Gradle signing flavors with different keys on Android

I have many flavors of my Android app, and I want all but one to use the same key. There is one that needs to use a different key.

How do I override the signingConfig for just 1 flavor of the app (but within the same build type e.g. "release")?

• I would like all builds by default to use the main release configuration.
• I only want to override 1 flavor
• I want to be able to run all release builds with a single gradlew assembleRelease command

This last point is important as I currently have over 120 different flavors and growing. In order to customise every single flavor individually is a lot of extra work.

Related posts I have tried:

Producing multiple builds signed with different keys from single build type

• this requires configuration for each flavor
• it doesn't seem to use my custom signingConfig anyway

Signing product flavors with gradle

• accepted solution doesn't work (for me)
• according to a comment this is possible by putting buildTypes inside the productFlavors but I do not understand how to do this.

Debug Signing Config on Gradle Product Flavors

• as explained on blog post: Building Multiple Editions of an Android App with Gradle
• it doesn't work actually it works perfectly
• but it doesn't scale well for 119 flavors

Overall, each solution seems to still use the default release config, instead of my custom config.

Important parts of my build.gradle look like this:

signingConfigs {
    releaseConfig {
        storeFile file('key')
        storePassword "pass"
        keyAlias "alias"
        keyPassword "pass"
    }

    custom {
        storeFile file('custom_key')
        storePassword "pass"
        keyAlias "alias"
        keyPassword "pass"
    }
}

productFlavors {
    apple {
        applicationId "demo.apple"
    }
    banana {
        applicationId "demo.banana"
    }

    // def customConfig = signingConfigs.custom
    custom {
        applicationId "custom.signed.app"
        // signingConfig customConfig
    }
 }


buildTypes {
    debug {
        applicationIdSuffix ".debug"
    }
    release {
         signingConfig signingConfigs.releaseConfig
         // productFlavors.custom.signingConfig signingConfigs.custom
    }
}

The Gradle Plugin User Guide says that you can:

have each release package use their own SigningConfig by setting each android.productFlavors.*.signingConfig objects separately.

This is demonstrated in this answer (Debug Signing Config on Gradle Product Flavors) and this blog post (Building Multiple Editions of an Android App with Gradle).

However, specifying a separate signingConfig line for each flavor does not scale well, and was out of scope of the question. Unfortunately none of the provided answers showed how to correctly override a signingConfig correctly.

The trick came from this answer (How to get the currently chose build variant in gradle?) which shows how to loop over build variants (and by extension, flavors).

My solution uses a loop to set the signingConfig on each flavor instead of having a separate line for that. This scales perfectly well. The "override" is done with a single line that specifies the custom config after the loop.

Place the following code inside the buildTypes.release block:

// loop over all flavors to set default signing config
productFlavors.all { flavor ->
    flavor.signingConfig signingConfigs.releaseConfig
}
// override default for single custom flavor
productFlavors.custom.signingConfig signingConfigs.custom

The below given code will use release1 as default signingConfig if signingConfig is not specified in the product flavor.

app/build.gradle

signingConfigs {
    debug {
        storeFile file("/home/.../debugkeystore.jks")
        storePassword "..."
        keyAlias "..."
        keyPassword "..."
    }
    release1 {
        storeFile file("/home/.../testkeystore1.jks")
        storePassword "..."
        keyAlias "..."
        keyPassword "..."
    }
    release2 {
        storeFile file("/home/.../testkeystore2.jks")
        storePassword "..."
        keyAlias "..."
        keyPassword "..."
    }
    release3 {
        storeFile file("/home/.../testkeystore3.jks")
        storePassword "..."
        keyAlias "..."
        keyPassword "..."
    }
}

defaultConfig {
    applicationId "com.example.signingproductflavors"
    minSdkVersion 15
    targetSdkVersion 24
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    signingConfig signingConfigs.release1
}

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
    debug { 
        signingConfig signingConfigs.debug
    }
}

productFlavors {
    blocks {
        applicationId "com.example.blocks"
        resValue 'string', 'APP_NAME', "Blocks"
    }
    cloud {
        applicationId "com.example.cloud"
        resValue 'string', 'APP_NAME', "Cloud"
        signingConfig signingConfigs.release2
    }
    deck {
        applicationId "com.example.deck"
        resValue 'string', 'APP_NAME', "Deck"
        signingConfig signingConfigs.release3
    }
}