public class MyModule implements VersionModule {
    @VersionCode({1, 2, 3}) // foo() is called when the app is updated to version code = 1, 2 and 3
    public void foo() {
    }
    @VersionCode(4) // bar() is called when the app is updated to version code = 4
    public void bar() {
    }
}

public class MyModule implements VersionModule {
    @VersionCode({1, 2, 3}) // foo() is called when the app is updated to version code = 1, 2 and 3
    public void foo() {
    }
    @VersionCode(4)
    @UpgradeOnly // bar() is called when the app is updated to version code = 4, and not called when the app is newly installed
    public void bar() {
    }
}

public class MyApp extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        Fit.initialize(this, new MyModule());
    }
}

Fit.getInstance().execute();

-keepattributes *Annotation*
-keepclassmembers class * {
    @jp.yokomark.fit.VersionCode *;
}