Unable to get the Cardview, E/RecyclerView: No adapter attached; skipping layout error , how to add adapter to recyclerView?

huangapple
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英文:

Unable to get the Cardview, E/RecyclerView: No adapter attached; skipping layout error , how to add adapter to recyclerView?

问题

以下是你提供的代码的中文翻译：

我正在使用Android Studio构建一个应用程序。在运行应用程序时，我遇到了“E/RecyclerView: No adapter attached; skipping layout”的问题。
由于我对Android Studio开发还很新，无法找出问题所在。我尝试了一些在线解决方案，但对我没有起作用。

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("请稍候...");
        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，有时候会出错，或者我可能犯了一个错误，请检查这两个地方，并给我一个纠正这个问题的想法。

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);
        }
    }
}
英文:

I'm using the android studio to build an application. I'm getting "E/RecyclerView: No adapter attached; skipping layout" when running the app.
Since I'm new to android studio development, unable to figure out the problem. I tried several solutions online, but it didn't work for me.

public class MainActivity extends AppCompatActivity {
RecyclerView recyclerView;
RecyclerViewAdapter adapter;
DatabaseReference mDatabase;
ProgressDialog progressDialog;
private List &lt;Upload&gt; 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&lt;&gt;();
progressDialog.setMessage(&quot;Please wait ...&quot;);
progressDialog.show();
mDatabase = FirebaseDatabase.getInstance().getReference(&quot;upload&quot;);
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();
}
});
}

Adapter
This is my adapter code, sometime it will be wrong or I had a mistake check these two and please give me an idea to correct this problem.

public class RecyclerViewAdapter extends  RecyclerView.Adapter&lt;RecyclerViewAdapter.MyViewHolder&gt;{
private Context mContext;
private List &lt;Upload&gt; uploads;
public RecyclerViewAdapter(Context mContext, List&lt;Upload&gt; 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);
}
}

}

答案1

得分: 1

你需要在 onCreate 方法中设置适配器，目前你是在监听器中设置的。我猜想你只需要将 recylerView.setAdapter(adapter) 移动到 onCreate 中，然后在你的监听器中设置数据和调用 notifyDataSetChanged。

应该是这样的：

@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));
    adapter = new RecyclerViewAdapter(getApplicationContext());
    recyclerView.setAdapter(adapter);
    progressDialog = new ProgressDialog(this);
    uploads = new ArrayList<>();
    progressDialog.setMessage("请稍候...");
    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();
        }
    });
}

适配器部分

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);
        }
    }
}
英文:

You have to set the adapter in onCreate method, right now you're doing it in a listener. My guess is you just need to move the recylerView.setAdapter(adapter) in onCreate and just set the datas and notifyDataSetChanged in your listener

It should look like this:

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&lt;&gt;();
    progressDialog.setMessage(&quot;Please wait ...&quot;);
    progressDialog.show();
    mDatabase = FirebaseDatabase.getInstance().getReference(&quot;upload&quot;);
    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();

        }
    });

}

Adapter

public class RecyclerViewAdapter extends  RecyclerView.Adapter&lt;RecyclerViewAdapter.MyViewHolder&gt;{
private Context mContext;
private List&lt;Upload&gt; uploads;
public RecyclerViewAdapter(Context mContext, List&lt;Upload&gt; uploads) {
this.mContext = mContext;
this.uploads = uploads;
}
public RecyclerViewAdapter(Context mContext) {
this.mContext = mContext;
}
public void setList(List&lt;Upload&gt; 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);
}
}

huangapple
  • 本文由 发表于 2020年5月3日 17:20:24
  • 转载请务必保留本文链接：https://go.coder-hub.com/61572159.html
  • android
  • android-recyclerview
  • android-studio
  • java
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