Develop Reference

TypeError: undefined is not an object (evaluating '_this.state.data)

The error occurs when I try to close the modal window. on the "Close" button. The error says that _this.state.data [imageKey] .urls' is not an object, but I pass the string.
I am receiving JSON from a custom API endpoint. I was able to iterate over the JSON and output some data, but the problem is with the string reference to the image. I am getting the error:
import React, { Component } from 'react';
import {
AppRegistry,
StyleSheet,
Text,
View,
TouchableWithoutFeedback,
Dimensions,
Modal,
ScrollView,
} from 'react-native';
import ImageElement from './component/ImageElement';
export default class App extends Component {
constructor(props) {
super(props);
this.state = {
modalVisible: false,
data: [],
};
}
componentDidMount() {
fetch('https://api.unsplash.com/photos/?client_id=cf49c08b444ff4cb9e4d126b7e9f7513ba1ee58de7906e4360afc1a33d1bf4c0')
.then((response) => response.json())
.then((data) => {
this.setState({
data: data,
});
});
}
// getImage() {
// return this.state.modalImage
// }
setModalVisible = (visible, imageKey) => {
this.setState({ modalImage: this.state.data[imageKey].urls.raw });
this.setState({ modalVisible: visible });
};
render() {
let images = this.state.data.map((val, key) => {
return (
<TouchableWithoutFeedback
key={key}
onPress={() => {
this.setModalVisible(true, key);
}}
>
<View style={styles.imagewrap}>
<ImageElement
author={{ url: val.user.profile_image.small }} // фото автора
imgsource={{ url: val.urls.small }} // работа автора
authorNameProp={val.user.name} // имя автора
></ImageElement>
</View>
</TouchableWithoutFeedback>
);
});
return (
<ScrollView>
<View style={styles.container}>
<Modal
style={styles.modal}
animationType={'fade'}
transparent={true}
visible={this.state.modalVisible}
onRequestClose={() => {}}
>
<View style={styles.modal}>
<Text
style={styles.text}
onPress={() => {
this.setModalVisible(false);
}}
>
Close
</Text>
<ImageElement imgsource={{ url: this.state.modalImage }}></ImageElement>
</View>
</Modal>
{images}
</View>
</ScrollView>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
flexDirection: 'row',
flexWrap: 'wrap',
backgroundColor: 'grey',
overflow: 'scroll',
},
imagewrap: {
margin: 5,
padding: 2,
height: Dimensions.get('window').height / 2 - 60,
width: Dimensions.get('window').width / 2 - 10,
},
modal: {
flex: 1,
padding: 10,
backgroundColor: 'rgba(0,0,0, 0.9)',
},
text: {
color: '#fff',
zIndex: 20,
position: 'absolute',
top: 50,
right: 30,
fontSize: 20,
},
user: {
color: '#fff',
zIndex: 20,
position: 'absolute',
top: 20,
left: 10,
},
});
AppRegistry.registerComponent('ImageGallery', () => ImageGallery);

Issue
Seems you missed passing an index in your close handler this.setModalVisible(false), imageKey is undefined, and thus this.state.data[undefined] is undefined and throws error when you access deeper into the nested properties.
Solution
Conditionally access the data value based on the visible value. Clear out the modalImage state when closing the modal.
setModalVisible = (visible, imageKey) => {
this.setState({
modalImage: visible ? this.state.data[imageKey].urls.raw : null,
modalVisible: visible,
});
}
Alternatively you can just use Optional Chaining to do null checks for you.
setModalVisible = (visible, imageKey) => {
this.setState({
modalImage: this.state.data[imageKey]?.urls?.raw,
modalVisible: visible,
});
}

