react-navigation标题居中问题

将默认导航标题样式改成如下即可

const TITLE_OFFSET = Platform.OS === 'ios' ? 70 : 56;
const defalutOption = {
    headerStyle: {
        backgroundColor: '#f2f2f2',
        height:40
    },
    headerTintColor: '#666',
    headerTitleStyle:{
        alignSelf:'center',
        textAlign: 'center',
        flex:1,
        fontSize:14
    },
    headerTitleContainerStyle:{
        left: TITLE_OFFSET,
        right: TITLE_OFFSET,
    }
}