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
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
其他回答
如果你在一个活动上使用片段,你可以这样做:
public abstract class BaseFragment extends Fragment {
private boolean mSaveView = false;
private SoftReference<View> mViewReference;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if (mSaveView) {
if (mViewReference != null) {
final View savedView = mViewReference.get();
if (savedView != null) {
if (savedView.getParent() != null) {
((ViewGroup) savedView.getParent()).removeView(savedView);
return savedView;
}
}
}
}
final View view = inflater.inflate(getFragmentResource(), container, false);
mViewReference = new SoftReference<View>(view);
return view;
}
protected void setSaveView(boolean value) {
mSaveView = value;
}
}
public class MyFragment extends BaseFragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
setSaveView(true);
final View view = super.onCreateView(inflater, container, savedInstanceState);
ListView placesList = (ListView) view.findViewById(R.id.places_list);
if (placesList.getAdapter() == null) {
placesList.setAdapter(createAdapter());
}
}
}
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);
}
}
对于一些正在寻找此问题解决方案的人来说,问题的根源可能在于您设置列表视图适配器的位置。在列表视图上设置适配器后,它将重置滚动位置。只是需要考虑一下。我移动设置适配器到我的onCreateView后,我们抓取引用到列表视图,它解决了我的问题。=)
为了澄清Ryan Newsom的精彩回答并针对片段进行调整通常情况下,我们想要从主ListView片段导航到细节片段然后再返回主ListView片段
private View root;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
if(root == null){
root = inflater.inflate(R.layout.myfragmentid,container,false);
InitializeView();
}
return root;
}
public void InitializeView()
{
ListView listView = (ListView)root.findViewById(R.id.listviewid);
BaseAdapter adapter = CreateAdapter();//Create your adapter here
listView.setAdpater(adapter);
//other initialization code
}
这里的“神奇”是,当我们从细节片段导航回ListView片段时,视图不会被重新创建,我们不设置ListView的适配器,所以一切都保持不变!
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
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