React Native error: Element type is invalid: expected a string or a class/function but got: object

导入自己写的组件时,加了括号,

import {MyListview} from './ui/base/xListview';

需修改成
import MyListview from './ui/base/xListview';

xListview里代码:
import React,{Component} from 'react';
import {ListView,Text,View} from 'react-native';


class MyListview extends Component{
    constructor(props) {
        super(props);
        console.log('222======', 22);
        const ds = new ListView.DataSource({rowHasChanged:(r1,r2) => r1 !== r2});
        this.state = {
            dataSource:ds.cloneWithRows(['111','222','444','555','333','6666','88888'])
        };
    };
    render() {
        return (
            <View style={{paddingTop:20}}>
                <ListView
                    dataSource={this.state.dataSource}
                    renderRow={(rowData) => <Text>{rowData}</Text>}
                >

                </ListView>
            </View>
        );
    };
};


module.exports = MyListview;