Android Button setOnClickListener call function to change text

Android
1

I have an app with multiple buttons and text line, I want to change the text depending on the language set in a menu. Ideally I want all the changes within a function to make the code easier, but the code does not work. I am not sure even if the function is been called, how do I change the text within the function?

MainActivity.kt

 package com.example.sandpit9

 import android.content.Intent
 import android.support.v7.app.AppCompatActivity
 import android.os.Bundle
 import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

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

    imageButton1.setOnClickListener{toast()}

    imageButton1.setOnClickListener{
        imageButton1.setImageResource(R.drawable.greenbutton)
        textView1.setText("test 1")

    }

}

private fun toast() {

    textView2.setText("test 2")
}

}

MainActivity.xml

    <?xml version="1.0" encoding="utf-8"?>
    <android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

<TextView
        android:text="TextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/textView1"
        android:layout_marginTop="8dp"
        app:layout_constraintTop_toBottomOf="@+id/imageButton1"
        android:layout_marginBottom="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        app:layout_constraintStart_toStartOf="parent"
        android:layout_marginLeft="8dp"
        android:layout_marginStart="8dp"
        android:textSize="34sp"/>
<ImageButton
        android:layout_width="174dp"
        android:layout_height="154dp"
        app:srcCompat="@drawable/download"
        android:id="@+id/imageButton1"
        app:layout_constraintEnd_toEndOf="parent"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        app:layout_constraintStart_toStartOf="parent"
        android:layout_marginLeft="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginBottom="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHorizontal_bias="0.542"
        app:layout_constraintVertical_bias="0.187"/>
<TextView
        android:text="textvar1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/textView2"
        android:textSize="34sp" android:layout_marginTop="108dp"
        app:layout_constraintTop_toBottomOf="@+id/imageButton1" android:layout_marginEnd="8dp"
        app:layout_constraintEnd_toEndOf="parent" android:layout_marginRight="8dp" android:layout_marginStart="8dp"
        app:layout_constraintStart_toStartOf="parent" android:layout_marginLeft="8dp"
        app:layout_constraintHorizontal_bias="0.535"/> 
        </android.support.constraint.ConstraintLayout>