Create Button in Kotlin Programmatically

In this very short blog post I am going to share with you how to create and add Button in Kotlin programmatically. To break it down in more details the code example below will cover:

Create Button programmatically in Kotlin
Handle Button onClick events
Change Button background color
Change Button text color
Add a Button in a ConstraintLayout

Using the ConstraintLayout

This example is very short and simple and thus has almost no other elements. So to be able to add and somehow position the Button within the view we will need to create an activity_button_example.xml file which contains an empty ConstraintLayout to which we will add the Button.

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:app="http://schemas.android.com/apk/res-auto"
   android:id="@+id/constraintLayout"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context="appsdeveloperblog.kotlin.codeexamples.ButtonExample">

</android.support.constraint.ConstraintLayout>

Create Button in Kotlin. Source code.

The BottonExample.kt below is the file in which we are going to create the button programmatically and add it into the ConstraintLayout.

package appsdeveloperblog.kotlin.codeexamples

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.support.constraint.ConstraintLayout
import android.widget.Button
import android.graphics.Color
import android.view.View


class ButtonExample : AppCompatActivity() {

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

        val constraintLayout = findViewById(R.id.constraintLayout) as ConstraintLayout
        val button = Button(this)
        button.layoutParams = ConstraintLayout.LayoutParams(ConstraintLayout.LayoutParams.WRAP_CONTENT, ConstraintLayout.LayoutParams.WRAP_CONTENT)
        button.text = "Click me"
        button.setOnClickListener(View.OnClickListener {
            button.text = "You just clicked me"
        })
        button.setBackgroundColor(Color.GREEN)
        button.setTextColor(Color.RED)
        constraintLayout.addView(button);
    }

}

You can now run your project and should be able to see a single Button with a label text on it set to “Click me” on a green background.

To learn more about Kotlin and how to use it to build native Android apps checkout the books and video courses below. They might help you to speed up your learning progress.