我有一个 FlatList,我试图每隔 X 秒滚动一次数据数组的每个索引。现在我的数组中只有两个项目,但可能还有更多。当前代码适用于前两次迭代,但似乎没有正确重置,我得到 scrollToIndex out of range error: index is 2 but maximum is 1
.我认为当 currentIndex
是 >= data.length
我的 if
声明将 setCurrentIndex
回到0,但它似乎不起作用。基本上我要做的是自动循环 Flatlist 中的项目,但每个项目都会暂停几秒钟。
/**
* Sample React Native App
* https://github.com/facebook/react-native
*
* @format
* @flow strict-local
*/
import 'react-native-gesture-handler';
import React, {useState, useEffect, useRef} from 'react';
import { NavigationContainer } from '@react-navigation/native';
import { createStackNavigator, HeaderBackButton } from '@react-navigation/stack';
import {
SafeAreaView,
StyleSheet,
ScrollView,
View,
Text,
StatusBar,
ImageBackground,
Image,
TextInput,
Button,
TouchableNativeFeedback,
TouchableWithoutFeedback,
TouchableOpacity,
Modal,
Pressable,
PanResponder,
FlatList,
Dimensions
} from 'react-native';
import { Immersive } from 'react-native-immersive';
import {
Header,
LearnMoreLinks,
Colors,
DebugInstructions,
ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';
import WineList from './screens/WineList';
import Home from './screens/Home';
import Rate from './screens/Rate';
import Thankyou from './screens/Thankyou';
const Stack = createStackNavigator();
const { width: windowWidth, height: windowHeight } = Dimensions.get("window");
const wineclub = require('./images/wineclub.png');
const gaspers = require('./images/gaspers.png');
const qrcode = require('./images/wineclubQR.png');
let ads = [
{
adImg: wineclub,
adTitle: 'Space will be limited so join online today!',
adInfo: ' Upon joining, both clubs will be billed our Trio Pre-Opening Promotion',
qrCodeImg: qrcode
},
{
adImg: gaspers,
adTitle: 'Coming Soon!',
adInfo: 'Gourmet chef designed menu. Stunning views. Modern romantic decor',
qrCodeImg: qrcode
}
]
function AdSlider({data}){
return(
<View style={{alignContent:'center', alignItems:'center', backgroundColor:'#4B4239', height:1400}}>
<Image source={data.adImg} style={{width:640,height:500}} ></Image>
<Text style={{color:'white', fontFamily:'LaoMN', fontSize:30, marginTop:20}}>{data.adTitle}</Text>
<Text style={{color:'white', fontFamily:'LaoMN', fontSize:20, marginTop:20, textAlign:'center'}} > {data.adInfo} </Text>
<View style={{flexDirection:'row', justifyContent:'flex-start', alignContent:'center', alignItems:'center', marginTop:20}}>
<Text style={{fontSize:40, color:'white', padding:20}}>Scan Here </Text>
<Image source={data.qrCodeImg}></Image>
</View>
</View>
)
}
const App: () => React$Node = () => {
Immersive.on()
Immersive.setImmersive(true)
const navigationRef = useRef(null);
const myRef = useRef(null);
const currentIndex = useRef(0);
const [modalVisible, setModalVisible] = useState(false);
const timerId = useRef(false);
const [timeForInactivityInSecond, setTimeForInactivityInSecond] = useState(
5
)
useEffect(() => {
resetInactivityTimeout()
},[])
const panResponder = React.useRef(
PanResponder.create({
onStartShouldSetPanResponderCapture: () => {
// console.log('user starts touch');
setModalVisible(false)
resetInactivityTimeout()
},
})
).current
const resetInactivityTimeout = () => {
clearTimeout(timerId.current)
timerId.current = setTimeout(() => {
// action after user has been detected idle
setModalVisible(true)
navigationRef.current?.navigate('Home');
}, timeForInactivityInSecond * 1000)
}
// for the slider
useEffect(() => {
const timer = setInterval(() => {
currentIndex.current = currentIndex.current === ads.length - 1
? 0
: currentIndex.current + 1;
myRef.current.scrollToIndex({
animated: true,
