java - Android 聊天在 DataSnapshot.getValue() 上崩溃

Question

这是我的第一个 Firebase 应用，我正在尝试检索聊天消息列表。循环停止，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

错误在这里

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

1. 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);
   
           }
   
       }
   

2. 聊天类

   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;
   }
   }
   

3. 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 Activity

导入 de.hdodenhof.circleimageview.CircleImageView;

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) {

            }
        });
    }
}

Answer 1

好消息，这很容易解决。

问题是您没有正确推送下图中的聊天数据。您只有 1 条聊天消息，而不是包含多个聊天的路径。

解决方案

你的数据库应该是这样的

突出显示的黄色键称为 push ids or push keys .

您很可能会像这样保存聊天数据:

FirebaseDatabase.getInstance().getReference().child("Chats").setValue(chatMessage);

您可以通过在 setValue 调用之前添加 push() 来实现您想要的目的。

FirebaseDatabase.getInstance().getReference().child("Chats").push().setValue(chatMessage);