Android webview 双指滑动

float OldX1 = 0;
webView.setOnTouchListener(new View.OnTouchListener() {
    @Override
    public boolean onTouch(View view, MotionEvent event) {
        switch (event.getAction()) {
        case MotionEvent.ACTION_POINTER_2_DOWN:
                if (event.getPointerCount() == 2) {
                        for (int i = 0; i < event.getPointerCount(); i++) {
                                if (i == 0) {
                                        OldX1 = event.getX(i);
                                        OldY1 = event.getY(i);
                                } else if (i == 1) {
                                        OldX2 = event.getX(i);
                                        OldY2 = event.getY(i);
                                }
                        }
                }
                break;
        case MotionEvent.ACTION_MOVE:
                if (event.getPointerCount() == 2) {
                        for (int i = 0; i < event.getPointerCount(); i++) {
                                if (i == 0) {
                                        NewX1 = event.getX(i);
                                        NewY1 = event.getY(i);
                                } else if (i == 1) {
                                        NewX2 = event.getX(i);
                                        NewY2 = event.getY(i);
                                }
                        }
                        float disOld = (float) Math.sqrt((Math.pow(OldX2 - OldX1, 2) + Math.pow(
                                        OldY2 - OldY1, 2)));
                        float disNew = (float) Math.sqrt((Math.pow(NewX2 - NewX1, 2) + Math.pow(
                                        NewY2 - NewY1, 2)));
                        Log.d("onTouch","disOld="+disOld+"|disNew="+disNew);
                        if (disOld - disNew >= 25) {
                                // 缩小
                                webView.zoomOut();

                        } else if(disNew - disOld >= 25){
                                // 放大
                                webView.zoomIn();
                        }
                        OldX1 = NewX1;
                        OldX2 = NewX2;
                        OldY1 = NewY1;
                        OldY2 = NewY2;
                }
        }

        return false;
    }
});