嘗試從Firebase接收數據時獲取空對象引用

Question

我正在嘗試從Firebase讀取數據，但是它對我不起作用。 數據庫中已經有數據，但是當我使用getUserFName時，該值為null。 因此，第二個代碼來自注冊活動，該活動為要匹配的數據庫創建身份驗證和ID。 id包含類UserInformation的數據。 所以這就是為什么我想知道為什么注冊時有數據時為什么會得到一個空對象。

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

您從錯誤的位置閱讀。

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());
    }
}

此外，請確保您具有Firebase數據庫中的讀取權限，如https://firebase.google.com/docs/database/security/quickstart