Android View隨手指移動

package com.lcj.test;

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class TouchView extends View {

    public TouchView(Context context) {
        super(context);
    }

    public TouchView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public TouchView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    boolean isInnerView = false;

    float downX;
    float downY;
    float moveX;
    float moveY;

    @Override
    public boolean onTouchEvent(MotionEvent event) {

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

                downX = event.getRawX();
                downY = event.getRawY();

                Rect rect = new Rect();
                int[] location = new int[2];
                getLocationOnScreen(location);
                rect.left = location[0];
                rect.top = location[1];
                rect.right = location[0] + this.getWidth();
                rect.bottom = location[1] + this.getHeight();
                if (rect.contains((int) event.getRawX(), (int) event.getRawY())) {
                    isInnerView = true;
                }
                break;
            case MotionEvent.ACTION_MOVE:
                moveX = event.getRawX();
                moveY = event.getRawY();
                float offsetX = moveX - downX;
                float offsetY = moveY - downY;
                if (isInnerView) {
                    this.setX(getX() + offsetX);
                    this.setY(getY() + offsetY);
                }
                downX = moveX;
                downY = moveY;
                break;
            case MotionEvent.ACTION_UP:
                isInnerView = false;
                break;
            default:
                break;
        }
        return true;
    }
}