回收站视图仅在我从房间数据库中删除后重新打开活动时更新

Posted 2023-05-07

【中文标题】回收站视图仅在我从房间数据库中删除后重新打开活动时更新

【英文标题】：Recycler view only updates when I reopen the Activity after deleting from Room Database

【发布时间】：2020-12-22 17:20:49

【问题描述】：

我有一个带有 Recycler 视图的片段，它显示了房间数据库中的内容。在我的适配器中，我有一个 ImageButton，单击该按钮会从列表中删除该项目。我可以确认该项目已从数据库中删除，但我的列表没有预期的行为。为了更新它，我必须再次打开活动。

回收站视图

public class WishlistFragment extends Fragment 
        private static WishlistAdapter mAdapter;
        private RecyclerView mRecyclerView;
        protected static List<String> wishlist;
        private Context context;
        protected static OnRestaurantClickedListener listener;
        private FirebaseAuth mAuth;

        public static WishlistAdapter getmAdapter() 
            return mAdapter;
        

        @Override
        public void onCreate(Bundle savedInstanceState) 
            super.onCreate(savedInstanceState);
            context = getContext();
            mAuth = FirebaseAuth.getInstance();
            wishlist = new ArrayList<>();
            mAdapter = new WishlistAdapter(context, wishlist,getActivity(),mAuth.getCurrentUser().getUid());
            LoadWishlistTask lwt=new LoadWishlistTask(getActivity(),wishlist,mAdapter,mAuth.getCurrentUser().getUid());
            lwt.execute();

        


        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
            View mContentView = inflater.inflate(R.layout.restaurants_list, container, false);
            mRecyclerView = mContentView.findViewById(R.id.recycler_view);
            mRecyclerView.setLayoutManager(new LinearLayoutManager(mContentView.getContext()));
            mRecyclerView.setAdapter(mAdapter);
            RecyclerView.ItemDecoration itemDecoration = new DividerItemDecoration(context, DividerItemDecoration.VERTICAL);
            mRecyclerView.addItemDecoration(itemDecoration);

            return mContentView;
        

        @Override
        public void onResume() 
            super.onResume();
        

        @Override
        public void onAttach(Activity activity) 
            super.onAttach(activity);
            try 
                listener = (OnRestaurantClickedListener) activity;
             catch (ClassCastException e) 
                throw new ClassCastException(activity.toString() + " must implement OnRestaurantClickedClicked");
            
        

适配器

public class WishlistAdapter extends RecyclerView.Adapter<WishlistAdapter.WishlistViewHolder> 
    private Context mContext;
    private List<String> mRestaurantIds;
    private Activity act;
    private String currentUserId;

    public WishlistAdapter(Context context, List<String> ids,Activity activity,String currentUser) 
        mRestaurantIds=ids;
        mContext = context;
        act=activity;
        currentUserId=currentUser;

    

    @Override
    public WishlistViewHolder onCreateViewHolder(ViewGroup parent, int viewType) 
        // Get layout inflater from context
        Context context = parent.getContext();
        LayoutInflater inflater = LayoutInflater.from(context);

        // Inflate layout
        View rView = inflater.inflate(R.layout.item_restaurant, parent, false);

        // Return a new holder instance
        return new WishlistViewHolder(rView);
    

    @Override
    public void onBindViewHolder(final WishlistViewHolder viewHolder, final int position) 
        // Get the data model based on position
        final String id = mRestaurantIds.get(position);

        getApi().getRestaurantDetails(Integer.parseInt(id), "75be9f9e2239fe637bf9cb1b46979d91")
                .enqueue(new Callback<Restaurant_>() 
                    @Override
                    public void onResponse(Call<Restaurant_> call, Response<Restaurant_> response) 
                        final TextView name=viewHolder.nameTextView;
                        name.setText(response.body().getName());
                        final TextView rating=viewHolder.ratingTextView;
                        rating.setText(response.body().getUserRating().getAggregateRating());
                        final ImageButton remove=viewHolder.removeButton;
                        remove.setOnClickListener(new View.OnClickListener() 
                            @Override
                            public void onClick(View view) 
                                Wishlist deletedRestaurant=new Wishlist(currentUserId,id);
                                RemoveWLTask rt=new RemoveWLTask(deletedRestaurant,act,WishlistFragment.wishlist);
                                rt.execute();
                            
                        );

                        viewHolder.itemView.setOnClickListener(new View.OnClickListener() 
                            @Override
                            public void onClick(View v) 
                                WishlistFragment.listener.onRestaurantClicked(id);
                            
                        );

                    

                    @Override
                    public void onFailure(Call<Restaurant_> call, Throwable t) 
                        AlertDialog.Builder builder = new AlertDialog.Builder(act);
                        builder.setMessage("Couldn´t load restaurant details");
                        AlertDialog mDialog = builder.create();
                        mDialog.show();
                    
                );

    
    @Override
    public int getItemCount() 
        return mRestaurantIds.size();
    

    private Retrofit getRetrofit() 
        return new Retrofit.Builder()
                .baseUrl("https://developers.zomato.com/api/v2.1/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();
    

    private ZomatoApi getApi() 
        return getRetrofit().create(ZomatoApi.class);
    


    public class WishlistViewHolder extends RecyclerView.ViewHolder 
        public TextView nameTextView;
        public TextView ratingTextView;
        public TextView distanceTextView;
        public ImageButton removeButton;

        public WishlistViewHolder(View itemView) 
            super(itemView);
            nameTextView = itemView.findViewById(R.id.restaurantName);
            ratingTextView=itemView.findViewById(R.id.restaurantRating);
            distanceTextView=itemView.findViewById(R.id.restaurantDistance);
            removeButton=itemView.findViewById(R.id.wishlistButton);


        

    

删除任务

public class RemoveWLTask extends AsyncTask<Void,Void,Void> 
    private Wishlist deletedRestaurant;
    private DB db;
    private Activity activity;
    private List<String> wishlist;

    public  RemoveWLTask (Wishlist deletedRestaurant, Activity activity,List<String> wishlist) 
        this.deletedRestaurant=deletedRestaurant;
        this.activity=activity;
        this.db= Room.databaseBuilder(activity.getApplicationContext(), DB.class, "sample-db").build();
        this.wishlist=wishlist;

    

    @Override
    protected Void doInBackground(Void... voids) 
        while (!isCancelled())
            db.daoAcess().deleteFromWishlist(deletedRestaurant);
            break;
        
        return null;
    

    @Override
    protected void onPostExecute (Void aVoid) 

        int index = wishlist.indexOf(deletedRestaurant);
        wishlist.remove(deletedRestaurant);
        WishlistFragment.getmAdapter().notifyItemRemoved(index);
        WishlistFragment.getmAdapter().notifyItemRangeChanged(index, wishlist.size());

    

【问题讨论】：

点击您的删除按钮，您会从 Room DB 中删除项目，但不会从适配器中删除项目，也不会通知数据集更改。您必须这样做，否则您的 recyclerview 将不会显示任何更新的数据，迫使您重新加载视图（从房间 db 获取所有新数据再次丢失已删除的项目）

其实问题出在论据上

【参考方案1】：

发现错误，我需要将 deletedRestaurant.getRestaurantId() 作为参数而不是 deletedRestaurant 传递