);mIv.setLayoutParams(params); //使layout更新}});findViewById(R.id.mTvMoveLeft).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {// 左 （默认处于顶部，所以看起来是左上）RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(mVgLp);params.addRule(RelativeLayout.ALIGN_PARENT_LEFT);mIv.setLayoutParams(params);}});findViewById(R.id.mTvCenter).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {// 居中RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(mVgLp);params.addRule(RelativeLayout.CENTER_IN_PARENT);mIv.setLayoutParams(params);}});findViewById(R.id.mTvLeftVer).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {// 左部垂直居中RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(mVgLp);params.addRule(RelativeLayout.ALIGN_PARENT_LEFT|RelativeLayout.CENTER_VERTICAL);mIv.setLayoutParams(params);}});findViewById(R.id.mTvRightBot).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {// 右下RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(mVgLp);params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);mIv.setLayoutParams(params);}});//  绿在蓝右边findViewById(R.id.mTvaGRightB).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {ViewGroup.LayoutParams vgLp = mTvGreen.getLayoutParams();RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(vgLp);params.addRule(RelativeLayout.RIGHT_OF,R.id.mTvBlue);mTvGreen.setLayoutParams(params);}});// 绿在蓝下边findViewById(R.id.mTvGElowB).setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {ViewGroup.LayoutParams vgLp = mTvGreen.getLayoutParams();RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(vgLp);params.addRule(RelativeLayout.BELOW,R.id.mTvBlue);mTvGreen.setLayoutParams(params);}});}
}
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布局xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayoutandroid:id="@+id/activity_main"xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:paddingBottom="@dimen/activity_vertical_margin"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"android:orientation="vertical"tools:context="com.amqr.movetest.MoveActivity"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"><TextViewandroid:id="@+id/mTvMoveLeft"android:layout_width="wrap_content"android:layout_height="wrap_content"android:background="#6600ff00"android:padding="10dp"android:layout_margin="10dp"android:text="黑色最左！！"/><TextViewandroid:id="@+id/mTvMoveRight"android:layout_width="wrap_content"android:layout_height="wrap_content"android:padding="10dp"android:background="#6600ff00"android:layout_margin="10dp"android:text="黑色最右！！"/><TextViewandroid:id="@+id/mTvCenter"android:layout_width="wrap_content"android:layout_height="wrap_content"android:background="#6600ff00"android:padding="10dp"android:layout_margin="10dp"android:text="黑色居中"/></LinearLayout><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"><TextViewandroid:id="@+id/mTvLeftVer"android:layout_width="wrap_content"android:layout_height="wrap_content"android:padding="10dp"android:background="#6600ff00"android:layout_margin="10dp"android:text="黑色靠左垂直居中"/><TextViewandroid:id="@+id/mTvRightBot"android:layout_width="wrap_content"android:layout_height="wrap_content"android:background="#6600ff00"android:padding="10dp"android:layout_margin="10dp"android:text="黑色右下角"/></LinearLayout><LinearLayoutandroid:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"><TextViewandroid:id="@+id/mTvaGRightB"android:layout_width="wrap_content"android:layout_height="wrap_content"android:padding="10dp"android:background="#6600ff00"android:layout_margin="10dp"android:text="绿在蓝右边"/><TextViewandroid:id="@+id/mTvGElowB"android:layout_width="wrap_content"android:layout_height="wrap_content"android:background="#6600ff00"android:padding="10dp"android:layout_margin="10dp"android:text="绿在蓝下边"/></LinearLayout><RelativeLayoutandroid:layout_width="match_parent"android:layout_height="200px"android:background="#66ff0000"><TextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="RelativeLayout"android:layout_centerInParent="true"/><ImageViewandroid:id="@+id/mIv"android:layout_width="30dp"android:layout_height="40px"android:background="#000"android:layout_centerHorizontal="true"/><TextViewandroid:id="@+id/mTvBlue"android:layout_width="20dp"android:layout_height="20dp"android:text="蓝"android:gravity="center"android:background="#660000ff"/><TextViewandroid:id="@+id/mTvGreen"android:layout_width="20dp"android:layout_height="20dp"android:text="绿"android:gravity="center"android:background="#6600ff00"android:layout_below="@id/mTvBlue"/></RelativeLayout>
</LinearLayout>
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