Question

在android中，我有一个按钮，当用户向上滚动时会出现，否则会消失。然而，当它出现时，我试图让它在3秒后再次消失，如果用户停止滚动（在空闲3秒后）。我尝试了以下代码，

   //detecting whether the user is scrolling up or down, to make the refresh button visible/invisible
        listView.setOnTouchListener(new View.OnTouchListener() {

            int scrollEventListSize = 5;
            float lastY;
            // Used to correct for occasions when user scrolls down(/up) but the onTouchListener detects it incorrectly. We will store detected up-/down-scrolls with -1/1 in this list and evaluate later which occured more often
            List<Integer> downScrolledEventsHappened;

            @Override
            public boolean onTouch(View v, MotionEvent event) {

                float diff = 0;
                if(event.getAction() == event.ACTION_DOWN){
                    lastY = event.getY();
                    downScrolledEventsHappened = new LinkedList<Integer>();
                }
                else if(event.getAction() == event.ACTION_MOVE){
                    diff = event.getY() - lastY;
                    lastY = event.getY();

                    if(diff>0)
                        downScrolledEventsHappened.add(1);
                    else
                        downScrolledEventsHappened.add(-1);

                    //List needs to be filled with some events, will happen very quickly
                    if(downScrolledEventsHappened.size() == scrollEventListSize+1){
                        downScrolledEventsHappened.remove(0);
                        int res=0;
                        for(int i=0; i<downScrolledEventsHappened.size(); i++){
                            res+=downScrolledEventsHappened.get(i);
                        }

                        if (res > 0) {
                            Log.i("INFO", "Scrolled up");
                            refreshButton.setVisibility(View.VISIBLE);
                        }
                        else {
                            Log.i("INFO", "Scrolled down");
                            refreshButton.setVisibility(View.INVISIBLE);
                        }
                    }
                }
                return false; // don't interrupt the event-chain
            }
        });





//Removing refresh button when user stops scrolling up or already at the top of the list.
listView.setOnScrollListener(new AbsListView.OnScrollListener() {
    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {

        if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {

                    new Handler().postDelayed(new Runnable() {
    @Override
    public void run() {

     refreshButton.setVisibility(View.INVISIBLE);
    }
}, 3000);



        }
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        if(firstVisibleItem == 0 && listIsAtTop()){
            System.out.println("List at Top....Refresh Button is disappearing...");
            refreshButton.setVisibility(View.INVISIBLE);
        }
    }
});

然而，这段代码并没有完全给我我想要的东西。确实，用户在空闲3秒后按钮消失，但是当用户再次向上滚动时，按钮也会消失！我的意思是，我需要一种机制，当用户再次向上滚动时，3秒钟消失的想法将被取消。我怎样才能做到这一点？谢谢。

Answer 1

当使用向上滚动时取消处理程序待处理事件并再次启动处理程序

类似这样的事情

 myHandler.removeCallbacks(myRunnable);

以这种方式启动处理程序

myHandler.postDelayed(myRunnable,LENGTH);

3秒后使按钮不可见，但如果用户向上滚动则不要使其不可见

1 个答案: