在 React Native 中没有移除事件监听器

Question

I have registered an event for handling the hardware back button press in the Home Screen . Whenever I click the back button when I am in the home screen , it will ask me for the exit confirmation alert box. I want this behaviour to happen only in the Home screen , not in any other screen. When I am in some other screen, let's say Setting Screen and I click the back button, it still shows me the exit confirmation alert box. It seems like the event I registered on the Home Screen has not been removed.

const backAction = () => {
    Alert.alert('Close the KhataBook app?', 'Are you sure you want to exit?', [
      {
        text: 'Cancel',
        onPress: () => null,
        style: 'cancel',
      },
      {text: 'YES', onPress: () => BackHandler.exitApp()},
    ]);
    return true;
  };

  useEffect(() => {
    const backHandler = BackHandler.addEventListener(
      'hardwareBackPress',
      backAction,
    );
    return () => backHandler.remove();
  }, []);

Answer 1

Try to remove listener like in docs, with removeEventListener method

  useEffect(() => {
    BackHandler.addEventListener("hardwareBackPress", backAction);

    return () =>
      BackHandler.removeEventListener("hardwareBackPress", backAction);
  }, []);

Answer 2

If you are using react navigation you can achieve that by doing the following:

  useFocusEffect(() => {
        const backHandler = BackHandler.addEventListener(
            'hardwareBackPress', ()=>{ navigation.goBack(); return true; });
        return () => {
            backHandler.remove();
        };
    });