Add WebView via onClick in Expo React-Native

I need a function that creates new screens with a webview in it.
The main screen of my expo app contains a button "add new Page" which links to a page with a form to add domain, Username, Password.
if this is done, I want a list of pages in my main screen with all pages. for example if I click on "myWebsite1" with the generated link http://user:password#myWebsite1.com this page should be shown in a webview. same for website2, 3 and so on.
Anyone an idea how to do this?
EDIT: I add some code I have right now. For each Task I create, the Domain, User and Password for the webview file should change and be saved at this specific task. (and also open onclick). I turn in a circle
this is my app.js which expo opens first, it contains a Flatlist:
import React, { Component } from "react";
import { AppRegistry, StyleSheet, Text, View, FlatList, AsyncStorage, Button, TextInput, Keyboard, Platform, TouchableWithoutFeedback } from "react-native";
const isAndroid = Platform.OS == "android";
const viewPadding = 10;
const things = {things}
export default class NodeList extends Component {
state = {
tasks: [ ],
text: ""
};
changeTextHandler = text => {
this.setState({ text: text });
};
addTask = () => {
let notEmpty = this.state.text.trim().length > 0;
if (notEmpty) {
this.setState(
prevState => {
let { tasks, text } = prevState;
return {
tasks: tasks.concat({ key: tasks.length, text: text }),
text: ""
};
},
() => Tasks.save(this.state.tasks)
);
}
};
deleteTask = i => {
this.setState(
prevState => {
let tasks = prevState.tasks.slice();
tasks.splice(i, 1);
return { tasks: tasks };
},
() => Tasks.save(this.state.tasks)
);
};
componentDidMount() {
Keyboard.addListener(
isAndroid ? "keyboardDidShow" : "keyboardWillShow",
e => this.setState({ viewMargin: e.endCoordinates.height + viewPadding })
);
Keyboard.addListener(
isAndroid ? "keyboardDidHide" : "keyboardWillHide",
() => this.setState({ viewMargin: viewPadding })
);
Tasks.all(tasks => this.setState({ tasks: tasks || [] }));
}
render() {
return (
<View
style={[styles.container, { paddingBottom: this.state.viewMargin }]}
>
<Text style={styles.appTitle}>Nodes</Text>
<FlatList
style={styles.list}
data={this.state.tasks}
renderItem={({ item, index }) =>
<View>
<View style={styles.listItemCont}>
<TouchableWithoutFeedback onPress={() => Linking.openURL('')}>
<Text style={styles.listItem}>
{item.text}
</Text>
</TouchableWithoutFeedback>
<Button color= "#00BC8C" title="✖" onPress={() => this.deleteTask(index)} />
</View>
<View style={styles.hr} />
</View>}
/>
<TextInput
style={styles.textInput}
onChangeText={this.changeTextHandler}
onSubmitEditing={this.addTask}
value={this.state.text}
placeholder="+ add Node"
returnKeyType="done"
returnKeyLabel="done"
/>
</View>
);
}
}
let Tasks = {
convertToArrayOfObject(tasks, callback) {
return callback(
tasks ? tasks.split("||").map((task, i) => ({ key: i, text: task })) : []
);
},
convertToStringWithSeparators(tasks) {
return tasks.map(task => task.text).join("||");
},
all(callback) {
return AsyncStorage.getItem("TASKS", (err, tasks) =>
this.convertToArrayOfObject(tasks, callback)
);
},
save(tasks) {
AsyncStorage.setItem("TASKS", this.convertToStringWithSeparators(tasks));
}
};
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: "center",
alignItems: "center",
backgroundColor: "#252525",
padding: viewPadding,
paddingTop: 24
},
list: {
width: "100%"
},
listItem: {
paddingTop: 4,
paddingBottom: 2,
fontSize: 18,
color:"#ffff"
},
hr: {
height: 1,
backgroundColor: "gray"
},
listItemCont: {
flexDirection: "row",
alignItems: "center",
justifyContent: "space-between",
paddingTop: 10,
},
textInput: {
height: 40,
paddingRight: 10,
paddingLeft: 10,
borderColor: "gray",
borderWidth: isAndroid ? 0 : 1,
width: "100%",
color:"#ffff"
},
appTitle: {
alignItems:"center",
justifyContent: "center",
paddingBottom: 45,
marginTop: 50,
fontSize: 25,
color:"#ffff"
}
});
AppRegistry.registerComponent("NodeList", () => NOdeList);
and here is my second screen, which contains the component for the WebView:
import React, { Component, useState } from "react";
import { BackHandler } from 'react-native';
import { WebView } from 'react-native-webview';
var $ = require( "jquery" );
export default class nodeView extends Component {
constructor(props) {
super(props);
this.WEBVIEW_REF = React.createRef();
}
componentDidMount() {
BackHandler.addEventListener('hardwareBackPress', this.handleBackButton);
}
componentWillUnmount() {
BackHandler.removeEventListener('hardwareBackPress', this.handleBackButton);
}
handleBackButton = ()=>{
this.WEBVIEW_REF.current.goBack();
return true;
}
onNavigationStateChange(navState) {
this.setState({
canGoBack: navState.canGoBack
});
}
render(){
return (
<WebView
source={{ uri: `https://${user}:${password}#${domain}` }}
ref={this.WEBVIEW_REF}
style={{ marginTop: 20 }}
onNavigationStateChange={this.onNavigationStateChange.bind(this)}
/>
)
}
}

