Android实现图片浮动随意拖拽效果

public class MoveImage extends ImageView {

 /**
 *
 * 浮动工具类
 *
 */
 private int lastX = 0;
 private int lastY = 0;

 private int dx;
 private int dy;
 private float movex = 0;
 private float movey = 0;

 private int screenWidth;
 private int screenHeight;

 public MoveImage(Context context, AttributeSet attrs) {
 super(context, attrs);
 screenWidth = ScreenUtils.getWidth(context);
 screenHeight = ScreenUtils.getHeight(context);
 }

 @Override
 public boolean onTouchEvent(MotionEvent event) {
 switch (event.getAction()) {
 case MotionEvent.ACTION_DOWN:
 lastX = (int) event.getRawX();
 lastY = (int) event.getRawY();
 movex = lastX;
 movey = lastY;
 break;
 case MotionEvent.ACTION_MOVE:
 dx = (int) event.getRawX() - lastX;
 dy = (int) event.getRawY() - lastY;

 int left = getLeft() + dx;
 int top = getTop() + dy;
 int right = getRight() + dx;
 int bottom = getBottom() + dy;
 if (left <0) {
 left = 0;
 right = left + getWidth();
 }
 if (right > screenWidth) {
 right = screenWidth;
 left = right - getWidth();
 }
 if (top <0) {
 top = 0;
 bottom = top + getHeight();
 }
 if (bottom > screenHeight) {
 bottom = screenHeight;
 top = bottom - getHeight();
 }
 layout(left, top, right, bottom);
 lastX = (int) event.getRawX();
 lastY = (int) event.getRawY();
 break;
 case MotionEvent.ACTION_UP:
 //避免滑出触发点击事件
 if ((int) (event.getRawX() - movex) != 0
 || (int) (event.getRawY() - movey) != 0) {
 return true;
 }
 break;
 default:
 break;
 }
 return super.onTouchEvent(event);
 }
}

private MoveImage iv_phone_bar;//签到图片
iv_phone_bar = (MoveImage) view.findViewById(R.id.iv_phone_bar);
iv_phone_bar.setOnClickListener(this);
// 签到
case R.id.iv_phone_bar:
 startActivity(new Intent(getActivity(), SignAcitvity.class));//点击跳转页面
 break;