android - Kotlin 的无服务身份验证

问题描述

作为一个新手，我尽我所能在我的应用程序中制作一个非常简单的身份验证页面。

这是我的 MainActivity 类：

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_auth)  // I replaced activity_main by activity_auth who is made for the sign in and sign up page with a bottom-menu-bar navigation
    var logUser = findViewById<EditText>(R.id.username)  //username
    var logPwd = findViewById<EditText>(R.id.password)   //password
    /*
    var btnGo = findViewById<Button>(R.id.BtnLogin)      // btn submit
    var btnHelp = findViewById<Button>(R.id.BtnHelp)     // btn pwd lost

    btnGo.setOnClickListener {
        val userName = logUser.text;
        val passWord = logPwd.text;
        Toast.makeText(this@MainActivity, "WELCOME $userName", Toast.LENGTH_LONG).show()

        // the code to validate the user_name and password combination will be here
        // if logUser + logPwd are good the user should be redirect to "activity_main"

        setContentView(R.layout.activity_main)*/

        val navView: BottomNavigationView = findViewById(R.id.nav_view)
        val navController = findNavController(R.id.nav_host_fragment)
        val appBarConfiguration = AppBarConfiguration(setOf(
            R.id.navigation_profil, R.id.navigation_home))
        setupActionBarWithNavController(navController, appBarConfiguration)
        navView.setupWithNavController(navController)
    //}
}

就像应用程序正确显示我的登录页面一样，但是如果我删除评论标签并尝试对按钮或 ID 采取行动，应用程序就会崩溃。有没有你觉得奇怪的错误或事情？

如果您需要，这是我的登录布局：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
    android:id="@+id/ll_main_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:background="#444444"
    android:padding="25dp"
    android:orientation="vertical">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="25dp"
        android:textColor="@color/pureGold"
        android:padding="30dp"
        android:text="@string/login"/>
    <EditText
        android:id="@+id/username"
        android:hint="@string/logUser"
        android:textColor="@color/pureWhite"
        android:textColorHint="#52afaa"
        android:textAlignment="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <EditText
        android:id="@+id/password"
        android:hint="@string/logPWD"
        android:textColor="@color/pureWhite"
        android:textColorHint="#52afaa"
        android:textAlignment="center"
        android:inputType="textPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <LinearLayout
        android:layout_width="289dp"
        android:layout_height="wrap_content">

        <Button
            android:id="@+id/BtnLogin"
            android:layout_width="143dp"
            android:layout_height="wrap_content"
            android:textColor="@color/pureBlack"
            android:text="@string/logButton1"
            android:textAllCaps="false" />

        <Button
            android:id="@+id/BtnHelp"
            android:layout_width="147dp"
            android:layout_height="wrap_content"
            android:textColor="@color/pureBlack"
            android:text="@string/logButton2"
            android:textAllCaps="false" />

    </LinearLayout>

</LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

这是崩溃日志：

2021-03-10 20:53:33.792 8439-8439/com.example.movie_catcher E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.movie_catcher, PID: 8439
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.movie_catcher/com.example.movie_catcher.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:223)
    at android.app.ActivityThread.main(ActivityThread.java:7656)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
    at com.example.movie_catcher.MainActivity.onCreate(MainActivity.kt:25)
    at android.app.Activity.performCreate(Activity.java:8000)
    at android.app.Activity.performCreate(Activity.java:7984)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)

标签： androidkotlinandroid-activity

android - Kotlin 的无服务身份验证

问题描述

解决方案

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