Android - What is the purpose of multiDexKeepProguard ? How does it compare to proguardFiles close in gradle?

Question

I have created a multidex app. But in regards to proguard i have the following in build.gradle:

    android {
    defaultConfig {
        ...
        multiDexEnabled true
    }
    productFlavors {
        dev {
            // Enable pre-dexing to produce an APK that can be tested on
            // Android 5.0+ without the time-consuming DEX build processes.
            minSdkVersion 21
        }
        prod {
            // The actual minSdkVersion for the production version.
            minSdkVersion 14
        }
    }
    buildTypes {
        release {
            minifyEnabled true
        ***    proguardFiles getDefaultProguardFile('proguard-android.txt'),
                                                 'proguard-rules.pro'
        }
    }
}
dependencies {
    compile 'com.android.support:multidex:1.0.1'
}

My question is about the progardFiles vs using multiDexKeepProguard. The documentation states:

File multiDexKeepProguard

Text file with additional ProGuard rules to be used to determine which classes are compiled into the main dex file.

If set, rules from this file are used in combination with the default rules used by the build system.

So if i do not use the multiDexKeepProguard then my classes still get compiled but may not end up in the main dex file, is that correct ? I am not clear how this differs from proguardFiles.

Android documentation also references this.

Answer 1

If you're enabling proguard in your application it's usually necessary to define proguard rules. proguardFiles are meant to be the instructions for progurard to minify or obfuscate your app.

multiDexKeepProguard is specifically for telling multidex which files are important to load at app startup and therefore what to keep in the main dex. As far as i'm aware, it just uses the proguard syntax as a convenience. This is optional and will usually only be set if there is an issue at runtime.