How to provide different Android app icons for different gradle buildTypes?

Figured it out. What you need to do is create a separate src folder called debug that holds the different icons. For example, if your project layout is as follows, and your launcher icon is called ic_launcher.png:

[Project Root]
  -[Module]
    -src
      -main
        -res
          -drawable-*
            -ic_launcher.png

Then to add a separate icon for the debug build type, you add:

[Project Root]
  -[Module]
    -src
      -main
        -res
          -drawable-*
            -ic_launcher.png
      -debug
        -res
          -drawable-*
            -ic_launcher.png

Then, when you build under the debug build type, it will use the ic_launcher found in the debug folder.

For getting different icons while using different flavors with multiple dimensions, such as:

flavorDimensions "color", "size"
productFlavors {
    black {
        dimension "color"
    }
    white {
        dimension "color"
    }

    big {
        dimension "size"
    }
    small {
        dimension "size"
    }
}

This can be achieved as:

First, put the debug resources in separate folders, such as:

src/blackDebug/res
src/whiteDebug/res

Second, put the key with multiple flavor dimensions is that the sourceset name must contain all the possible flavor combinations, even if some of these dimensions do not affect the icon.

sourceSets {
    // Override the icons in debug mode
    blackBigDebug.res.srcDir 'src/blackDebug/res'
    blackSmallDebug.res.srcDir 'src/blackDebug/res'
    whiteBigDebug.res.srcDir 'src/whiteDebug/res'
    whiteSamllDebug.res.srcDir 'src/whiteDebug/res'
}

Just to make it clear, the following will not work when multiple dimensions are in use:

sourceSets {
    // Override the icons in debug mode
    blackDebug.res.srcDir 'src/blackDebug/res'
    whiteDebug.res.srcDir 'src/whiteDebug/res'
}

You can specify the icon in the product flavor's partial AndroidManifest.xml file as well:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools">
    <application
        tools:replace="android:icon"
        android:icon="@drawable/alternative_icon" />
</manifest>

This will overwrite the icon that you specify in the original AndroidManifest.xml

This is a handy approach although it has an important downside... both launchers will be put into your apk. – Bartek Lipinski

The better way: InsanityOnABun's answer

AndroidManifest.xml

<manifest 

    ...
        <application
        android:allowBackup="true"
        android:icon="${appIcon}"
        android:roundIcon="${appIconRound}"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

    ...

    </application>

</manifest>

build.gradle

android {

    ...
        productFlavors{
        Test{
            versionName "$defaultConfig.versionName" + ".test"
            resValue "string", "app_name", "App-Test"
            manifestPlaceholders = [
                    appIcon: "@mipmap/ic_launcher_test",
                    appIconRound: "@mipmap/ic_launcher_test_round"
            ]
        }

        Product{
            resValue "string", "app_name", "App"
            manifestPlaceholders = [
                    appIcon: "@mipmap/ic_launcher",
                    appIconRound: "@mipmap/ic_launcher_round"
            ]
        }
    }
}

the Github url:Build multi-version App with Gradle