RecyclerView 在片段内的权限检查后第一次启动时不加载数据

Question

RecyclerView 适配器在权限检查后首次启动时不加载数据。我必须重新点击选项卡才能获取数据。

我已经访问过/尝试过这些链接 -

-- RecyclerView doesn't load data in first launch using FirebaseRecyclerAdapter

-- RecyclerView doesn't load items on first start of activity

-- recyclerview not loading adapter values in a fragment

但是还没有任何效果。 尝试设置全局适配器，所以我可以从 onResume() 调用 notifyDataSetChanged()。还是不行。

这是代码 -

onCreateView() -

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_third, container, false);

    recyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);

    if (checkAndRequestPermissions()) {
        loadSongList();
    }

    return view;
}

onRequestPermissionResult -

loadSongList();  // method

loadSongList() -

private void loadSongList() {
    loadAudio();
    initRecyclerView();
}

loadAudio() -

loadAudio() // accessing data from content resolver

initRecyclerView()-

private void initRecyclerView() {
    if (mAudioList != null && mAudioList.size() > 0) {
        AudioAdapter adapter = new AudioAdapter(mAudioList, getActivity());
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
        recyclerView.setLayoutManager(linearLayoutManager);
        DIviderItemDecoration dividerItemDecoration = new DIviderItemDecoration(getContext(), linearLayoutManager.getOrientation());
        recyclerView.addItemDecoration(dividerItemDecoration);
        recyclerView.setAdapter(adapter);

        RecyclerViewItemClick.addTo(recyclerView).setOnItemClickListener(new RecyclerViewItemClick.OnItemClickListener() {
            @Override
            public void onItemClicked(RecyclerView recyclerView, int position, View v) {
                // life sucks
            }
        });
    }
}

编辑：

loadAudio() -

private void loadAudio() {
    ContentResolver contentResolver = getActivity().getContentResolver();
    Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    String selection = MediaStore.Audio.Media.IS_MUSIC + "!= 0";
    String sortOrder = MediaStore.Audio.Media.TITLE + " ASC";
    Cursor cursor = contentResolver.query(uri, null, selection, null, sortOrder);

    if (cursor != null && cursor.getCount() > 0) {
        mAudioList = new ArrayList<>();
        while (cursor.moveToNext()) {
            String data = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));
            String title = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE));
            String album = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM));
            String artist = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST));

            Long albumId = cursor.getLong(cursor
                    .getColumnIndexOrThrow(MediaStore.Audio.Media._ID));
            Long artWorkId = cursor.getLong(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ALBUM_ID));

            int duration = cursor.getInt(cursor
                    .getColumnIndexOrThrow(MediaStore.Audio.Media.DURATION));

            Uri sArtworkUri = Uri
                    .parse("content://media/external/audio/albumart");
            Uri albumArtUri = ContentUris.withAppendedId(sArtworkUri, artWorkId);

            // Save to audioList
            mAudioList.add(new Audio(albumId, data, title, album, artist, albumArtUri, duration));
        }
    }
    if (cursor != null) {
        cursor.close();
    }

}

音频适配器 -

public class AudioAdapter extends RecyclerView.Adapter<AudioAdapter.CustomViewHolder> {

List<Audio> mList = Collections.emptyList();
Context mContext;

public AudioAdapter(List<Audio> list, Context context) {
    mList = list;
    mContext = context;
}


@Override
public CustomViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.custom_row, parent, false);
    return new CustomViewHolder(v);
}

@Override
public void onBindViewHolder(CustomViewHolder holder, int position) {
    Audio audio = mList.get(position);

    holder.title.setText(audio.getTitle());
    holder.description.setText(audio.getArtist());

    Glide.with(mContext).load(audio.imageId).asBitmap()
            .centerCrop()
            .diskCacheStrategy(DiskCacheStrategy.RESULT)
            .skipMemoryCache(true)
            .placeholder(R.drawable.headset_2)
            .into(holder.imageView);

