Android 实现可拖动的ImageView

代码实现：

public class DraggableImageView extends AppCompatImageView {private float lastTouchX;private float lastTouchY;public DraggableImageView(Context context) {super(context);init();}public DraggableImageView(Context context, AttributeSet attrs) {super(context, attrs);init();}public DraggableImageView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);init();}private void init() {setClickable(true);}@Overridepublic boolean onTouchEvent(MotionEvent event) {final int action = event.getActionMasked();switch (action) {case MotionEvent.ACTION_DOWN:lastTouchX = event.getRawX();lastTouchY = event.getRawY();break;case MotionEvent.ACTION_MOVE:float x = event.getRawX();float y = event.getRawY();x = Math.max(0,x);y = Math.max(0,y);float dx = x - lastTouchX;float dy = y - lastTouchY;//边界控制ViewGroup pa = (ViewGroup) getParent();float lx = Math.max(0,dx+getX());float ly = Math.max(0,dy+getY());lx = Math.min(lx,pa.getWidth()-getWidth());ly = Math.min(ly,pa.getHeight()-getHeight());setX(lx);setY(ly);lastTouchX = x;lastTouchY = y;break;case MotionEvent.ACTION_UP:case MotionEvent.ACTION_CANCEL:break;case MotionEvent.ACTION_POINTER_UP:lastTouchX = event.getRawX();lastTouchY = event.getRawX();break;}return true;}
}