Question

我无法弄清楚为什么我的userId字符串会回来null。请帮忙。

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //get firebase auth instance
    auth = FirebaseAuth.getInstance();
    mDatabaseReference = FirebaseDatabase.getInstance().getReference();
    Intent intent = getIntent();
    carName = intent.getStringExtra("carname");

    //get current user
    if (auth.getCurrentUser().getUid() != null) {
        userId = auth.getCurrentUser().getUid();
    }
    authStateListener = new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
            FirebaseUser user = firebaseAuth.getCurrentUser();
            if (user != null) {
                Log.d(TAG, "AUTH STATE SIGNED IN");
                userId = user.getUid();
                getCarName();
                mDatabaseReference.child("cars").setValue(userId);
            } else {
                //User is Signed out
                Log.d(TAG, "AUTH STATE SIGNED OUT");
                startActivity(new Intent(MainActivity.this, LoginActivity.class));
            }
        }
    };
    auth.addAuthStateListener(authStateListener);

    //set views
    setContentView(R.layout.activity_main);
    final TextView carNameTV = (TextView) findViewById(R.id.car_name);
    final TextView carAddressTV = (TextView) findViewById(R.id.car_notes);
    final TextView carCountTV = (TextView) findViewById(R.id.count);
    plusOneButton = (Button) findViewById(R.id.buttonIn);
    minusOneButton = (Button) findViewById(R.id.buttonOut);
    signOut = (Button) findViewById(R.id.sign_out_button);
    editCar = (Button) findViewById(R.id.edit_car_button);



    mDatabaseReference = FirebaseDatabase.getInstance().getReference().child("cars").child(userId);

我能够通过在侦听器之前添加此if语句来绕过它。我宁愿不让它看起来那样。任何帮助表示赞赏。

Answer 1

onAuthStateChanged()回调是异步的。在用户登录之前，不会使用有效的用户ID触发。

声明：

 mDatabaseReference = FirebaseDatabase.getInstance().getReference().child("cars").child(userId);

在侦听器回调中为userId分配值之前执行。

即使在if语句中，用户也会返回null

1 个答案: