[英]Update RecyclerView while keeping its scroll position
更新内容后如何在RecyclerView
保持当前滚动位置?
在onCreate
我设置了一个重复执行的任务,如下所示:
private void setRepeatingAsyncTask() {
final Handler handler = new Handler();
Timer timer = new Timer();
TimerTask task = new TimerTask() {
@Override
public void run() {
handler.post(new Runnable() {
public void run() {
try {
new getArrivals().execute(station_id);
} catch (Exception e) {
// error, do something
}
}
});
}
};
timer.schedule(task, 0, 30000); // interval of 30 seconds
}
AsyncTask
将在数据库中查询最新列表内容:
private class getArrivals extends AsyncTask<Long, Void, Long>{
@Override
protected void onPreExecute(){
//emptyMessage.setVisibility(VISIBLE);
//recyclerView.setVisibility(GONE);
}
@Override
protected Long doInBackground(Long... params) {
long station_id = params[0];
station = db.stationModel().getStationById(station_id);
arrivals = db.arrivalModel().getNextArrivalsByStation(station_id, StaticClass.getDays());
return station_id;
}
@Override
protected void onPostExecute(Long result){
if(getSupportActionBar() != null) {
getSupportActionBar().setTitle(capitalize(station.name));
}
refreshList();
}
}
完成任务后,我要求刷新列表:
private void refreshList(){
arrivalListAdapter = new ArrivalListAdapter(getApplicationContext(), arrivals);
staggeredGridLayoutManager = new StaggeredGridLayoutManager(1, StaggeredGridLayoutManager.VERTICAL);
recyclerView.setLayoutManager(staggeredGridLayoutManager);
recyclerView.setAdapter(arrivalListAdapter);
Log.d("arrivals", arrivals.size()+"");
arrivalListAdapter.notifyDataSetChanged();
if(arrivals.size() == 0){
emptyMessage.setVisibility(VISIBLE);
recyclerView.setVisibility(GONE);
new fetchArrivalsFromSource().execute(station.id);
}else{
emptyMessage.setVisibility(GONE);
recyclerView.setVisibility(VISIBLE);
}
}
我很确定问题的原因是我每次都要设置适配器。 我尝试用初始任务设置它,但是导致列表根本没有更新。
您可以获取当前位置,刷新适配器并平滑滚动到上一个位置,如下所示:
RecyclerView.SmoothScroller smoothScroller = new LinearSmoothScroller(context) {
@Override protected int getVerticalSnapPreference() {
return LinearSmoothScroller.SNAP_TO_START;
}
};
然后将位置设置为滚动到:
smoothScroller.setTargetPosition(position);
layoutManager.startSmoothScroll(smoothScroller);
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.