问题
I m trying to extract android volley response to a member variable of the same class. I used callback interfaces to perform this task :
public void getData(MyCustomListener customListener) {
JsonArrayRequest arrayRequest = new JsonArrayRequest(Request.Method.POST, url,
response -> {
Log.i("response",response.toString());
customListener.onResponse(completeCart);
},
error -> Log.i("Volley_error", error.getMessage())) {
...
CustomerListener interface:
public interface MyCustomListener {
public void onResponse(Object response);
public void onError(String error_response);
}
And inside onCreateView method of the fragment :
getData(new MyCustomListener() {
@Override
public void onResponse(Object response) {
completeCartProItems.addAll((List<CompleteCartProItem>) response);
}
@Override
public void onError(String error_response) {}
});
When I put a debug pointer at completeCartProItems.addAll((List<CompleteCartProItem>) response); response is not empty but completeCartProItems arraylist is shown as empty.
Variables :
I need to pass this completeCartProItems to a Adapter named CartItem_ScrollerAdapter which has implemented to a RecycleView.
This implementation also inside the onCreateView of the fragment. right after calling getData() method :
cart_item_scrollerAdapter = new CartItem_ScrollerAdapter(getActivity(), completeCartProItems);
I put debug pointer inside the constructor of the CartItem_ScrollerAdapter as well.
But it also shows that the List parameter of the constructor is empty.
How to pass not empty ArrayList to the adapter given below ?? Any suggestions will be appreciable. Thank you.
UPDATE
Adapter class :
public class CartItem_ScrollerAdapter extends RecyclerView.Adapter<CartItem_ScrollerAdapter.CartItemViewHolder> {
private LayoutInflater inflater;
private List<CompleteCartProItem> completeCartProItems = new ArrayList<>();
private Context context;
public CartItem_ScrollerAdapter(Context context, List<CompleteCartProItem> completeCartProItems) {
this.inflater = LayoutInflater.from(context);
this.context = context;
this.completeCartProItems = completeCartProItems;
}
@Override
public CartItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.cart_item, parent, false);
CartItemViewHolder cartItemViewHolder = new CartItemViewHolder(view);
return cartItemViewHolder;
}
@Override
public void onBindViewHolder(CartItemViewHolder holder, int position) {
CompleteCartProItem proItem = completeCartProItems.get(position);
CartDetails details = (CartDetails) MyApplication.getAndroidSession().getAttribute("cart");
holder.cart_pro_name.setText(proItem.getP_name());
holder.cart_pro_price.setText("Rs " + (proItem.getP_dscPer() != 0 ? details.getDiscountPrice(proItem.getP_price(), proItem.getP_dscPer()) : proItem.getP_price()));
holder.cart_pro_qnty.setText(details.getQntyOfProduct(proItem.getPid(), proItem.getP_size()) + "");
holder.cart_pro_size.setText(proItem.getP_size());
String image_url = "http://10.0.2.2:8080/ECommerceApp/" + proItem.getP_img();
Picasso.with(context).load(image_url).into(holder.cart_pro_img);
}
@Override
public int getItemCount() {
return completeCartProItems != null ? completeCartProItems.size() : 0;
}
class CartItemViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
TextView cart_pro_name;
TextView cart_pro_price;
TextView cart_pro_qnty;
TextView cart_pro_size;
ImageView cart_pro_img;
ImageButton cart_remove_btn;
Button cart_change;
public CartItemViewHolder(View itemView) {
super(itemView);
cart_pro_name = (TextView) itemView.findViewById(R.id.cart_item_product_name);
cart_pro_price = (TextView) itemView.findViewById(R.id.cart_item_product_price);
cart_pro_size = (TextView) itemView.findViewById(R.id.cart_item_size);
cart_pro_img = (ImageView) itemView.findViewById(R.id.cart_product_img);
cart_pro_qnty = (TextView) itemView.findViewById(R.id.cart_item_qnty);
//===============================================================================================
cart_remove_btn = (ImageButton) itemView.findViewById(R.id.remove_item_btn);
cart_change = (Button) itemView.findViewById(R.id.cart_item_change_btn);
cart_pro_img.setOnClickListener(this);
