[英]How do I pass state variables from one screen to another in a React Native Project?
[英]React Native: How do I pass the answer from application state as a prop and not the internal state of the card
所以我有一个组件给我以下问题:
测试步骤: 1. 登录手机。 2. 在 Activity Feed 上,回答第一个 Get Involved 问题。 3. 滚动到最后一个 Get Involved 问题并回答。 4. 滚动回第一个回答的 Get Involved 问题。
预期结果:仍应选择第一个“参与”问题的答案。
实际结果:未选中
所以似乎问题是更新父级上的一些 state 的回调,但父级没有将 yes/no 属性传递给该组件,并且卸载它以节省我的渲染
在后端,在数据库中,答案被记录下来,但它没有保留在 UI 中。 我注意到下面的辅助函数,特别是this.props.onPress()
返回undefined
。
class GetInvolvedFeedCard extends PureComponent {
static propTypes = {
onPress: PropTypes.func.isRequired,
style: PropTypes.oneOfType([PropTypes.number, PropTypes.object]),
title: PropTypes.string.isRequired
};
constructor(props) {
super(props);
const helper = `${
this.props.title.endsWith("?") ? "" : "."
} Your NFIB preferences will be updated.`;
this.state = {
noSelected: false,
yesSelected: false,
helper
};
}
_accept = () => {
this.setState({ yesSelected: true, noSelected: false }, () => {
this.props.onPress(true);
});
};
_decline = () => {
this.setState({ noSelected: true, yesSelected: false }, () => {
this.props.onPress(false);
});
};
render() {
return (
<Card style={this.props.style}>
<View style={feedContentStyles.header}>
<View style={feedContentStyles.contentType}>
<Text style={feedContentStyles.title}>{"GET INVOLVED"}</Text>
</View>
</View>
<Divider />
<View style={feedContentStyles.content}>
<View style={styles.content}>
<Text style={styles.blackTitle}>
{this.props.title}
<Text style={styles.italicText}>{this.state.helper}</Text>
</Text>
</View>
<View style={styles.footer}>
<TouchableOpacity onPress={this._decline}>
<Text
style={[
styles.btnText,
styles.noBtn,
this.state.noSelected ? styles.selected : null
]}
>
{"NO"}
</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this._accept}>
<Text
style={[
styles.btnText,
this.state.yesSelected ? styles.selected : null
]}
>
{"YES"}
</Text>
</TouchableOpacity>
</View>
</View>
</Card>
);
}
}
因此,state 似乎由父组件管理,而不是 Redux。
尚不清楚的是,它是否正在卸载定义onPress
的组件。 听起来是这样。
只是滚动,所以有一个由卡片组成的活动提要,其中一些呈现 boolean 类型的问题你想参与吗? 否 是,当用户选择任一响应,然后向下滚动一定数量,然后向上滚动回到同一个问题时,就像用户从未回答过它一样。 我注意到,当用户选择 NO 时,_handleGetInvolved function 中的 this.props.handleUpdateGetInvolved({tained: items }) 仅在用户选择 YES 时才会触发:
_handleGetInvolved = (response, entity) => {
if (response !== entity.IsSelected) {
const isTopic = entity.Category !== "GetInvolved";
const items = [
{
...entity,
IsSelected: response
}
];
if (isTopic) {
this.props.handleUpdateTopics({ topics: items });
} else {
this.props.handleUpdateGetInvolved({ involved: items });
}
}
};
每个答案的辅助函数本身总是在GetInvolvedFeedCard
组件内返回 undefined :
_accept = () => {
this.setState({ yesSelected: true, noSelected: false }, () => {
this.props.onPress(true);
console.log(
"this is the accept helper function: ",
this.props.onPress(true)
);
});
};
_decline = () => {
this.setState({ noSelected: true, yesSelected: false }, () => {
this.props.onPress(false);
console.log(
"this is the decline helper function: ",
this.props.onPress(false)
);
});
};
render() {
return (
<Card style={this.props.style}>
<View style={feedContentStyles.header}>
<View style={feedContentStyles.contentType}>
<Text style={feedContentStyles.title}>{"GET INVOLVED"}</Text>
</View>
</View>
<Divider />
<View style={feedContentStyles.content}>
<View style={styles.content}>
<Text style={styles.blackTitle}>
{this.props.title}
<Text style={styles.italicText}>{this.state.helper}</Text>
</Text>
</View>
<View style={styles.footer}>
<TouchableOpacity onPress={this._decline}>
<Text
style={[
styles.btnText,
styles.noBtn,
this.state.noSelected ? styles.selected : null
]}
>
{"NO"}
</Text>
</TouchableOpacity>
<TouchableOpacity onPress={this._accept}>
<Text
style={[
styles.btnText,
this.state.yesSelected ? styles.selected : null
]}
>
{"YES"}
</Text>
</TouchableOpacity>
</View>
如果我没记错的话,所有这些都是由ActivityFeed
组件整体呈现的:
const { height } = Dimensions.get("window");
export class ActivityFeed extends PureComponent {
static propTypes = {
displayAlert: PropTypes.bool,
feed: PropTypes.array,
fetchFeed: PropTypes.func,
getCampaignDetails: PropTypes.func,
handleContentSwipe: PropTypes.func,