Create WebView. Create State Which Controls WebView. Add Listener To Button

How to parse and get data from webservice which is returning a list of array

Hi Every one I am trying to get data from webservice which is returning me XML.I used the Xml to JSON dependency to return me data in JSON but another problem is it is returning me the data in an array and the app cant display the data.But it comes out in the terminal just fine
Here is the image
import React from 'react';
import {
StyleSheet, View, ActivityIndicator, FlatList, Text, TouchableOpacity,
} from 'react-native';
export default class Source extends React.Component {
static navigationOptions = ({ navigation }) => ({
title: 'Source Listing',
headerStyle: { backgroundColor: '#fff' },
headerTitleStyle: { textAlign: 'center', flex: 1 },
});
constructor(props) {
super(props);
this.state = {
loading: true,
dataSource: [],
};
}
FlatListItemSeparator = () => (
<View style={{
height: 0.5,
width: '100%',
backgroundColor: 'rgba(0,0,0,0.5)',
}}/>
)
renderItem=data => <TouchableOpacity style={styles.list}>
<Text style={styles.lightText}>{data.item.name}</Text>
<Text style={styles.lightText}>{data.item.email}</Text>
<Text style={styles.lightText}>{data.item.company.name}</Text>
</TouchableOpacity>
render() {
if (this.state.loading) {
return (
<View style={styles.loader}>
<ActivityIndicator size="large" color="#0c9"/>
</View>
);
}
return (
<View style={styles.container}>
<FlatList
data= {this.state.dataSource}
ItemSeparatorComponent = {this.FlatListItemSeparator}
renderItem= {item => this.renderItem(item)}
keyExtractor= {item => item.id.toString()}
/>
</View>
);
}
}
const { parseString } = require('react-native-xml2js');
fetch('http://192.168.200.133/apptak_service/apptak.asmx/Get_Item_Master')
.then(response => response.text())
.then((response) => {
parseString(response, (err, result) => {
console.log(response);
});
}).catch((err) => {
console.log('fetch', err);
});
const styles = StyleSheet.create({
container: {
flex: 1,
backgroundColor: '#fff',
},
loader: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#fff',
},
list: {
paddingVertical: 4,
margin: 5,
backgroundColor: '#fff',
},
});
Is there any way i can display the data in the app as single string entity

