RecyclerView doesn't display items until scrolling
This question has been asked multiple times, but these answers do not apply to me. I would like a more general answer as to what is causing this question in general.
I have a recyclerview in my activity layout. The recyclerview lines are a constraint layout with one image view and text:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="50dp"
android:clickable="true">
<ImageView
android:id="@+id/file_icon"
android:layout_width="50dp"
android:layout_height="50dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
<TextView
android:text="File"
android:id="@+id/file_name"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintLeft_toRightOf="@+id/file_icon"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintRight_toRightOf="parent"/>
</android.support.constraint.ConstraintLayout>
There are several elements in this string structure. I have configured the adapter correctly. However, when I launch my application, the text images displayed on the screen are not displayed until I scroll and scroll up. Basically, in order for these text images to be displayed, they must be discarded from the display and re-entered. Here is my adapter code:
public class FileViewAdapter extends RecyclerView.Adapter<FileViewAdapter.Viewholder> {
private Context context;
private List<File> files;
public FileViewAdapter(Context context, List<File> files) {
this.context = context;
this.files = files;
}
public FileViewAdapter(Context context){
this.context = context;
}
@Override
public Viewholder onCreateViewHolder(ViewGroup viewGroup, int i) {
LayoutInflater inflater = LayoutInflater.from(context);
View layout = inflater.inflate(R.layout.file_list_item, viewGroup, false);
return new Viewholder(layout);
}
@Override
public void onBindViewHolder(Viewholder viewholder, int i) {
File file = files.get(i);
if (file.isDirectory()) {
viewholder.fileIcon.setImageDrawable(
context.getResources().getDrawable(R.drawable.ic_folder_black_24dp));
viewholder.wholeThing.setOnClickListener(null);
} else {
viewholder.fileIcon.setImageDrawable(
context.getResources().getDrawable(R.drawable.ic_insert_drive_file_black_24dp));
viewholder.wholeThing.setOnClickListener(null);
}
viewholder.fileName.setText(file.getName());
}
@Override
public int getItemCount() {
return files.size();
}
public void clear() {
files.clear();
notifyDataSetChanged();
}
public void addAll(List<File> newFiles) {
files.addAll(newFiles);
notifyDataSetChanged();
}
class Viewholder extends RecyclerView.ViewHolder {
View wholeThing;
ImageView fileIcon;
TextView fileName;
public Viewholder(View itemView) {
super(itemView);
wholeThing = itemView;
fileIcon = (ImageView) itemView.findViewById(R.id.file_icon);
fileName = (TextView) itemView.findViewById(R.id.file_name);
}
}
}
EDIT: How do I call the adapter constructor on an activity.
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_file_viewer);
recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
}
@Override
public void onResume() {
adapter = new Adapter(this, /*A list of File items*/);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
}
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The problem from what I can see is that notifyDataSetChanged doesn't work in UiThread, so if you run urD's SetData method like this it will work.
this.runOnUiThread(new Runnable() {
public void run() {
mAdapter.setNewData(newDataListForAdapter);
mAdapter.notifyDataSetChanged();
}
});
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Try it. Hope this will be helpful.
RecyclerView recyclerView;
FileViewAdapter adapter;
List<File> files = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_file_viewer);
recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
adapter = new FileViewAdapter(this, files);
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
}
@Override
public void onResume() {
super.onResume();
files = getFiles();//fetch files
adapter.notifyDataSetChanged();//update UI
}
public List<File> getFiles() {
//fetch files
//...
return files;
}
By the way, I didn't find that the situation with you happened. There may be some errors in your code that you did not show us.
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As silly as it sounds, calling this line of code after setting the data for the recyclerView helped me with this problem:
recyclerView.smoothScrollToPosition(0)
PS: The technologies I've used may have something to do with this: RJava, Retrofit2, NavigationUI, Fragments, LiveData, and Databinding.
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