When using the TabNavigator the initial screen is loaded twice for some reason. This can be seen by adding an Alert or console.log in componentDidMount. I've replicated this in the SimpleTabs and StacksInTabs example. The SimpleStack example doesn't load twice.

const MyNavScreen = ({ navigation, banner }) => { Alert.alert(banner); return ( <ScrollView style={styles.container}> ....... </ScrollView> ); }