[Android_Kotlin code]Creade Button

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:padding="10dp"
        android:text="@string/btn"
        android:textColor="@color/black"
        app:backgroundTint="@color/white" />

<string name="btn">Button</string>

import android.widget.Button

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        // set id from activity_main.xml
        val button = findViewById<Button>(R.id.button)

        // button event
        button?.setOnClickListener()
        {
            // set event
            //Toast.makeText(this@MainActivity, "button test", Toast.LENGTH_LONG).show()
        }
    }

}