Component out of sync in React Native

I'm working with my React Native project where I have like a "form" in which the user selects what day and between what hours they're available. There are two components involved:
The parent one: It has two time selectors and the day selector component
The child one: This is the day selector component. It displays the days in the week so the user can select whatever days they want.
This is the DaySelector:
import * as React from "react";
import { View, Text, StyleSheet, Button, Alert } from "react-native";
import { TouchableOpacity } from "react-native-gesture-handler";
import colors from "../assets/constants/style-variables";
interface Item {
selected: Boolean;
day: String;
}
function Day(props) {
return (
<TouchableOpacity
onPress={props.onPress}
style={props.selected ? styles.buttonActive : styles.button}
>
<Text>{props.day}</Text>
</TouchableOpacity>
);
}
export default class DaySelector extends React.Component<
{ onChange },
{ selectedItems: undefined | Item[]; items: Item[] }
> {
constructor(props) {
super(props);
this.state = {
selectedItems: [],
items: [
{
selected: false,
day: "Lu",
},
{
selected: false,
day: "Ma",
},
{
selected: false,
day: "Mi",
},
{
selected: false,
day: "Ju",
},
{
selected: false,
day: "Vi",
},
{
selected: false,
day: "Sa",
},
{
selected: false,
day: "Do",
},
],
};
}
onPress = (index) => {
let items = [...this.state.items];
let item = { ...items[index] };
item.selected = !item.selected;
items[index] = item;
this.setState({ items });
this.setState((prevState) => ({
selectedItems: prevState.items.filter((i) => i.selected),
}));
this.props.onChange(this.state.selectedItems);
};
render() {
return (
<View>
<View style={styles.container}>
{this.state.items.map((item, index) => {
return (
<Day
key={index}
selected={item.selected}
day={item.day}
onPress={this.onPress.bind(this, index)}
/>
);
})}
</View>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flexDirection: "row",
},
button: {
margin: 5,
borderColor: colors.lightGray,
borderWidth: 2,
borderRadius: 40,
padding: 7,
},
buttonActive: {
margin: 5,
borderColor: colors.primary,
borderWidth: 2,
backgroundColor: colors.primary,
borderRadius: 50,
padding: 7,
},
});
As you can see, it collects all the days selected and passes them into the onChange prop. That way I can access the results in my parent component, which is this one:
import React, { useState, useCallback, useReducer } from "react";
import { useMutation } from "#apollo/react-hooks";
import { REGISTER } from "../Queries";
import Loader from "../components/Loader";
import DateTimePicker from "#react-native-community/datetimepicker";
import { View, StyleSheet } from "react-native";
import colors from "../assets/constants/style-variables";
import { TouchableOpacity } from "react-native-gesture-handler";
import PrimaryText from "../assets/constants/PrimaryText";
import DaySelector from "../components/DaySelector";
function reducer(state, action) {
switch (action.type) {
case "refresh-days":
return {
dayList: action.value,
};
default:
return state;
}
}
export default function ScheduleSelect({ navigation, route }) {
const [loadingRegistration, setLoadingRegistration] = useState(null);
const [showTimePicker1, setShowTimePicker1] = useState(false);
const [showTimePicker2, setShowTimePicker2] = useState(false);
const [time1, setTime1] = useState(null);
const [time2, setTime2] = useState(null);
const [{ dayList }, dispatch] = useReducer(reducer, { dayList: [] });
const show1 = () => {
setShowTimePicker1(true);
};
const show2 = () => {
setShowTimePicker2(true);
};
const handleTimePick1 = (_event, selectedTime) => {
setShowTimePicker1(false);
if (selectedTime !== undefined) {
