Android Manifest Error _ the app does not run

Question

I am making an app that runs login_nb first. There was not problem until I added userinfoinput.kt to this project, but it made some errors after that.

My code manifest code is :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.nb_main">


    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Nb_main"
        android:usesCleartextTraffic="true">

        <activity android:name=".SignUp" />
        <activity android:name=".photoboard" />
        <activity android:name=".addPhoto" />
        <activity android:name=".textboard" />
        <activity android:name=".login_nb">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" /> <!-- Move this to set the initial activity -->

                <category android:name="android.intent.category.LAUNCHER" /> <!-- Move this to set the initial activity -->
            </intent-filter>
        </activity>
        <activity android:name=".popup_color" />
        <activity android:name=".built" />
        <activity android:name=".userinfoinput"/>
        <!--
               Set to true if your app is Standalone, that is, it does not require the handheld
               app to run.
        -->
        <activity
            android:name=".square"
            android:label="@string/title_activity_square" />
        <activity android:name=".MainActivity" />
    </application>

And the error message is as following :

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.nb_main, PID: 9057
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.nb_main/com.example.nb_main.login_nb}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3194)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
    at android.os.Handler.dispatchMessage(Handler.java:107)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
    at android.content.ContextWrapper.getPackageName(ContextWrapper.java:145)
    at android.content.ComponentName.<init>(ComponentName.java:131)
    at android.content.Intent.<init>(Intent.java:6510)
    at com.example.nb_main.login_nb.<init>(login_nb.kt:24)
    at java.lang.Class.newInstance(Native Method)
    at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:95)
    at androidx.core.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:45)
    at android.app.Instrumentation.newActivity(Instrumentation.java:1243)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3182)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016) 
    at android.os.Handler.dispatchMessage(Handler.java:107) 
    at android.os.Looper.loop(Looper.java:214) 
    at android.app.ActivityThread.main(ActivityThread.java:7356) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930) 

I/Process: Sending signal. PID: 9057 SIG: 9

Please tell me what I've done wrong. I use kotlin mainly, but I can somehow understand java also.

Answer 1

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
    at android.content.ContextWrapper.getPackageName(ContextWrapper.java:145)
    at android.content.ComponentName.<init>(ComponentName.java:131)
    at android.content.Intent.<init>(Intent.java:6510)
    at com.example.nb_main.login_nb.<init>(login_nb.kt:24)

In login_nb.kt row 24 there's some instance init code that instantiates an Intent. It's too early with regards to activity lifecycle. At init phase the activity is not yet ready to be used as a Context. The usual place for such init code is the activity's onCreate().