[英]React Native: setState doesn't work when calling try-catch function
我試圖用從另一個文件導入的此代碼調用APP,它工作正常:
import FormData from 'FormData';
import AsyncStorage from '@react-native-community/async-storage';
let formData = new FormData();
formData.append('userId', '1'); // < this is what I want to change
formData.append('key', '***'); //my key
export function getScoreFromAPI () {
return fetch('https://www.globalfidelio.com/gfn_arcol/api/transaction.php',{
method : 'POST',
headers : {
'Accept': 'application/json',
'Content-Type': 'multipart/form-data'
},
body : formData
} )
.then((response) => {
return response.json()
})
.catch((error) => console.log("l'erreure est: " + error))
}
但是現在我想將我的userId從1更改為Asyncstorage的常量,因此我決定將代碼更改為此:
constructor(props) {
super(props)
this.state = { infos: [], userId: '' }
}
componentWillMount() {
this.getScoreFromAPI().then(data => {
this.setState({ infos: data })
});
console.log(this.state.infos);
AsyncStorage.getItem(USERID_STORED)
.then((data) => {
if (data) {
this.setState({userId:data})
}
});
}
async getScoreFromAPI() {
let formData = new FormData();
formData.append('userId', this.state.userId);
formData.append('key', '***'); //my key
try {
let response = await fetch('https://www.globalfidelio.com/gfn_arcol/api/transaction.php',{
method: 'POST',
headers: {
'Accept': 'application/json',
'Content-Type': 'multipart/form-data'
},
body: formData
})
let res = await response.json();
} catch(error) {
console.warn("errors are " + error);
}
};
使用try-catch函數,但是當我在ComponentWillMount()
調用getScoreFromAPI()
,無法使用接收到的數據設置狀態,信息中仍然有一個空數組:[]
我的問題:
我如何用第一個文件中asyncstorage中的值替換userId中的'1'?
如果不可能的話,我對setState info:[]所做的操作已顯示了數據
getScoreFromAPI
不返回任何內容,這就是為什么setState
不起作用的原因。 try
and catch
,promise具有自己的錯誤處理機制(.catch()方法)。 .then()
相比.then()
我認為回調更易讀,並且導致的錯誤更少。 這就是我要做的:
constructor(props)
{
super(props);
this.state = { infos: [], userId: '' };
this.onSuccess = this.onSuccess.bind(this);
this.onFailure = this.onFailure.bind(this);
}
componentWillMount()
{
// Get userID from local storage, then call your API
AsyncStorage.getItem(YOUR_KEY)
.then(userID=> {
if (userID)
{
this.setState({ userId : userID }, () => {
this.getScoreFromAPI(this.onSuccess, this.onFailure);
});
}
});
}
onSuccess(data)
{
this.setState({
infos : data
});
}
onFailure(err)
{
console.warn('Error ' + err);
}
getScoreFromAPI(onSuccess, onFailure)
{
let formData = new FormData();
formData.append('userId', this.state.userId);
formData.append('key', '***'); //your key
fetch('https://www.globalfidelio.com/gfn_arcol/api/transaction.php', {
method : 'POST',
headers: {
'Accept': 'application/json',
'Content-Type': 'multipart/form-data'
},
body: formData
})
.then(res => res.json())
.then(json => {
onSuccess(json);
})
.catch(err => {
onFailure(err);
});
}
我已經將您的代碼簡化為一個getScoreFromAPI
鏈,在該鏈中,從AsyncStorage獲取userId
之后將執行getScoreFromAPI調用,然后將響應存儲到infos
狀態,同時在出現錯誤時返回null
並將錯誤記錄到控制台。 先前未從getScoreFromAPI
返回數據,因此該值將始終為null
。 我尚未測試此代碼,但這將為您提供一個良好的工作基礎:
import FormData from 'FormData';
import AsyncStorage from '@react-native-community/async-storage';
export default class Test {
constructor() {
this.state = {
infos: null,
userId: ''
};
}
componentDidMount() {
AsyncStorage.getItem(this.state.userId)
.then(userID => {
this.setState({ userId: userID || '' });
})
.then(() => {
return this.getScoreFromAPI();
})
.then(data => {
this.setState({ infos: data });
})
.catch(console.error);
}
getScoreFromAPI = () => {
const formData = new FormData();
formData.append('userId', this.state.userId);
formData.append('key', '***'); //my key
fetch('https://www.globalfidelio.com/gfn_arcol/api/transaction.php', {
method: 'POST',
headers: {
Accept: 'application/json',
'Content-Type': 'multipart/form-data'
},
body: formData
})
.then(response => {
// use response data here
return response.json();
})
.catch(e => {
console.error(e);
return null;
});
};
}
終於完成了 我嘗試了一下,它起作用了。 謝謝大家
這是我所做的:
...
const USERID_STORED = "userid_stored";
const GSM_STORED = "gsm_stored";
...
class ScoreList extends React.Component {
constructor(props) {
super(props)
this.state = { infos: [], userId: '', gsmStored: '', }
}
componentWillMount() {
AsyncStorage.getItem(USERID_STORED)
.then(userId => {
this.setState({ userId: userId});
this.getScoreFromAPI(this.state.userId).then(data => {
this.setState({ infos: data });
});
});
AsyncStorage.getItem(GSM_STORED)
.then(gsmStore => {
this.setState({ gsmStored: gsmStore});
});
}
getScoreFromAPI (userId) {
let formData = new FormData();
formData.append('userId', userId);
formData.append('key', '***');
return fetch('https://***',{
method : 'POST',
headers : {
'Accept': 'application/json',
'Content-Type': 'multipart/form-data'
},
body : formData
} )
.then((response) => {
return response.json()
})
.catch((error) => console.log("l'erreure est: " + error))
};
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