我有一个很长的ListView,用户可以在返回前一个屏幕之前滚动它。当用户再次打开这个ListView时,我希望列表被滚动到与之前相同的位置。关于如何实现这一点,你有什么想法吗?
当前回答
试试这个:
// save index and top position
int index = mList.getFirstVisiblePosition();
View v = mList.getChildAt(0);
int top = (v == null) ? 0 : (v.getTop() - mList.getPaddingTop());
// ...
// restore index and position
mList.setSelectionFromTop(index, top);
Explanation: ListView.getFirstVisiblePosition() returns the top visible list item. But this item may be partially scrolled out of view, and if you want to restore the exact scroll position of the list you need to get this offset. So ListView.getChildAt(0) returns the View for the top list item, and then View.getTop() - mList.getPaddingTop() returns its relative offset from the top of the ListView. Then, to restore the ListView's scroll position, we call ListView.setSelectionFromTop() with the index of the item we want and an offset to position its top edge from the top of the ListView.
其他回答
难道不是简单的android:saveEnabled="true"在ListView xml声明足够吗?
Parcelable state;
@Override
public void onPause() {
// Save ListView state @ onPause
Log.d(TAG, "saving listview state");
state = listView.onSaveInstanceState();
super.onPause();
}
...
@Override
public void onViewCreated(final View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// Set new items
listView.setAdapter(adapter);
...
// Restore previous state (including selected item index and scroll position)
if(state != null) {
Log.d(TAG, "trying to restore listview state");
listView.onRestoreInstanceState(state);
}
}
最好的解决方案是:
// save index and top position
int index = mList.getFirstVisiblePosition();
View v = mList.getChildAt(0);
int top = (v == null) ? 0 : (v.getTop() - mList.getPaddingTop());
// ...
// restore index and position
mList.post(new Runnable() {
@Override
public void run() {
mList.setSelectionFromTop(index, top);
}
});
你必须在邮件和线程中调用!
我的答案是Firebase和位置0是一个变通办法
Parcelable state;
DatabaseReference everybody = db.getReference("Everybody Room List");
everybody.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
state = listView.onSaveInstanceState(); // Save
progressBar.setVisibility(View.GONE);
arrayList.clear();
for (DataSnapshot messageSnapshot : dataSnapshot.getChildren()) {
Messages messagesSpacecraft = messageSnapshot.getValue(Messages.class);
arrayList.add(messagesSpacecraft);
}
listView.setAdapter(convertView);
listView.onRestoreInstanceState(state); // Restore
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
和convertView
位置0 a添加一个您不使用的空白项
public class Chat_ConvertView_List_Room extends BaseAdapter {
private ArrayList<Messages> spacecrafts;
private Context context;
@SuppressLint("CommitPrefEdits")
Chat_ConvertView_List_Room(Context context, ArrayList<Messages> spacecrafts) {
this.context = context;
this.spacecrafts = spacecrafts;
}
@Override
public int getCount() {
return spacecrafts.size();
}
@Override
public Object getItem(int position) {
return spacecrafts.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@SuppressLint({"SetTextI18n", "SimpleDateFormat"})
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = LayoutInflater.from(context).inflate(R.layout.message_model_list_room, parent, false);
}
final Messages s = (Messages) this.getItem(position);
if (position == 0) {
convertView.getLayoutParams().height = 1; // 0 does not work
} else {
convertView.getLayoutParams().height = RelativeLayout.LayoutParams.WRAP_CONTENT;
}
return convertView;
}
}
我已经看到这个工作暂时不打扰用户,我希望它为您工作
用于从实现LoaderManager的ListActivity派生的活动。LoaderCallbacks使用SimpleCursorAdapter,它不能恢复onReset()中的位置,因为活动几乎总是重新启动,并且当详细信息视图关闭时适配器被重新加载。诀窍是恢复onLoadFinished()中的位置:
在onListItemClick ():
// save the selected item position when an item was clicked
// to open the details
index = getListView().getFirstVisiblePosition();
View v = getListView().getChildAt(0);
top = (v == null) ? 0 : (v.getTop() - getListView().getPaddingTop());
在onLoadFinished ():
// restore the selected item which was saved on item click
// when details are closed and list is shown again
getListView().setSelectionFromTop(index, top);
在onBackPressed ():
// Show the top item at next start of the app
index = 0;
top = 0;
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