我无法从Firebase中获取值并将它们以片段形式放入TextView中

Question

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。我还用碎片做了底部导航。我想从Firebase中获取这些值(name，mail)，并将其放到profile片段中的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;
    }
}

Answer 1

假设您的数据库结构类似于以下内容：

Firebase-root
   |
   --- users
         |
         --- uid
              |
              --- name: "John"
              |
              --- email: "[e-mail]"

要打印姓名和电子邮件，请使用以下代码使用模型类：

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);

如果您想使用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/[e-mail]