为GridView添加点击空白地方的响应函数

 public interface OnTouchBlankPositionListener {
        /**
         * 
         * @return 是否要终止事件的路由
         */
        boolean onTouchBlankPosition();
    }
    
    public void setOnTouchBlankPositionListener(OnTouchBlankPositionListener listener) {
        mTouchBlankPosListener = listener;
    }
    
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        
        if(mTouchBlankPosListener != null) {
            if (!isEnabled()) {
                // A disabled view that is clickable still consumes the touch
                // events, it just doesn‘t respond to them.
                return isClickable() || isLongClickable();
            }
                
            if(event.getActionMasked() == MotionEvent.ACTION_UP) {
                final int motionPosition = pointToPosition((int)event.getX(), (int)event.getY());
                if( motionPosition == Blank_POSITION ) {
                    return mTouchBlankPosListener.onTouchBlankPosition();
                }
            }
        }

        return super.onTouchEvent(event);
    }