Handling back button in React Native, Navigator on Android

In addition to answer above, handling code should be something like this

var navigator; 

React.BackAndroid.addEventListener('hardwareBackPress', () => {
    if (navigator && navigator.getCurrentRoutes().length > 1) {
        navigator.pop();
        return true;
    }
    return false;
});

in render code:

<Navigator ref={(nav) => { navigator = nav; }} />