Publish your Flutter App - Android APK Signing and Release

In this guide we will learn how to sign the release version of APK or AAB (Android App Bundle) to publish our flutter app to android play store.

flutter release apk

How to sign the APK or app bundle created using flutter ?

To publish your app on Play Store, you need to give your app a digital signature.

step 1 : Create a new keystore file ; if you have an existing keystore then skip this step

• Run command in your terminal for linux/mac

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 -storetype JKS -keyalg RSA -keysize 2048 -validity 10000 -alias key

• Fill in the required info inside the terminal

Enter keystore password: test@12345 
        Re-enter new password: test@12345
    
        What is your first and last name?
        [test]:  test
        What is the name of your organizational unit?
        [test]:  test
        What is the name of your organization?
        [test]:  test
        What is the name of your City or Locality?
        [test]:  test
        What is the name of your State or Province?
        [test]:  test
        What is the two-letter country code for this unit?
        [tt]:  tt
        Is CN=test, OU=test, O=test, L=test, ST=test, C=tt correct?
        [no]:  yes
        
//OUTPUT
 Generating 2,048 bit RSA key pair and self-signed certificate (SHA256withRSA) with a validity of 10,000 days
                for: CN=test, OU=test, O=test, L=test, ST=test, C=tt
        [Storing /home/<user name>/key.jks]

• Keep the keystore file private; do not check it into public source control.
• Always keep a backup of the keystore file.

Common errors while signing the app

Command 'keytool' not found
run command :
sudo apt install openjdk-11-jre-headless
or 
sudo apt install openjdk-8-jre-headless

step 2 : Reference the keystore from the app

• Create a file name key.properties in your android folder

Write the following lines inside the newly created file

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>

• Keep the key.properties file private; do not check it into public source control.
• Always keep a backup of the key.properties file.

step 3 : Configure signing in gradle

Navigate to /android/app/build.gradle file.

1. Replace the following

android {

with

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 config info

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

Now, every release build of your app will be signed automatically

step 4 : how to create APK file or Android App Bundle using flutter ?

• How to build an android app bundle (AAB) using flutter ?

Running flutter build defaults to a release build

flutter build appbundle

Note : release bundle for your app is created at /build/app/outputs/bundle/release/app.aab

• How to build APK file using flutter ?

flutter build apk

Note : the above command “flutter build apk” builds a fat apk

OR

flutter build apk --split-per-abi

Note : the above command generated two APK files

• armeabi-v7a (32-bit) APK
• arm64-v8a (64-bit) APK

Bonus Tip : Do not forget to :

• Add a launcher icon to you app : refer our icon guide - android app icon
• Review App Manifest File, AndroidManifest.xml, located in <app dir>/android/app/src/main

1. Application Name [android : label in <application> tag]
2. uses-permission [Permission requested by your app]

• Review the build configuration, Gradle build file, build.gradle, located in <app dir>/android/app

Navigate to defaultConfig code block and verify

1. applicationId - unique app id
2. versionCode & versionName - Setting the version property in pubspec.yaml
3. minSdkVersion & targetSdkVersion - API level on which your app is designed to run

Useful Resources

Flutter Official Docs - Deployment Guide

To learn more about flutter - Flutter Developer Guide

Originally published at https://blog.akshatapp.com on November 20, 2019.