RecyclerView：没有连接适配器--为什么我一直得到这个错误？

Question

只是想在回收器中显示我数据库中的信息。一切正常。将显示对象。

但logcat说：

E/RecyclerView: No adapter attached; skipping layout

这是我的代码（displayimages.java）

    public class DisplayImages extends AppCompatActivity {
    DatabaseReference databaseReference;

    RecyclerView recyclerView;

    RecyclerView.Adapter adapter;
    ProgressDialog progressDialog;

    List<ImageUploadInfo> list = new ArrayList<>();

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_images);

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

        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(DisplayImages.this));

        progressDialog = new ProgressDialog(DisplayImages.this);
        progressDialog.setMessage("Loading Images From Firebase.");
        progressDialog.show();

        // Setting up Firebase image upload folder path in databaseReference.
        // The path is already defined in MainActivity.
        databaseReference = FirebaseDatabase.getInstance().getReference(Main.Database_Path);

        databaseReference.addValueEventListener(new ValueEventListener() {
            @override
            public void onDataChange(DataSnapshot snapshot) {

                for (DataSnapshot postSnapshot : snapshot.getChildren()) {

                    ImageUploadInfo imageUploadInfo = postSnapshot.getValue(ImageUploadInfo.class);

                    list.add(imageUploadInfo);
                }

                adapter = new RecyclerViewAdapter(getApplicationContext(), list);

                recyclerView.setAdapter(adapter);
                progressDialog.dismiss();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

                progressDialog.dismiss();

            }
        });

    }

如果有什么不同的话，这是我在MainActivity中写的关于DataBase_Path的内容：

public class Main extends AppCompatActivity implements View.OnClickListener {

DatabaseReference databaseReference;
public static final String Database_Path = "All_Image_Uploads_Database";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    databaseReference = FirebaseDatabase.getInstance().getReference(Database_Path);

如您所见，我已经为RecycleView附加了一个适配器。那么为什么我总是得到这个错误呢？

我读过与同一问题有关的其他问题，但都没有帮助。

Answer 1

您需要在设置layour管理器之后设置适配器，否则将得到您看到的错误消息。

recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
    recyclerView.setHasFixedSize(true);
//don't set adapter here
    recyclerView.setLayoutManager(new LinearLayoutManager(DisplayImages.this));

//set adapter here

此外，您可以先用一个空列表设置适配器，然后当您收到来自firebase的回调时，您可以更新该列表并在适配器上调用notifyDatasetChanged（）。您看到的问题是由于这样一个事实，即在过程的很晚（当您的firebase调用返回时）才真正设置适配器

像这样：

recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(DisplayImages.this));
adapter = new RecyclerViewAdapter(getApplicationContext(), list);
 recyclerView.setAdapter(adapter);


databaseReference.addValueEventListener(new ValueEventListener() {
            @override
            public void onDataChange(DataSnapshot snapshot) {

                for (DataSnapshot postSnapshot : snapshot.getChildren()) {

                    ImageUploadInfo imageUploadInfo = postSnapshot.getValue(ImageUploadInfo.class);

                    list.add(imageUploadInfo);
                }
               adapter.notifyDatasetChanged();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

                progressDialog.dismiss();

            }
        });