cart_remove_btn.setOnClickListener(this);
cart_change.setOnClickListener(this);
}
@Override
public void onClick(View v) {
}
}
}
Fragment :
public class CartFragment extends Fragment {
private RecyclerView cart_horizontal_scroller;
private CartItem_ScrollerAdapter cart_item_scrollerAdapter;
private Button purchase_button;
private List<CompleteCartProItem> completeCartProItems = new ArrayList<>();
public CartFragment() {
// Required empty public constructor
}
public void getData(MyCustomListener<CompleteCartProItem> customListener) {
if (MyApplication.getAndroidSession().getAttribute("cart") != null) {
Log.i("cart_null", "NOT null");
RequestQueue requestQueue = VolleySingleton.getsInstance().getRequestQueue();
CartDetails cartDetails = (CartDetails) MyApplication.getAndroidSession().getAttribute("cart");
CopyOnWriteArrayList<CartItem> jsonSendArray = cartDetails.getShoppingList();
final String jsonString = new Gson().toJson(jsonSendArray,
new TypeToken<CopyOnWriteArrayList<CartItem>>() {
}.getType());
Log.i("json_object", jsonString);
String url = "http://10.0.2.2:8080/ECommerceApp/getAllProductsAction";
JsonArrayRequest arrayRequest = new JsonArrayRequest(Request.Method.POST, url,
response -> {
List<CompleteCartProItem> completeCart = new Gson().fromJson(response.toString(),
new TypeToken<List<CompleteCartProItem>>() {
}.getType());
Log.i("response", completeCart.get(0).getP_name());
customListener.onResponse(completeCart);
}, error -> Log.i("Volley_error", error.getMessage())) {
@Override
public Map<String, String> getHeaders() throws AuthFailureError {
Map<String, String> params = new HashMap<>();
params.put("Content-Type", "application/json");
params.put("cartList", jsonString);
return params;
}
};
arrayRequest.setRetryPolicy(new RetryPolicy() {
@Override
public int getCurrentTimeout() {
return 5000;
}
@Override
public int getCurrentRetryCount() {
return 5000;
}
@Override
public void retry(VolleyError error) throws VolleyError {
}
});
requestQueue.add(arrayRequest);
} else {
Log.i("cart_null", "null");
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_cart, container, false);
cart_horizontal_scroller = (RecyclerView) view.findViewById(R.id.horizontal_scrollView_cart_items);
getData(new MyCustomListener<CompleteCartProItem>() {
@Override
public void onResponse(List<CompleteCartProItem> response) {
completeCartProItems.addAll(response);
//completeCartProItems.add(new CompleteCartProItem(1, 2340.0, "Extra Orient Top", "Orient", "", "S", 5));
Log.i("check", completeCartProItems.get(0).getP_name());
}
@Override
public void onError(String error_response) {
}
});
cart_item_scrollerAdapter = new CartItem_ScrollerAdapter(getActivity(), completeCartProItems);
cart_horizontal_scroller.setAdapter(cart_item_scrollerAdapter);
cart_horizontal_scroller.setLayoutManager(new LinearLayoutManager(getActivity(),
LinearLayoutManager.HORIZONTAL, false));
purchase_button = (Button) view.findViewById(R.id.purchase_btn);
purchase_button.setOnClickListener(v -> {
Toast t = Toast.makeText(getActivity(), "Worked", Toast.LENGTH_LONG);
t.show();
});
return view;
}
}
回答1:
Ok. In reference to the comment above, I am writing some steps you should try since I do not have a clear picture of what might be wrong.
Let's start with your MyCustomListener. I do not know why are you setting the response type to Object. If it is to use this in multiple requests then you can modify it like the following with generics
public interface MyCustomListener<T> {
public void onResponse(T response);
public void onError(String error_response);
}
then use it like this when a callback is needed
getData(new MyCustomListener<List<CompleteCartProItem>>() {
@Override
public void onResponse(List<CompleteCartProItem> response) {
completeCartProItems.addAll(response);
}
@Override
public void onError(String error_response) {
//handle error
}
});
Also make sure you are not re-initialising completeCartProItems elsewhere after the callback.
Not really sure if the following will fix your issue but make sure that your callback is executed in the UI thread, too.
来源：https://stackoverflow.com/questions/35835338/accessing-volley-response-with-callback-interfaces