handleUpdateGetInvoved: PropTypes.func,
handleUpdateTopics: PropTypes.func,
hideUndoAlert: PropTypes.func,
lastSwippedElement: PropTypes.object,
loading: PropTypes.bool,
navigation: PropTypes.object,
setSelectedAlert: PropTypes.func,
setSelectedArticle: PropTypes.func,
setSelectedEvent: PropTypes.func,
setSelectedSurvey: PropTypes.func.isRequired,
undoSwipeAction: PropTypes.func,
userEmailIsValidForVoterVoice: PropTypes.bool
};
constructor(props) {
super(props);
this.prompted = false;
this.state = {
refreshing: false,
appState: AppState.currentState
};
}
async componentDidMount() {
AppState.addEventListener("change", this._handleAppStateChange);
if (!this.props.loading) {
const doRefresh = await cache.shouldRefresh("feed");
if (this.props.feed.length === 0 || doRefresh) {
this.props.fetchFeed();
}
cache.incrementAppViews();
}
}
componentWillUnmount() {
AppState.removeEventListener("change", this._handleAppStateChange);
}
_handleAppStateChange = async appState => {
if (
this.state.appState.match(/inactive|background/) &&
appState === "active"
) {
cache.incrementAppViews();
const doRefresh = await cache.shouldRefresh("feed");
if (doRefresh) {
this.props.fetchFeed();
}
}
this.setState({ appState });
};
_keyExtractor = ({ Entity }) =>
(Entity.Key || Entity.Id || Entity.CampaignId || Entity.Code).toString();
_gotoEvent = event => {
cache.setRouteStarter("MainDrawer");
this.props.setSelectedEvent(event);
const title = `${event.LegislatureType} Event`;
this.props.navigation.navigate("EventDetails", { title });
};
_gotoSurveyBallot = survey => {
cache.setRouteStarter("MainDrawer");
this.props.setSelectedSurvey(survey);
this.props.navigation.navigate("SurveyDetails");
};
_gotoArticle = article => {
cache.setRouteStarter("MainDrawer");
this.props.setSelectedArticle(article);
this.props.navigation.navigate("ArticleDetails");
};
_onAlertActionButtonPress = async item => {
cache.setRouteStarter("MainDrawer");
await this.props.setSelectedAlert(item.Entity);
this.props.getCampaignDetails();
if (this.props.userEmailIsValidForVoterVoice) {
this.props.navigation.navigate("Questionnaire");
} else {
this.props.navigation.navigate("UnconfirmedEmail");
}
};
_onSwipedOut = (swippedItem, index) => {
this.props.handleContentSwipe(this.props, { swippedItem, index });
};
_handleGetInvolved = (response, entity) => {
if (response !== entity.IsSelected) {
const isTopic = entity.Category !== "GetInvolved";
const items = [
{
...entity,
IsSelected: response
}
];
if (isTopic) {
this.props.handleUpdateTopics({ topics: items });
} else {
this.props.handleUpdateGetInvoved({ involved: items });
}
}
};
renderItem = ({ item, index }) => {
const { Type, Entity } = item;
if (Type === "EVENT") {
return (
<SwippableCard onSwipedOut={() => this._onSwipedOut(item, index)}>
<EventFeedCard
style={styles.push}
mainActionButtonPress={() => this._gotoEvent(Entity)}
event={Entity}
/>
</SwippableCard>
);
}
if (["SURVEY_SURVEY", "SURVEY_BALLOT"].includes(Type)) {
return (
<SwippableCard onSwipedOut={() => this._onSwipedOut(item, index)}>
<SurveyBallotFeedCard
style={styles.push}
survey={Entity}
handleViewDetails={() => this._gotoSurveyBallot(Entity)}
/>
</SwippableCard>
);
}
if (Type === "SURVEY_MICRO") {
return (
<SwippableCard onSwipedOut={() => this._onSwipedOut(item, index)}>
<MicroSurvey style={styles.push} selectedSurvey={Entity} />
</SwippableCard>
);
}
if (Type === "ALERT") {
return (
<SwippableCard onSwipedOut={() => this._onSwipedOut(item, index)}>
<ActionAlertFeedCard
datePosted={Entity.StartDateUtc}
style={styles.push}
title={Entity.Headline}
content={Entity.Alert}
mainActionButtonPress={() => this._onAlertActionButtonPress(item)}
secondaryActionButtonPress={() => {
this.props.setSelectedAlert(Entity);
// eslint-disable-next-line
this.props.navigation.navigate("ActionAlertDetails", {
content: Entity.Alert,
id: Entity.CampaignId,
title: Entity.Headline
});
}}
/>
</SwippableCard>
);
}
if (Type === "ARTICLE") {
return (
<SwippableCard onSwipedOut={() => this._onSwipedOut(item, index)}>
<ArticleFeedCard
content={Entity}
style={styles.push}
mainActionButtonPress={() => this._gotoArticle(Entity)}
/>