}

@Override
public int getItemCount() {
    return mList.size();
}

@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
    super.onAttachedToRecyclerView(recyclerView);
}

public void insert(int position, Audio list) {
    mList.add(position, list);
    notifyItemChanged(position);
}

public void remove(Audio list) {
    int position = mList.indexOf(list);
    mList.remove(position);
    notifyItemRemoved(position);
}


static class CustomViewHolder extends RecyclerView.ViewHolder {

    CardView cv;
    TextView title;
    TextView description;
    ImageView imageView;

    public CustomViewHolder(View itemView) {
        super(itemView);

        cv = (CardView) itemView.findViewById(R.id.cardView);
        title = (TextView) itemView.findViewById(R.id.playList_name);
        description = (TextView) itemView.findViewById(R.id.album_artist);
        imageView = (ImageView) itemView.findViewById(R.id.imageView1);
    }
}}

UDPATE： checkAndRequestPermission -

private boolean checkAndRequestPermissions() {
    if (SDK_INT >= Build.VERSION_CODES.M) {
        int permissionReadPhoneState = ContextCompat.checkSelfPermission(getContext(), (Manifest.permission.READ_PHONE_STATE));
        int permissionStorage = ContextCompat.checkSelfPermission(getContext(), Manifest.permission.READ_EXTERNAL_STORAGE);
        List<String> listPermissionsNeeded = new ArrayList<>();

        if (permissionReadPhoneState != PackageManager.PERMISSION_GRANTED) {
            listPermissionsNeeded.add(Manifest.permission.READ_PHONE_STATE);
        }

        if (permissionStorage != PackageManager.PERMISSION_GRANTED) {
            listPermissionsNeeded.add(Manifest.permission.READ_EXTERNAL_STORAGE);
        }

        if (!listPermissionsNeeded.isEmpty()) {
            requestPermissions(listPermissionsNeeded.toArray(new String[listPermissionsNeeded.size()]), REQUEST_ID_MULTIPLE_PERMISSIONS);
            return false;
        } else {
            return true;
        }
    }
    return false;
}

删除 ActivityCompat 并仅调用 requestPermission 后，片段正在接收回调，但现在我收到错误消息。下面的logcat -

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.ArrayList.get(int)' on a null object reference
                                                                                          at com.example.ansh.sharedpreferencessimple.service.MusicService.playSong(MusicService.java:167)
                                                                                          at com.example.ansh.sharedpreferencessimple.ThirdFragment$2.onItemClicked(ThirdFragment.java:196)
                                                                                          at com.example.ansh.sharedpreferencessimple.helper.RecyclerViewItemClick$1.onClick(RecyclerViewItemClick.java:21)
                                                                                          at android.view.View.performClick(View.java:6205)
                                                                                          at android.view.View$PerformClick.run(View.java:23653)
                                                                                          at android.os.Handler.handleCallback(Handler.java:751)
                                                                                          at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                          at android.os.Looper.loop(Looper.java:154)
                                                                                          at android.app.ActivityThread.main(ActivityThread.java:6682)
                                                                                          at java.lang.reflect.Method.invoke(Native Method)
                                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
                                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)

任何帮助将不胜感激，谢谢。

Answer 1

这是您问题的答案。

您的 loadAudio() 方法填充了您的 mAudioList，这是您的数组列表或列出它的任何内容。

所以，主要问题是，当您在 initRecyclerView() 中调用 loadAudio() 和 initRecyclerView() 时，mAudioList 仍然为空，因为此时您的 mAudioList 没有在 loadAudio() 中填满。

因此，您的答案的问题是在 loadAudio() 函数的末尾调用 initRecyclerView() ，这将解决您的问题。

例如

private void loadAudio()
{
     // Get your arraylist of audio and all the stuff
     if (cursor != null)
     {
         cursor.close();
     }
    // Call init function here.
       initRecyclerView();
}