我正在开发一个包含购物车管理的电子商务应用程序。现在我有一个片段（CartFragment）和一个连接到recyclerView的适配器（ShowCartAdapter）。
我在一个片段中进行了三次网络呼叫（即1.将项目添加到购物车，2。在购物车中显示项目，3。从购物车中删除项目）。
上面的片段附加到一个活动（ProductDetailActivity）。将项目添加到购物车并在购物车中显示项目是完美的，但第三个即从购物车中删除项目令我不安。我的{{1}中有一个图标删除一个项目，点击我要从 angularPlayer.play();
删除该项目，现在我从适配器发送一个唯一ID项目到片段但它在cardview上给我空指针我点击那个图标。可能活动不再附加到该片段。下面是我的适配器，片段和活动的代码片段。请帮助我!!!
CartFragment
recyclerviewAdapterShowCart
ProgressDialog(progressDialog=new ProgressDialog(getActivity());)ProductDetailActivity
public class CartFragment extends Fragment implements RetrofitTaskListener<AddCart> {
private ProgressDialog progressDialog;
private RecyclerView recyclerView;
private AdapterAddCart adapter;
private AdapterShowCart adapterShowCart;
private boolean loading = true;
AddCart addCartList;
int pageIndex;
private LinearLayoutManager linearLayoutManager;
private String email1,articlCode,image,quantity,cost;
private static final String STARTING_TEXT = "Four Buttons Bottom Navigation";
private Button btnCheckout;
private FragmentTransaction fragmentTransaction;
private int frag,cartSize;
private TextView cartEmptyTxt;
private Context context;
private SharedPreferences sharedPreference;
private SharedPreferences.Editor editor;
private SessionManager session;
private EditText cmntTxt;
public CartFragment() {
// Required empty public constructor
}
public static CartFragment newInstance(int text) {
Bundle args = new Bundle();
args.putInt(STARTING_TEXT, text);
CartFragment sampleFragment = new CartFragment();
sampleFragment.setArguments(args);
return sampleFragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
articlCode = getArguments().getString("artCode");
image = getArguments().getString("image");
quantity = getArguments().getString("quantity");
cost = getArguments().getString("cost");
frag = getArguments().getInt("fragment");
View view = inflater.inflate(R.layout.fragment_cart, container, false);
cmntTxt = (EditText)view.findViewById(R.id.comment_txt);
getActivity().getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);
session = new SessionManager(getActivity().getApplicationContext());
sharedPreference = getActivity().getSharedPreferences("CART",0);
editor = sharedPreference.edit();
((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("Cart");
btnCheckout = (Button)view.findViewById(R.id.btnCheckout);
cartEmptyTxt = (TextView)view.findViewById(R.id.emptytxt);
cartEmptyTxt.setVisibility(View.GONE);
if (!session.isLoggedIn()) {
cartEmptyTxt.setVisibility(View.VISIBLE);
btnCheckout.setVisibility(View.GONE);
cmntTxt.setVisibility(View.GONE);
}
btnCheckout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
FragmentManager fm = getFragmentManager();
fragmentTransaction = fm.beginTransaction();
AddressFragment addressFragment = new AddressFragment();
fragmentTransaction.replace(R.id.fragmentContainer,addressFragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit(); }
});
pageIndex = 0;
recyclerView = (RecyclerView)view.findViewById(R.id.cart_recycler_view);
linearLayoutManager=new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(linearLayoutManager);
SQLiteHandler sqLiteHandler = new SQLiteHandler(getActivity());
List<SessionModel> sessionModelList = sqLiteHandler.getUserDetails();
Bundle arguments = getArguments();
if (arguments != null) {
for (SessionModel sm : sessionModelList){
email1 = sm.getEmail();
}
if (frag == 6){
callCartService(email1,articlCode,cost,quantity);
}else if (email1!=null){
callGetCart(email1);
}
}
return view;
}
