React Native 实现首页双击退出

最近在做一个跨平台的项目,刚用Tab-Navigator做完首页底部导航菜单,发现个问题,Android返回键一按下,app就退出了,这不符合app的玩法啊,各种找解决方案,终于实现了.暂时先做个记录,后面在详细完善下全局的返回键处理

var firstClick = 0;
export default class MainActivity extends React.Component {

    constructor(props) {
        super(props);
        this.state = {
            selectedTab: 'home',
        }
        this.handleBack = this.handleBack.bind(this);
    }

    componentDidMount() {
        BackHandler.addEventListener('hardwareBackPress', this.handleBack)
    }

    componentWillUnmount() {
        BackHandler.removeEventListener('hardwareBackPress', this.handleBack)
    }

    handleBack = () => {
        var timestamp = (new Date()).valueOf();
        if (timestamp - firstClick > 2000) {
            firstClick = timestamp;
            ToastAndroid.show('再按一次退出', ToastAndroid.SHORT);
            return true;
        } else {
            return false;
        }

    }

QQ图片20170517172741.png