MainActivity.kt
package com.cfsuman.kotlintutorials
import android.app.Activity
import android.content.Context
import android.graphics.*
import android.os.Bundle
import android.text.method.ScrollingMovementMethod
import android.util.Base64
import android.widget.*
import java.io.ByteArrayOutputStream
import java.io.IOException
class MainActivity : Activity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// get the widgets reference from XML layout
val imageView = findViewById<ImageView>(R.id.imageView)
val textView = findViewById<TextView>(R.id.textView)
// make text view text scrollable
textView.movementMethod = ScrollingMovementMethod()
// get the bitmap from assets folder
val bitmap = assetsToBitmap("flower.jpg")
bitmap?.apply {
// encode this bitmap to base64 string
val base64String = toBase64String()
// show base64 string of bitmap
textView.text = base64String
// decode base64 string to bitmap
val decodedBitmap:Bitmap? = base64String.toBitmap()
// show decoded bitmap in image view
imageView.setImageBitmap(decodedBitmap)
}
}
}
// extension function to get bitmap from assets
fun Context.assetsToBitmap(fileName:String):Bitmap?{
return try {
val stream = assets.open(fileName)
BitmapFactory.decodeStream(stream)
} catch (e: IOException) {
e.printStackTrace()
null
}
}
// extension function to encode bitmap to base64 string
fun Bitmap.toBase64String():String{
ByteArrayOutputStream().apply {
compress(Bitmap.CompressFormat.JPEG,90,this)
return Base64.encodeToString(toByteArray(),Base64.DEFAULT)
}
}
// extension function to decode base64 string to bitmap
fun String.toBitmap():Bitmap?{
Base64.decode(this,Base64.DEFAULT).apply {
return BitmapFactory.decodeByteArray(this,0,size)
}
}
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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/rootLayout"
android:background="#DCDCDC"
android:padding="24dp">
<TextView
android:id="@+id/textView"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_marginBottom="8dp"
android:fontFamily="sans-serif"
android:textSize="18sp"
app:layout_constraintBottom_toTopOf="@+id/imageView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text=" Base64 String" />
<ImageView
android:id="@+id/imageView"
android:layout_width="0dp"
android:layout_height="250dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
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