为什么我无法从Firebase实时数据库检索用户名和密码

Question

我想使用Firebase实时数据库中存储的用户名和密码登录。但是我的代码不起作用。我包括我的数据库图片和代码。请帮助我。

这是数据库映像：

这是我的主要活动代码MainActivity.java

databaseReference=FirebaseDatabase.getInstance().getReference("Client");
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Query query = databaseReference.child("Client").orderByChild("username").equalTo(editTextUsername.getText().toString().trim());
            query.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {

                        for (DataSnapshot user : dataSnapshot.getChildren()) {
                            Users usersBean = user.getValue(Users.class);
                            if (usersBean.password.equals(editTextPassword.getText().toString().trim())) {
                                Toast.makeText(MainActivity.this, "success", Toast.LENGTH_SHORT).show();
                            } else {
                                Toast.makeText(MainActivity.this, "wrong", Toast.LENGTH_SHORT).show();
                            }
                        }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });
        }
    });

这是我的用户java类Users.java

    public class Users {
    String email;
    String id;
    String password;
    String username;

    public Users() {

    }

    public Users(String email, String id, String password, String username) {
        this.email = email;
        this.id = id;
        this.password = password;
        this.username = username;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }
}

Answer 1

要解决此问题，请更改以下代码行：

databaseReference=FirebaseDatabase.getInstance().getReference("Client");

到

databaseReference=FirebaseDatabase.getInstance().getReference();

由于您在查询中使用对Client的调用，因此无需获取.child("Client")节点的引用。

编辑：

要解决您根据注释获得的错误，请将id类中Users属性的类型从String更改为long，然后将获取方法更改为和这样的二传手：

public class Users {
    String email;
    long id;
    String password;
    String username;

    public Users() {

    }

    public Users(String email, long id, String password, String username) {
        this.email = email;
        this.id = id;
        this.password = password;
        this.username = username;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }
}