Android多点触摸交互处理

在FrameLayout中学习Android的单点和多点触摸交互，并实现图像拖拽移动，放大和缩小。

单点触摸
即为view设置监听事件setOnTouchListener，通过MotionEvent event获得触摸的相关操作，如event.getAction()获取触摸的动作，event.getX()，event.getY(）分别获取触摸点的坐标。

        View view = inflater.inflate(R.layout.fragment_touch, container, false);        view.setOnTouchListener(new View.OnTouchListener() {            @Override            public boolean onTouch(View v, MotionEvent event) {                switch (event.getAction()) {                    case MotionEvent.ACTION_DOWN:                        System.out.println("ACTION_DOWN");                        break;                    case MotionEvent.ACTION_MOVE:                        System.out.println("ACTION_MOVE");                         System.out.println(String.format("X:%f,Y:%f", event.getX(), event.getY()));                        break;                    case MotionEvent.ACTION_UP:                        System.out.println("ACTION_UP");                        break;                }                return true;

}

多点触摸
只要使用event.getPointerCount()就能得到触摸点的个数。多个触摸点的坐标也可以通过event.getX(int index)，event.getX(int index)获取，index从0开始。

图像拖拽移动，放大和缩小。
我们利用event的相关操作获取触摸点的信息并将它通过layoutParams传递给图片参数设置，从而控制图像的位置大小，达到移动，放大和缩小。

   @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        // Inflate the layout for this fragment        View view = inflater.inflate(R.layout.fragment_touch, container, false);        iv_move = (ImageView) view.findViewById(R.id.iv_move);        tv_xy= (TextView) view.findViewById(R.id.tv_xy);        view.setOnTouchListener(new View.OnTouchListener() {            @Override            public boolean onTouch(View v, MotionEvent event) {                switch (event.getAction()) {                    case MotionEvent.ACTION_DOWN:                        System.out.println("ACTION_DOWN");                        break;                    case MotionEvent.ACTION_MOVE:                        System.out.println("ACTION_MOVE");//                        System.out.println(String.format("X:%f,Y:%f", event.getX(), event.getY()));//                        System.out.println(event.getPointerCount());                        tv_xy.setText(String.format("X:%f,Y:%f", event.getX(), event.getY()));                        layoutParams = (FrameLayout.LayoutParams) iv_move.getLayoutParams();//                        layoutParams.setMargins((int) event.getX(),(int) event.getY(),0,0);                        if (event.getPointerCount()>=2) {                            float offsetX = event.getX(0) - event.getX(1);                            float offsetY = event.getY(0) - event.getY(1);                            currentdistance = (float) Math.sqrt(offsetX * offsetX + offsetY * offsetY);                            if (lastdistance < 0) {                                lastdistance = currentdistance;                            } else if (lastdistance - currentdistance < 5) {                                System.out.println("放大");                                layoutParams.width = (int) (iv_move.getWidth() *1.05f);                                layoutParams.height = (int) (iv_move.getHeight() * 1.05f);                                lastdistance = currentdistance;                            } else if (lastdistance - currentdistance > 5) {                                System.out.println("缩小");                                layoutParams.width = (int) (iv_move.getWidth() *0.95f);                                layoutParams.height = (int) (iv_move.getHeight() * 0.95f);                                lastdistance = currentdistance;                            }                        }                        iv_move.setLayoutParams(layoutParams);                        break;                    case MotionEvent.ACTION_UP:                        System.out.println("ACTION_UP");                        break;                }                return true;            }        });        return view;    }

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