DataSnapshot 无法转换为适配器 [关闭]

Posted 2023-05-07

【中文标题】DataSnapshot 无法转换为适配器 [关闭]

【英文标题】：DataSnapshot cannot be cast to Adapter [closed]

【发布时间】：2021-12-05 11:28:58

【问题描述】：

我有一个问题，我正在为 RecyclerView 创建一个适配器，为了创建它，我使用 FirebaseRecyclerAdapter 扩展了这个类，但是我得到一个错误，我不知道如何解决它，也许有人可以告诉我一些事情.我在网上找到了一个类似的例子，可以通过这种方式扩展一个类，但是要么我做错了，要么不再可以以这种方式扩展类。非常感谢您的帮助

这是我的适配器：

public class PostAdapterTest extends FirebaseRecyclerAdapter <Posts, PostAdapterTest.postsViewHolder>  //error the error is here
    private BottomSheetDialog bottomSheetDialog;
    private Context mContext;
    private Boolean downloadOrOpen = false;
    private boolean buttonStatus = true;
    private DatabaseReference likesRef = FirebaseDatabase.getInstance().getReference("Likes");
    private FirebaseUser mFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();

    private String difficulty = null;

    private int likesCounter;
    private ReadWritePermissions mReadWritePermissions;

    public PostAdapterTest(@NonNull FirebaseRecyclerOptions<Posts> postsFirebaseRecyclerOptions,  ReadWritePermissions mReadWritePermissions, Context mContext)
    
        super(postsFirebaseRecyclerOptions);
        this.mContext = mContext;
        this.mReadWritePermissions = mReadWritePermissions;
    

    @Override
    protected void onBindViewHolder(@NonNull PostAdapterTest.postsViewHolder holder, int position, @NonNull Posts model) 
        final String postKey = getRef(position).getKey();
        String postUid = model.getPostId();

        holder.nickname.setText(model.getNickname());
        holder.country.setText(model.getCountry());
        holder.title.setText(model.getCountry());
        holder.days.setText(model.getDays());
        holder.kilometers.setText(model.getKilometers());
        holder.description.setText(model.getDescription());

        difficulty = model.getDifficulty();

        holder.map.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 
                Uri mapUri = Uri.parse(model.getMap());
                mapOptions(mapUri);
            
        );

        holder.comments.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 
                CommentsFragment commentsFragment = new CommentsFragment();
                Bundle args = new Bundle();
                args.putString("postId", postUid);

                commentsFragment.setArguments(args);

                FragmentTransaction fragmentTransaction = ((FragmentActivity)mContext).getSupportFragmentManager().beginTransaction();
                fragmentTransaction.replace(R.id.frame_container, commentsFragment);
                fragmentTransaction.addToBackStack(null);
                fragmentTransaction.commit();

            
        );

        holder.setLikeButtonStatus(postKey);

        holder.likes.setOnClickListener(new View.OnClickListener() 
            @Override
            public void onClick(View v) 
                buttonStatus = true;

                likesRef.addValueEventListener(new ValueEventListener() 
                    @Override
                    public void onDataChange(@NonNull DataSnapshot snapshot) 
                        if(buttonStatus == true)
                        
                            if(snapshot.child(postKey).hasChild(mFirebaseUser.getUid()))
                            
                                likesRef.child(postKey).child(mFirebaseUser.getUid()).removeValue();
                                buttonStatus = false;
                            else
                            
                                likesRef.child(postKey).child(mFirebaseUser.getUid()).setValue(true);
                                buttonStatus = false;
                            
                        
                    

                    @Override
                    public void onCancelled(@NonNull DatabaseError error) 

                    
                );

                switch (difficulty)
                
                    case "Easy":
                        holder.difficulty.setImageResource(R.drawable.ic_easy);
                        break;

                    case "Difficult":
                        holder.difficulty.setImageResource(R.drawable.ic_difficult);
                        break;

                    case "Hard":
                        holder.difficulty.setImageResource(R.drawable.ic_hard);
                        break;
                

                ArrayList<Slider> sliderArrayList = new ArrayList<>();

                Picasso.get().load(model.getAvatarUri()).into(holder.avatarUri);
            
        );
    