setTime1(selectedTime);
}
};
const handleTimePick2 = (_event, selectedTime) => {
setShowTimePicker2(false);
if (selectedTime !== undefined) {
setTime2(selectedTime);
}
};
return (
<View>
<View style={styles.container}>
<PrimaryText fontSize={20} margin={22} textAlign={"center"}>
Recibirás turnos en estos horarios:
</PrimaryText>
<View style={styles.cardHolder}>
<View style={styles.card}>
<View style={styles.timeHelper}>
<PrimaryText textAlign={"center"}>Desde</PrimaryText>
</View>
{time1 && (
<TouchableOpacity onPress={show1}>
<View style={styles.timeSelected}>
<PrimaryText textAlign={"center"} fontSize={36}>
{`${time1?.getHours()}:${
time1.getMinutes() < 10
? "0" + time1.getMinutes()
: time1.getMinutes()
}`}
</PrimaryText>
</View>
</TouchableOpacity>
)}
{!time1 && (
<TouchableOpacity style={styles.clockEdit} onPress={show1}>
<PrimaryText
fontSize={36}
letterSpacing={2}
textAlign={"center"}
>
--:--
</PrimaryText>
</TouchableOpacity>
)}
{showTimePicker1 && (
<DateTimePicker
value={new Date()}
testID="dateTimePicker"
mode={"time"}
is24Hour={true}
display="default"
onChange={handleTimePick1}
/>
)}
</View>
<PrimaryText fontSize={36} margin={7}>
-
</PrimaryText>
<View style={styles.card}>
<View style={styles.timeHelper}>
<PrimaryText textAlign={"center"}>Hasta</PrimaryText>
</View>
{time2 && (
<TouchableOpacity onPress={show2}>
<View style={styles.timeSelected}>
<PrimaryText textAlign={"center"} fontSize={36}>
{`${time2?.getHours()}:${
time2.getMinutes() < 10
? "0" + time2.getMinutes()
: time2.getMinutes()
}`}
</PrimaryText>
</View>
</TouchableOpacity>
)}
{!time2 && (
<TouchableOpacity style={styles.clockEdit} onPress={show2}>
<PrimaryText
fontSize={36}
letterSpacing={2}
textAlign={"center"}
>
--:--
</PrimaryText>
</TouchableOpacity>
)}
{showTimePicker2 && (
<DateTimePicker
value={new Date()}
testID="dateTimePicker"
mode={"time"}
is24Hour={true}
display="default"
onChange={handleTimePick2}
/>
)}
</View>
</View>
{time2?.getTime() < time1?.getTime() && (
<PrimaryText color={colors.warning}>
Por favor, seleccioná horarios válidos
</PrimaryText>
)}
<PrimaryText margin={5}> Los días: </PrimaryText>
<View style={styles.card}>
<DaySelector
onChange={(value) => dispatch({ type: "refresh-days", value })}
/>
</View>
</View>
<View style={styles.buttonWrapper}>
<TouchableOpacity
style={styles.button}
onPress={() => {
console.log(dayList);
}}
>
<PrimaryText color={colors.iceWhite}>SIGUIENTE</PrimaryText>
</TouchableOpacity>
</View>
</View>
);
}
const styles = StyleSheet.create({
container: {
height: "88%",
justifyContent: "center",
paddingTop: 15,
alignItems: "center",
},
clockEdit: {
padding: 7,
},
button: {
alignSelf: "flex-end",
backgroundColor: colors.primary,
padding: 7,
margin: 15,
borderRadius: 15,
},
buttonWrapper: {
justifyContent: "flex-end",
alignItems: "flex-end",
paddingRight: 15,
},
card: {
flexDirection: "row",
justifyContent: "center",
minWidth: "35%",
backgroundColor: colors.iceWhite,
borderRadius: 10,
padding: 20,
marginBottom: 10,
shadowColor: "#000",
shadowOffset: {
width: 0,
height: 2,
},
shadowOpacity: 0.25,
shadowRadius: 3.84,
elevation: 5,
},
cardHolder: {
flexDirection: "row",
alignItems: "center",
},
timeHelper: {
justifyContent: "center",
position: "absolute",
marginTop: 5,
},
timeSelected: {
alignItems: "center",
justifyContent: "center",
},
editIcon: {
right: 3,
top: 3,
position: "absolute",
},
});
The problem is that when I console.log the value of the onChange prop, I get the items out of sync. To try and solve this, you see that I used a reducer, since the task is dependent of the result of the action. However, it does not change anything and still returns "outdated" information.
How can I sync both of the components?

