Sunday, January 21, 2018

android kotlin - Button on click listener example

MainActivity.kt 

package com.cfsuman.kotlintutorials

import android.graphics.Color
import android.os.Bundle
import android.view.View
import android.widget.*
import androidx.appcompat.app.AppCompatActivity


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

        // Get the widgets from XML layout
        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.parseColor("#7C0A02")
                )
            }
        })

        // Another way to set button click listener
        button3.setOnClickListener({ v->
            counter++
            textView.text = "Click counter : $counter"
            v.setBackgroundColor(
                Color.parseColor("#2E5894")
            )
        })

        // Another way to set button click listener
        button4.setOnClickListener{
            counter++;
            textView.text = "Click counter : $counter"
            it.setBackgroundColor(
                Color.parseColor("#4B6F44")
            )
        }
    }
}
activity_main.xml 

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/rootLayout"
    android:padding="24dp"
    android:background="#F8F8F8">

    <TextView
        android:id="@+id/text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:fontFamily="sans-serif"
        android:padding="16dp"
        android:text="Click Counter"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="24dp"
        android:text="First Button"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/text_view" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4dp"
        android:text="Second Button"
        app:layout_constraintStart_toStartOf="@+id/button"
        app:layout_constraintTop_toBottomOf="@+id/button" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4dp"
        android:text="Third Button"
        app:layout_constraintStart_toStartOf="@+id/button2"
        app:layout_constraintTop_toBottomOf="@+id/button2" />

    <Button
        android:id="@+id/button4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4dp"
        android:text="Fourth Button"
        app:layout_constraintStart_toStartOf="@+id/button3"
        app:layout_constraintTop_toBottomOf="@+id/button3" />

</androidx.constraintlayout.widget.ConstraintLayout>
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