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android - java.lang.RuntimeException：无法启动活动 ComponentInfo{at.mksquad.swapit/at.mksquad.swapit.ui.screenflow.main.MainActivity}？

问题描述

我正在开发新应用程序，但是当我在调试模式下运行项目时，出现以下异常

java.lang.RuntimeException: Unable to start activity ComponentInfo{at.mksquad.swapit/at.mksquad.swapit.ui.screenflow.main.MainActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2976)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3113)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:113)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:71)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1858)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:201)
        at android.app.ActivityThread.main(ActivityThread.java:6820)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:922)
     Caused by: java.lang.NullPointerException
        at at.mksquad.swapit.data.sources.auth.AuthSourceFirebase.getUidOfLoggedInUser(AuthSourceFirebase.kt:18)
        at at.mksquad.swapit.features.auth.AuthManager.getUidOfLoggedInUser(AuthManager.kt:28)
        at at.mksquad.swapit.data.repositories.UserRepository.getUid(UserRepository.kt:30)
        at at.mksquad.swapit.utils.UserUtil.createNewUser(UserUtil.kt:17)
        at at.mksquad.swapit.data.repositories.UserRepository.loadUser(UserRepository.kt:90)
        at at.mksquad.swapit.ui.screenflow.main.SharedViewModel.<init>(SharedViewModel.kt:12)
        at at.mksquad.swapit.ui.screenflow.main.SharedViewModelFactory.create(SharedViewModelFactory.kt:14)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:187)
        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
        at androidx.lifecycle.ViewModelLazy.getValue(ViewModelProvider.kt:54)
        at androidx.lifecycle.ViewModelLazy.getValue(ViewModelProvider.kt:41)
        at at.mksquad.swapit.ui.screenflow.main.MainActivity.getSharedViewModel(Unknown Source:2)
        at at.mksquad.swapit.ui.screenflow.main.MainActivity.prepareViews(MainActivity.kt:765)
        at at.mksquad.swapit.ui.screenflow.main.MainActivity.onCreate(MainActivity.kt:194)
        at android.app.Activity.performCreate(Activity.java:7224)


        at android.app.Activity.performCreate(Activity.java:7213)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2956)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3113) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:113) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:71) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1858) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:201) 
        at android.app.ActivityThread.main(ActivityThread.java:6820) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:922) 

下面跟随我的 MainActivity.kt https://gist.github.com/kyodgorbek/2a369fcbb2138cb9e25c0855514dc162代码

我想知道我到底在哪里犯了错误我已经运行调试模式但逐步运行但它没有显示任何内容，但在 AuthSourceFirebase.kt 中的以下代码中指出异常

object AuthSourceFirebase {
    fun isUserLoggedIn(): Boolean {
        return FirebaseAuth.getInstance().currentUser != null
    }

    fun getUidOfLoggedInUser(): String {
        return FirebaseAuth.getInstance().currentUser!!.uid // this line cause exception
    }

    fun loginUser(
        activity: Activity,
        mail: String,
        password: String,
        loginCallback: AuthManager.UserLoginCallback
    ) {
        Timber.d("Starting process to login..")
        FirebaseAuth.getInstance().signInWithEmailAndPassword(
            mail,
            password
        ).addOnCompleteListener(activity) {
            if (it.isSuccessful) {
                loginCallback.onCallback(null)
            }
        }
            .addOnFailureListener { e ->
                val error = e as FirebaseAuthException
                Timber.d("Error logging in, code: %s", error.errorCode)
                loginCallback.onCallback(
                    LibFirebaseErrors.getErrorFromErrorCode(
                        activity,
                        error.errorCode
                    )
                )
            }
    }

    fun registerUser(
        activity: Activity,
        mail: String,
        password: String,
        registrationCallback: AuthManager.UserRegistrationCallback
    ) {
        Timber.d("Starting process to register..")
        FirebaseAuth.getInstance().createUserWithEmailAndPassword(
            mail,
            password
        ).addOnCompleteListener(activity) {
            if (it.isSuccessful) {
                registrationCallback.onCallback(null)
            }
        }
            .addOnFailureListener { e ->
                val error = e as FirebaseAuthException
                Timber.d("Error logging in, code: %s", error.errorCode)
                registrationCallback.onCallback(
                    LibFirebaseErrors.getErrorFromErrorCode(activity, error.errorCode)
                )
            }
    }

    fun sendPasswordResetMail(
        activity: Activity,
        mail: String,
        resetPwMailCallback: AuthManager.UserResetPwMailCallback
    ) {
        Timber.d("Starting process to reset password..")
        FirebaseAuth.getInstance().sendPasswordResetEmail(mail)
            .addOnCompleteListener(activity) {
                if (it.isSuccessful) {
                    resetPwMailCallback.onCallback(null)
                }
            }
            .addOnFailureListener { e ->
                val error = e as FirebaseAuthException
                Timber.d("Error sending mail, code: %s", error.errorCode)
                resetPwMailCallback.onCallback(
                    LibFirebaseErrors.getErrorFromErrorCode(
                        activity,
                        error.errorCode
                    )
                )
            }
    }

    fun logUserOut(context: Context){
        UserRepository.deleteUserLocal(context)
        FirebaseAuth.getInstance().signOut()
    }
}

我已经尝试过我的方法以避免空指针异常，因为它不起作用

fun getUidOfLoggedInUser(): String {

        if(FirebaseAuth.getInstance().currentUser?.uid == null){
            FirebaseAuth.getInstance().signOut()
        }
        return FirebaseAuth.getInstance().currentUser!!.uid
    }

标签： androidkotlinandroid-activityruntimeexception

解决方案

您得到的错误看起来像一个常规的空指针异常。根据此处的异常堆栈跟踪：

Caused by: java.lang.NullPointerException
    at at.mksquad.swapit.data.sources.auth.AuthSourceFirebase.**getUidOfLoggedInUser(AuthSourceFirebase.kt:18)**
    at at.mksquad.swapit.features.auth.AuthManager.getUidOfLoggedInUser(AuthManager.kt:28)
    at at.mksquad.swapit.data.repositories.UserRepository.getUid(UserRepository.kt:30)

和

fun getUidOfLoggedInUser(): String {
    return FirebaseAuth.getInstance().currentUser!!.uid // this line cause exception
}

确保您的 currentUser 不为空。请检查 Firebase 身份验证是否已处理且当前用户会话是否处于活动状态。

像这样更新您的代码：

**fun getUidOfLoggedInUser(): String {

    if(FirebaseAuth.getInstance().currentUser == null || FirebaseAuth.getInstance().currentUser?.uid == null){
        FirebaseAuth.getInstance().signOut() return
    }
    return FirebaseAuth.getInstance().currentUser!!.uid
}**

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