我很少看到关于这种情况的相关问题，但找不到任何解决办法，所以我的问题就这样。
我已经列出了包含4个片段的列表，im在frag编号3（catalog）中将数据传递给用户，这个frag为cardview保留recyclerview im尝试为将调用dialogfragment的卡实现onclicklistner，我知道最有效的方法是为viewholder使用接口，我面临一个问题recyclerview适配器构造器。
这是目录碎片：
public class CatalogFragment extends Fragment implements CustomAdapter.OnItemClickListener {
private FloatingActionButton mSharedFab;
private List<MyProducts> productsList;
//Creating Views
private RecyclerView recyclerView;
private RecyclerView.LayoutManager layoutManager;
private RecyclerView.Adapter adapter;
private CustomAdapter.OnItemClickListener listener;//////LISTNER FOR DIALOG???
//Volley Request
private RequestQueue requestQueue;
//request counter
private int requestCount = 1;
private static final String URL_INDEX = "http://myserverip/product.php";
//Tag values to read from json
public static final String TAG_IMAGE_URL = "product_img";
public static final String TAG_PRODUCT_SN = "product_serial_num";
public static final String TAG_PRODUCT_TITLE = "product_title";
public static final String TAG_PRODUCT_PRICE = "product_price";
public static final String TAG_PRODUCT_DESCRIPTION = "product_description";
public CatalogFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_catalog, container, false);
recyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
layoutManager = new LinearLayoutManager(getActivity().getApplicationContext(), LinearLayoutManager.VERTICAL, false);
recyclerView.setLayoutManager(layoutManager);
//recyclerView.setHasFixedSize(true);
RecyclerView.ItemAnimator itemAnimator = new DefaultItemAnimator();
itemAnimator.setAddDuration(1000);
itemAnimator.setRemoveDuration(1000);
recyclerView.setItemAnimator(itemAnimator);
//Initializing our product list
productsList = new ArrayList<>();
requestQueue = Volley.newRequestQueue(getActivity().getApplicationContext());
// fetch data
getData();
//initialize adapter
adapter = new CustomAdapter(listener, productsList, getActivity());
//Adding adapter to recyclerview
recyclerView.setAdapter(adapter);
return view ;
}
@Override
public void onItemClicked(View v) {
DialogAddToCartFragment df= new DialogAddToCartFragment();
df.show(getFragmentManager(), "Dialog");
}
适配器用3个参数实例化，使用customadapter。
CustomAdapter类：
public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
public interface OnItemClickListener {
void onItemClicked(View v);
}
private OnItemClickListener listener;
//Image loader inst for image
private ImageLoader imageLoader;
private Context context;
public Snackbar snackbar;
String title;
//List all products
List<MyProducts> myProducts;
public CustomAdapter( OnItemClickListener listener, List<MyProducts> myProducts, Context context)
{
super();
this.listener = listener;
this.myProducts = myProducts;
this.context = context;
}
@Override
public CustomAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.product_list, parent, false);
ViewHolder viewHolder = new ViewHolder(v);
return viewHolder;
}
@Override
public void onBindViewHolder(CustomAdapter.ViewHolder holder, int position) {
if( myProducts != null) {
MyProducts myProducts1 = myProducts.get(position);
imageLoader = ImageVolley.getInstance(context).getImageLoader();
imageLoader.get(myProducts1.getProductImage(), ImageLoader.getImageListener(holder.imageView, R.drawable.android_store_log, android.R.drawable.ic_dialog_alert));
title = myProducts1.getProductTitle();
//Showing data to the views
holder.imageView.setImageUrl(myProducts1.getProductImage(), imageLoader);
holder.textViewProductTitle.setText(myProducts1.getProductTitle());
holder.textViewProductDescription.setText(myProducts1.getProductDescription());
holder.textViewProductSerialNumber.setText(myProducts1.getProductSn());
holder.textViewProductPrice.setText(myProducts1.getProductPrice());
}
}
@Override
public int getItemCount() {
return myProducts.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
//Views
public NetworkImageView imageView;
public TextView textViewProductTitle;
public TextView textViewProductDescription;
public TextView textViewProductSerialNumber;
public TextView textViewProductPrice;
//Initializing Views
public ViewHolder(final View itemView) {
super(itemView);
imageView = (NetworkImageView) itemView.findViewById(R.id.imageViewProduct);
textViewProductTitle = (TextView) itemView.findViewById(R.id.textViewProductTitle);
textViewProductDescription = (TextView) itemView.findViewById(R.id.textViewProductDescription);
textViewProductSerialNumber = (TextView) itemView.findViewById(R.id.textViewProductSerialNumber);
textViewProductPrice = (TextView) itemView.findViewById(R.id.textViewProductPrice);
itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
listener.onItemClicked(v);/////////DIALOG LISTENER????
}
});
}
}
对话片段：
public class DialogAddToCartFragment extends DialogFragment {
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
View view = getActivity().getLayoutInflater().inflate(R.layout.fragment_dialog_add_to_cart, new LinearLayout(getActivity()), false);
// Retrieve layout elements
//TextView title = (TextView) view.findViewById(R.id.text_title);
// Set values
//title.setText("Not perfect yet");
// Build dialog
Dialog builder = new Dialog(getActivity());
builder.requestWindowFeature(Window.FEATURE_NO_TITLE);
builder.getWindow().setBackgroundDrawable(new ColorDrawable(Color.GREEN));
builder.setContentView(view);
return builder;
}
}
当我点击卡片时，程序关闭：（
这是日志：
07-12 08:42:22.685 2808-2808/com.example.get2i.androidstore E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.get2i.androidstore, PID: 2808
java.lang.NullPointerException: Attempt to invoke interface method 'void com.example.get2i.androidstore.CustomAdapter$OnItemClickListener.onItemClicked(android.view.View)' on a null object reference
at com.example.get2i.androidstore.CustomAdapter$ViewHolder$1.onClick(CustomAdapter.java:102)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
我应该用什么来指示catalogfrag中的customadapter.onitemclicklistener侦听器？如有任何建议，欢迎垂询，谢谢！
最佳答案
我应该如何说明customadapter.onitemclicklistener
目录框中的侦听器？
因为在将对象传递给类构造函数之前忘记初始化它。按以下方式操作：
listener=this;
adapter = new CustomAdapter(listener, productsList, getActivity());
...