无法获取 Cardview、E/RecyclerView：未连接适配器； 跳过布局错误，如何将适配器添加到 recyclerView？

Question

我正在使用 android 工作室来构建应用程序。 我在运行应用程序时收到“E/RecyclerView：未连接适配器；跳过布局”。 由于我是 android 工作室开发的新手，无法找出问题所在。 我在网上尝试了几种解决方案，但对我不起作用。

public class MainActivity extends AppCompatActivity {

RecyclerView recyclerView;
RecyclerViewAdapter adapter;
DatabaseReference mDatabase;
ProgressDialog progressDialog;
private List <Upload> uploads;



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

    recyclerView = findViewById(R.id.recyclerview_id);
    recyclerView.setLayoutManager(new GridLayoutManager(this,3));
    progressDialog = new ProgressDialog(this);
    uploads = new ArrayList<>();
    progressDialog.setMessage("Please wait ...");
    progressDialog.show();
    mDatabase = FirebaseDatabase.getInstance().getReference("upload");
    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

            progressDialog.dismiss();
            for (DataSnapshot postsnapshot : dataSnapshot.getChildren()) {
            Upload upload = postsnapshot.getValue(Upload.class);
            uploads.add(upload);

            }
            adapter = new RecyclerViewAdapter(getApplicationContext(),uploads);
            recyclerView.setAdapter(adapter);
            adapter.notifyDataSetChanged();
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

            progressDialog.dismiss();

        }
    });

}

适配器这是我的适配器代码，有时它会出错或者我有错误检查这两个，请给我一个解决这个问题的想法。

public class RecyclerViewAdapter extends  RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder>{

private Context mContext;
private List <Upload> uploads;

public RecyclerViewAdapter(Context mContext, List<Upload> uploads) {
    this.mContext = mContext;
    this.uploads = uploads;
}



@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

    View view;
    LayoutInflater inflater = LayoutInflater.from(mContext);
    view = inflater.inflate(R.layout.card_view_item,parent,false);

    return new MyViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

    final  Upload upload = uploads.get(position);
    holder.tv_book_title.setText(upload.getName());

    Glide.with(mContext).load(upload.getUrl()).into(holder.imd_book_thumbnail);
}

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

public class MyViewHolder extends RecyclerView.ViewHolder {

    TextView tv_book_title;
    ImageView imd_book_thumbnail;
    CardView cardView;

    public MyViewHolder(@NonNull View itemView) {
        super(itemView);

        tv_book_title = itemView.findViewById(R.id.book_title_id);
        imd_book_thumbnail = itemView.findViewById(R.id.book_img_id);
        cardView = itemView.findViewById(R.id.card_view_id);
    }
}

}

Answer 1

您必须在onCreate方法中设置适配器，现在您正在侦听器中执行此操作。 我的猜测是你只需要在onCreate中移动recylerView.setAdapter(adapter)并在你的listener器中设置数据和notifyDataSetChanged

它应该如下所示：

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

    recyclerView = findViewById(R.id.recyclerview_id);
    recyclerView.setLayoutManager(new GridLayoutManager(this,3));
    adapter = new RecyclerViewAdapter(getApplicationContext());
    recyclerView.setAdapter(adapter)
    progressDialog = new ProgressDialog(this);
    uploads = new ArrayList<>();
    progressDialog.setMessage("Please wait ...");
    progressDialog.show();
    mDatabase = FirebaseDatabase.getInstance().getReference("upload");
    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

            progressDialog.dismiss();
            for (DataSnapshot postsnapshot : dataSnapshot.getChildren()) {
                Upload upload = postsnapshot.getValue(Upload.class);
                uploads.add(upload);
            }
            adapter.setList(uploads);
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

            progressDialog.dismiss();

        }
    });

}

适配器

public class RecyclerViewAdapter extends  RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder>{

private Context mContext;
private List<Upload> uploads;

public RecyclerViewAdapter(Context mContext, List<Upload> uploads) {
    this.mContext = mContext;
    this.uploads = uploads;
}

public RecyclerViewAdapter(Context mContext) {
    this.mContext = mContext;
}

public void setList(List<Upload> uploads) {
    this.uploads = uploads
}

@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

    View view;
    LayoutInflater inflater = LayoutInflater.from(mContext);
    view = inflater.inflate(R.layout.card_view_item,parent,false);

    return new MyViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

    final  Upload upload = uploads.get(position);
    holder.tv_book_title.setText(upload.getName());

    Glide.with(mContext).load(upload.getUrl()).into(holder.imd_book_thumbnail);
}

@Override
public int getItemCount() {
    return uploads == null ? 0 : uploads.size();
}

public class MyViewHolder extends RecyclerView.ViewHolder {

    TextView tv_book_title;
    ImageView imd_book_thumbnail;
    CardView cardView;

    public MyViewHolder(@NonNull View itemView) {
        super(itemView);

        tv_book_title = itemView.findViewById(R.id.book_title_id);
        imd_book_thumbnail = itemView.findViewById(R.id.book_img_id);
        cardView = itemView.findViewById(R.id.card_view_id);
    }
}