This problems might come from your setState in your first component. you are calling the setState and then use the state straight after. But setState is asynchronous. So when you call your onChange, the state is still the previous one.
The prototype of setState is
setState(callback: (currentState) => newState | newState, afterSetState: (newState) => void)
So you can use the afterSetState callback to receive the new state and call your props.onChange
Also you are calling setState twice, but you could call it once and manipulate the state to return all in one.
However, if I could give you an advice, it'd be better controlling the state from the parent instead of the child. It avoids you calling a setState in the child and call the onChange in the parent which will set the state somewhere else again.

How to view multiple capture image horizontally in react native?

I just want to capture image using camera API
Then Store it in array
then view one by one image horizontally in React native
import React, { Component } from 'react';
import {
Platform,
StyleSheet,
Text,
View,
TouchableOpacity,
Image,
PixelRatio
} from 'react-native';
import ImagePicker from 'react-native-image-picker';
let ret;
export default class Location extends Component {
constructor(props){
super(props);
this.state = {
latitude: null,
longitude: null,
address: 'address',
MyAddress: null,
error: null,
};
}
state = {
avatarSource: null,
videoSource: null
};
selectPhotoTapped() {
const options = {
quality: 1.0,
maxWidth: 500,
maxHeight: 500,
storageOptions: {
skipBackup: true
}
};
To get Image, I used this.
ImagePicker.showImagePicker(options, (response) => {
console.log('Response = ', response);
if (response.didCancel) {
console.log('User cancelled photo picker');
}
else if (response.error) {
console.log('ImagePicker Error: ', response.error);
}
else if (response.customButton) {
console.log('User tapped custom button: ', response.customButton);
}
else {
let source = { uri: response.uri };
// You can also display the image using data:
//let source = { uri: 'data:image/jpeg;base64,' + response.data };
this.setState({
avatarSource: source
});
}
});
}
Then how to process to view list of image like adpater.
return (
<View style={{ flexGrow: 1, alignItems: 'center', justifyContent: 'center' }}>
To show the image in one view ,i have done this. i want to view multiple image like view pager.Like [] [] [] []
<TouchableOpacity onPress={this.selectPhotoTapped.bind(this)}>
<View style={[styles.avatar, styles.avatarContainer, {marginBottom: 20}]}>
{ this.state.avatarSource === null ? <Text>Select a Photo</Text> :
<Image style={styles.avatar} source={this.state.avatarSource} />
}
</View>
</TouchableOpacity>
</View>
)
}
}
After few hours i have done this
First save image uri in array then show in list..
let dataStorage = [{uri: response.uri}, ...this.state.dataStorage]
this.setState({dataStorage})
<FlatList
horizontal
data={this.state.dataStorage}
renderItem={({ item: rowData }) => {
return (
<View style={[styles.avatar, styles.avatarContainer, {marginBottom: 20}]}>
{ <Image style={styles.avatar} source={{uri:rowData.uri}} /> }
</View>
);
}
}
keyExtractor={(item, index) => index}
/>

Using Expo's ImagePicker this can be achieved.
Below is my code that might help you.
Note: Its performance is slow but it works.
1) state:
constructor(props) {
super(props);
this.state = {
images: []
};
}
2) openCamera function:
openCamera = async () => {
const { status } = await Permissions.askAsync(
Permissions.CAMERA,
Permissions.CAMERA_ROLL
);
this.setState({
hasCameraPermission: status === 'granted',
hasGalleryPermission: status === 'granted'
});
if (this.state.hasCameraPermission && this.state.hasGalleryPermission) {
ImagePicker.launchCameraAsync({
aspect: [1, 1],
quality: 0.2,
base64: true
})
.then(async result => {
if (!result.cancelled) {
await this.setState({
images: this.state.images.concat(result.uri)
});
Alert.alert(
'Add another picture? ',
null,
[
{
text: 'Yes',
onPress: () => this.openCamera()
},
{ text: 'No' }
],
{ cancelable: false }
);
}
console.log(this.state.images);
})
.catch(error => console.log(error));
}
};
3) To display Image:
showImages = () => {
let temp_image = [];
this.state.images.map((item, index) => {
let tempKey = item + '123';
temp_image.push(
<View key={tempKey}>
<View
key={index}
style={{
height: 100,
width: 100,
borderColor: '#dddddd'
}}
>
<Image
key={index}
source={{ uri: item }}
style={{
flex: 1,
flexDirection: 'row',
backgroundColor: 'silver',
padding: 5,
borderRadius: 5,
height: null,
width: null,
margin: 3,
resizeMode: 'cover'
}}
/>
</View>
<View key={index + 1}>
<TouchableOpacity
key={index + 2}
style={{
flex: 1,
justifyContent: 'center',
alignSelf: 'center',
width: '100%'
}}
onPress={() => {
this.removeImage(index);
this.forceUpdate();
}}
>
<Text
key={index + 3}
style={{
alignSelf: 'center',
color: '#CE3C3E',
fontWeight: 'bold'
}}
>
Delete
</Text>
</TouchableOpacity>
</View>
</View>
);
});
console.log('state images: ', this.state.images);
return temp_image;
};
4) To delete image:
removeImage = index => {
Alert.alert('Delete this image?', null, [
{
text: 'Yes',
onPress: () => {
this.state.images.splice(index, 1);
// console.log(this.state.images);
this.forceUpdate();
}
},
{ text: 'No' }
]);
};
5) And in render() function:
<ScrollView horizontal={true} style={{ flex: 1, flexDirection: 'row' }} >
{this.showImages()}
</ScrollView>