Android-监听View的两个指尖是放大和缩小

  
private double nLenStart = 0;//监听 WebView所用手势


@Override            public boolean onTouch(View v, MotionEvent event) {                int nCnt = event.getPointerCount();                int n = event.getAction();                if ((event.getAction() & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_POINTER_DOWN && 2 == nCnt)//<span style="color:#ff0000;">2表示两个手指</span>                {                    for (int i = 0; i < nCnt; i++) {                        float x = event.getX(i);                        float y = event.getY(i);                        Point pt = new Point((int) x, (int) y);                    }                    int xlen = Math.abs((int) event.getX(0) - (int) event.getX(1));                    int ylen = Math.abs((int) event.getY(0) - (int) event.getY(1));                    nLenStart = Math.sqrt((double) xlen * xlen + (double) ylen * ylen);                } else if ((event.getAction() & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_POINTER_UP && 2 == nCnt) {                    for (int i = 0; i < nCnt; i++) {                        float x = event.getX(i);                        float y = event.getY(i);                        Point pt = new Point((int) x, (int) y);                    }                    int xlen = Math.abs((int) event.getX(0) - (int) event.getX(1));                    int ylen = Math.abs((int) event.getY(0) - (int) event.getY(1));                    double nLenEnd = Math.sqrt((double) xlen * xlen + (double) ylen * ylen);                    if (nLenEnd > nLenStart)//通过两个手指开始距离和结束距离，来判断放大缩小                    {                        Toast.makeText(getApplicationContext(), "放大", Toast.LENGTH_SHORT).show();                        tv_web_danGe.getSettings().setTextSize(WebSettings.TextSize.LARGER);                        tv_web_danGe.reload();                        tv_web_danGe.loadDataWithBaseURL(null, getHtmlData(content),"text/html","UTF-8",null);//显示WebView                    } else {                        Toast.makeText(getApplicationContext(), "缩小", Toast.LENGTH_SHORT).show();                        tv_web_danGe.getSettings().setTextSize(WebSettings.TextSize.NORMAL);                        tv_web_danGe.reload();                        tv_web_danGe.loadDataWithBaseURL(null, getHtmlData(content),"text/html","UTF-8",null);//显示WebView                    }                }                return false;            }