Sunday, January 21, 2018

android kotlin - Button on click listener example

MainActivity.kt

package com.cfsuman.kotlinexamples

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


class MainActivity : AppCompatActivity() {

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

        // Get the widgets
        val textView = findViewById<TextView>(R.id.text_view)
        val button = findViewById<Button>(R.id.button);
        val button2 = findViewById<Button>(R.id.button2);
        val button3 = findViewById<Button>(R.id.button3);
        val button4 = findViewById<Button>(R.id.button4);

        // Counter to count button click
        var counter: Int = 0;

        // Set a click listener for button widget
        button.setOnClickListener{
            counter++
            textView.text = "Click counter : $counter"
        }

        // Another way to set button click listener
        button2.setOnClickListener(object: View.OnClickListener {
            override fun onClick(v: View?) {
                counter++
                textView.text = "Click counter : $counter"
                v?.setBackgroundColor(Color.MAGENTA)
            }
        })

        // Another way to set button click listener
        button3.setOnClickListener({
            v->
            counter++
            textView.text = "Click counter : $counter"
            v.setBackgroundColor(Color.RED)

        })

        // Another way to set button click listener
        button4.setOnClickListener{
            counter++;
            textView.text = "Click counter : $counter"
            it.setBackgroundColor(Color.YELLOW)
        }
    }
}
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/root_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp"
    >
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        />
    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button2"
        />
    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button3"
        />
    <Button
        android:id="@+id/button4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button4"
        />
    <TextView
        android:id="@+id/text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello Kotlin!"
        android:textSize="18sp"
        android:textStyle="bold"
        />
</LinearLayout>