react native 里listview组件 的clonewithrows参数不能访问外部变量？

Question

updata(){

        let newData;
        fetch('http://127.0.0.1:8080/news',{method:'post',headers:{}})
            .then((response) => response.json())
            .then((responseJson) => {
                newData=responseJson.greet;this.setState({refreshing:false});alert(newData)
            })
            .catch((error) => {
                console.error(error);
            });

        const ds = new ListView.DataSource({rowHasChanged: (r1, r2) => r1 !== r2});

        this.setState({

            dataSource:ds.cloneWithRows(['ff',newData])
        })
    }

这边最后一行dataSource:ds.cloneWithRows(['ff',newData])，显示newData是空的，但上面alert显示newData值时字符串‘hello’，这是为啥？

Answer 1

let newData;
        fetch('http://127.0.0.1:8080/news',{method:'post',headers:{}})
            .then((response) => response.json())
            .then((responseJson) => {
                newData=responseJson.greet;
                this.setState({
                    dataSource:ds.cloneWithRows(['ff',newData]),
                    refreshing:false,
                });
            })
            .catch((error) => {
                console.error(error);
            
            this.setState({
                    refreshing:false,
                });
            });

setState放到回调里面去