需要有关将数据从适配器发送到片段的说明

Question

我想将数据从适配器发送到已经打开的片段。 在主活动中，已经打开了两个片段，片段 A 和片段 B。在片段 A 中，我放置了一个回收器视图和卡片视图。单击其中一个卡片视图时，我想将其数据发送到片段 B。我在调用mCallbacks时得到一个NPE。

if (mCallbacks != null){
mCallbacks.onItemClicked(strStockName);}

在这种情况下，我使用了接口。但我需要更多的解释。

这是我的适配器的代码：

public class adapterStock extends RecyclerView.Adapter<adapterStock.ViewHolder> {
private String[] stockNameDataSet;
private Context mContext;
//==============================================
//---- interface
public interface Callbacks{
public void onItemClicked(String StockName);
}
private Callbacks mCallbacks;
//==============================================

public adapterStock(Context context, String[] DataSet){
stockNameDataSet = DataSet;
mContext = context;
}
@NonNull
@Override
public adapterStock.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
LayoutInflater layoutInflater = LayoutInflater.from(viewGroup.getContext());
View view = layoutInflater.inflate(R.layout.cv_stock, viewGroup, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
final String strStockName = stockNameDataSet[position];
holder.tbxStockName.setText(stockNameDataSet[position]);
holder.cardView.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
Snackbar.make(view, "Stock "+strStockName, Snackbar.LENGTH_LONG).show();
if (mCallbacks != null){
mCallbacks.onItemClicked(strStockName);
}
}
});
}
@Override
public int getItemCount() {
return stockNameDataSet.length;
}
public static class ViewHolder extends RecyclerView.ViewHolder{
public View view;
public TextView tbxStockName;
public CardView cardView;
public ViewHolder(View v){
super (v);
tbxStockName = (TextView) v.findViewById(R.id.cvTbxItemStockName);
cardView = (CardView) v.findViewById(R.id.cvStock);
}
}
public void setCallbacks(Callbacks callbacks){
this.mCallbacks = callbacks;
}
}

这是片段 A：

public class AFrag extends Fragment implements adapterStock.Callbacks {
private String strStockName;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.frag_A, container, false);
tbxStock = (TextView) view.findViewById(R.id.tbxR);
return view;
}
@Override
public void onItemClicked(String StockName) {
Toast.makeText(getActivity(), "Stock terpilih " + StockName, Toast.LENGTH_LONG).show();
tbxStock.setText(strStockName);
}
}

建议不胜感激。谢谢。

Answer 1

一旦创建了 adapterStock 实例，就在您的片段 A 中包含，setCallbacks(this(。

Answer 2

setCallbacks(this( in your fragment

Answer 3

更改此内容

public adapterStock(Context context, String[] DataSet){
stockNameDataSet = DataSet;
mContext = context;
}

对此

public adapterStock(Context context, String[] DataSet, Callbacks mCallbacks){
stockNameDataSet = DataSet;
mContext = context;
this.mCallbacks=mCallbacks;
}

在片段的adapterStock实例中，将mCallbacks作为this传递(即new adapterStock(context, dataset,this)(

注意：另外两个答案也正确