Flatlist React-Native 组件防止我的数组填充导致应用程序崩溃
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【中文标题】Flatlist React-Native 组件防止我的数组填充导致应用程序崩溃【英文标题】：Flatlist React-Native component prevents my array from populating causing app to crash 【发布时间】：2020-07-30 12:54:19 【问题描述】：我正在尝试从后端加载屏幕上的一些项目：
async function loadIncidents()
try
const response = await api.get("incidents");
const theData = response.data;
console.log(theData);
setIncidents(theData);
console.log(incidents);
catch (e)
console.error(e.message);
useEffect(() =>
loadIncidents();
, []);
它确实有效，我可以在日志中看到我的数据，但只有当负责呈现每个项目的平面列表没有被评论时，它才不会填充我的数组并向我显示错误：
传播不可迭代实例的尝试无效。为了 可迭代的非数组对象必须有 Symbol.iterator 方法。 - node_modules@babel\runtime\helpers\nonIterableSpread.js:2:22 在 _nonIterableSpread - node_modules@babel\runtime\helpers\toConsumableArray.js:10:111 在 _toConsumableArray * src\pages\Incidents\index.js:54:6 in Incidents - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:10696:27 在 renderWithHooks 中 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:12842:6 在更新函数组件中 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:307:15 在 invokeGuardedCallbackImpl - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:531:36 在调用GuardedCallback - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:20488:8 在开始工作$$1 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:19370:24 在 performUnitOfWork - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:19347:39 在 workLoopSync - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18997:22 在渲染根 * [本机代码]：renderRoot中的null - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18709:28 在 runRootCallback * [本机代码]：runRootCallback 中的 null - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5642:32 在 runWithPriority$argument_1 - 不稳定的runWithPriority中的node_modules\scheduler\cjs\scheduler.development.js:643:23 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5638:22 在 flushSyncCallbackQueueImpl - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5627:28 在flushSyncCallbackQueue - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18556:30 在 scheduleUpdateOnFiber - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:11484:17 在 dispatchAction * [本机代码]：dispatchAction 中的 null * src\pages\Incidents\index.js:29:18 在 loadIncidents - node_modules\regenerator-runtime\runtime.js:45:44 在 tryCatch - 调用中的 node_modules\regenerator-runtime\runtime.js:274:30 - node_modules\regenerator-runtime\runtime.js:45:44 在 tryCatch - 调用中的 node_modules\regenerator-runtime\runtime.js:135:28 - PromiseImpl.resolve.then$argument_0 中的 node_modules\regenerator-runtime\runtime.js:145:19 - node_modules\promise\setimmediate\core.js:37:14 在 tryCallOne - setImmediate$argument_0 中的 node_modules\promise\setimmediate\core.js:123:25 - node_modules\react-native\Libraries\Core\Timers\JSTimers.js:146:14 在 _callTimer - _callImmediatesPass 中的 node_modules\react-native\Libraries\Core\Timers\JSTimers.js:194:17 - node_modules\react-native\Libraries\Core\Timers\JSTimers.js:458:30 在 callImmediates * [本机代码]：callImmediates 中的 null - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:407:6 在 __callImmediates - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:143:6 在 __guard$argument_0 - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:384:10 在 __guard - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:142:17 在 __guard$argument_0 * [本机代码]：flushedQueue中的null * [native code]:null in callFunctionReturnFlushedQueue
警告：%s：应实现错误边界 getDerivedStateFromError()。在该方法中，将状态更新返回到 显示错误消息或回退 UI。，RootErrorBoundary - node_modules\react-native\Libraries\YellowBox\YellowBox.js:63:8 in console.error - node_modules\expo\build\environment\muteWarnings.fx.js:27:24 错误 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:645:36 在警告WithoutStack - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18056:16 在回调中 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:7595:16 在回调回调 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:7639:19 在 commitUpdateEffects - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:7630:22 在提交更新队列中 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:17116:10 在提交生命周期中 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:20002:23 在 commitLayoutEffects - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:307:15 在 invokeGuardedCallbackImpl - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:531:36 在调用GuardedCallback - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:19768:10 在 commitRootImpl * [本机代码]：commitRootImpl 中的 null - 不稳定的runWithPriority中的node_modules\scheduler\cjs\scheduler.development.js:643:23 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:19590:4 在 commitRoot * [本机代码]：commitRoot 中的 null - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18709:28 在 runRootCallback * [本机代码]：runRootCallback 中的 null - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5642:32 在 runWithPriority$argument_1 - 不稳定的runWithPriority中的node_modules\scheduler\cjs\scheduler.development.js:643:23 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5638:22 在 flushSyncCallbackQueueImpl - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5627:28 在flushSyncCallbackQueue - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18556:30 在 scheduleUpdateOnFiber - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:11484:17 在 dispatchAction * [本机代码]：dispatchAction 中的 null * src\pages\Incidents\index.js:29:18 在 loadIncidents - node_modules\regenerator-runtime\runtime.js:45:44 在 tryCatch - 调用中的 node_modules\regenerator-runtime\runtime.js:274:30 - node_modules\regenerator-runtime\runtime.js:45:44 在 tryCatch - 调用中的 node_modules\regenerator-runtime\runtime.js:135:28 - PromiseImpl.resolve.then$argument_0 中的 node_modules\regenerator-runtime\runtime.js:145:19 - node_modules\promise\setimmediate\core.js:37:14 在 tryCallOne - setImmediate$argument_0 中的 node_modules\promise\setimmediate\core.js:123:25 - node_modules\react-native\Libraries\Core\Timers\JSTimers.js:146:14 在 _callTimer - _callImmediatesPass 中的 node_modules\react-native\Libraries\Core\Timers\JSTimers.js:194:17 - node_modules\react-native\Libraries\Core\Timers\JSTimers.js:458:30 在 callImmediates * [本机代码]：callImmediates 中的 null - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:407:6 在 __callImmediates - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:143:6 在 __guard$argument_0 - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:384:10 在 __guard r - _callImmediatesPass 中的 node_modules\react-native\Libraries\Core\Timers\JSTimers.js:194:17 - node_modules\react-native\Libraries\Core\Timers\JSTimers.js:458:30 在 callImmediates * [本机代码]：callImmediates 中的 null - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:407:6 在 __callImmediates - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:143:6 在 __guard$argument_0 - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:384:10 在 __guard - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:142:17 在 __guard$argument_0 * [本机代码]：flushedQueue中的null * [native code]:null in callFunctionReturnFlushedQueue
看起来 Flatlist 正在阻止我的函数 loadIncidents() 填充我的数组，当 Flatlist 存在并调用我的变量时，数组返回空。我尝试了几种方法来调试它，但都不起作用。 这是 Flatlist，没什么特别的：
<FlatList
data=incidents
style=styles.incidentList
keyExtractor=(incident) => String(incident.id)
showsVerticalScrollIndicator=false
renderItem=( item: incident ) => (
<View style=styles.incident>
<Text style=styles.incidentProperty>NGO:</Text>
<Text style=styles.incidentValue>incident.name</Text>
</View>
)
/>
【问题讨论】：
【参考方案1】：FlatList 应该接收数组作为数据，你得到的错误是你给了它 Object，因为你发布了你从 api 响应中得到的。
看来你需要
setIncidents(theData.incidents)
相反。
关于这个的另一件事
setIncidents(theData);
console.log(incidents)
一般来说，
SetState 是异步调用，因此记录的变量无论如何都会是前一个
【讨论】：
谢谢，你是对的，它是一个对象。我无法正确准备好 json 格式，我可能会使用 typescript 来避免这些情况，在 react native 中调试已经足够复杂了。 真心推荐Reactotron 尽可能方便调试【参考方案2】：
API 调用返回的数据
> Object "config": Object
> "adapter": [Function xhrAdapter],
> "baseURL": "http://192.168.xxx.xxx:3333",
> "data": undefined,
> "headers": Object
> "Accept": "application/json, text/plain, */*",
> ,
> "maxContentLength": -1,
> "method": "get",
> "params": Object
> "page": 1,
> ,
> "timeout": 0,
> "transformRequest": Array [
> [Function transformRequest],
> ],
> "transformResponse": Array [
> [Function transformResponse],
> ],
> "url": "/incidents",
> "validateStatus": [Function validateStatus],
> "xsrfCookieName": "XSRF-TOKEN",
> "xsrfHeaderName": "X-XSRF-TOKEN", , "data": Object
> "incidents": Array [
> Object
> "city": "Vancouver",
> "description": "details of the Incident report",
> "email": "info@apade.ca",
> "id": 3,
> "name": "Apade",
> "ngo_id": "5209f9ae",
> "state": "BC",
> "title": "IR 2",
> "value": 110,
> "whatsapp": "604 123 1234",
> ,
> Object
> "city": "Vancouver",
> "description": "details of the Incident report",
