react-native StackNavigator中的条件标头

const StackNavigatorConfig = {
  initialRouteName: 'Home',
  defaultNavigationOptions: {
    title: 'Default Title',
  },
  navigationOptions: ({ navigation }) => ({
    title: navigation.getParam('customTitle', 'Default Title'),
  }),
};

const AppNavigator = createStackNavigator(RouteConfigs, StackNavigatorConfig);

class HomeScreen extends React.Component {
  static navigationOptions = ({ navigation }) => {
    const customTitle = navigation.getParam('customTitle', 'Default Title');
    return {
      title: customTitle,
    };
  };

  componentDidMount() {
    this.props.navigation.setParams({ customTitle: 'Custom Title' });
  }

  // ...
}