java - 尝试从 firebase 接收数据时获取空对象引用

Question

我正在尝试从 Firebase 读取数据，但它对我不起作用。数据库中已经有数据，但当我使用 getUserFName 时，它​​说该值为空。所以第二个代码来自注册 Activity ，它创建一个身份验证和一个 ID，以便将数据库匹配在一起。 id 保存 UserInformation 类的数据。所以这就是为什么我想知道为什么当我注册时有数据时我得到一个空对象。

databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot ds : dataSnapshot.getChildren()) {
                    UserInformation userInformation = new UserInformation();
                    userInformation.setUserFName(ds.child(userID).getValue(UserInformation.class).getUserFName());
                    userInformation.setUserLName(ds.child(userID).getValue(UserInformation.class).getUserLName());
                    userInformation.setUserEmail(ds.child(userID).getValue(UserInformation.class).getUserEmail());
                    userInformation.setUserDescription(ds.child(userID).getValue(UserInformation.class).getUserDescription());

                    fName.setText(userInformation.getUserFName());
                    lName.setText(userInformation.getUserLName());
                    email.setText(userInformation.getUserEmail());
                    aboutYou.setText(userInformation.getUserDescription());
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
firebaseAuth.createUserWithEmailAndPassword(email.getText().toString().trim(), password.getText().toString().trim())
                                        .addOnCompleteListener(NewUserActivity.this, new OnCompleteListener<AuthResult>() {
                                            @Override
                                            public void onComplete(@NonNull Task<AuthResult> task) {
                                                if (task.isSuccessful()) {
                                                    Toast.makeText(NewUserActivity.this, "Account Created. Sign in!", Toast.LENGTH_SHORT).show();

                                                    String id = firebaseAuth.getCurrentUser().getUid();
                                                    UserInformation userInformation = new UserInformation(firstName.getText().toString(), lastName.getText().toString(), email.getText().toString(),
                                                            password.getText().toString());
                                                    databaseReference.child(id).setValue(userInformation);

                                                    Intent created = new Intent(NewUserActivity.this, LoginActivity.class);
                                                    startActivity(created);
                                                    finish();
                                                } else if (password.getText().toString().length() < 6){
                                                    Toast.makeText(NewUserActivity.this, "Password at least 6 characters", Toast.LENGTH_SHORT).show();
                                                    progressDialog.dismiss();
                                                } else{
                                                    Toast.makeText(NewUserActivity.this, "Email already exists", Toast.LENGTH_SHORT).show();
                                                    progressDialog.dismiss();
                                                }

                                            }
                                        });

Answer 1

您从错误的位置阅读。

databaseReference.child(userID).addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        UserInformation userInformation = dataSnapshot.getValue(UserInformation.class);
        fName.setText(userInformation.getUserFName());
        lName.setText(userInformation.getUserLName());
        email.setText(userInformation.getUserEmail());
        aboutYou.setText(userInformation.getUserDescription());
    }
}

另请确保您拥有 Firebase 数据库的读取权限，如 https://firebase.google.com/docs/database/security/quickstart 所示