React-native component's componentDidMount() is not called under NavigatorIOS

I create a component with ListView under the structure: TabBarIOS>NavigatorIOS>ListView. I try to fetch data in componentDidMount(). But it didn't work unless I fetch it in componentWillMount(). Why?

I've put my work here https://github.com/chiakie/MyAwesomeProject
In MotorcycleList.js, componentDidMount() seem to never be called.