Firebase getCurrentUser在新的android活动中返回null [英] Firebase getCurrentUser is returning null in new android activity

问题描述

LoginActivity：

 私有FirebaseAuth firebaseAuth; 
私有FirebaseAuth.AuthStateListener mAuthListener; 
 
 @Override 
 protected void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.activity_login）; 
 
 firebaseAuth = FirebaseAuth.getInstance（）; 
 $ b mAuthListener = new FirebaseAuth.AuthStateListener（）{
 @Override $ b $ public void onAuthStateChanged（@NonNull FirebaseAuth firebaseAuth）{
 FirebaseUser user = firebaseAuth.getCurrentUser（）; 
 if（user！= null）{
 //用户登录
 Log.d（TAG，onAuthStateChanged：signed_in：+ user.getUid（））; 
 finish（）; 
 startActivity（new Intent（LoginActivity.this，MainActivity.class））; 
 
} else {
 //用户签出
 Log.d（TAG，onAuthStateChanged：signed_out）; 
} 
} 
}; 
 
 $ / code> 

MainActivity：



  public FirebaseAuth firebaseAuth; 
 
 @Override 
 protected void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.activity_main）; 
 
 
 firebaseAuth = FirebaseAuth.getInstance（）; 
 
 FirebaseUser firebaseUser = firebaseAuth.getCurrentUser（）; 
 
 
 if（firebaseUser == null）{
 // finish（）; 
 // startActivity（new Intent（MainActivity.this，LoginActivity.class））; 
} else {
 Log.d（TAG，用户不是NULLL。他的电子邮件是：+ firebaseUser.getEmail（））; 
 
 
 button.setOnClickListener（new OnClick（）{
 startActivity（new Intent（ActivityB.class））; 
}）; 
 
 $ / code> 

ActivityB：



 私人FirebaseAuth firebaseAuth; 
 
 protected void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.activity_add_friend）; 
 FirebaseUser user = FirebaseAuth.getInstance（）。getCurrentUser（）; 
 //这里用户总是为空
} 
  

好的，这正在发生：
我正在成功登录到应用程序，在 MainActivity.java 它打印的用户不是空的。但是当按下按钮时， ActivityB.java 正在启动，但用户和 FirebaseAuth 始终为空。 p>



我之前在 MainActivity.java 中添加了一个 authListener 我发现每当我从MainActivity开始一个新的活动时，监听器被触发，并且它的用户将是空的。



那么为什么当我启动一个Intent时，以及如何从不同的活动访问 firebaseAuth 和 currentUser ？


解决方案

今天我有同样的问题。经过你的问题后，我又检查了我的代码，发现我的错误。我在第一次活动结束时使用了signout（）。我删除后，我的代码工作正常。



我正在使用文档中给出的authStateListener。设置onCreate方法中的侦听器。函数getCurrentUser（）设置一个后台任务来获取当前用户，所以监听器是重要的。



onCreate（）

<$ （@NonNull FirebaseAuth firebaseAuth）{
FirebaseAser user = firebaseAuth.getCurrentUser（）{code> ）;
if（user！= null）{
//用户登录
String UserId = mCurrentUser.getUid（）;
mCurrentUser = user;
Toast.makeText（ListActivity.this，USER ID\\\
+ mUserId，Toast.LENGTH_SHORT）.show（）;

else {
Toast.makeText（ListActivity.this，no id got，Toast.LENGTH_SHORT）.show（）;
}

}
};


在onStart或onResume方法中，我调用getCurrentUser（）方法



onResume（）

  mCurrentUser = mAuth.getCurrentUser（）; 
  

在连线速度较慢的情况下

  mCurrentUser = user;在onCreate（）中的
  

会解决这个问题。
个人而言，我更喜欢在onStart（）中使用getcurrentuser方法，以便在应用程序运行在缓慢的Internet上时获取用户的一些时间。

我希望这能解决你的问题。
谢谢。

LoginActivity:

private FirebaseAuth firebaseAuth;
private FirebaseAuth.AuthStateListener mAuthListener;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    firebaseAuth = FirebaseAuth.getInstance();

    mAuthListener = new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
            FirebaseUser user = firebaseAuth.getCurrentUser();
            if (user != null) {
                // User is signed in
                Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
                finish();
                startActivity(new Intent(LoginActivity.this, MainActivity.class));

            } else {
                // User is signed out
                Log.d(TAG, "onAuthStateChanged:signed_out");
            }
        }
    };
}

MainActivity:

public  FirebaseAuth firebaseAuth;

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    firebaseAuth = FirebaseAuth.getInstance();

    FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();


    if (firebaseUser == null) {
        //finish();
        //startActivity(new Intent(MainActivity.this, LoginActivity.class));
    } else {
        Log.d(TAG, "THE USER IS NOT NULLL. his email is: " +      firebaseUser.getEmail());
   }

    button.setOnClickListener(new OnClick(){
         startActivity(new Intent(ActivityB.class));
    });
}

ActivityB:

private FirebaseAuth firebaseAuth;

 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_add_friend);
    FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    //Here the user is always null
  }

Okay so the scenario that is happening: I'm logging in successfully to the app, in MainActivity.java it's printing that the user is not null. But when I press the button, ActivityB.java is launching but the user and the FirebaseAuth is always null.

I previously added a authListener in MainActivity.java and I figured out that whenever I start a new activity from the MainActivity the listener is triggered and its user would be null.

So why is the listener triggered when I start an Intent, and how do I access the firebaseAuth and currentUser from different activities?

解决方案

I had this same problem today. After going through your problem i again checked my code and i found my mistake.I was using signout() at the end of my 1st activity. After i removed that my code is working fine.

I am using the authStateListener given in the documentation.Set the listener in onCreate method. Funtion getCurrentUser() sets an background task to fetch current user so the listener is important.

onCreate()

mAuthListener = new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
            FirebaseUser user = firebaseAuth.getCurrentUser();
            if (user != null) {
                // User is signed in
                String UserId = mCurrentUser.getUid();
                mCurrentUser = user;
                Toast.makeText(ListActivity.this, "USER ID\n"+mUserId,Toast.LENGTH_SHORT).show();
            }
            else {
                Toast.makeText(ListActivity.this, "no id got", Toast.LENGTH_SHORT).show();
            }

        }
    };

In onStart or onResume method i am calling the getCurrentUser() method

onResume()

 mCurrentUser = mAuth.getCurrentUser();

in case of slow connection

mCurrentUser = user;

in onCreate() will take care of the problem. Personally i prefer to use getcurrentuser method in onStart() so that it gets some time to fetch the user if the app is running on a slow internet.

I hope this solves your problem. Thank You.

这篇关于Firebase getCurrentUser在新的android活动中返回null的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！