要求：

1.通过手指移动来拖动图片

2.控制图片不能超出屏幕显示区域

技术点:

1.MotionEvent处理

2.对View进行动态定位(layout)

activity_main.xml：

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent" >

android:id="@+id/iv_main"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:src="@drawable/test"/>

MainActivity:

public class MainActivity extends Activity implements OnTouchListener {

private ImageView iv_main;

private RelativeLayout parentView;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

iv_main = (ImageView) findViewById(R.id.iv_main);

parentView = (RelativeLayout) iv_main.getParent();

/*

int right = parentView.getRight(); //0

int bottom = parentView.getBottom(); //0

Toast.makeText(this, right+"---"+bottom, 1).show();

*/

//设置touch监听

iv_main.setOnTouchListener(this);

}

private int lastX;

private int lastY;

private int maxRight;

private int maxBottom;

@Override

public boolean onTouch(View v, MotionEvent event) {

//得到事件的坐标

int eventX = (int) event.getRawX();

int eventY = (int) event.getRawY();

switch (event.getAction()) {

case MotionEvent.ACTION_DOWN:

//得到父视图的right/bottom

if(maxRight==0) {//保证只赋一次值

maxRight = parentView.getRight();

maxBottom = parentView.getBottom();

}

//第一次记录lastX/lastY

lastX =eventX;

lastY = eventY;

break;

case MotionEvent.ACTION_MOVE:

//计算事件的偏移

int dx = eventX-lastX;

int dy = eventY-lastY;

//根据事件的偏移来移动imageView

int left = iv_main.getLeft()+dx;

int top = iv_main.getTop()+dy;

int right = iv_main.getRight()+dx;

int bottom = iv_main.getBottom()+dy;

//限制left >=0

if(left<0) {

right += -left;

left = 0;

}

//限制top

if(top<0) {

bottom += -top;

top = 0;

}

//限制right <=maxRight

if(right>maxRight) {

left -= right-maxRight;

right = maxRight;

}

//限制bottom <=maxBottom

if(bottom>maxBottom) {

top -= bottom-maxBottom;

bottom = maxBottom;

}

iv_main.layout(left, top, right, bottom);

//再次记录lastX/lastY

lastX = eventX;

lastY = eventY;

break;

default:

break;

}

return true;//所有的motionEvent都交给imageView处理

}

}

以上就是本文的全部内容，希望本文的内容对大家的学习或者工作能带来一定的帮助，同时也希望多多支持脚本之家！