I am developing a simple login and register android app and everything have been coded and no errors were issued. The app can be ran successfully and all, but, the screen doesn't show the launcher activity. Like, it only shows up and then immediately close the app. I hope someone can catch what I am trying to say here. Also, I'm 100% sure that i have registered the activities on the manifest file.
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.READ_PHONE_STATE"/>
<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/AppTheme"
tools:ignore="GoogleAppIndexingWarning">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
<category android:name="android.intent.category.DEFAULT"/>
</intent-filter>
</activity>
<activity
android:name=".LoginActivity">
</activity>
<activity
android:name=".RegisterActivity">
</activity>
<service android:name=".MyFirebaseMessagingService">
<intent-filter>
<action android:name="com.google.firebase.MESSAGING_EVENT"/>
</intent-filter>
</service>
<service android:name=".MyFirebaseInstanceIDService">
<intent-filter>
<action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
</intent-filter>
</service>
<meta-data
android:name="android.app.alertbox"
android:resource="@xml/automotive_app_desc"/>
</application>
</manifest>
And this is what i get from the error log.
Caused by: kotlin.KotlinNullPointerException
at com.example.acer.alertbox.MainActivity.onCreate(MainActivity.kt:17)
at android.app.Activity.performCreate(Activity.java:6910)
at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2746)
at
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2864)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1567)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:6523)
at java.lang.reflect.Method.invoke(Native Method)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:941)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:831)
This is my MainActivity.kt code:
package com.example.acer.alertbox
import android.content.Intent
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val btnLogin: Button? = null
val btnRegister: Button? = null
btnLogin!!.setOnClickListener {
val intent = Intent(this@MainActivity, LoginActivity::class.java)
startActivity(intent)
}
btnRegister!!.setOnClickListener {
val regIntent = Intent(this@MainActivity, RegisterActivity::class.java)
startActivity(regIntent)
}
}
}
*Update: I have solved the issues by removing the null pointers. I did not know that there was any error because I did not check nor did I know how to open the Log Error so that is why I did not know this type of question has been asked before. I'm a new android developer by the way.