react native + expo で todoapp を作ってるのですが、新しいtodoを追加する処理で「undefined is not an object」というエラーが出てしまいます

行き詰っております。どなたかご教授くださると幸いです。

コード↓

javascript
1import React, { Component } from 'react';
2import {
3  Platform,
4  StatusBar,
5  StyleSheet,
6  View,
7  Text,
8  ScrollView,
9  FlatList,
10  KeyboardAvoidingView,
11} from 'react-native';
12import {
13  Input,
14  Button,
15} from'react-native-elements'
16import Icon from 'react-native-vector-icons/Feather'
17
18export default class App extends Component {
19  constructor(props) {
20    super(props)
21    this.state= {
22      todo: [],
23      currentIndex: 0,
24      inputText: "",
25    }
26  }
27
28  onAddItem(){
29    let title = this.state.inputText
30    if(title == ""){
31      return
32    }
33    let index = this.state.currentIndex + 1
34    let newTodo = {title: title, index: index, done: false}
35    let todo = [...this.state.todo, newTodo]
36    this.setState({
37      todo: todo,
38      currentIndex: index,
39      inputText: "",
40    })
41
42  }
43
44  render() {
45    return(
46      <KeyboardAvoidingView style={styles.container} behavior="padding">
47
48        {/* todo list */}
49        <ScrollView style={styles.todolist}>
50          <FlatList
51            data={this.state.todo}
52            renderItem={({item}) => <Text>{item.title}</Text>}
53            keyExtractor={(item) => item.index.toString()}
54          />
55        </ScrollView>
56
57        {/* 新しい todo を追加するところ */}
58        <View style={styles.input}>
59          {/* text 入力欄 */}
60          <Input
61            containerStyle={styles.inputText}
62            onChange={(text) => this.setState({inputText: text.text})}
63            value={this.state.inputText}
64          />
65          {/* 追加ボタン */}
66          <Button
67            icon={
68              <Icon
69                name='plus'
70                size={30}
71                color='white'
72              />
73            }
74            title=""
75            onPress={this.onAddItem}
76            buttonStyle={styles.inputButton}
77          />
78        </View>
79
80      </KeyboardAvoidingView>
81    )
82  }
83}
84
85const styles = StyleSheet.create({
86  container: {
87    flex: 1,
88    paddingTop: Platform.OS == 'ios' ? 20 : StatusBar.currentHeight,
89  },
90
91  todolist: {
92    flex: 1,
93  },
94  input: {
95    height: 50,
96    flexDirection: 'row',
97    paddingRight: 10,
98  },
99
100  inputText: {
101    paddingLeft: 10,
102    paddingRight: 10,
103    flex: 1,
104  },
105  inputButton: {
106    width: 48,
107    height: 48,
108    borderWidth: 0,
109    borderColor: 'yellowgreen',
110    borderRadius: 48,
111    backgroundColor: 'green'
112  }
113})

出てきてしまったエラー↓

javascript
1undefined is not an object (evaluating 'this.state.inputText')
2onAddItem
3    C:\Users\nkawa\Documents\Expo\TodoApp\App.js:33:27
4touchableHandlePress
5    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Components\Touchable\TouchableNativeFeedback.android.js:187:45
6_performSideEffectsForTransition
7    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Components\Touchable\Touchable.js:803:34
8_receiveSignal
9    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Components\Touchable\Touchable.js:717:44
10touchableHandleResponderRelease
11    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Components\Touchable\Touchable.js:435:24
12invokeGuardedCallbackImpl
13    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:92:15
14invokeGuardedCallback
15    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:306:36
16invokeGuardedCallbackAndCatchFirstError
17    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:330:30
18executeDispatch
19    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:699:42
20executeDispatchesInOrder
21    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:726:20
22executeDispatchesAndRelease
23    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:884:29
24forEachAccumulated
25    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:863:16
26runEventsInBatch
27    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:1050:6
28runExtractedEventsInBatch
29    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:1075:19
30<unknown>
31    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:2713:6
32batchedUpdates$1
33    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:15311:14
34batchedUpdates
35    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:2616:31
36_receiveRootNodeIDEvent
37    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:2711:17
38receiveTouches
39    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\Renderer\oss\ReactNativeRenderer-dev.js:2787:28
40__callFunction
41    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:349:47
42<unknown>
43    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:106:26
44__guard
45    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:297:10
46callFunctionReturnFlushedQueue
47    C:\Users\nkawa\Documents\Expo\TodoApp\node_modules\react-native\Libraries\BatchedBridge\MessageQueue.js:105:17
48