Android 如何判断ListView的滚动方向_java listview scrolldirection

Android 如何判断ListView的滚动方向，直接看代码：

        mListView.setOnScrollListener(new OnScrollListener() {
            int scrollState;
            
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                this.scrollState = scrollState;
            }
 
            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                View v = view.getChildAt(0);
                int top = (v == null) ? 0 : v.getTop();                
                int scrollDirection = SCROLL_STOP;
                if (firstVisibleItem > mLastTopIndex) {
                    scrollDirection = SCROLL_UP;
                } else if (firstVisibleItem < mLastTopIndex) {
                    scrollDirection = SCROLL_DOWN;
                } else {
                    if(top < mLastTopPixel) {
                        scrollDirection = SCROLL_UP;
                    } else if(top > mLastTopPixel) {
                        scrollDirection = SCROLL_DOWN;
                    }
                }
                mLastTopIndex = firstVisibleItem;
                mLastTopPixel = top;
                
                if (scrollDirection == SCROLL_DOWN) {
 
                } else if (scrollDirection == SCROLL_UP) {
 
                }
            }
        });