Fehler im RecyclerView-Adapter beim Erstellen der App

Question

Ich habe den RecyclerView und seinen Adapter hinzugefügt, aber wenn ich die App erstelle, wird in der Nachrichtenansicht in Android Studio ein Erstellungsfehler angezeigt. Es zeigt auf den Fehler in RecycleAdapter, den ich erstellt habe.

Error:(63, 12) error: cannot access ScrollingView 
class file for android.support.v4.view.ScrollingView not found 

Error:(20, 8) error: cannot access NestedScrollingChild 
class file for android.support.v4.view.NestedScrollingChild not found 

Error:(20, 88) error: type argument CategoryRecycleAdapter.ViewHolder is not within bounds of type-variable VH 

where VH is a type-variable: 
VH extends android.support.v7.widget.RecyclerView.ViewHolder declared in class Adapter 
Error:(30, 9) error: cannot find symbol variable this 

Error:(31, 9) error: cannot find symbol variable this 

Error:(34, 5) error: method does not override or implement a method from a supertype 

Error:(37, 16) error: an enclosing instance that contains CategoryRecycleAdapter.ViewHolder is required 

Error:(40, 5) error: method does not override or implement a method from a supertype 
Error:(55, 9) error: cannot find symbol method notifyDataSetChanged() 

Error:(58, 5) error: method does not override or implement a method from a supertype 

Hier ist der Code of Adapter:

public class CategoryRecycleAdapter extends RecyclerView.Adapter<CategoryRecycleAdapter.ViewHolder> { 

Context mContext; 
ArrayList<Category> alData; 


public CategoryRecycleAdapter() { 
} 

public CategoryRecycleAdapter(Context mContext, ArrayList<Category> alData) { 
    this.mContext = mContext; 
    this.alData = alData; 
} 

@Override 
public CategoryRecycleAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
    View view = LayoutInflater.from(mContext).inflate(R.layout.row_category, parent, false); 
    return new CategoryRecycleAdapter.ViewHolder(view); 
} 

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

    holder.tvName.setText("" + alData.get(position).displayName); 
    Picasso.with(mContext) 
      .load(alData.get(position).iconUrl) 
      .into(holder.ivCategory); 

} 

public void addAll(ArrayList<Category> data) { 
    if (data != null) { 
     alData.clear(); 
     alData.addAll(data); 
    } 
    notifyDataSetChanged(); 
} 

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

public class ViewHolder extends RecyclerView.ViewHolder { 
    TextView tvName; 
    ImageView ivCategory; 

    public ViewHolder(View itemView) { 
     super(itemView); 
     tvName = (TextView) itemView.findViewById(R.id.tvCategory); 
     ivCategory = (ImageView) itemView.findViewById(R.id.ivCategory); 
    } 
}} 

Answer 1

Ich glaube, diese Linie Ihre Schuld daran ist:

public class CategoryRecycleAdapter extends RecyclerView.Adapter<CategoryRecycleAdapter.ViewHolder> 

Sie verweisen die darunter liegende ViewHolder der Klasse CategoryRecycleAdapter. Versuchen Sie, den ViewHolder zu erweitern, den Sie als private innere Klasse deklarieren.

public class ViewHolder extends RecyclerView.ViewHolder 

diese Revision machen und lassen Sie mich wissen, wenn es nicht funktioniert:

public class CategoryRecycleAdapter extends RecyclerView.Adapter<ViewHolder> 

Answer 2

diese Änderungen an Ihrem Code Hersteller:

public class CategoryRecycleAdapter extends RecyclerView.Adapter< RecyclerView.ViewHolder> 

und

@Override 
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) 

und

@Override 
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) 

Änderung der Rückgabetyp von onCreateViewHolderCategoryRecycleAdapter.ViewHolder-RecyclerView.ViewHolder

Dies sollte das Problem lösen.