如何在android中实现管理员和用户的自动登录？我的代码已经崩溃了

Question

如何实现管理员和用户的多重自动登录？有两种类型的帐户，首先是买方帐户(Dashboard1)和卖方帐户(仪表板)

登录和关闭后，应用程序将引用仪表板活动。应该做出什么改变，使其指向特定的活动。

val currentUserID1 = FirestoreClass().getCurrentUserID1()
val currentUserID = FirestoreClass().getCurrentUserID()

                if (currentUserID1.isNotEmpty()) {
                    // Launch dashboard screen.
                    startActivity(Intent(this@Splash1Activity, Dashboard1Activity::class.java))
                } else if (currentUserID.isNotEmpty()&&currentUserID1.isEmpty()) {
                    // Launch dashboard screen.
                    startActivity(Intent(this@Splash1Activity, DashboardActivity::class.java))
                }else {
                    // Launch the Login Activity
                    startActivity(Intent(this@Splash1Activity, Login1Activity::class.java))
                }
                finish() // Call this when your activity is done and should be closed.

    /**
     * A function to get the user id of current logged user.
     */
    fun getCurrentUserID(): String {
        // An Instance of currentUser using FirebaseAuth
        val currentUser = FirebaseAuth.getInstance().currentUser

        // A variable to assign the currentUserId if it is not null or else it will be blank.
        var currentUserID = ""
        if (currentUser != null) {
            currentUserID = currentUser.uid
        }

        return currentUserID
    }


    fun getCurrentUserID1(): String {
        // An Instance of currentUser using FirebaseAuth
        val currentUser = FirebaseAuth.getInstance().currentUser

        // A variable to assign the currentUserId if it is not null or else it will be blank.
        var currentUserID = ""
        if (currentUser != null) {
            currentUserID = currentUser.uid
        }

        return currentUserID
    }

错误日志：

2021-10-22 12:07:44.259 10095-10095/com.shop.shopkar E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.shop.shopkar, PID: 10095
    java.lang.NullPointerException
        at com.android.shopkar.firestore.FirestoreClass.getUserDetails1$lambda-6(FirestoreClass.kt:182)
        at com.android.shopkar.firestore.FirestoreClass.$r8$lambda$Zke3QkRIZzRRvIj5tck_XAhIVPs(FirestoreClass.kt)
        at com.android.shopkar.firestore.FirestoreClass$$ExternalSyntheticLambda37.onSuccess(Unknown Source)
        at com.google.android.gms.tasks.zzn.run(Unknown Source)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:5438)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:738)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:628)

Answer 1

假设SplashActivity是启动应用程序时显示的第一个活动，那么您共享的代码将根据身份验证状态将用户重定向到DashboardActivity或LoginActivity。但这并不完全正确，因为您正在检查UID是否为空。要知道用户是否已登录，您应该检查是否为空：

val auth = FirebaseAuth.getInstance()
val currentUser = auth.currentUser
if(currentUser == null) {
    startActivity(Intent(this@SplashActivity,LoginActivity::class.java))
} else {
    startActivity(Intent(this@SplashActivity, DashboardActivity::class.java))
}

但是，此机制仅在用户打开应用程序时才起作用并重定向用户。

在使用应用程序时注销如何？

在这种情况下，SplashActivity中现有代码没有任何帮助。因此，要知道用户何时发出声音，您必须使用一个侦听器，该侦听器应该添加到DashboardActivity中，并且应该如下所示：

val authStateListener = AuthStateListener { auth ->
    val firebaseUser = auth.currentUser
    if (firebaseUser == null) {
        val intent = Intent(this@DashboardActivity, LoginActivity::class.java)
        startActivity(intent)
        finish()
    }
}

由于它是一个侦听器，您需要根据活动的生命周期添加和删除它。因此，首先必须在DashboardActivity中创建一个FirebaseAuth对象：

val firebaseAuth = FirebaseAuth.getInstance()

然后在onStart()中附加监听程序

override fun onStart() {
    super.onStart()
    firebaseAuth.addAuthStateListener(authStateListener)
}

并相应地在onStop()中将其删除

override fun onStop() {
    super.onStop()
    firebaseAuth.removeAuthStateListener(authStateListener)
}

由于您使用的是Kotlin编程语言，因此我建议您检查：

• https://github.com/alexmamo/FireApp

它包含了您在一个干净的MVVM架构中寻找的确切机制。这是一个为学习目的而设计的应用程序。

附注:不需要任何处理程序。