    @NonNull
    @Override
    public PostAdapterTest.postsViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) 
        View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.posts, parent, false);
        return new PostAdapterTest.postsViewHolder(view);
    

    class postsViewHolder extends RecyclerView.ViewHolder
    
        public CircleImageView avatarUri;
        public TextView nickname, country, title, days, likesNum, kilometers,description, fileSize, fileName;
        public SliderView mSliderView;
        public ImageView comments, save, difficulty;
        public ImageButton likes;
        public ImageButton more;
        public LinearLayout map;

        public postsViewHolder(@NonNull View itemView) 
            super(itemView);

            avatarUri = itemView.findViewById(R.id.posts_profile_picture);
            nickname = itemView.findViewById(R.id.posts_nickname);
            country = itemView.findViewById(R.id.posts_country);
            title = itemView.findViewById(R.id.posts_title);
            days = itemView.findViewById(R.id.posts_days);
            difficulty = itemView.findViewById(R.id.posts_difficulty);
            mSliderView = itemView.findViewById(R.id.posts_images);
            likes = itemView.findViewById(R.id.posts_likes);
            comments = itemView.findViewById(R.id.posts_comments);
            save = itemView.findViewById(R.id.posts_save);
            likesNum = itemView.findViewById(R.id.posts_likes_number);
            description = itemView.findViewById(R.id.posts_description);
            more = itemView.findViewById(R.id.posts_more);
            kilometers = itemView.findViewById(R.id.posts_distance);
            fileSize = itemView.findViewById(R.id.posts_uploaded_file_size);
            fileName = itemView.findViewById(R.id.posts_uploaded_file_name);
            map = itemView.findViewById(R.id.posts_map_layout);
        

        public void setLikeButtonStatus(final String key)
        
            mFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();

            likesRef.addValueEventListener(new ValueEventListener() 
                @Override
                public void onDataChange(@NonNull DataSnapshot snapshot) 
                    likesCounter = (int)snapshot.child(key).getChildrenCount();
                    if(snapshot.child(key).hasChild(mFirebaseUser.getUid()))
                    
                        likes.setImageResource(R.drawable.ic_liked_red);
                        likesNum.setText(likesCounter + " Likes");
                    else if(likesCounter == 0)
                    
                        likes.setImageResource(R.drawable.ic_unliked_red);
                        likesNum.setText("");
                    else
                    
                        likes.setImageResource(R.drawable.ic_unliked_red);
                        likesNum.setText(likesCounter + " Likes");
                    
                

                @Override
                public void onCancelled(@NonNull DatabaseError error) 

                
            );
        
    

    private void mapOptions(Uri mapUri)
    
       
    

Logcat：

Process: com.company.android.myapplication, PID: 8349
    java.lang.ClassCastException: com.google.firebase.database.DataSnapshot cannot be cast to com.company.android.myapplication.Posts
        at com.company.android.myapplication.test.PostAdapterTest.onBindViewHolder(PostAdapterTest.java:44)
        at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:149)
        at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:7254)
        at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:7337)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:6194)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6460)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6300)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6296)
        at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2330)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1631)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1591)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:668)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4309)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:4012)
        at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4578)

【问题讨论】：

您在哪一行代码中遇到了这个错误？

@AlexMamo 适配器类的第一行我在那里写了评论

您的标题与堆栈跟踪不匹配

【参考方案1】：

java.lang.ClassCastException：com.google.firebase.database.DataSnapshot 无法转换为 com.company.android.myapplication.Posts

您不能将DataSnapshot 转换为您自己的pojo Posts，您必须从DataSnapshot 获取value。此外，请确保 DataSnapshot 架构和您的 pojo Posts 架构正确匹配，以将 DataSnapshot 值解析为 Posts。

另外，直接从适配器进行查询或调用活动或进行 Firebase 事务是非常糟糕的方法。您应该将回调传递给适配器并处理片段/活动的逻辑。

【讨论】：

你能给我举个例子吗？

帖子 post = (Posts) postSnapshot.child("posts").getValue();

同样的问题是我无法完成类或活动中的所有逻辑，因为我有几个活动需要填充 RecyclerView，因此我得到了重复的代码

那么您应该找到更好的方法来满足您的要求。