我的 recyclerview 需要来自不同线程中的数据库访问的数据，但随后我得到“未连接适配器”

Question

I want to populate my RecyclerView, which from what I've heard, needs to be done in the main thread (?). But I want to populate said RecyclerView with info from my Room, which said query cannot be done in the main thread. How do I get around this? I've already tried running all ui related actions in a runOnUiThread():

public void updateTeams(){
        new Thread(new Runnable() {
            public void run() {
                AppDatabase db = AppDatabase.getInstance(getApplicationContext());
                final List<Team> allTeams = db.teamDao().getAll();
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        RecyclerView recyclerView = findViewById(R.id.teamRecyclerView);
                        TeamRecyclerViewAdapter adapter = new TeamRecyclerViewAdapter(TeamsActivity.this, allTeams);
                        recyclerView.setAdapter(adapter);
                        recyclerView.setLayoutManager(new LinearLayoutManager(TeamsActivity.this));
                    }
                });
            }
        }).start();
    }

I get E/RecyclerView: No adapter attached; skipping layout E/RecyclerView: No adapter attached; skipping layout and an unpopulated recyclerview

updateTeams() is called in the onCreate() of the activity. It is also called in onActivityResult() in the same activity. Does that make a difference?

Answer 1

Try to initialize your RecyclerView and Adapter inside onCreate like below:

private RecyclerView recyclerView;
private TeamRecyclerViewAdapter adapter;
private List<Team> allTeams;

@Override
protected void onCreate(Bundle savedInstanceState) {
    ...

    allTeams = new ArrayList<>();
    RecyclerView recyclerView = findViewById(R.id.teamRecyclerView);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    TeamRecyclerViewAdapter adapter = new TeamRecyclerViewAdapter(this, allTeams);
    recyclerView.setAdapter(adapter);

    ...
}

And inside runnable just update the data list and notify the adapter like below:

public void run() {
    AppDatabase db = AppDatabase.getInstance(getApplicationContext());
    allTeams = db.teamDao().getAll();
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            adapter.notifyDataSetChanged();
        }
    });
}