Question

我的问题是，当我第一次运行我的应用程序时，它不会加载片段中的数据，只有当我关闭然后打开它时，歌曲才会显示出来。我该如何解决？

我有5个选项卡，其中包含保存歌曲数据并使用自定义recyclerview适配器显示它们的数组列表。

检查权限和setupViewPager在我的MainActivity.java内部

然后我制作了单独的Tab类（Tab1.java，Tab2.java等）

问题是在授予权限后，它仅显示我的viewpager布局，但不显示所有歌曲的recyclerview。

仅当我退出应用程序或切换选项卡时，它才有效。

检查权限

// Permission read-write storage, read phone-state
private void checkUserPermission() {
    Log.d("TAG", "checkUserPermissions: asking for user permissions!");
    String [] permissions = { Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_PHONE_STATE};
        if (ContextCompat.checkSelfPermission(this.getApplicationContext(), permissions[0]) == PackageManager.PERMISSION_GRANTED &&
                ContextCompat.checkSelfPermission(this.getApplicationContext(), permissions[1]) == PackageManager.PERMISSION_GRANTED &&
                ContextCompat.checkSelfPermission(this.getApplicationContext(), permissions[2]) == PackageManager.PERMISSION_GRANTED) {
        setupViewPager();
        }else {
        ActivityCompat.requestPermissions(MainActivity.this, permissions, REQUEST_CODE);
        }
}

@Override
public void onRequestPermissionsResult(int requestcode, @NonNull String[]
        permissions, @NonNull int[] grantResults) {
    switch (requestcode){
        case 123:
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                setupViewPager();
            }else{
                Toast.makeText(getApplicationContext(), "Permission Denied", Toast.LENGTH_SHORT).show();
                checkUserPermission();
                break;
            }
        default:
    }
    super.onRequestPermissionsResult(requestcode, permissions,
            grantResults);

}

setupViewPager

private void setupViewPager() {
    //TabLayout
    tabLayout = findViewById(R.id.tabLayout);
    tabLayout.addTab(tabLayout.newTab().setText("Songs"));
    tabLayout.addTab(tabLayout.newTab().setText("Albums"));
    tabLayout.addTab(tabLayout.newTab().setText("Artists"));
    tabLayout.addTab(tabLayout.newTab().setText("Genres"));
    tabLayout.addTab(tabLayout.newTab().setText("Playlist"));
    tabLayout.setTabGravity(TabLayout.MODE_FIXED);

    viewPager = findViewById(R.id.viewPager);
    tabsAdapter = new TabsAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
    viewPager.setAdapter(tabsAdapter);
    viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            viewPager.setCurrentItem(tab.getPosition());
        }

        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }

        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });

}

TAB：在这里我会显示所有歌曲

  @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View rootView = inflater.inflate(R.layout.fragment_tab1, container, false);
    recyclerViewSongs = rootView.findViewById(R.id.recyclerViewSongs);
    activeSongTab1 = rootView.findViewById(R.id.activeSongTab1);

    albumIvBottom = rootView.findViewById(R.id.albumIvBottom);
    tvCurrSongTitle = rootView.findViewById(R.id.tvCurrSongTitle);
    tvCurrSongArtist = rootView.findViewById(R.id.tvCurrSongArtist);

    Main.musicList = Main.songs.songs;

    // Connects the song list to an adapter
    // (thing that creates several Layouts from the song list)
    if ((Main.musicList != null) && (! Main.musicList.isEmpty())) {
        AllSongsAdapter allSongsAdapter = new AllSongsAdapter(getContext(), Main.musicList);
        recyclerViewSongs.setLayoutManager(new LinearLayoutManager(getActivity()));
        recyclerViewSongs.setHasFixedSize(true);
        recyclerViewSongs.setAdapter(allSongsAdapter);
        Log.i(TAG, "List is not empty");
    }else{
        Log.i(TAG, "List is empty");
    }

    recyclerViewSongs.addOnItemTouchListener(new OnItemClickListeners(getContext(), new OnItemClickListeners.OnItemClickListener() {
        @TargetApi(Build.VERSION_CODES.O)
        @Override
        public void onItemClick(View view, int position) {
            Toast.makeText(getContext(), "You Clicked position: " + position, Toast.LENGTH_SHORT).show();
            playAudio(position);
            //Fetch current song details
            tvCurrSongTitle.setText(Main.musicList.get(position).getTitle());
            tvCurrSongArtist.setText(Main.musicList.get(position).getArtist());