public void callCartService(String email,String artCode,String price,String qty){
showProgreass();
pageIndex = pageIndex + 1;
String url = String.format(ServerConfigStage.ADD_CART(),email,artCode,price,qty);
RetrofitTask task = new RetrofitTask<>(CartFragment.this, CommonUtility.HTTP_REQUEST_TYPE.POST, CommonUtility.CallerFunction.ADD_CART_FUNCTION, url,getActivity());
task.execute();
}
public void callGetCart(String email){
showProgreass();
pageIndex = pageIndex + 1;
String url = String.format(ServerConfigStage.GET_CART(),email);
RetrofitTask task = new RetrofitTask<>(CartFragment.this, CommonUtility.HTTP_REQUEST_TYPE.POST, CommonUtility.CallerFunction.GET_CART, url,getActivity());
task.execute();
}
public void delItemCart(String email,String itemId){
adapterShowCart = new AdapterShowCart(getContext(),CartFragment.this);
showProgreass();
String url = String.format(ServerConfigStage.DEL_ITEM_CART(),email,itemId);
RetrofitTask task = new RetrofitTask<>(CartFragment.this, CommonUtility.HTTP_REQUEST_TYPE.POST, CommonUtility.CallerFunction.DEL_ITEM_CART, url,getActivity());
task.execute();
}
public void showProgreass(){
progressDialog=new ProgressDialog(getActivity());
progressDialog.setIndeterminate(true);
progressDialog.setMessage("Please Wait...");
progressDialog.setCanceledOnTouchOutside(false);
progressDialog.setCancelable(false);
progressDialog.show();
}
public void stopProgress(){
if(progressDialog!=null && progressDialog.isShowing())
progressDialog.cancel();
}
@Override
public void onRetrofitTaskComplete(Response<AddCart> response, Context context, CommonUtility.CallerFunction _callerFunction) {
stopProgress();
if (response.isSuccess()) {
if (response.body() != null) {
addCartList =response.body();
if (_callerFunction == CommonUtility.CallerFunction.ADD_CART_FUNCTION){
if (addCartList.getStatus() == 0){
cartSize = addCartList.getDeatils().size();
editor.putInt("CART_ITEMS",cartSize);
editor.commit();
Toast.makeText(context, addCartList.getResponse(), Toast.LENGTH_SHORT).show();
if (adapter == null) {
adapter = new AdapterAddCart(context, R.layout.row_cart, addCartList);
recyclerView.setAdapter(adapter);
}
}else
if(addCartList.getStatus()>0) {
cartSize = addCartList.getDeatils().size();
editor.putInt("CART_ITEMS",cartSize);
editor.commit();
if (adapter == null) {
adapter = new AdapterAddCart(context, R.layout.row_cart, addCartList);
recyclerView.setAdapter(adapter);
}
adapter.notifyDataSetChanged();
}else {cartSize = addCartList.getDeatils().size();
editor.putInt("CART_ITEMS",cartSize);
editor.commit();
if (adapter == null) {
adapter = new AdapterAddCart(context, R.layout.row_cart, addCartList);
recyclerView.setAdapter( adapter );;
}
adapter.notifyDataSetChanged();
Toast.makeText(context, addCartList.getResponse(), Toast.LENGTH_SHORT).show();
}
}else if (_callerFunction == CommonUtility.CallerFunction.GET_CART){
if (addCartList.getStatus() == 0){
if (addCartList.getCart().size()>0){
cartSize = addCartList.getCart().size();
editor.putInt("CART_ITEMS",cartSize);
editor.commit();
}
}else
if(addCartList.getStatus()>0) {
if (addCartList.getCart().size()>0){
cartSize = addCartList.getCart().size();
editor.putInt("CART_ITEMS",cartSize);
editor.commit();}
if (adapterShowCart == null) {
adapterShowCart = new AdapterShowCart(context, R.layout.row_cart, addCartList);
recyclerView.setAdapter(adapterShowCart);
;
}
adapterShowCart.notifyDataSetChanged();
}else {
cartEmptyTxt.setVisibility(View.VISIBLE);
}
//Toast.makeText(context, addCartList.getResponse(), Toast.LENGTH_SHORT).show();
