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In this tutorial, you will learn how to create an Android application using Kotlin that displays a blinking image infinitely. The tutorial will guide you through the process of setting up the user interface with an ImageView to show the blinking image. You'll implement logic in MainActivity.kt to toggle the visibility of the ImageView periodically, creating the blinking effect using a Handler or a similar mechanism for timing intervals. This approach will ensure that the image alternates between visible and invisible states, producing a continuous blinking effect. By following this step-by-step guide, you'll gain practical experience in handling UI animation through periodic updates and enhancing visual feedback in your Kotlin-based Android applications.
Submitted on July 07, 2024

To create an Android app where an image blinks infinitely, you can achieve this by using a ‘Handler’ to toggle the visibility of the ‘ImageView’ at regular intervals. Here's how you can implement this in Kotlin:

Step-by-Step Implementation:

  1. Create a New Android Project:

    • Open Android Studio and create a new project with an Empty Activity template.

  2. Add an ImageView to activity_main.xml:

    • Open ‘res/layout/activity_main.xml’ and add an ‘ImageView’ that will display the blinking image.

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

    <ImageView
        android:id="@+id/imageViewBlink"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher_foreground"
        android:layout_centerInParent="true"/>

</RelativeLayout>

    • Replace ‘@drawable/ic_launcher_foreground’ with the drawable resource you want to use for blinking.

3. Implement MainActivity.kt

  • Open ‘MainActivity.kt’ and implement the logic to toggle the visibility of the ImageView to create the blinking effect.

package com.example.blinkingimage

import android.os.Bundle
import android.os.Handler
import androidx.appcompat.app.AppCompatActivity
import android.widget.ImageView

class MainActivity : AppCompatActivity() {

    private lateinit var imageViewBlink: ImageView
    private var blinkHandler: Handler = Handler()
    private var isBlinkVisible = true
    private val blinkInterval: Long = 500 // Blink interval in milliseconds

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

        imageViewBlink = findViewById(R.id.imageViewBlink)

        // Start blinking
        blinkHandler.post(blinkRunnable)
    }

    private val blinkRunnable: Runnable = object : Runnable {
        override fun run() {
            if (isBlinkVisible) {
                imageViewBlink.alpha = 0f // Hide the image
            } else {
                imageViewBlink.alpha = 1f // Show the image
            }
            isBlinkVisible = !isBlinkVisible
            blinkHandler.postDelayed(this, blinkInterval)
        }
    }

    override fun onDestroy() {
        super.onDestroy()
        // Remove callbacks to prevent memory leaks
        blinkHandler.removeCallbacks(blinkRunnable)
    }
}

Explanation:

  • activity_main.xml

    • Contains an ‘ImageView’ (‘imageViewBlink) that displays the blinking image (‘@drawable/ic_launcher_foreground in this example).

  • MainActivity.kt:

    • onCreate():
      • Initializes the ‘imageViewBlink’.
      • Starts the blinking effect using a Handler (‘blinkHandler’) and a Runnable (‘blinkRunnable’).
    • blinkRunnable:
      • Toggles the visibility (alpha) of ‘imageViewBlink’ between 0 (invisible) and 1 (visible) at regular intervals (‘blinkInterval’).
      • Uses ‘postDelayed()’ to schedule the next toggle after ‘blinkInterval’ milliseconds.
    • onDestroy():
      • Cleans up by removing callbacks from the Handler to prevent memory leaks when the activity is destroyed.

Testing:

  • Run the app on an emulator or a physical device.
  • Observe the ‘ImageView’ (‘imageViewBlink’) to see the blinking effect with the image toggling visibility at regular intervals.

This implementation allows you to create a simple blinking effect for an ‘ImageView’ in an Android app using Kotlin. You can customize the blinking interval (‘blinkInterval’) and adjust other properties of the ‘ImageView’ as needed for different blinking effects or UI requirements.