Java 我无法从Firebase获取值，并将它们放入片段中的TextView

在我的应用程序中，我创建了登录和注册页面，并将用户名和电子邮件保存到我的Firebase数据库中。我还使用fragment进行了底部导航。我想从Firebase获取这些值（名称、邮件），并将其放入profile fragment中的TextView中。当我尝试这个时，我的应用程序崩溃了。我怎样才能解决这个问题

public class ProfileFragment extends Fragment {
    private FirebaseDatabase mFirebaseDatabase;
    private FirebaseAuth mAuth;
    private String userID;

    private TextView tName;
    private TextView tEmail;


    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View profileView = inflater.inflate(R.layout.fragment_profile, null);

        tName=profileView.findViewById(R.id.tv_name);
        tEmail=profileView.findViewById(R.id.tv_email);


        mAuth=FirebaseAuth.getInstance();
        mFirebaseDatabase=FirebaseDatabase.getInstance();
        final DatabaseReference myRef=mFirebaseDatabase.getReference("users");
        FirebaseUser user=mAuth.getCurrentUser();
        userID=user.getUid();

        myRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for(DataSnapshot ds: dataSnapshot.getChildren()){
                    User user=new User();
                    user.setUserName(ds.child(userID).getValue(User.class).getUserName());
                    user.setUserEmail(ds.child(userID).getValue(User.class).getUserEmail());

                    tName.setText(user.getUserName());
                    tEmail.setText(user.getUserEmail());
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {}
        });

        return profileView;
    }
}

---

在xml文件夹中创建文件

<?xml version="1.0" encoding="utf-8"?>
<defaultsMap>
    <entry>
       <key>email</key>
       <value>name</value>
</entry>

---

假设您的数据库结构与此类似：

Firebase-root
   |
   --- users
         |
         --- uid
              |
              --- name: "John"
              |
              --- email: "john@email.com"

要打印姓名和电子邮件，请使用模型类使用以下代码：

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference uidRef = rootRef.child("users").child(uid);
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        User user = dataSnapshot.getValue(User.class);
        String name = user.getUserName();
        tName.setText(name);
        String email = user.getUserEmail();
        tEmail.setText(email);
        Log.d("TAG", name + " / " + email);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
uidRef.addListenerForSingleValueEvent(valueEventListener);

如果要使用String类更简单地打印它们，请使用以下代码：

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = rootRef.child("users").child(uid);
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        String name = dataSnapshot.child("name").getValue(String.class);
        tName.setText(name);
        String email = dataSnapshot.child("email").getValue(String.class);
        tEmail.setText(email);
        Log.d("TAG", name + " / " + email);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
uidRef.addListenerForSingleValueEvent(valueEventListener);

---

在这两种情况下，输出都是：

John/john@email.com

我们需要查看您的数据库结构：）同时发布您的错误！ı没有足够的代表上载图像。我可以很容易地解释，在我的firebase数据库中，有用户引用，在用户引用中，有几个子名称用户id和子值名称emailFATAL EXCEPTION:main Process:com.example.burak.anonstezapp，PID:22212 java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“java.lang.String com.example.burak.anonstezapp.User.getUserName（）”。感谢您的帮助，您救了我：）

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = rootRef.child("users").child(uid);
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        String name = dataSnapshot.child("name").getValue(String.class);
        tName.setText(name);
        String email = dataSnapshot.child("email").getValue(String.class);
        tEmail.setText(email);
        Log.d("TAG", name + " / " + email);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
uidRef.addListenerForSingleValueEvent(valueEventListener);