Preparing an Android app for release

During a typical development cycle, you test an app using flutter run at the command line, or by using the Run and Debug options in your IDE. By default, Flutter builds a debug version of your app.

When you’re ready to prepare a release version of your app, for example to publish to the Google Play Store, this page can help. Before publishing, you might want to put some finishing touches on your app. This page covers the following topics:

Adding a launcher icon

When a new Flutter app is created, it has a default launcher icon. To customize this icon, you might want to check out the flutter_launcher_icons package.

Alternatively, you can do it manually using the following steps:

  1. Review the Material Design product icons guidelines for icon design.

  2. In the <app dir>/android/app/src/main/res/ directory, place your icon files in folders named using configuration qualifiers. The default mipmap- folders demonstrate the correct naming convention.

  3. In AndroidManifest.xml, update the application tag’s android:icon attribute to reference icons from the previous step (for example, <application android:icon="@mipmap/ic_launcher" ...).

  4. To verify that the icon has been replaced, run your app and inspect the app icon in the Launcher.

Signing the app

To publish on the Play Store, you need to give your app a digital signature. Use the following instructions to sign your app.

Create a keystore

If you have an existing keystore, skip to the next step. If not, create one by running the following at the command line:

On Mac/Linux, use the following command:

keytool -genkey -v -keystore ~/key.jks -keyalg RSA -keysize 2048 -validity 10000 -alias key

On Windows, use the following command:

keytool -genkey -v -keystore c:/Users/USER_NAME/key.jks -keyalg RSA -keysize 2048 -validity 10000 -alias key

Reference the keystore from the app

Create a file named <app dir>/android/key.properties that contains a reference to your keystore:

storePassword=<password from previous step>
keyPassword=<password from previous step>
keyAlias=key
storeFile=<location of the key store file, such as /Users/<user name>/key.jks>

Configure signing in gradle

Configure signing for your app by editing the <app dir>/android/app/build.gradle file.

  1. Replace the following:

       android {
    

    With the keystore information from your properties file:

       def keystoreProperties = new Properties()
       def keystorePropertiesFile = rootProject.file('key.properties')
       if (keystorePropertiesFile.exists()) {
           keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
       }
    
       android {
    
  2. Replace the following:

       buildTypes {
           release {
               // TODO: Add your own signing config for the release build.
               // Signing with the debug keys for now,
               // so `flutter run --release` works.
               signingConfig signingConfigs.debug
           }
       }
    

    With the signing configuration info:

       signingConfigs {
           release {
               keyAlias keystoreProperties['keyAlias']
               keyPassword keystoreProperties['keyPassword']
               storeFile file(keystoreProperties['storeFile'])
               storePassword keystoreProperties['storePassword']
           }
       }
       buildTypes {
           release {
               signingConfig signingConfigs.release
           }
       }
    

Release builds of your app will now be signed automatically.

Enabling Proguard

By default, Flutter does not obfuscate or minify the Android host. If you intend to use third-party Java, Kotlin, or Android libraries, you might want to reduce the size of the APK or protect that code from reverse engineering.

For information on obfuscating Dart code, see Obfuscating Dart Code in the Flutter wiki.

Step 1 - Configure Proguard

Create a /android/app/proguard-rules.pro file and add the rules listed below.

## Flutter wrapper
-keep class io.flutter.app.** { *; }
-keep class io.flutter.plugin.**  { *; }
-keep class io.flutter.util.**  { *; }
-keep class io.flutter.view.**  { *; }
-keep class io.flutter.**  { *; }
-keep class io.flutter.plugins.**  { *; }

This configuration only protects Flutter engine libraries. Any additional libraries (for example, Firebase) require adding their own rules.

Step 2 - Enable obfuscation and/or minification

Open the /android/app/build.gradle file and locate the buildTypes definition. Inside the release configuration section, set the minifiyEnabled and useProguard flags to true. You must also point Proguard to the file you created in step 1:

android {

    ...

    buildTypes {

        release {

            signingConfig signingConfigs.release

            minifyEnabled true
            useProguard true

            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

        }
    }
}

Reviewing the app manifest

Review the default App Manifest file, AndroidManifest.xml, located in <app dir>/android/app/src/main and verify that the values are correct, especially:

  • application: Edit the android:label in the application tag to reflect the final name of the app.