            //Fetch album art activeSong
            //loadAlbumArtBottom();
        }
    }));

    activeSongTab1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent activeSong = new Intent(getContext(), SongActivity.class);
            startActivity(activeSong);
        }
    });

    return rootView;
}

RecyclerView适配器

 public class AllSongsAdapter extends RecyclerView.Adapter<AllSongsAdapter.SongHolder>{
private LayoutInflater songInf;
private Context context;

private ArrayList<Song> musicList;

public AllSongsAdapter(Context context, ArrayList<Song> musicList) {
    super();
    this.musicList = musicList;
    this.context = context;
    songInf = LayoutInflater.from(context);

}

public static class SongHolder extends RecyclerView.ViewHolder {
    TextView tvSongTitle,tvArtistName;
    ImageView albumIv;
    public SongHolder(final View itemView) {
        super(itemView);
        tvSongTitle = itemView.findViewById(R.id.tvSongTitle);
        tvArtistName = itemView.findViewById(R.id.tvArtistName);
        albumIv = itemView.findViewById(R.id.albumIv);
        //tvIndex = itemView.findViewById(R.id.tvIndex);

    }

}

@NonNull
@Override
public SongHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int position) {
    View view = songInf.inflate(R.layout.song_layout, viewGroup, false);
    return new SongHolder(view);
}

@Override
public void onBindViewHolder(@NonNull SongHolder holder, final int position) {
    //holder.tvIndex.setText(String.format(Locale.US, "%d", position));

    Song currentSong = musicList.get(position);

    String title = currentSong.getTitle();
    if (title.isEmpty()){
        holder.tvSongTitle.setText("<Unknown>");
    }else{
        holder.tvSongTitle.setText(currentSong.getTitle());
    }

    String artist = currentSong.getArtist();
    if (artist.isEmpty()){
        holder.tvArtistName.setText("<Unknown>");
    }else {
        holder.tvArtistName.setText(currentSong.getArtist());
    }

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

    Picasso.with(context)
            .load(albumArtUri)
            .placeholder(R.drawable.no_album)
            .error(R.drawable.no_album)
            .resize(220,220)
            .centerCrop()
            .into(holder.albumIv);

}

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

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


}

TabsAdapter

public class TabsAdapter extends FragmentStatePagerAdapter{
int numberOfTabs;

public TabsAdapter(FragmentManager fm, int NumberOfTabs) {
    super(fm);
    this.numberOfTabs = NumberOfTabs;
}

@Override
public Fragment getItem(int position) {
    switch (position){
        case 0:
            return new Tab1();
        case 1:
            return new Tab2();
        case 2:
            return new Tab3();
        case 3:
            return new Tab4();
        case 4:
            return new Tab5();
        default: return null;
    }

}

@Override
public int getCount() {
    return numberOfTabs;
}
}

Answer 1

尝试添加类似permissionRequested的布尔值，如果权限请求通过，则将其设置为true，然后在您的onResume中使用它：

if(permissionRequested){ setupViewPager(); permissionRequested = false; }

您的viewPager依靠fragmentmanager，并且在活动完全恢复之前调用onRequestPermissionsResult，这会在添加片段时导致奇怪的行为。

也：

您绝不应在onRequestPermissionsResult内部重新请求被拒绝的许可。

如果用户选中“不再询问”，这将导致无限循环的重新请求（用户不可见），并且会干扰您的活动。权限请求是一项叠加活动，因此您将不断收到onPause onStart回调。

当我第一次运行我的应用程序并授予权限时，它不会加载歌曲

1 个答案: