Add functionality for button click

e01-first-application/app/src/main/java/com/example/e01firstapplication/MainActivity.kt

@@ -2,10 +2,20 @@ package com.example.e01firstapplication
 
 import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
+import android.view.View
+import android.widget.TextView
 
 class MainActivity : AppCompatActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
     }
-}
\ No newline at end of file
+
+    // View class need to be used in parameter, even it is not used
+    fun buttonClicked(view: View) {
+        // activity_main layout has textView id in TextView element
+        // find it and change text
+        val textView = findViewById<TextView>(R.id.textView)
+        textView.text = resources.getString(R.string.button_clicked_txt)
+    }
+}

e01-first-application/app/src/main/res/layout/activity_main.xml

 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout
-    xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
@@ -8,12 +7,25 @@
     tools:context=".MainActivity">
 
     <TextView
+        android:id="@+id/textView"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="Hello World!"
         app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintLeft_toLeftOf="parent"
-        app:layout_constraintRight_toRightOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toTopOf="parent" />
 
+    <Button
+        android:id="@+id/button2"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="40dp"
+        android:onClick="buttonClicked"
+        android:text="@string/button_txt"
+        app:layout_constraintBottom_toTopOf="@+id/textView"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        tools:text="@string/button_txt" />
+
 </androidx.constraintlayout.widget.ConstraintLayout>
\ No newline at end of file

e01-first-application/app/src/main/res/values-fi/strings.xml

+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">First Application(fi)</string>
+    <string name="button_txt">Click me!(fi)</string>
+    <string name="button_clicked_txt">Button clicked!(fi)</string>
+</resources>
\ No newline at end of file

e01-first-application/app/src/main/res/values/strings.xml

 <resources>
-    <string name="app_name">E01 First Application</string>
+    <string name="app_name">First Application</string>
+    <string name="button_txt">Click Me!</string>
+    <string name="button_clicked_txt">Button was clicked!</string>
 </resources>
\ No newline at end of file