Javascript TypeError:undefined不是React Native中的对象（计算'；addTodo（标题、说明）。然后'；）

我有个例外 TypeError:undefined不是对象（计算'addTodo（title，description.）。然后'） 函数工作正常，状态更新正常，但未按预期工作

AddTodo.js：

import { useNavigation } from '@react-navigation/native';
import React , {useContext, useState} from 'react';
import { View } from 'react-native';
import { Input , Button} from 'react-native-elements';
import { TextInput } from 'react-native-gesture-handler';
import {cardContext} from '../contextApi/cardContext';


const NewTodoInput = () =>{
const { addTodo } = useContext(cardContext);
const navigation = useNavigation();


const [title , setTitle] = useState()
const [description , setDescription] = useState()

const handleOnSubmit = ()=>{
    
    addTodo(title,description)
    .then((data)=>{
        navigation.navigate('TodoApp');
        console.log('Added Succesfully : ' + data);
    })
    .catch((e)=>{console.log(e)});

}
return (
    <View>
    <Input 
    placeholder = 'Title'
    onChangeText= {(val)=>{setTitle(val)}}
    />
    <Input 
    placeholder = 'Your todo'
    multiline = {true}
    onChangeText = {(val) => {setDescription(val)}}
    />
    <Button 
        buttonStyle= {{backgroundColor : 'black'}}
        title = 'Submit'
        onPress = {handleOnSubmit}
        
        
    />
    </View>

)

}

export default NewTodoInput ;

---

附言：-在我添加then和catch方法之前，handleonSubmit运行良好。现在我收到了错误，但我的状态仍在添加中。

如果您想更改addTodo，使其返回注释中所述的承诺，则如下所示：

const addTodo = (title , description) =>{
   setData( [...data , {title : title, Description : description}] )
   return new Promise((resolve, reject) => {
       resolve("data") // Do something here preferable what you need inside .then()
                      })
}

---

addTodo

不返回

Promise

这就是为什么您没有

。然后在
handleOnSubmit（）
@norbitrial中（）

如何更改

addTodo

以返回承诺。

TypeError: undefined is not an object (evaluating 'addTodo(title, description).then')
- node_modules\react-native\Libraries\LogBox\LogBox.js:148:8 in registerError
- node_modules\react-native\Libraries\LogBox\LogBox.js:59:8 in errorImpl
- node_modules\react-native\Libraries\LogBox\LogBox.js:33:4 in console.error
- node_modules\expo\build\environment\react-native-logs.fx.js:27:4 in error
- node_modules\react-native\Libraries\Core\ExceptionsManager.js:104:6 in reportException
- node_modules\react-native\Libraries\Core\ExceptionsManager.js:171:19 in handleException
- node_modules\react-native\Libraries\Core\setUpErrorHandling.js:24:6 in handleError
- node_modules\expo-error-recovery\build\ErrorRecovery.fx.js:9:32 in ErrorUtils.setGlobalHandler$argument_0
- node_modules\regenerator-runtime\runtime.js:63:36 in tryCatch
- node_modules\regenerator-runtime\runtime.js:293:29 in invoke
- node_modules\regenerator-runtime\runtime.js:63:36 in tryCatch
- node_modules\regenerator-runtime\runtime.js:154:27 in invoke
- node_modules\regenerator-runtime\runtime.js:164:18 in PromiseImpl.resolve.then$argument_0
- node_modules\react-native\node_modules\promise\setimmediate\core.js:37:13 in tryCallOne
- node_modules\react-native\node_modules\promise\setimmediate\core.js:123:24 in setImmediate$argument_0
- node_modules\react-native\Libraries\Core\Timers\JSTimers.js:130:14 in _callTimer
- node_modules\react-native\Libraries\Core\Timers\JSTimers.js:181:14 in _callImmediatesPass
- node_modules\react-native\Libraries\Core\Timers\JSTimers.js:441:30 in callImmediates
- node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:387:6 in __callImmediates
- node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:135:6 in __guard$argument_0
- node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:364:10 in __guard
- node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:134:4 in flushedQueue
* [native code]:null in flushedQueue
* [native code]:null in invokeCallbackAndReturnFlushedQueue

TypeError: undefined is not an object (evaluating 'addTodo(title, description).then')
- node_modules\react-native\Libraries\LogBox\LogBox.js:148:8 in registerError
- node_modules\react-native\Libraries\LogBox\LogBox.js:59:8 in errorImpl
- node_modules\react-native\Libraries\LogBox\LogBox.js:33:4 in console.error
- node_modules\expo\build\environment\react-native-logs.fx.js:27:4 in error
- node_modules\react-native\Libraries\Core\ExceptionsManager.js:104:6 in reportException
- node_modules\react-native\Libraries\Core\ExceptionsManager.js:171:19 in handleException
- node_modules\react-native\Libraries\Core\setUpErrorHandling.js:24:6 in handleError
- node_modules\expo-error-recovery\build\ErrorRecovery.fx.js:9:32 in ErrorUtils.setGlobalHandler$argument_0
- node_modules\regenerator-runtime\runtime.js:63:36 in tryCatch
- node_modules\regenerator-runtime\runtime.js:293:29 in invoke
- node_modules\regenerator-runtime\runtime.js:63:36 in tryCatch
- node_modules\regenerator-runtime\runtime.js:154:27 in invoke
- node_modules\regenerator-runtime\runtime.js:164:18 in PromiseImpl.resolve.then$argument_0
- node_modules\react-native\node_modules\promise\setimmediate\core.js:37:13 in tryCallOne
- node_modules\react-native\node_modules\promise\setimmediate\core.js:123:24 in setImmediate$argument_0
- node_modules\react-native\Libraries\Core\Timers\JSTimers.js:130:14 in _callTimer
- node_modules\react-native\Libraries\Core\Timers\JSTimers.js:181:14 in _callImmediatesPass
- node_modules\react-native\Libraries\Core\Timers\JSTimers.js:441:30 in callImmediates
- node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:387:6 in __callImmediates
- node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:135:6 in __guard$argument_0
- node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:364:10 in __guard
- node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:134:4 in flushedQueue
* [native code]:null in flushedQueue
* [native code]:null in invokeCallbackAndReturnFlushedQueue

const addTodo = (title , description) =>{
   setData( [...data , {title : title, Description : description}] )
   return new Promise((resolve, reject) => {
       resolve("data") // Do something here preferable what you need inside .then()
                      })
}