Preparing an Android App for Release

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2023-12-01

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

When you’re ready to prepare a release version for Android, for example to publish to the Google Play Store, follow the steps on this page.

Review the App Manifest

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

application: Edit the android:label in the application tag to reflect the final name of the app.
uses-permission: Remove the android.permission.INTERNET permission if your application code does not need Internet access. The standard template includes this tag to enable communication between Flutter tools and a running app.

Review 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.

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, if you want to do it manually, here’s how:

Review the Android Launcher Icons guidelines for icon design.
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.
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" ...).
To verify the icon has been replaced, run your app using flutter run 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: keytool -genkey -v -keystore ~/key.jks -keyalg RSA -keysize 2048 -validity 10000 -alias key

Note: Keep this file private; do not check it into public source control.

Note: keytool might not be in your path. It is part of the Java JDK, which is installed as part of Android Studio. For the concrete path, run flutter doctor -v and see the path printed after ‘Java binary at:’, and then use that fully qualified path replacing java with keytool.

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, e.g. /Users/<user name>/key.jks>

Note: Keep this file private; do not check it into public source control.

Configure signing in gradle

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

Replace:

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 {

Replace:

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:

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 or Android libraries, you may 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 /android/app/proguard-rules.pro file and add 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.**  { *; }

The configuration above only protects Flutter engine libraries. Any additional libraries (for example, Firebase) require their own rules to be added.

Step 2 - Enable obfuscation and/or minification

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

android {

    ...

    buildTypes {

        release {

            signingConfig signingConfigs.release

            minifyEnabled true
            useProguard true

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

        }
    }
}

Note: Obfuscation and minification can considerably extend compile time of the Android application.

Building a release APK

This section describes how to build a release APK. If you completed the signing steps in the previous section, the release APK will be signed.

Using the command line:

cd <app dir> (replace <app dir> with your application’s directory).
Run flutter build apk (flutter build defaults to --release).

The release APK for your app is created at <app dir>/build/app/outputs/apk/release/app-release.apk.

Installing a release APK on a device

Follow these steps to install the APK built in the previous step on a connected Android device.

Using the command line:

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

Publishing an APK to the Google Play Store

For detailed instructions on publishing the release version of an app to the Google Play Store, see the Google Play publishing documentation.

Building a release app bundle

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

From the command line:

Enter cd <app dir>. (Replace <app, dir> with your application’s directory.)
Run flutter build appbundle. (Running flutter build defaults to a release build.)
To generate a different variant of bundle, you can enter `flutter build appbundle --release --target-platform=android-arm`.
This generates a bundle for android-arm.

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

Testing an app Bundle

An app bundle can be tested in multiple ways. This section describes a couple ways in which to test an app bundle.

Offline using the bundle tool

If you have done done so already, download bundletool from the GitHub repository.
Generate a set of APKs from your app bundle.
Deploy the APKs to connected devices.

Online using Google Play

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.
Follow these steps to upload your bundle to the Play Store.