请版主:这不是一个重复的问题，请阅读以下信息。
在问这个问题之前，我已经尝试了几乎所有可用的解决方案，但没有一个对我有用，有些导致崩溃，有些根本不起作用(我是初学者，有可能我在我的代码中做错了什么，我不会责怪任何人在 SO 上可用的答案不适合我的情况)。下面是我的代码，请看一下:
fragment_tab1.xml(包含 recyclerview):
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
android:layout_width="match_parent"
android:background="#333333"
android:orientation="vertical"
xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="96dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="42dp"
android:background="@color/colorPrimaryDark"
android:id="@+id/sort1"
android:orientation="horizontal">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/sort"
android:layout_marginLeft="10dp"
android:fontFamily="@font/quicksand"
android:textStyle="bold"
android:text="Sort by:"
android:textColor="#ffffff"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
style="@style/Widget.AppCompat.Button.Colored"
android:text="Oldest first"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
style="@style/Widget.AppCompat.Button.Colored"
android:text="Newest first"/>
</LinearLayout>
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_below="@id/sort1"
android:clipToPadding="false"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:padding="5dp" />
</RelativeLayout>
</LinearLayout>
fragment tab1.java
public class tab1 extends Fragment {
RecyclerView mRecyclerView;
FirebaseDatabase mFirebaseDatabase;
DatabaseReference mRef;
LinearLayoutManager manager;
private static final String TAG = "tab1";
ProgressDialog progressDialog;
View rootView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
//Returning the layout file after inflating
//Change R.layout.tab1 in you classes
rootView = inflater.inflate(R.layout.fragment_tab1, container, false);
return rootView;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view);
manager = new LinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(manager);
mRecyclerView.setItemViewCacheSize(20);
mRecyclerView.setDrawingCacheEnabled(true);
mFirebaseDatabase = FirebaseDatabase.getInstance();
mRef = mFirebaseDatabase.getReference("memes");
mFirebaseDatabase.getInstance().getReference().keepSynced(true);
progressDialog = new ProgressDialog(getActivity());
progressDialog.setMessage("Please Wait");
progressDialog.show();
}
public void onStart() {
super.onStart();
FirebaseRecyclerAdapter<Model, ViewHolder> firebaseRecyclerAdapter =
new FirebaseRecyclerAdapter<Model, ViewHolder>(
Model.class,
R.layout.row2,
ViewHolder.class,
mRef
) {
@Override
protected void populateViewHolder(ViewHolder viewHolder, Model model, int position) {
viewHolder.setDetails(getActivity(), model.getTitle(), model.getDesc(), model.getImage());
progressDialog.cancel();
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
ViewHolder viewHolder = super.onCreateViewHolder(parent, viewType);
viewHolder.setOnClickListener(new ViewHolder.ClickListener(){
@Override
public void onItemClick(View view, int position){
//get data from firebase here
String mTitle = getItem(position).getTitle();
String mDesc= getItem(position).getDesc();
String mImage = getItem(position).getImage();
//pass this data to new activity
Intent intent = new Intent(view.getContext(), ArticleDetail.class);
intent.putExtra("title", mTitle);// put title
intent.putExtra("desc", mDesc);// put description
intent.putExtra("image", mImage); //put image urls
startActivity(intent);
}
@Override
public void onItemLongClick(View view, int position){
//TODO your own implementation on long item click
}
});
return viewHolder;
}
};
mRecyclerView.setAdapter(firebaseRecyclerAdapter);
}
@Override
public void onPause() {
super.onPause();
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(getActivity());
View firstChild = mRecyclerView.getChildAt(0);
int firstVisiblePosition = mRecyclerView.getChildAdapterPosition(firstChild);
int offset = firstChild.getTop();
Log.d(TAG, "Postition: " + firstVisiblePosition);
Log.d(TAG, "Offset: " + offset);
preferences.edit()
.putInt("position", firstVisiblePosition)
.putInt("offset", offset)
.apply();
}
@Override
public void onResume(){
super.onResume();
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
@Override
public void onViewStateRestored(@Nullable Bundle savedInstanceState) {
super.onViewStateRestored(savedInstanceState);
}
}
最佳答案
付出了这么多天，尝试了很多解决方案后，终于找到了解决我问题的有效方法，感谢https://stackoverflow.com/a/42563804/2128364
我已将工作解决方案移至另一种方法，以使其在 fragment 中工作。
也许这可以挽救某人的一天，这是它的工作原理:
- onConfigurationChanged(如原始解决方案中所建议的)、onSaveInstanceState 或 onViewRestoredState 方法不起作用，因此您需要 onPause 和 onResume 方法来分别保存和恢复状态。
- 您必须在 onPause 方法中保存状态:
mBundleRecyclerViewState = new Bundle();
mListState = mRecyclerView.getLayoutManager().onSaveInstanceState();
mBundleRecyclerViewState.putParcelable(KEY_RECYCLER_STATE, mListState);
- 然后在 onResume 方法中恢复:
if (mBundleRecyclerViewState != null) {
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
mListState = mBundleRecyclerViewState.getParcelable(KEY_RECYCLER_STATE);
mRecyclerView.getLayoutManager().onRestoreInstanceState(mListState);
}
}, 50);
}
mRecyclerView.setLayoutManager(staggeredGridLayoutManager);
关于android - 从其他 Activity 返回到同一 fragment 时，如何保存和恢复 fragment 中 RecyclerView 的滚动位置？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52587745/