Reactjs React Native null不是对象'；this.state.dataSource.map'；

实际上，我试图在react native中使用fetch方法，方法如下/prenotazioni返回以下json

[{"DESCLI_PTV":"We","ORAIN_PTV":"2019-10-09T10:00:00.000Z"},{"DESCLI_PTV":"igor","ORAIN_PTV":"2019-10-09T11:00:00.000Z"},{"DESCLI_PTV":"Giovanni","ORAIN_PTV":"2019-10-09T12:00:00.000Z"},{"DESCLI_PTV":"Veronica","ORAIN_PTV":"2019-10-09T14:00:00.000Z"},{"DESCLI_PTV":"We","ORAIN_PTV":"2019-10-09T13:00:00.000Z"},{"DESCLI_PTV":"Giovanni","ORAIN_PTV":"2019-10-09T20:00:00.000Z"},{"DESCLI_PTV":"Igor","ORAIN_PTV":"2019-10-10T11:00:00.000Z"},{"DESCLI_PTV":"Giovanni","ORAIN_PTV":"2019-10-10T13:00:00.000Z"},{"DESCLI_PTV":"We","ORAIN_PTV":"2019-10-10T12:00:00.000Z"},{"DESCLI_PTV":"We","ORAIN_PTV":"2019-10-10T15:00:00.000Z"},{"DESCLI_PTV":"Igor Mytyuk","ORAIN_PTV":"2019-10-11T14:10:00.000Z"}]

但当我试图运行应用程序时，它返回错误

'null不是对象（正在评估'this.state.dataSource.map'）

这里是Dashboard.JS

import React from 'react';
import { FlatList, ActivityIndicator, Text, View  } from 'react-native';

export default class Dashboard extends React.Component {

      constructor(props){
        super(props);
        this.state ={ isLoading: true}
      }

      componentDidMount(){
        return fetch('192.168.100.160:3000/prenotazioni')
          .then((response) => response.json())
          .then((responseJson) => {

            this.setState({
              isLoading: false,
              dataSource: responseJson,
            }, function(){

            });

          })
          .catch((error) =>{
            console.error(error);
          });
      }



      render(){

        if(this.state.isLoading){
          return(
            <View style={{flex: 1, padding: 20}}>
              <ActivityIndicator/>
            </View>
          )
        }

        return(
          <View style={{flex: 1, paddingTop:20}}>
            <FlatList
              data={this.state.dataSource}
              renderItem={({item}) => <Text>{item.DESCLI_PTV}, {item.ORAIN_PTV}</Text>}
              keyExtractor={({id}, index) => id}
            />
          </View>
        );
      }
    }

从“React”导入React；
从“react native”导入{FlatList，ActivityIndicator，Text，View}；
导出默认类Dashboard扩展React.Component{
建造师（道具）{
超级（道具）；
this.state={isLoading:true}
}
componentDidMount（）{
返回获取（'192.168.100.160:3000/prenotazioni'）
.then（（response）=>response.json（））
.然后（（responseJson）=>{
这是我的国家({
孤岛加载：false，
数据来源：responseJson，
}，函数（）{
});
})
.catch（（错误）=>{
控制台错误（error）；
});
}
render（）{
if（此.state.isLoading）{
返回(
)
}
返回(
{item.DESCLI_PTV}，{item.ORAIN_PTV}
keyExtractor={（{id}，索引）=>id}
/>
);
}
}
在
状态下缺少
数据源：[]
。所以试试看

this.state ={ isLoading: true, dataSource: [] }

状态中缺少
数据源：[]
。所以试试看

this.state ={ isLoading: true, dataSource: [] }