Android开发 ListView的OnScrollListener详解

OnScrollListener接口是定义在AbsListView中的，而AbsListView的直接子类有GridView和ListView，非直接子类有ExpandableListView。OnScrollListener的完整路径是frameworks\base\core\java\Android\widget\AbsListView.java

其源码如下：

/**  * Interface definition for a callback to be invoked when the list or grid  * has been scrolled.  */  public interface OnScrollListener {        /**      * The view is not scrolling. Note navigating the list using the trackball counts as      * being in the idle state since these transitions are not animated.      */  /*scrollState有三种状态，分别是SCROLL_STATE_IDLE、SCROLL_STATE_TOUCH_SCROLL、SCROLL_STATE_FLING SCROLL_STATE_IDLE是当屏幕停止滚动时SCROLL_STATE_TOUCH_SCROLL是当用户在以触屏方式滚动屏幕并且手指仍然还在屏幕上时 SCROLL_STATE_FLING是当用户由于之前划动屏幕并抬起手指，屏幕产生惯性滑动时*/    public static int SCROLL_STATE_IDLE = 0;        /**      * The user is scrolling using touch, and their finger is still on the screen      */      public static int SCROLL_STATE_TOUCH_SCROLL = 1;        /**      * The user had previously been scrolling using touch and had performed a fling. The      * animation is now coasting to a stop      */      public static int SCROLL_STATE_FLING = 2;        /**      * Callback method to be invoked while the list view or grid view is being scrolled. If the      * view is being scrolled, this method will be called before the next frame of the scroll is      * rendered. In particular, it will be called before any calls to      * {@link Adapter#getView(int, View, ViewGroup)}.      *      * @param view The view whose scroll state is being reported      *      * @param scrollState The current scroll state. One of {@link #SCROLL_STATE_IDLE},      * {@link #SCROLL_STATE_TOUCH_SCROLL} or {@link #SCROLL_STATE_IDLE}.      */      public void onScrollStateChanged(AbsListView view, int scrollState);        /**      * Callback method to be invoked when the list or grid has been scrolled. This will be      * called after the scroll has completed      * @param view The view whose scroll state is being reported      * @param firstVisibleItem the index of the first visible cell (ignore if      *        visibleItemCount == 0)      * @param visibleItemCount the number of visible cells      * @param totalItemCount the number of items in the list adaptor      */      public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,              int totalItemCount);  /*   * 参数view表示被滚动的listview * 参数firstVisibleItem 表示在当前屏幕显示的第一个listItem在整个listView里面的位置（下标从0开始）  * 参数visibleItemCount表示在现时屏幕可以见到的ListItem(部分显示的ListItem也算)总数  * 参数 totalItemCount表示ListView的ListItem总数 */  }