How to convert a Base64 string into a Bitmap image in Android app?

This example demonstrates how to do I in android.
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"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:gravity="center_horizontal"
   android:orientation="vertical"
   android:padding="16dp">
   <ImageView
      android:id="@+id/imageView"
      android:layout_width="match_parent"
      android:layout_height="match_parent" />
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Base64 string into a BitMap image in Android App"
      android:textSize="16sp"
      android:textStyle="bold|italic" />
</LinearLayout>
Step 3 − Add the following code to src/MainActivity.java
import android.annotation.SuppressLint;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.util.Base64;
import android.widget.ImageView;
import java.io.ByteArrayOutputStream;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
   ImageView imageView;
   @SuppressLint("WrongThread")
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      imageView = findViewById(R.id.imageView);
      ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
      Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image);
      bitmap.compress(Bitmap.CompressFormat.PNG, 100, byteArrayOutputStream);
      byte[] imageBytes = byteArrayOutputStream.toByteArray();
      String imageString = Base64.encodeToString(imageBytes, Base64.DEFAULT);
      imageBytes = Base64.decode(imageString, Base64.DEFAULT);
      Bitmap decodedImage = BitmapFactory.decodeByteArray(imageBytes, 0, imageBytes.length);
      imageView.setImageBitmap(decodedImage);
   }
}
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.sample">
   <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 the 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 −