  • uses-permission: Add the android.permission.INTERNET permission if your application code needs Internet access. The standard template does not include this tag but allows Internet access during development to enable communication between Flutter tools and a running app.

Reviewing the build configuration

Review the default Gradle build file file, build.gradle, located in <app dir>/android/app and verify the values are correct, especially:

  • defaultConfig:

    • applicationId: Specify the final, unique (Application Id)appid

    • versionCode & versionName: Specify the internal app version number, and the version number display string. You can do this by setting the version property in the pubspec.yaml file. Consult the version information guidance in the versions documentation.

    • minSdkVersion & targetSdkVersion: Specify the minimum API level, and the API level on which the app is designed to run. Consult the API level section in the versions documentation for details.

Building the app for release

You have two possible release formats when publishing to the Play Store.

  • App bundle (preferred)
  • APK

Build an app bundle

This section describes how to build a release app bundle. If you completed the signing steps, the app bundle will be signed.

From the command line:

  1. Enter cd <app dir>
    (Replace <app dir> with your application’s directory.)
  2. Run flutter build appbundle
    (Running flutter build defaults to a release build.)

The release bundle for your app is created at <app dir>/build/app/outputs/bundle/release/app.aab.

By default, the app bundle contains your Dart code and the Flutter runtime compiled for armeabi-v7a (32-bit) and arm64-v8a (64-bit).

Test the app bundle

An app bundle can be tested in multiple ways—this section describes two.

Offline using the bundle tool

  1. If you haven’t done so already, download bundletool from the GitHub repository.
  2. Generate a set of APKs from your app bundle.
  3. Deploy the APKs to connected devices.

Online using Google Play

  1. Upload your bundle to Google Play to test it. You can use the internal test track, or the alpha or beta channels to test the bundle before releasing it in production.
  2. Follow these steps to upload your bundle to the Play Store.

Build an APK

Although app bundles are preferred over APKs, there are stores that don’t yet support app bundles. In this case, build a release APK for each target ABI (Application Binary Interface).

If you completed the signing steps, the APK will be signed.

From the command line:

  1. Enter cd <app dir>
    (Replace <app dir> with your application’s directory.)
  2. Run flutter build apk --split-per-abi
    (The flutter build command defaults to --release.)

This command results in two APK files:

  • <app dir>/build/app/outputs/apk/release/app-armeabi-v7a-release.apk
  • <app dir>/build/app/outputs/apk/release/app-arm64-v8a-release.apk

Removing the --split-per-abi flag results in a fat APK that contains your code compiled for all the target ABIs. Such APKs are larger in size than their split counterparts, causing the user to download native binaries that are not applicable to their device’s architecture.

Install an APK on a device

Follow these steps to install the APK on a connected Android device.

From the command line:

  1. Connect your Android device to your computer with a USB cable.
  2. Enter cd <app dir> where <app dir> is your application directory.
  3. Run flutter install.

Publishing to the Google Play Store

For detailed instructions on publishing your app to the Google Play Store, see the Google Play launch documentation.

Android release FAQ

Here are some commonly asked questions about deployment for Android apps.

When should I build app bundles versus APKs?

The Google Play Store recommends that you deploy app bundles over APKs because they allow a more efficient delivery of the application to your users. However, if you’re distributing your application by means other than the Play Store, an APK may be your only option.

What is a fat APK?

A fat APK is a single APK that contains binaries for multiple ABIs embedded within it. This has the benefit that the single APK runs on multiple architectures and thus has wider compatibility, but it has the drawback that its file size is much larger, causing users to download and store more bytes when installing your application. When building APKs instead of app bundles, it is strongly recommended to build split APKs, as described in build an APK using the --split-per-abi flag.

What are the supported target architectures?

When building your application in release mode, Flutter apps can be compiled for armeabi-v7a (32-bit) and arm64-v8a (64-bit). Flutter does not currently support building for x86 Android (See Issue 9253).

How do I sign the app bundle created by flutter build appbundle?

See Signing the app.

How do I build a release from within Android Studio?

In Android Studio, open the existing android/ folder under your app’s folder. Then, select build.gradle (Module: app) in the project panel:

screenshot of gradle build script menu

Next, select the build variant. Click Build > Select Build Variant in the main menu. Select any of the variants in the Build Variants panel (debug is the default):

screenshot of build variant menu

The resulting app bundle or APK files are located in build/app/outputs within your app’s folder.