A Gradle plugin helps to proxy all the BuildConfig fields in the Android project.

override fun attachBaseContext(newBase: Context?) {
    super.attachBaseContext(newBase)
    //Initial all the build config configurations.
    BuildConfigDelegate.initialModuleBuildConfig(newBase)
}

# Get all the flavors.
Set
   
     flavorSet = BuildConfigDelegate.getFlavorSet()
BuildConfigDelegate.setCurrentFlavor(flavor)

   

override fun onItemStateChanged(key: Long, selected: Boolean) {
    super.onItemStateChanged(key, selected)
    if (selected) {
        //Current flavor
        val flavor = buildFlavorAdapter[key.toInt()]
        BuildConfigDelegate.setCurrentFlavor(flavor)
        //Initial the text again and check the value.
        binding.textBuildConfig.text = "ServerUrl:${BuildConfig.SERVER_URL}\n" +
                "FlavorName:${BuildConfig.FLAVOR_NAME}"
    }
}

collectAndroidDevDebugBuildConfig
collectAndroidDevReleaseBuildConfig

generateAndroidDevDebugBuildConfigDelegate
generateAndroidDevReleaseBuildConfigDelegate

SERVER_URL=http://www.server.com-> `BuildConfig#(app/library)http://www.server.com`

private static final String TEST_TEXT = new StringBuilder().append("This is server:") .append(BuildConfigDelegate.getString("library","SERVER_URL","default value") .append(" and this is the token:") .append(BuildConfigDelegate.getString("library","ACCESS_TOKEN","default value").toString() ">

private static final String SERVER_URL = BuildConfig.SERVER_URL -> 
private static final String SERVER_URL = BuildConfigDelegate.getString("app/library/...","SERVER_URL","default value")


private static final String TEST_TEXT = "This is server:"+BuildConfig.SERVER_URL+" and this is the token:"+BuildConfig.ACCESS_TOKEN; ->
private static final String TEST_TEXT = new StringBuilder().append("This is server:")
                            .append(BuildConfigDelegate.getString("library","SERVER_URL","default value")
                            .append(" and this is the token:")
                            .append(BuildConfigDelegate.getString("library","ACCESS_TOKEN","default value").toString()

//All the BuildConfig fields. The key means the module name, the value means the all the BuildConfig fields.
public static final Map
   
    > getFlavorClassFields() {
    return buildConfigDelegate.flavorClassFields;
}
//The current build flavor. 
public static final String getCurrentFlavor() {
    return buildConfigDelegate.currentFlavor;
}
//The initial package build flavor.
public static final String getPackageFlavor() {
    return buildConfigDelegate.packageFlavor;
}

//All the build flavors
public static final Set
    
      getFlavorSet() {
    return buildConfigDelegate.flavorSet;
}
//Change the current flavor programmatically.
public static final void setCurrentFlavor(String flavor) {
    buildConfigDelegate.currentFlavor = flavor;
}