This is similar to how you would customize a stack navigator — there are some properties that are set when you initialize the tab navigator and others that can be customized per-screen in navigationOptions.
// You can import Ionicons from @expo/vector-icons if you use Expo or
tabBarIcon is a property on navigationOptions, so we know we can use it on our screen components, but in this case chose to put it in the createBottomTabNavigator configuration in order to centralize the icon configuration for convenience.
tabBarIcon is a function that is given the focused state, tintColor, and horizontal param, which is a boolean. If you take a peek further down in the configuration you will see tabBarOptions and activeTintColor and inactiveTintColor. These default to the iOS platform defaults, but you can change them here. The tintColor that is passed through to the tabBarIcon is either the active or inactive one, depending on the focused state (focused is active). The orientation state horizontal is true when the device is in landscape, otherwise is false for portrait.
Read the full API reference for further information on createBottomTabNavigator configuration options.
From UI perspective this component is ready to use, but you still need to find some way to pass down the badge count properly from somewhere else, like using React Context, Redux, MobX or event emitters.
// You should pass down the badgeCount in some other ways like React Context API, Redux, MobX or event emitters.
Usually tabs don't just display one screen — for example, on your Twitter feed, you can tap on a tweet and it brings you to a new screen within that tab with all of the replies. You can think of this as there being separate navigation stacks within each tab, and that's exactly how we will model it in React Navigation.
Why do we need a TabNavigator instead of TabBarIOS or some other component?#
It's common to attempt to use a standalone tab bar component without integrating it into the navigation library you use in your app. In some cases, this works fine! You should be warned, however, that you may run into some frustrating unanticipated issues when doing this.
For example, React Navigation's TabNavigator takes care of handling the Android back button for you, while standalone components typically do not. Additionally, it is more difficult for you (as the developer) to perform actions such as "jump to this tab and then go to this screen" if you need to call into two distinct APIs for it. Lastly, mobile user interfaces have numerous small design details that require that certain components are aware of the layout or presence of other components — for example, if you have a translucent tab bar, content should scroll underneath it and the scroll view should have an inset on the bottom equal to the height of the tab bar so you can see all of the content. Double tapping the tab bar should make the active navigation stack pop to the top of the stack, and doing it again should scroll the active scroll view in that stack scroll to the top. While not all of these behaviors are implemented out of the box yet with React Navigation, they will be and you will not get any of this if you use a standalone tab view component.
A tab navigator contains a stack and you want to hide the tab bar on specific screens#