}else if (_callerFunction == CommonUtility.CallerFunction.DEL_ITEM_CART){
if (addCartList.getStatus()>0){
if (adapterShowCart == null) {
adapterShowCart = new AdapterShowCart(context, R.layout.row_cart, addCartList);
recyclerView.setAdapter(adapterShowCart);
}adapterShowCart.notifyDataSetChanged();
}
}
}
}
}
@Override
public void onRetrofitTaskFailure(Throwable t) {
stopProgress();
// Toast.makeText(getActivity(),"Fail to load Data",Toast.LENGTH_LONG).show();
if (getActivity()!= null)
{
getActivity().finish();
}
}
public void myFragmentMethod(){
// make sure to double check casts (to YourActivity) like these before invoking
((ProductDetailActivity)getActivity()).myOnResume();
}
}
栈跟踪
public class AdapterShowCart extends RecyclerView.Adapter<AdapterShowCart.ViewHolder>{
private AddCart addCartList;
private RemoveItemCommunication removeItemCommunication;
private CartFragment cartFragment = new CartFragment();
Context context;
private int layoutResourceId,cart;
private SharedPreferences sharedPreferences;
public AdapterShowCart(Context context, int layoutResourceId, AddCart addCarts) {
this.context = context;
this.layoutResourceId = layoutResourceId;
this.addCartList = addCarts;
}
public AdapterShowCart(Context context, CartFragment cartFragment) {
this.context = context;
this.cartFragment=cartFragment;
}
public void setOnClickListener(RemoveItemCommunication removeItemCommunication1){
removeItemCommunication = removeItemCommunication1;
}
@Override
public AdapterShowCart.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.row_cart, viewGroup, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(AdapterShowCart.ViewHolder viewHolder, int i) {
viewHolder.tv_android.setText("Price :"+" "+addCartList.getCart().get(i).getPrice());
viewHolder.tv_art_number.setText("Article No. :"+" "+addCartList.getCart().get(i).getItemCode());
viewHolder.tvQty.setText("Quantity :"+""+addCartList.getCart().get(i).getCartQuantity());
//viewHolder.img_android.setImageResource(products.get(i).getAndroid_image_url());
Picasso.with(context).load(addCartList.getCart().get(i).getURL()).resize(240, 120).into(viewHolder.img_android);
}
@Override
public int getItemCount() {
// cart = sharedPreferences.getInt("CART_ITEMS",0);
return addCartList.getCart().size();
}
class ViewHolder extends RecyclerView.ViewHolder{
private TextView tv_android,tv_art_number,tvQty;
private ImageView img_android,remove;
private int pos;
private CardView cardView;
public ViewHolder(View view) {
super(view);
tv_android = (TextView)view.findViewById(R.id.tvTitle);
tv_art_number=(TextView)view.findViewById(R.id.tvNumber);
cardView = (CardView)view.findViewById(R.id.card_view);
img_android = (ImageView) view.findViewById(R.id.mealImage);
tvQty=(TextView)view.findViewById(R.id.tvQty);
remove=(ImageView)view.findViewById(R.id.removeItem);
remove.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
int pos = getAdapterPosition();
cartFragment.delItemCart(addCartList.getEmail(),addCartList.getCart().get(pos).getId());
}
});
cardView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
pos = getAdapterPosition();
}
});
}
}
}
答案 0 :(得分：1)
getActivity返回null的原因是，您正在使用cart片段的实例，该实例已在适配器类中初始化，该类未附加到任何活动。 所以请将CartFragment的一个实例从CartFragment传递给适配器类以解决问题。在AdapterShowCart类中有一个构造函数，其中传递了cart片段实例，但它在片段中的delItemCart（String email，String itemId）中被调用（我不明白为什么这样做）。
答案 1 :(得分：0)
在AdapterShowCart第80行中，您正在触发一个操作，该操作尝试使用对不再存在的上下文的引用从资源中获取值。
据推测，ProductDetailActivity.this会导致问题。