Flatlist React-Native 组件阻止我的数组填充导致应用程序崩溃

Question

我正在尝试从后端在屏幕上加载一些项目：

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 Flatlist 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无效尝试。 为了可迭代，非数组对象必须具有 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在事件中 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:10696:27 在 renderWithHooks - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:12842:6 在 updateFunctionComponent -invokeGuardedCallbackImpl 中的 node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:307:15 -invokeGuardedCallback 中的 node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:531:36 -node_modules \react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:20488:8 在 beginWork$$1 - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:19370:24 在 performUnitOfWork - node_modules \react-native\Libraries\Renderer\impleme ntations\ReactNativeRenderer-dev.js:19347:39 in workLoopSync - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18997:22 in renderRoot * [native code]:null in renderRoot - node_modules\react -native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18709:28 in runRootCallback * [native code]:null in runRootCallback - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5642： 32 在 runWithPriority$argument_1 - node_modules\scheduler\cjs\scheduler.development.js:643:23 在不稳定的runWithPriority - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5638:22 在flushSyncCallbackQueueImpl - node_modules\ react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5627:28 in flushSyncCallbackQueue - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18556:30 in sc heduleUpdateOnFiber - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:11484:17 in dispatchAction * [native code]:null in dispatchAction * src\pages\Incidents\index.js:29:18 in loadIncidents - tryCatch 中的 node_modules\regenerator-runtime\runtime.js:45:44 - 调用中的 node_modules\regenerator-runtime\runtime.js:274:30 - tryCatch 中的 node_modules\regenerator-runtime\runtime.js:45:44 - node_modules \regenerator-runtime\runtime.js:135:28 in invoke - node_modules\regenerator-runtime\runtime.js:145:19 in PromiseImpl.resolve.then$argument_0 - node_modules\promise\setimmediate\core.js:37:14在 tryCallOne - node_modules\promise\setimmediate\core.js:123:25 在 setImmediate$argument_0
- node_modules\react-native\Libraries\Core\Timers\JSTimers.js:146:14 在 _callTimer - node_modules\react-native\Libraries\Core\Timers\JSTimers.js:194:17 在 _callImmediatesPass - node_modules\react-native \Libraries\Core\Timers\JSTimers.js:458:30 在 callImmediates * [本机代码]：null 在 callImmediates - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:407:6 在 __callImmediates - node_modules\react- native\Libraries\BatchedBridge\MessageQueue.js:143:6 在 __guard$argument_0 - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:384:10 在 __guard - node_modules\react-native\Libraries\BatchedBridge\MessageQueue。 js:142:17 in __guard$argument_0 * [native code]:null in flushedQueue * [native code]:null in callFunctionReturnFlushedQueue

警告：%s：错误边界应实现 getDerivedStateFromError()。 在该方法中，返回 state 更新以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 in warningWithoutStack - 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 在回调中 - 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 commitUpdateQueue - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js： 17116:10 在 commitLifeCycles - node_modu les\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:20002:23 在 commitLayoutEffects - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:307:15 in invokeGuardedCallbackImpl - node_modules\ react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:531:36 in invokeGuardedCallback - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:19768:10 in commitRootImpl * [native code] :null 在 commitRootImpl - node_modules\scheduler\cjs\scheduler.development.js:643:23 在unstable_runWithPriority - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:19590:4 在 commitRoot * [本机代码]:null 在 commitRoot - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:18709:28 in runRootCallback * [native code]:null 在 runRootCallback node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5642:32 in runWithPriority$argument_1 - node_modules\scheduler\cjs\scheduler.development.js:643:23 in stable_runWithPriority - node_modules\react-native\ Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5638:22 在 flushSyncCallbackQueueImpl - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:5627:28 在 flushSyncCallbackQueue - node_modules\react-native\Libraries\ Renderer\implementations\ReactNativeRenderer-dev.js:18556:30 在 scheduleUpdateOnFiber - node_modules\react-native\Libraries\Renderer\implementations\ReactNativeRenderer-dev.js:11484:17 在 dispatchAction * [native code]:null 在 dispatchAction * src \pages\Incidents\index.js:29:18 in loadIncidents - node_modules\regenerator-runtime\runtime.js:45:44 in tryCatch - node_modules\regenerator-runtime\runtime.js:274:30 in invoke - node_modules\regenerator -运行时\运行时 e.js:45:44 in tryCatch - node_modules\regenerator-runtime\runtime.js:135:28 in invoke - node_modules\regenerator-runtime\runtime.js:145:19 in PromiseImpl.resolve.then$argument_0 - node_modules\ tryCallOne 中的 promise\setimediate\core.js:37:14 - setImmediate$argument_0 中的 node_modules\promise\setimmediate\core.js:123:25
- node_modules\react-native\Libraries\Core\Timers\JSTimers.js:146:14 在 _callTimer - node_modules\react-native\Libraries\Core\Timers\JSTimers.js:194:17 在 _callImmediatesPass - node_modules\react-native \Libraries\Core\Timers\JSTimers.js:458:30 在 callImmediates * [本机代码]：null 在 callImmediates - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:407:6 在 __callImmediates - node_modules\react- native\Libraries\BatchedBridge\MessageQueue.js:143:6 in __guard$argument_0 - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:384:10 in __guard r - node_modules\react-native\Libraries\Core\Timers \JSTimers.js:194:17 in _callImmediatesPass - node_modules\react-native\Libraries\Core\Timers\JSTimers.js:458:30 in callImmediates * [native code]:null in callImmediates - node_modules\react-native\Libraries\ BatchedBridge\MessageQueue.js:407:6 在 __callImmediates - node_modules\r eact-native\Libraries\BatchedBridge\MessageQueue.js:143:6 in __guard$argument_0 - node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:384:10 in __guard - node_modules\react-native\Libraries\BatchedBridge\ MessageQueue.js:142:17 in __guard$argument_0 * [native code]:null in flushedQueue * [native code]:null in callFunctionReturnFlushedQueue

看起来 Flatlist 正在阻止我的 function 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，但都行不通。 这是 Flatlist，没有什么特别的：

<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>
     )}
 />

Answer 1

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。 可能是您正在取回未解析的 json object？ 如果是这样尝试使用 JSON.parse 将 json 字符串转换为 js 结构

Answer 2

从 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, }

Answer 3

FlatList应该接收 arrays 作为数据，你得到的错误是你给了它 Object ，正如你发布的那样，你从 api 响应中得到。

看起来你需要

---

 setIncidents(theData.incidents)

---

反而。

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