> "email": "info@apade.ca",
> "id": 6,
> "name": "Apade",
> "ngo_id": "5209f9ae",
> "state": "BC",
> "title": "IR 4",
> "value": 120,
> "whatsapp": "604 123 1234",
> ,
> Object
> "city": "Vancouver",
> "description": "details of the Incident report",
> "email": "info@apade.ca",
> "id": 7,
> "name": "Apade",
> "ngo_id": "5209f9ae",
> "state": "BC",
> "title": "IR 5",
> "value": 120,
> "whatsapp": "604 123 1234",
> ,
> Object
> "city": "Vancouver",
> "description": "details of the Incident report",
> "email": "info@apade.ca",
> "id": 8,
> "name": "Apade",
> "ngo_id": "5209f9ae",
> "state": "BC",
> "title": "IR 6",
> "value": 120,
> "whatsapp": "604 123 1234",
> ,
> Object
> "city": "Vancouver",
> "description": "details of the Incident report",
> "email": "info@apade.ca",
> "id": 9,
> "name": "Apade",
> "ngo_id": "5209f9ae",
> "state": "BC",
> "title": "IR 7",
> "value": 120,
> "whatsapp": "604 123 1234",
> ,
> ], , "headers": Object
> "access-control-allow-origin": "*",
> "cache-control": "public, max-age=0",
> "connection": "keep-alive",
> "content-length": "1015",
> "content-type": "application/json; charset=utf-8",
> "date": "Fri, 17 Apr 2020 17:18:17 GMT",
> "etag": "W/\"3f7-qB7SdnrSk8xOqSo8f9RGhorMNdk\"",
> "x-powered-by": "Express",
> "x-total-count": "12", , "request": XMLHttpRequest
> "DONE": 4,
> "HEADERS_RECEIVED": 2,
> "LOADING": 3,
> "OPENED": 1,
> "UNSENT": 0,
> "_aborted": false,
> "_cachedResponse": undefined,
> "_hasError": false,
> "_headers": Object
> "accept": "application/json, text/plain, */*",
> ,
> "_incrementalEvents": false,
> "_lowerCaseResponseHeaders": Object
> "access-control-allow-origin": "*",
> "cache-control": "public, max-age=0",
> "connection": "keep-alive",
> "content-length": "1015",
> "content-type": "application/json; charset=utf-8",
> "date": "Fri, 17 Apr 2020 17:18:17 GMT",
> "etag": "W/\"3f7-qB7SdnrSk8xOqSo8f9RGhorMNdk\"",
> "x-powered-by": "Express",
> "x-total-count": "12",
> ,
> "_method": "GET",
> "_requestId": null,
> "_response": "\"incidents\":[\"id\":3,\"title\":\"IR 2\",\"description\":\"details of the Incident
> report\",\"value\":110,\"ngo_id\":\"5209f9ae\",\"name\":\"Apade\",\"email\":\"info@apade.ca\",\"whatsapp\":\"604
> 123
> 1234\",\"city\":\"Vancouver\",\"state\":\"BC\",\"id\":6,\"title\":\"IR
> 4\",\"description\":\"details of the Incident
> report\",\"value\":120,\"ngo_id\":\"5209f9ae\",\"name\":\"Apade\",\"email\":\"info@apade.ca\",\"whatsapp\":\"604
> 123
> 1234\",\"city\":\"Vancouver\",\"state\":\"BC\",\"id\":7,\"title\":\"IR
> 5\",\"description\":\"details of the Incident
> report\",\"value\":120,\"ngo_id\":\"5209f9ae\",\"name\":\"Apade\",\"email\":\"info@apade.ca\",\"whatsapp\":\"604
> 123
> 1234\",\"city\":\"Vancouver\",\"state\":\"BC\",\"id\":8,\"title\":\"IR
> 6\",\"description\":\"details of the Incident
> report\",\"value\":120,\"ngo_id\":\"5209f9ae\",\"name\":\"Apade\",\"email\":\"info@apade.ca\",\"whatsapp\":\"604
> 123
> 1234\",\"city\":\"Vancouver\",\"state\":\"BC\",\"id\":9,\"title\":\"IR
> 7\",\"description\":\"details of the Incident
> report\",\"value\":120,\"ngo_id\":\"5209f9ae\",\"name\":\"Apade\",\"email\":\"info@apade.ca\",\"whatsapp\":\"604
> 123 1234\",\"city\":\"Vancouver\",\"state\":\"BC\"]",
> "_responseType": "",
> "_sent": true,
> "_subscriptions": Array [],
> "_timedOut": false,
> "_trackingName": "unknown",
> "_url": "http://192.168.xxx.xxx:3333/incidents?page=1",
> "readyState": 4,
> "responseHeaders": Object
> "Access-Control-Allow-Origin": "*",
> "Cache-Control": "public, max-age=0",
> "Connection": "keep-alive",
> "Content-Length": "1015",
> "Content-Type": "application/json; charset=utf-8",
> "Date": "Fri, 17 Apr 2020 17:18:17 GMT",
> "ETag": "W/\"3f7-qB7SdnrSk8xOqSo8f9RGhorMNdk\"",
> "X-Powered-By": "Express",
> "X-Total-Count": "12",
> ,
> "responseURL": "http://192.168.xxx.xxx:3333/incidents?page=1",
> "status": 200,
> "timeout": 0,
> "upload": XMLHttpRequestEventTarget ,
> "withCredentials": true, , "status": 200, "statusText": undefined,
【讨论】：
【参考方案3】：你能把整个组件的代码和事件数据的结构发过来吗？ 该消息说您正在尝试传播不可迭代的实例。可能是你正在取回一个未解析的 json 对象？ 如果是这样尝试使用 JSON.parse 将 json 字符串转换为 js 结构
【讨论】：
我在此处添加了代码：github.com/yamgarcia/Be-The-Hero-NGOs/blob/master/mobile/src/… 在调试时，我将第 62-64 行中的以上是关于Flatlist React-Native 组件防止我的数组填充导致应用程序崩溃的主要内容，如果未能解决你的问题，请参考以下文章
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