自定义控件实现图片随着手指移动

//布局怡然是自定义布局
MainActivity中还是什么都没有
下面是自定义类的代码

/**
 * date:2018/11/2
 * author:王加辉(家辉辉辉)
 * function: 继承式自定义控件
 */
@SuppressLint("AppCompatCustomView")
public class RectangleImageView extends ImageView  {


    private int lastX;
    private int lastY;


    public RectangleImageView(Context context) {
        this(context,null);
    }

    public RectangleImageView(Context context,  AttributeSet attrs) {
        this(context, attrs,0);
    }

    public RectangleImageView(Context context,  AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        //初始化控件


    }

    /**
     * 触摸事件
     * */
    @Override
    public boolean onTouchEvent(MotionEvent event) {

        //获取到手指处的x,y轴
        int x = (int) event.getX();
        int y = (int) event.getY();

        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:

                lastX = x;
                lastY = y;

                break;
            case MotionEvent.ACTION_MOVE:

                int offX = x - lastX ;
                int offY = y - lastY ;

                movingXY(offX,offY);

                    break;
            case MotionEvent.ACTION_UP:

                break;
        }
        return true;
}

    private void movingXY(int offX, int offY) {
        //移动View
        layout(getLeft() + offX , getTop() + offY , getRight() + offX , getBottom()+offY);
    }

    //测量
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    }

    //布局
    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);

    }

    //绘制,继承的图片所以不用
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

    }

}