react-native解决跳转至外部app，返回之后的回调方法

第一步监听

   AppState.addEventListener('change', this._handleAppStateChange);

第二部：

handleAppStateChange = (currentAppState) => {

        if(this.lastAppState === 'background' && currentAppState === 'active') {

            //refresh

            let baseId = this.props.navigation.state.params.id;

            let eid = this.props.navigation.state.params.eid;

            this.getSignaturePageWord2ImagesResp(baseId, eid);

        }

        this.lastAppState = currentAppState;

      }

第三部：

 componentWillUnmount = ()=>{

    // Remove the listener when you are done

    AppState.removeEventListener('change', this._handleAppStateChange);

    }