在我的应用程序中,我有一个由ArrayAdapter支持的ListView.在其中我正在检测OnScrollListener#onScroll方法中的事件以查找列表的结尾.我注意到在手机(MyTouch)上,跟踪球和手势/触摸滚动都会触发事件两次.在模拟器上,我通过滚轮和点击药物滚动获得相同的行为.但是在模拟器中,如果我使用向下箭头按钮滚动事件只触发一次.

这是代码：

this.view.setOnScrollListener(new OnScrollListener() {
    @Override
    public void onScroll(final AbsListView view, final int first, 
                                final int visible, final int total) {
        // detect if last item is visible
        if (visible < total && (first + visible == total)) {
            Log.d("OnScrollListener - end of list", "fvi: " + 
               first + ", vic: " + visible + ", tic: " + total);
            // this line gets called twice
            onLastListItemDisplayed(total, visible);
        }
    }
}

如何抑制或处理此行为？我只需要一个事件,并且尽量不要恢复到像布尔字段那样的愚蠢的黑客攻击.

据我所知 – 两个事件都有相同的堆栈跟踪

Thread [<3> main] (Suspended (breakpoint at line 116 in SearchResultsView$4)) 
 SearchResultsView$4.onScroll(AbsListView, int, int, int) line: 116 
 ListView(AbsListView).invokeOnItemScrollListener() line: 655 
 ListView.arrowScrollImpl(int) line: 2256 
 ListView.arrowScroll(int) line: 2172 
 ListView.commonKey(int, int, KeyEvent) line: 1977 
 ListView.onKeyMultiple(int, int, KeyEvent) line: 1929 
 KeyEvent.dispatch(KeyEvent$Callback) line: 899 
 ListView(View).dispatchKeyEvent(KeyEvent) line: 3647 
 ListView(ViewGroup).dispatchKeyEvent(KeyEvent) line: 744 
 ListView.dispatchKeyEvent(KeyEvent) line: 1909 
 FrameLayout(ViewGroup).dispatchKeyEvent(KeyEvent) line: 746 
 LinearLayout(ViewGroup).dispatchKeyEvent(KeyEvent) line: 746 
 PhoneWindow$DecorView(ViewGroup).dispatchKeyEvent(KeyEvent) line: 746 
 PhoneWindow$DecorView.superDispatchKeyEvent(KeyEvent) line: 1708 
 PhoneWindow.superDispatchKeyEvent(KeyEvent) line: 1197 
 SearchResultsView(Activity).dispatchKeyEvent(KeyEvent) line: 1967 
 PhoneWindow$DecorView.dispatchKeyEvent(KeyEvent) line: 1684 
 ViewRoot.deliverKeyEventToViewHierarchy(KeyEvent, boolean) line: 2329 
 ViewRoot.handleFinishedEvent(int, boolean) line: 2299 
 ViewRoot.handleMessage(Message) line: 1621 
 ViewRoot(Handler).dispatchMessage(Message) line: 99 
 Looper.loop() line: 123 
 ActivityThread.main(String[]) line: 4203 
 Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method] 
 Method.invoke(Object, Object...) line: 521 
 ZygoteInit$MethodAndArgsCaller.run() line: 791 
 ZygoteInit.main(String[]) line: 549 
 NativeStart.main(String[]) line: not available [native method]

附： Bug is created

P.P.S.并通过非常有用的回复关闭轨迹球和触摸屏非常快速地发送几个运动事件.此行为是预期的.

解决方法:

由于谷歌的优秀人士说这就像预期的那样,处理这个对我有用的问题是一种丑陋的野蛮方式.基本上这里的假设是,在发布事件时,我将上次保存的第一项索引与onScroll调用中传递的索引进行比较.我只会处理事件,如果这些不匹配：

    this.view.setOnScrollListener(new OnScrollListener() {
        private int lastSavedFirst = -1;
        @Override
        public void onScroll(final AbsListView view, final int first, final int visible, final int total) {
            // detect if last item is visible
            if (visible < total && (first + visible == total)) {
                // only process first event
                if (first != lastSavedFirst) {
                    lastSavedFirst = first;
                    Log.d("OnScrollListener - end of list", "fvi: " + first + ", vic: " + visible + ", tic: "
                            + total);
                    onLastListItemDisplayed(total, visible);
                }
            }
        }

        @Override
        public void onScrollStateChanged(final AbsListView view, final int scrollState) {
            // Log.d("OnScrollListener", "state: " + scrollState);
        }
    });