多点触摸技术

//多点触摸  放大，缩小
public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_main);

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // TODO Auto-generated method stub
        // 两点触摸
        if (event.getPointerCount() == 2) {
            if (event.getAction() == MotionEvent.ACTION_MOVE) {
                int historySize = event.getHistorySize();
                if (historySize == 0) {
                    return true;
                }
                // 获取第一个手指当前的纵坐标
                float currentY1 = event.getY(0);
                // 获取第一个手指当前最新的历史的纵坐标
                float historyY1 = event.getHistoricalY(0, historySize - 1);
                // 获取第二个手指当前的纵坐标
                float currentY2 = event.getY(2);
                // 获取第二个手指当前最新的历史的纵坐标
                float historyY2 = event.getHistoricalY(1, historySize - 1);
                // 两手指当前纵坐标的距离
                float distance = Math.abs(currentY1 - currentY2);
                // 两手指最新的历史纵坐标的距离
                float historyDistance = Math.abs(historyY1 - historyY2);

                if (distance > historyDistance) {
                    Log.i("-====>", "放大");
                } else if (distance < historyDistance) {
                    Log.i("-====>", "缩小");
                } else {
                    Log.i("-====>", "移动");
                }
            }
        }
        return super.onTouchEvent(event);
    }

}