Custom navigators

A navigator is any React component that has a router on it, to define the navigation behavior. Each navigator is given a navigation prop, which allows the parent to control the navigation state.

Extending Navigators

It is possible to take an existing Navigator and extend its behavior, using the following approach:

const MyStack = createStackNavigator({ ... });

class CustomNavigator extends React.Component {
  static router = MyStack.router;
  render() {
    const { navigation } = this.props;

    return <MyStack navigation={navigation} />;
  }
}

Now it is possible to render additional things, observe the navigation prop, and override behavior of the router:

const MyStack = createStackNavigator({ ... });

class CustomNavigator extends React.Component {
  static router = {
    ...MyStack.router,
    getStateForAction: (action, lastState) => {
      // check for custom actions and return a different navigation state.
      return MyStack.router.getStateForAction(action, lastState);
    },
  };
  componentDidUpdate(lastProps) {
    // Navigation state has changed from lastProps.navigation.state to this.props.navigation.state
  }
  render() {
    const { navigation } = this.props;

    return (
      <View>
        <MyStack navigation={navigation} />
        {...}
      </View>
    );
  }
}

Navigator Navigation Prop

The navigation prop passed down to a navigator only includes state, dispatch, and addListener. This is the current state of the navigator, and an event channel to send action requests.

All navigators are controlled components: they always display what is coming in through props.navigation.state, and their only way to change the state is to send actions into props.navigation.dispatch.

Navigators can specify custom behavior to parent navigators by customizing their router. For example, a navigator is able to specify when actions should be blocked by returning null from router.getStateForAction. Or a navigator can specify custom URI handling by overriding router.getActionForPathAndParams to output a relevant navigation action, and handling that action in router.getStateForAction.

Navigation State

The navigation state that is passed into a navigator's props.navigation.state has the following structure:

{
  index: 1, // identifies which route in the routes array is active
  routes: [
    {
      // Each route needs a name, which routers will use to associate each route
      // with a react component
      routeName: 'MyRouteName',

      // A unique id for this route, used to keep order in the routes array:
      key: 'myroute-123',

      // Routes can have any additional data. The included routers have `params`
      ...customRouteData,
    },
    ...moreRoutes,
  ]
}

Navigation Dispatchers

A navigator can dispatch navigation actions, such as 'Go to a URI', 'Go back'.

The dispatcher will return true if the action was successfully handled, otherwise false.

API for building custom navigators

To help developers implement custom navigators, the following utilities are provided with React Navigation:

createNavigator

Note: The createNavigator API has changed in version 2. The old doc for v1 can be accessed here: https://v1.reactnavigation.org/docs/custom-navigators.html

This utility combines a router and a navigation view together in a standard way:

import { createNavigator } from "react-navigation";

const AppNavigator = createNavigator(NavigationView, router, navigationConfig);

The new AppNavigator can be rendered as such:

<AppNavigator
  navigation={{ state, dispatch, addListener }}
  screenProps={...}
/>

Then the view will be rendered in the following way:

<NavigationView
  screenProps={screenProps}
  navigation={navigation}
  navigationConfig={navigationConfig}
  descriptors={descriptors}
/>

The navigation prop is the same navigation prop that was passed into the navigator.

Both navigationConfig and screenProps are simply passed through, as defined above.

Most information about child screens comes through the descriptors prop. The descriptors is an object map of route keys to scene descriptors. There is one descriptor for each child route.

Scene Descriptors

A scene descriptor has the following properties:

• getComponent, a function that returns the component for the screen
• options, the flattened navigationOptions for the route
• navigation, the child navigation prop, including actions and the route state
• state, the navigation state for the child screen (a shortcut for navigation.state)
• key, the key of the route (a shortcut for navigation.state.key)