Android Studio/Kotlin - findViewById crash my app

Question

The program stop when it reach the findViewById and I can't figure out why :

    override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.splash_screen)

    handler.postDelayed({ setContentView(R.layout.activity_main) }, 500) // 5 seconds
    val imageView: ImageView = findViewById(R.id.splashScreenIMG)
    Glide.with(this).load(R.drawable.sligames_waiting).into(imageView)
}

    fun showButtons()
{
    val view: View = findViewById(R.id.boutonOui)
    val cx = view.width / 2
    val cy = view.height / 2
    val finalRadius = hypot(cx.toDouble(), cy.toDouble()).toFloat()
    val anim = ViewAnimationUtils.createCircularReveal(view, cx, cy, 0f, finalRadius)
    // make the view visible and start the animation
    view.visibility = View.VISIBLE
    anim.duration = 1500
    anim.start()
}

I execute this function from another file with this line :

MainActivity().showButtons()

Here's the stack trace :

2020-06-01 12:55:02.783 22557-22557/com.example.yourmajesty E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.yourmajesty, PID: 22557
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
    at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:163)
    at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:174)
    at android.content.Context.obtainStyledAttributes(Context.java:738)
    at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:692)
    at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:659)
    at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:479)
    at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:214)
    at com.example.yourmajesty.MainActivity.showButtons(MainActivity.kt:122)
    at com.example.yourmajesty.Dialog.dialogChanger(Dialog.kt:26)
    at com.example.yourmajesty.MainActivity$dialogBoxDiseappear$2.run(MainActivity.kt:190)
    at android.os.Handler.handleCallback(Handler.java:883)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7695)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:516)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)

Thanks in advance

Answer 1

MainActivity().showButtons()

You can't initiate an object from your activity. You can only launch it and bundle data with its Intent

Please refere to this thread If you're trying to communicate with MainActvitiy from a fragment