index: currentIndex.current ,
});
}, 5000);
return () => clearInterval(timer);
}, []);
return (
<NavigationContainer ref={navigationRef} >
<View {...panResponder.panHandlers} style={{ flex:1}}>
<TouchableWithoutFeedback >
<Modal
animationType="slide"
transparent={false}
hardwareAccelerated={false}
visible={modalVisible}
>
<FlatList
ref={myRef}
data={ads}
renderItem={({ item, index }) => {
return <AdSlider key={index} data={item} dataLength={ads.length} />;
}}
pagingEnabled
horizontal
showsHorizontalScrollIndicator={false}
/>
</Modal>
</TouchableWithoutFeedback>
<Stack.Navigator navigationOptions={{headerTintColor: '#ffffff',}} screenOptions={{
headerTintColor: '#ffffff',
cardStyle: { backgroundColor: '#4B4239' },
}} >
<Stack.Screen name="Home"
component={Home} options={{
headerShown: false,
}} />
<Stack.Screen name="WineList" component={WineList} options={{
title: 'Exit',
headerStyle: {
backgroundColor: '#4B4239',
},
headerTintColor: '#fff',
headerTitleStyle: {
fontWeight: 'bold',
},
}}/>
<Stack.Screen name="Rate" component={Rate} options={{
title: 'Back to Selections',
headerStyle: {
backgroundColor: '#4B4239',
},
headerTintColor: '#fff',
headerTitleStyle: {
fontWeight: 'bold',
},
}}/>
<Stack.Screen name="Thankyou" component={Thankyou}
options={
{
headerShown: false,
title: 'Home',
headerStyle: {
backgroundColor: '#4B4239',
},
headerTintColor: '#fff',
headerTitleStyle: {
fontWeight: 'bold',
},
}}/>
</Stack.Navigator>
</View>
</NavigationContainer>
);
};
export default App;
最佳答案
您收到此错误是因为您传递了 item
作为data
到AdSlider
组件,它没有任何 length
属性当然因此它返回 undefined
对于 data.length
并且不计算表达式 currentIndex === data.length - 1
它变成currentIndex === undefined - 1
因此currentIndex
将增加 1
没有停止,它将达到 2
的值这是超出范围的。
您的代码有几个问题。
AdSlider
在 App
之外零件。data
到AdSlider
而您正试图将其作为 data.length
,很明显它不会工作,因为 data
是 item
这是一个对象而不是数组。AdSlider
中的效果。 , 在 App
中只设置一个效果并更改 currentIndex
成为一个 ref 而不是一个状态变量,因为你不需要它改变状态来重新渲染,因为你正在调用 scrollToIndex
用于强制列表更新和重新渲染。使用 state 和
setTimeout
使其工作如果你想用
currentIndex
制作代码处于状态(您不需要),您可以在 App
中移动效果组件和更改data.length
与 ads.length
它会起作用。const App: () => React$Node = () => {
Immersive.on()
Immersive.setImmersive(true)
const navigationRef = useRef(null);
const myRef = useRef(null);
const [currentIndex, setCurrentIndex] = useState(0);
useEffect(() => {
myRef.current.scrollToIndex({
animated: true,
index: currentIndex ,
});
}, [currentIndex]);
useEffect(()=> {
const timer = setTimeout(()=> {
// Change data.length to ads.length here
const nextIndex = currentIndex === ads.length - 1
? 0
: currentIndex + 1;
setCurrentIndex(nextIndex);
}, 5000);
return () => clearTimeout(timer);
}, [currentIndex]);
...
}
使用 ref 和 setInterval
使其工作最好的办法是转换
currentIndex
成为引用并使用 setInterval
而不是 setTimeout
每 5 秒调用一次循环计时器:const App: () => React$Node = () => {
Immersive.on()
Immersive.setImmersive(true)
const navigationRef = useRef(null);
const myRef = useRef(null);
// Make currentIndex a ref instead of a state variable,
// because we don't need the re-renders
// nor to trigger any effects depending on it
const currentIndex = useRef(0);
useEffect(() => {
// Have a timer call the function every 5 seconds using setInterval
const timer = setInterval(() => {
// Change data.length to ads.length here
currentIndex.current = currentIndex.current === ads.length - 1
? 0
: currentIndex.current + 1;
myRef.current.scrollToIndex({
animated: true,
index: currentIndex.current,
});
}, 5000);
return () => clearInterval(timer);
}, []);
...
}
您可以查看有效的 Expo Snack here .
关于javascript - FlatList scrollToIndex 超出范围,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/65895710/