收到错误 com.google.firebase.database.DatabaseException：无法将 java.util.HashMap 类型的值转换为字符串

Question

我正在尝试检索用户保存的数据并使用回收站视图将其显示在他们的个人资料页面中。当我运行我的应用程序以查看是否一切正常但我的应用程序不断崩溃并停止工作时。我得到的错误是com.google.firebase.database.DatabaseException: Failed to convert value of type java.util.HashMap to String。我以前有这个工作，但我不确定现在是什么问题。谁能帮我解决这个问题。提前致谢。 Updated database

图像适配器

public class ImageAdapter extends RecyclerView.Adapter<ImageAdapter.ImageViewHolder>{

    private Context mContext;
    private ArrayList<UserInformation> users;

    public ImageAdapter(Context context, ArrayList<UserInformation> uploads){
        mContext = context;
        users = uploads;

    }

    @NonNull
    @Override
    public ImageViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View V = LayoutInflater.from(mContext).inflate(R.layout.cardview, parent, false);
        return new ImageViewHolder(V);


    }

    @Override
    public void onBindViewHolder(@NonNull ImageViewHolder holder, int position) {
        //String uploadCurrent=users.get(position).getmImageUrl();

        holder.txt1.setText(users.get(position).getAction());
        Picasso.get().load(users.get(position).getmImageUrl()).fit().centerCrop().into(holder.imageView);

    }

    @Override
    public int getItemCount() {
        return users.size();

    }

    public class ImageViewHolder extends RecyclerView.ViewHolder{
        public ImageView imageView;
        public TextView txt1;

        public ImageViewHolder(@NonNull View itemView) {
            super(itemView);

            imageView=itemView.findViewById(R.id.imageview);
            //txt1=itemView.findViewById(R.id.action);
        }
    }
}

模型类

  public UserInformation(String  mImageUrl,  String cate, String action, String headline, String websiteurl) {

        this.mImageUrl =  mImageUrl;
        this.cate = cate;
        this.action = action;
        this.headline = headline;
        this.websiteurl = websiteurl;

    }

    public UserInformation() {

    }

    public String getmImageUrl() {
        return mImageUrl;
    }

    public void setmImageUrl(String mImageUrl) {
        this.mImageUrl = mImageUrl;
    }


    public String getCategory() {
        return cate;
    }

    public void setCategory(String category) {
        this.cate = cate;
    }

    public String getAction() {
        return action;
    }

    public void setAction(String action) {
        this.action = action;
    }

    public String getHeadline() {
        return headline;
    }

    public void setHeadline(String header) {
        this.headline = headline;
    }

    public String getWebsiteurl() {
        return websiteurl;
    }

    public void setWebsiteurl(String websiteurl) {
        this.websiteurl = websiteurl;
    }
}

主类

recyclerView = findViewById(R.id.recyclerView);
RecyclerView.LayoutManager layoutManager = new GridLayoutManager(getApplicationContext(),3);

recyclerView.setLayoutManager(layoutManager);
myUploads = new ArrayList<UserInformation>();
aAdapter = new ImageAdapter(ProfileActivity.this, myUploads);
recyclerView.setAdapter(aAdapter);
aAdapter.notifyDataSetChanged();

h=new Handler();

databaseReference = FirebaseDatabase.getInstance().getReference("Users");
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

firebaseStorage = FirebaseStorage.getInstance();
storageReference = firebaseStorage.getReference();

firebaseUser = firebaseAuth.getInstance().getCurrentUser();
t=findViewById(R.id.none);

    databaseReference.child(uid).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

            for (DataSnapshot postsnapshot : dataSnapshot.getChildren()) {

                UserInformation upload=postsnapshot.getValue(UserInformation.class);


                myUploads.add(upload);
                 aAdapter = new ImageAdapter(ProfileActivity.this, myUploads);
                 recyclerView.setAdapter(aAdapter);

            }

Answer 1

据我所知，您的阅读代码归结为：

databaseReference = FirebaseDatabase.getInstance().getReference("Users");
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

databaseReference.child(uid).addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

        for (DataSnapshot postsnapshot : dataSnapshot.getChildren()) {

            UserInformation upload=postsnapshot.getValue(UserInformation.class);


            myUploads.add(upload);
             aAdapter = new ImageAdapter(ProfileActivity.this, myUploads);
             recyclerView.setAdapter(aAdapter);

        }

这意味着您将一个侦听器附加到数据库中的/Users/$uid，并且您的onDataChange 将使用单个用户的数据快照进行调用。

在这种情况下，您不需要在 onDataChange 中循环遍历 snapshot.getChildren()，因为您已经将侦听器作为目标来读取精确路径上的单个快照。所以：

databaseReference = FirebaseDatabase.getInstance().getReference("Users");
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

databaseReference.child(uid).addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

        UserInformation upload = dataSnapshot.getValue(UserInformation.class);

        myUploads.add(upload);
        aAdapter = new ImageAdapter(ProfileActivity.this, myUploads);
        recyclerView.setAdapter(aAdapter);
    }