Firebase身份验证导致致命执行：（java.lang.NullPointerException）

Question

从我创建项目开始，这就非常有效。但突然间开始崩溃。注册活动工作正常。但是这个登录活动正在崩溃。

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.durden, PID: 7921
    java.lang.NullPointerException
        at com.example.durden.activity.SignInActivity.onCreate$lambda-2(SignInActivity.kt:49)
        at com.example.durden.activity.SignInActivity.$r8$lambda$ZBrxDCm4vr69l-PuE690AA_KCF8(Unknown Source:0)
        at com.example.durden.activity.SignInActivity$$ExternalSyntheticLambda1.onClick(Unknown Source:4)
        at android.view.View.performClick(View.java:7125)
        at android.view.View.performClickInternal(View.java:7102)
        at android.view.View.access$3500(View.java:801)
        at android.view.View$PerformClick.run(View.java:27336)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

class SignInActivity : AppCompatActivity() {

    // getting the references from firebase
    private var auth: FirebaseAuth? = null
    private var firebaseUser: FirebaseUser? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // gets the view binding of sign_in_activity
        val binding = ActivitySignInBinding.inflate(layoutInflater)

        setContentView(binding.root)

        // ends this activity and goes to sign up page if needed
        binding.gotoSignUp.setOnClickListener {
            val intent = Intent(
                this@SignInActivity,
                SignUpActivity::class.java
            )
            startActivity(intent)
            finish()
        }

        binding.btnSignIn.setOnClickListener {

            // storing the entered email and password
            val email = binding.SImail.text.toString()
            val password = binding.SIpass.text.toString()

            // checks if the values are entered
            if (TextUtils.isEmpty(email) && TextUtils.isEmpty(password)) {
                Toast.makeText(applicationContext,"email and password are required", Toast.LENGTH_SHORT).show()
            }

            // signs in the user using firebase data
            else {
                auth!!.signInWithEmailAndPassword(email, password)
                    .addOnCompleteListener(this) {
                        if (it.isSuccessful) {
                            binding.SImail.setText("")
                            binding.SIpass.setText("")

                            // after sign in takes to user page
                            val intent = Intent(
                                this@SignInActivity,
                                UserActivity::class.java
                            )
                            startActivity(intent)
                            finish()
                        }
                        else {
                            Toast.makeText( applicationContext, "Invalid password or email", Toast.LENGTH_SHORT).show()
                        }
                    }
            }
        }

    }
}

Firebase 身份验证导致 Android 致命异常

这听起来和我的问题很相似，但我还是不明白为什么会这样。

Answer 1

您将视图膨胀了两次，这是错误的：

val binding = ActivitySignInBinding.inflate(layoutInflater)
// setContentView(binding.root)

Answer 2

您永远不会初始化auth，这意味着当您执行auth！！. signInSusEmailAndPassword（email，密码）时，您会得到一个异常。

在您的onCreate中初始化auth，如步骤2所示，以防止错误。

// Initialize Firebase Auth
auth = Firebase.auth

NullPointerExceptions非常普遍，因此我强烈建议您学习如何自己解决这些问题。为此，请查看：

• 什么是 Kotlin 双爆炸 （！！） 运算符？
• 不幸的是，MyApp已经停止了。我该如何解决这个问题？
• 什么是 NullPointerException，如何修复它？