空對象上的onClick（int）引用

Question

我有這個自定義列表適配器，我出於某種原因可以使txtTitle與偵聽器一起工作，但按鈕總是返回空對象。有沒有一種特定的方式來在像這樣的回收站中添加按鈕？我以與其他回收器適配器相同的方式實施它，除非它們中沒有按鈕。

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

    private List<resource_list> listItems; 
private Context context; 
resource_list_adapter.OnItemClickListener onItemClickListener; 

public resource_list_adapter(List<resource_list> listItems, Context context) { 
    this.listItems = listItems; 
    this.context = context; 
} 

@Override 
public resource_list_adapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
    View v = LayoutInflater.from(parent.getContext()) 
      .inflate(R.layout.resource_list, parent, false); 
    return new ViewHolder(v); 
} 

@Override 
public void onBindViewHolder(ViewHolder holder, final int position) { 
    resource_list listItem = listItems.get(position); 
    Double resource = listItem.getCurrent().doubleValue()/listItem.getMax().doubleValue(); 

    holder.txtTitle.setText(listItem.getTxtTitle() + ": " + listItem.getCurrent().toString() + "/" + listItem.getMax().toString() + " (" + String.valueOf((int)(100*resource)) + "%)"); 
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) { 
     holder.pgResource.setProgressTintList(ColorStateList.valueOf(Color.rgb(listItem.getRed(),listItem.getGreen(),listItem.getBlue()))); 
    } 
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) { 
     holder.pgResource.setProgress((int)(100*resource), true); 
    } 

    holder.btnAddResource.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      onItemClickListener.onResourceClick(position); 
     } 
    }); 
    holder.btnSubtractResource.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      onItemClickListener.onResourceClick(position); 
     } 
    }); 

    holder.btnAddResource.setOnLongClickListener(new View.OnLongClickListener() { 
     @Override 
     public boolean onLongClick(View v) { 
      onItemClickListener.onLongResourceClick(position); 
      return true; 
     } 
    }); 
    holder.btnSubtractResource.setOnLongClickListener(new View.OnLongClickListener() { 
     @Override 
     public boolean onLongClick(View v) { 
      onItemClickListener.onLongResourceClick(position); 
      return true; 
     } 
    }); 

} 

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

public class ViewHolder extends RecyclerView.ViewHolder { 

    public TextView txtTitle; 
    public ProgressBar pgResource; 
    public Button btnAddResource; 
    public Button btnSubtractResource; 

    public ViewHolder(View itemView) { 
     super(itemView); 
     txtTitle = (TextView) itemView.findViewById(R.id.txtTitle); 
     btnAddResource = (Button) itemView.findViewById(R.id.btnAdditionResource); 
     btnSubtractResource = (Button) itemView.findViewById(R.id.btnSubtractResource); 
     pgResource = (ProgressBar) itemView.findViewById(R.id.pgResource); 
    } 
} 
public void setOnItemClickListener(resource_list_adapter.OnItemClickListener onItemClickListener){ 
    this.onItemClickListener = onItemClickListener; 
} 

public interface OnItemClickListener{ 
    void onResourceClick(int position); 
    void onLongResourceClick(int position); 
} 
} 

這就是我在我的活動中實現它的方式。

我對我的活動執行implements resource_list_adapter.OnItemClickListener。

聲明變量：

private RecyclerView recyclerResource; 
private resource_list_adapter resourceAdapter; 
private List<resource_list> resourceList; 
private List<String> resourceKeyList; 

這是我如何調用的方法 - 同一個地方我稱之爲從其他適配器所有其他方法。

@Override 
    public void onResourceClick(int position) { 
     Toast.makeText(getContext(), "Test", Toast.LENGTH_SHORT).show(); 
     /*Intent intent = new Intent(getActivity(), AttributeDescription.class); 
     intent.putExtra("SelectedCharacter", Home_Tab.activeCharacter); 
     intent.putExtra("name", attributeKeyList.get(position).toString()); 
     intent.putExtra("category", "Attribute"); 
     if (character.Edit.equals("True")){ 
      intent.putExtra("mode", "Edit"); 
     } 
     else{ 
      intent.putExtra("mode", "View"); 
     } 
     startActivity(intent);*/ 
    } 

    @Override 
    public void onLongResourceClick(final int position) { 
     /*if (character.Edit.equals("True")){ 
      AlertDialog.Builder builder = new AlertDialog.Builder(getActivity()); 
      builder.setTitle("Remove Attribute"); 
      builder.setPositiveButton("Remove", new DialogInterface.OnClickListener() { 
       public void onClick(DialogInterface dialog, int id) { 
        character.removeAttribute(attributeKeyList.get(position).toString(), "Attribute"); 
        attributeKeyList.remove(position); 
       } 
      }) 
        .setNegativeButton("Cancel", new DialogInterface.OnClickListener() { 
         public void onClick(DialogInterface dialog, int id) { 
          // User cancelled the dialog 
         } 
        }); 
      // Create the AlertDialog object and return it 
      AlertDialog dialog = builder.create(); 
      dialog.show(); 
     }*/ 
    } 

這是我如何在我的init（）方法中設置偵聽器到我的適配器（與其餘部分相同）。

resourceAdapter = new resource_list_adapter(resourceList, getContext()); 
resourceAdapter.setOnItemClickListener(this); 

Answer 1

您必須在不設置點擊偵聽器的情況下製作新的RecyclerViewAdapter。例如，當你獲得新數據時，你調用notifyDataSetChanged，不要創建一個全新的適配器。

如果你總想強迫自己實現一個點擊監聽器（因爲你有沒有空檢查），明確地傳遞給它的構造

final resource_list_adapter.OnItemClickListener onItemClickListener; 

public resource_list_adapter(List<resource_list> listItems, Context context, resource_list_adapter.OnItemClickListener listener) { 
    this.listItems = listItems; 
    this.context = context; 
    onItemClickListener = listener; 
}