How to convert an image into base64 String in Android using Kotlin?

This example demonstrates how to convert an image into a Base64 string on Android using Kotlin.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?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"
   android:padding="8dp"
   tools:context=".MainActivity">
   <TextView
      android:id="@+id/textView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:layout_centerInParent="true"
      android:textSize="12sp"
      android:textColor="@android:color/background_dark"
      android:textStyle="bold" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.kt

import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.os.Bundle
import android.util.Base64
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import java.io.ByteArrayOutputStream
class MainActivity : AppCompatActivity() {
   lateinit var textView: TextView
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      textView = findViewById(R.id.textView)
      val byteArrayOutputStream = ByteArrayOutputStream()
      val bitmap = BitmapFactory.decodeResource(resources, R.drawable.image)
      bitmap.compress(Bitmap.CompressFormat.JPEG, 100, byteArrayOutputStream)
      val imageBytes: ByteArray = byteArrayOutputStream.toByteArray()
      val imageString: String = Base64.encodeToString(imageBytes, Base64.DEFAULT)
      textView.text = imageString
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="app.com.q11">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen