Android : สอบถามปัญหาเรื่อง pinch zoom tablelayout ครับ

 gestureDetector = new GestureDetector(this, new GestureListener());
        mScaleDetector = new ScaleGestureDetector(this, new ScaleGestureDetector.SimpleOnScaleGestureListener() {
            public boolean onScaleBegin(ScaleGestureDetector detector) {
                return true;
            }

            @Override
            public boolean onScale(ScaleGestureDetector detector) {
                float scale = 1 - detector.getScaleFactor();
                float prevScale = mScale;
                mScale = mScale + scale;

                if (mScale < 0.5f) // Minimum scale condition
                    mScale = 0.5f;

                if (mScale > 1f) // Maximum scale condition
                    mScale = 1f;

                float fx = detector.getFocusX();
                float fy = detector.getFocusY();

                itbl_main.setPivotX(fx);
                itbl_main.setPivotY(fy);
                itbl_main.setScaleX(1f / mScale);
                itbl_main.setScaleY(1f / mScale);
                return true;
            }
        });
    }

    @Override
    public boolean dispatchTouchEvent(MotionEvent event) {
        super.dispatchTouchEvent(event);
        mScaleDetector.onTouchEvent(event);
        gestureDetector.onTouchEvent(event);
        return gestureDetector.onTouchEvent(event);
    }

    private class GestureListener extends GestureDetector.SimpleOnGestureListener {
        @Override
        public boolean onDown(MotionEvent e) {
            return true;
        }

        // event when double tap occurs
        @Override
        public boolean onDoubleTap(MotionEvent e) {
            // double tap fired.
            return true;
        }
    }