java Android聊天在DataSnapshot上崩溃。getValue（）

1 月，2 周 Questions & Answers 387

这是我的第一个Firebase应用程序，我正在尝试检索聊天信息列表。循环停止了，我不知道为什么以及如何修复它

错误：

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.venomapps.amchat.Model.Chat

错误就在这里

Chat chat = snapshot.getValue(Chat.class);

误差函数

    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        mchat.clear();
        for (DataSnapshot snapshot : dataSnapshot.getChildren()){
            Chat chat = snapshot.getValue(Chat.class);
            if(chat.getReceiver().equals(myid) && chat.getSender().equals(userid) ||
                    chat.getReceiver().equals(userid) && chat.getSender().equals(myid)){
                mchat.add(chat);
            }

            messageAdapter = new MessageAdapter(MessageActivity.this, mchat, imageurl);
            recyclerView.setAdapter(messageAdapter);

        }

    }

聊天课

public class Chat {

private String sender;
private String receiver;
private String message;

public Chat(String sender, String receiver, String message) {
    this.sender = sender;
    this.receiver = receiver;
    this.message = message;
}

public Chat() {

}

public String getSender() {
    return sender;
}

public void setSender(String sender) {
    this.sender = sender;
}

public String getReceiver() {
    return receiver;
}

public void setReceiver(String receiver) {
    this.receiver = receiver;
}

public String getMessage() {
    return message;
}

public void setMessage(String message) {
    this.message = message;
}
}

适配器

public class MessageAdapter extends RecyclerView.Adapter<MessageAdapter.ViewHolder> {

public static final int MSG_TYPE_LEFT = 0;
public static final int MSG_TYPE_RIGHT = 1;

private Context mContext;
private List<Chat> mChat;
private String imageurl;

FirebaseUser fuser;

public MessageAdapter(Context mContext, List<Chat> mChat, String imageurl){
    this.mChat = mChat;
    this.mContext = mContext;
    this.imageurl = imageurl;
}

@NonNull
@Override
public MessageAdapter.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    if (viewType == MSG_TYPE_RIGHT) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.chat_item_right, parent, false);
        return new MessageAdapter.ViewHolder(view);
    } else {
        View view = LayoutInflater.from(mContext).inflate(R.layout.chat_item_left, parent, false);
        return new MessageAdapter.ViewHolder(view);
    }
}

@Override
public void onBindViewHolder(@NonNull MessageAdapter.ViewHolder holder, int position) {

    Chat chat = mChat.get(position);

    holder.show_message.setText(chat.getMessage());

    if(imageurl.equals("default")){
        holder.profile_image.setImageResource(R.mipmap.ic_launcher);
    } else {
        Glide.with(mContext).load(imageurl).into(holder.profile_image);
    }

}

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

public class ViewHolder extends RecyclerView.ViewHolder{

    public TextView show_message;
    public ImageView profile_image;

    public ViewHolder(View itemView){
        super(itemView);

        show_message = itemView.findViewById(R.id.show_message);
        profile_image = itemView.findViewById(R.id.profile_image);
    }
}

@Override
public int getItemViewType(int position) {
    fuser = FirebaseAuth.getInstance().getCurrentUser();
    if(mChat.get(position).getSender().equals(fuser.getUid())){
        return MSG_TYPE_RIGHT;
    } else {
        return MSG_TYPE_LEFT;
    }
}
}

编辑：因为我无法确定问题出在哪里

Structure Image

整个消息活动

导入de.hdodenhof。圆形图像视图。圆形图像视图

public class MessageActivity extends AppCompatActivity {

    CircleImageView profile_image;
    TextView username;

    FirebaseUser fuser;
    DatabaseReference reference;

    ImageButton btn_send;
    EditText text_send;

    MessageAdapter messageAdapter;
    List<Chat> mchat;

    RecyclerView recyclerView;

    Intent intent;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_message);


        // Toolbar
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle("");
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        toolbar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });


        // Recycler View
        recyclerView = findViewById(R.id.recycler_view);
        recyclerView.setHasFixedSize(true);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getApplicationContext());
        linearLayoutManager.setStackFromEnd(true);
        recyclerView.setLayoutManager(linearLayoutManager);



        profile_image = findViewById(R.id.profile_image);
        username = findViewById(R.id.username);
        btn_send = findViewById(R.id.btn_send);
        text_send = findViewById(R.id.text_send);

        intent = getIntent();
        final String userid = intent.getStringExtra("userid");
        fuser = FirebaseAuth.getInstance().getCurrentUser();



        btn_send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String msg = text_send.getText().toString();
                if(!msg.equals("")){
                    sendMessage(fuser.getUid(), userid, msg);
                } else {
                    Toast.makeText(MessageActivity.this, "You can't send empty message", Toast.LENGTH_SHORT).show();
                }
                text_send.setText("");
            }
        });


        reference = FirebaseDatabase.getInstance().getReference("Users").child(userid);

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                User user = dataSnapshot.getValue(User.class);
                username.setText(user.getUsername());
                if(user.getImageURL().equals("default")){
                    profile_image.setImageResource(R.mipmap.ic_launcher);
                } else {
                    Glide.with(MessageActivity.this).load(user.getImageURL()).into(profile_image);
                }

                readMessage(fuser.getUid(), userid, user.getImageURL());
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }

    private void sendMessage(String sender, String receiver, String message){

        DatabaseReference reference = FirebaseDatabase.getInstance().getReference();

        HashMap<String, Object> hashMap = new HashMap<>();
        hashMap.put("sender", sender);
        hashMap.put("receiver", receiver);
        hashMap.put("message", message);

        reference.child("Chats").push().setValue(hashMap);
    }

    private void readMessage(final String myid, final String userid, final String imageurl){
        mchat = new ArrayList<>();

        reference = FirebaseDatabase.getInstance().getReference("Chats");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            /*public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                mchat.clear();
                for (DataSnapshot snapshot : dataSnapshot.getChildren()){
                    Chat chat = snapshot.getValue(Chat.class);
                    if(chat.getReceiver().equals(myid) && chat.getSender().equals(userid) ||
                        chat.getReceiver().equals(userid) && chat.getSender().equals(myid)){
                            mchat.add(chat);
                    }

                    messageAdapter = new MessageAdapter(MessageActivity.this, mchat, imageurl);
                    recyclerView.setAdapter(messageAdapter);

                }

            } */




            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                mchat.clear();
                for (DataSnapshot snapshot : dataSnapshot.getChildren()){
                    Chat chat = snapshot.getValue(Chat.class);
                    if(chat.getReceiver().equals(myid) && chat.getSender().equals(userid) ||
                            chat.getReceiver().equals(userid) && chat.getSender().equals(myid)){
                        mchat.add(chat);
                    }

                    messageAdapter = new MessageAdapter(MessageActivity.this, mchat, imageurl);
                    recyclerView.setAdapter(messageAdapter);

                }

            }








            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }
}

共 (1) 个答案

# 1 楼答案
好消息，这很容易解决

问题是您没有正确地推送下图中的聊天数据。你只需要一条聊天信息，而不是有几个聊天的路径

解决方案

您的数据库应该如下所示

突出显示的黄色键称为push ids or push keys

您很可能正在保存聊天数据，如下所示：
```
FirebaseDatabase.getInstance().getReference().child("Chats").setValue(chatMessage);
```
您可以通过在setValue调用之前添加push()来完成所需的操作
```
FirebaseDatabase.getInstance().getReference().child("Chats").push().setValue(chatMessage);
```

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java Android聊天在DataSnapshot上崩溃。getValue（）

共 (1) 个答案

# 1 楼答案

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