Navigation events

You can listen to various events emitted by React Navigation to get notified of certain events, and in some cases, override the default action. There are few core events that work for every navigator, as well as navigator specific events that work for only for certain navigators.

Following are the built-in events available with every navigator:

• focus - This event is emitted when the screen comes into focus
• blur - This event is emitted when the screen goes out of focus
• beforeRemove (version 5.7+ only) - This event is emitted when the user is leaving the screen, there's a chance to prevent the user from leaving
• state (advanced) - This event is emitted when the navigator's state changes

Apart from these, each navigator can emit their own custom events. For example, stack navigator emits transitionStart and transitionEnd events, tab navigator emits tabPress event etc. You can find details about the events emitted on the individual navigator's documentation.

Each callback registered as an event listener receive an event object as its argument. The event object contains few properties:

• data - Additional data regarding the event passed by the navigator. This can be undefined if no data was passed.
• target - The route key for the screen that should receive the event. For some events, this maybe undefined if the event wasn't related to a specific screen.
• preventDefault - For some events, there may be a preventDefault method on the event object. Calling this method will prevent the default action performed by the event (such as switching tabs on tabPress). Support for preventing actions are only available for certain events like tabPress and won't work for all events.

There are 2 ways to listen to events:

navigation.addListener

Inside a screen, you can add listeners on the navigation prop with the addListener method. The addListener method takes 2 arguments: type of the event, and a callback to be called on the event. It returns a function that can be called to unsubscribe from the event.

Example:

const unsubscribe = navigation.addListener('tabPress', e => {
  // Prevent default action
  e.preventDefault();
});

Normally, you'd add an event listener in React.useEffect for function components. For example:

function Profile({ navigation }) {
  React.useEffect(() => {
    const unsubscribe = navigation.addListener('focus', () => {
      // do something
    });

    return unsubscribe;
  }, [navigation]);

  return <ProfileContent />;
}

The unsubscribe function can be returned as the cleanup function in the effect.

For class components, you can add the event in the componentDidMount lifecycle method and unsubscribe in componentWillUnmount:

class Profile extends React.Component {
  componentDidMount() {
    this._unsubscribe = navigation.addListener('focus', () => {
      // do something
    });
  }

  componentWillUnmount() {
    this._unsubscribe();
  }

  render() {
    // Content of the component
  }
}

One thing to keep in mind is that you can only listen to events from the immediate navigator with addListener. For example, if you try to add a listener in a screen that's inside a stack that's nested in a tab, it won't get the tabPress event. If you need to listen to an event from a parent navigator, you may use navigation.getParent() to get a reference to parent navigator's navigation prop and add a listener.

listeners prop on Screen

Sometimes you might want to add a listener from the component where you defined the navigator rather than inside the screen. You can use the listeners prop on the Screen component to add listeners. The listeners prop takes an object with the event names as keys and the listener callbacks as values.

Example:

<Tab.Screen
  name="Chat"
  component={Chat}
  listeners={{
    tabPress: e => {
      // Prevent default action
      e.preventDefault();
    },
  }}
/>

You can also pass a callback which returns the object with listeners. It'll receive navigation and route as the arguments.

Example:

<Tab.Screen
  name="Chat"
  component={Chat}
  listeners={({ navigation, route }) => ({
    tabPress: e => {
      // Prevent default action
      e.preventDefault();

      // Do something with the `navigation` object
      navigation.navigate('AnotherPlace');
    },
  })}
/>