com.google.firebase.database.DatabaseException：

Question

com.google.firebase.database.DatabaseException：无法将 java.lang.String 类型的对象转换为类型...

还有一个错误没有连接适配器；跳过布局 - 但似乎不是严重错误 ///// 请帮助，我是编程新手，这个项目对我来说非常重要。/////

我的消息活动

public class MessageActivity extends AppCompatActivity {

CircleImageView ivProfileImage;

TextView tvUsername;

ImageButton btnSend;

EditText text_send;

MessageAdapter messageAdapter;

List<Chat> mChat;

FirebaseUser firebaseUser;

DatabaseReference databaseReference;

RecyclerView recycler_view;

Intent intent;

@Override

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_message);

    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 = findViewById(R.id.recycler_view);

    recycler_view.setHasFixedSize(true);

    LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getApplicationContext());

    linearLayoutManager.setStackFromEnd(true);

    recycler_view.setLayoutManager(linearLayoutManager);

    ivProfileImage = findViewById(R.id.ivProfileImage);

    tvUsername = findViewById(R.id.tvUsername);

    btnSend = findViewById(R.id.btnSend);

    text_send = findViewById(R.id.text_send);

    intent = getIntent();

    final String userid = intent.getStringExtra("userid");

    firebaseUser = FirebaseAuth.getInstance().getCurrentUser();

    });

Answer 1

使用以下代码行时：databaseReference.child("Chats").push().setValue(hashMap);DatabaseReference 的push()方法：创建对自动生成的子位置的引用。这基本上意味着，您正在使用节点Chat下的自动生成键创建一个新对象Chats，在您的架构中应该如下所示：Firebase-root&nbsp; |&nbsp; --- Chats&nbsp; &nbsp; &nbsp; &nbsp;|&nbsp; &nbsp; &nbsp; &nbsp;--- pushedId&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;--- message: "fggfg"&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;--- receiver: "0AQZ ... FK02"&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;|&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;--- sender: "CqjS ... QqE3"但不幸的是，这不是您的数据库中的样子。看，在Chats节点下，没有推送的id，你的属性直接存在于Chats节点下。要解决这个问题，请删除节点下存在的那些属性并使用以下代码行Chats添加对象：ChatChat chat = new Chat(sender, receiver, message);DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();DatabaseReference chatsRef = rootRef.child("Chats");String key = chatsRef.child("Chats").push().getKey();chatsRef.child(key).setValue(chat);你的问题将得到解决。

Answer 2

您正在尝试将字符串文本转换为聊天类型。用这个 -&nbsp;String chat = snapshot.getValue(String.class);代替&nbsp;Chat chat = snapshot.getValue(Chat.class);