android.view.View$OnUnhandledKeyEventListener

Make the changes in your build.gradle (app level) to downgrade to version 27 as below. Then sync and build project. Hopefully it will fix the issue..

compileSdkVersion 27

targetSdkVersion 27

implementation 'com.android.support:appcompat-v7:27.1.1'

If using Android X and androidx.core:core and/or androidx.appcompat:appcompat, update androidx.core:core to 1.4.0-alpha01 and/or androidx.appcompat:appcompat to 1.3.0-alpha01

As mentioned by documentation, first, your Activity should be extend from AppCompatActivity().

Second, in your project styles, Base.Theme.AppCompat.Light.DarkActionBar is set which means it does have a DarkActionBar but you already have a Toolbar in your layout. So, simply, change:

Base.Theme.AppCompat.Light.DarkActionBar

to:

Theme.AppCompat.Light.NoActionBar

Then, (in java-kotlin side), setup the Toolbar:

// Note that the Toolbar defined in the layout has the id "my_toolbar"
    setSupportActionBar(findViewById(R.id.my_toolbar))

And give the Toolbar an id.

<android.support.v7.widget.Toolbar
   android:id="@+id/my_toolbar"
   android:layout_width="match_parent"
   android:layout_height="?attr/actionBarSize"
   android:background="?attr/colorPrimary"
   android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
   app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>

Then you should be good to go.