Android实现图片拖动效果

 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"/>

publicclassMainActivityextendsActivityimplementsOnTouchListener {

 privateImageView iv_main;

 privateRelativeLayout parentView;

 @Override

 protectedvoidonCreate(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);

 }

 privateintlastX;

 privateintlastY;

 privateintmaxRight;

 privateintmaxBottom;

 @Override

 publicbooleanonTouch(View v, MotionEvent event) {

  //得到事件的坐标

  inteventX = (int) event.getRawX();

  inteventY = (int) event.getRawY();

  switch(event.getAction()) {

  caseMotionEvent.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;

  caseMotionEvent.ACTION_MOVE:

   //计算事件的偏移

   intdx = eventX-lastX;

   intdy = eventY-lastY;

   //根据事件的偏移来移动imageView

   intleft = iv_main.getLeft()+dx;

   inttop = iv_main.getTop()+dy;

   intright = iv_main.getRight()+dx;

   intbottom = 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;

  }

  returntrue;//所有的motionEvent都交给imageView处理

 }

}