这段时间学了不少的知识，从今天开始来写一些android方面的文章。

在android中，用到最多而且比较难的空间应该是listview，相信大家有时候会用到getScrollY这个属性，但是大家有没有在listview中使用过这个呢？如果你去试一试就知道了，这个属性在listview中是没有什么效果的，网上有不少这个知识，但是我看了很长时间，感觉都不好，所以今天给大家推荐一种写法。

public class ListScrollDistanceCalculator implements OnScrollListener {

    private ScrollDistanceListener mScrollDistanceListener;

    private boolean mListScrollStarted;

    private int mFirstVisibleItem;

    private int mFirstVisibleHeight;

    private int mFirstVisibleTop, mFirstVisibleBottom;

    private int mTotalScrollDistance;

    @Override

    public void onScrollStateChanged(AbsListView view, int scrollState) {

        if (view.getCount() == 0) return;

        switch (scrollState) {

            case SCROLL_STATE_IDLE: {

                mListScrollStarted = false;

                break;

            }

            case SCROLL_STATE_TOUCH_SCROLL: {

                final View firstChild = view.getChildAt(0);

                mFirstVisibleItem = view.getFirstVisiblePosition();

                mFirstVisibleTop = firstChild.getTop();

                mFirstVisibleBottom = firstChild.getBottom();

                mFirstVisibleHeight = firstChild.getHeight();

                mListScrollStarted = true;

                mTotalScrollDistance = 0;

                break;

            }

        }

    }

    public int getTotalScrollDistance() {

        return mTotalScrollDistance;

    }

    @Override

    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

        if (totalItemCount == 0 || !mListScrollStarted) return;

        final View firstChild = view.getChildAt(0);

        final int firstVisibleTop = firstChild.getTop(), firstVisibleBottom = firstChild.getBottom();

        final int firstVisibleHeight = firstChild.getHeight();

        final int delta;

        if (firstVisibleItem > mFirstVisibleItem) {

            mFirstVisibleTop += mFirstVisibleHeight;

            delta = firstVisibleTop - mFirstVisibleTop;

        } else if (firstVisibleItem < mFirstVisibleItem) {

            mFirstVisibleBottom -= mFirstVisibleHeight;

            delta = firstVisibleBottom - mFirstVisibleBottom;

        } else {

            delta = firstVisibleBottom - mFirstVisibleBottom;

        }

        mTotalScrollDistance += delta;

        if (mScrollDistanceListener != null) {

            mScrollDistanceListener.onScrollDistanceChanged(delta, mTotalScrollDistance);

        }

        mFirstVisibleTop = firstVisibleTop;

        mFirstVisibleBottom = firstVisibleBottom;

        mFirstVisibleHeight = firstVisibleHeight;

        mFirstVisibleItem = firstVisibleItem;

    }

    public void setScrollDistanceListener(ScrollDistanceListener listener) {

        mScrollDistanceListener = listener;

    }

    public static interface ScrollDistanceListener {

        void onScrollDistanceChanged(int delta, int total);

    }

}