</SwippableCard>
);
}
//prettier-ignore
if (Type === 'NOTIFICATION' && Entity.Code === 'INDIVIDUAL_ADDRESS_HOME_MISSING') {
return (
<MissingAddressCard
style={styles.push}
navigate={() => this.props.navigation.navigate('HomeAddress')}
/>
);
}
if (["PREFERENCE_TOPIC", "PREFERENCE_INVOLVEMENT"].includes(Type)) {
return (
<SwippableCard onSwipedOut={() => this._onSwipedOut(item, index)}>
<GetInvolvedFeedCard
style={styles.push}
title={Entity.DisplayText}
onPress={response => this._handleGetInvolved(response, Entity)}
/>
</SwippableCard>
);
}
return null;
};
_onRefresh = async () => {
try {
this.setState({ refreshing: true });
this.props
.fetchFeed()
.then(() => {
this.setState({ refreshing: false });
})
.catch(() => {
this.setState({ refreshing: false });
});
} catch (e) {
this.setState({ refreshing: false });
}
};
_trackScroll = async event => {
try {
if (this.prompted) {
return;
}
const y = event.nativeEvent.contentOffset.y;
const scrollHeight = height * 0.8;
const page = Math.round(Math.floor(y) / scrollHeight);
const alert = await cache.shouldPromtpPushNotificationPermissions();
const iOS = Platform.OS === "ios";
if (alert && iOS && page > 1) {
this.prompted = true;
this._openPromptAlert();
}
} catch (e) {
return false;
}
};
_openPromptAlert = () => {
Alert.alert(
"Push Notifications Access",
"Stay engaged with NFIB on the issues and activities you care about by allowing us to notify you using push notifications",
[
{
text: "Deny",
onPress: () => {
cache.pushNotificationsPrompted();
},
style: "cancel"
},
{
text: "Allow",
onPress: () => {
OneSignal.registerForPushNotifications();
cache.pushNotificationsPrompted();
}
}
],
{ cancelable: false }
);
};
_getAlertTitle = () => {
const { lastSwippedElement } = this.props;
const { Type } = lastSwippedElement.swippedItem;
if (Type.startsWith("PREFERENCE")) {
return "Preference Dismissed";
}
switch (Type) {
case "EVENT":
return "Event Dismissed";
case "SURVEY_BALLOT":
return "Ballot Dismissed";
case "SURVEY_SURVEY":
return "Survey Dismissed";
case "SURVEY_MICRO":
return "Micro Survey Dismissed";
case "ARTICLE":
return "Article Dismissed";
case "ALERT":
return "Action Alert Dismissed";
default:
return "Dismissed";
}
};
render() {
if (this.props.loading && !this.state.refreshing) {
return <Loading />;
}
const contentStyles =
this.props.feed.length > 0 ? styles.content : emptyStateStyles.container;
return (
<View style={styles.container}>
<FlatList
contentContainerStyle={contentStyles}
showsVerticalScrollIndicator={false}
data={this.props.feed}
renderItem={this.renderItem}
keyExtractor={this._keyExtractor}
removeClippedSubviews={false}
onRefresh={this._onRefresh}
refreshing={this.state.refreshing}
ListEmptyComponent={() => (
<EmptyState navigation={this.props.navigation} />
)}
scrollEventThrottle={100}
onScroll={this._trackScroll}
/>
{this.props.displayAlert && (
<BottomAlert
title={this._getAlertTitle()}
onPress={this.props.undoSwipeAction}
hideAlert={this.props.hideUndoAlert}
/>
)}
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1
},
content: {
paddingHorizontal: scale(8),
paddingTop: scale(16),
paddingBottom: scale(20)
},
push: {
marginBottom: 16
}
});
const mapState2Props = ({
activityFeed,
auth: { userEmailIsValidForVoterVoice },
navigation
}) => {
return {
...activityFeed,
userEmailIsValidForVoterVoice,
loading: activityFeed.loading || navigation.deepLinkLoading
};
};
export default connect(mapState2Props, {
fetchFeed,
getCampaignDetails,
handleUpdateGetInvoved,
handleUpdateTopics,
setSelectedAlert,
setSelectedArticle,
setSelectedEvent,
setSelectedSurvey,
handleContentSwipe,
undoSwipeAction,
hideUndoAlert
})(ActivityFeed);
这就是 Get Involved 卡的样子:
因此,当用户单击NO或YES ,然后将该卡片滚动离开视图时,期望当他们将该卡片滚动回视图NO或YES时,无论选择哪一个,都应该仍然存在。
此外,只有当用户一直滚动到活动提要的底部然后返回时,选择的答案才会消失,但如果用户只滚动到活动提要卡的一半并返回到此“参与其中”卡,则选择的答案不会不是 go。
我相信下面的 SO 文章答案正是发生在我身上的事情: React Native - FlatList - Internal State 。
因此,这里的答案似乎是将应用程序 state 的答案作为道具传递并基于该道具进行渲染,而不是卡的内部 state 但我不完全确定它的外观或如何将它们组合在一起.
constructor(props) {
super(props);
// const helper = `${
// this.props.title.endsWith("?") ? "" : "."
// } Your NFIB preferences will be updated.`;
this.state = {
noSelected: false,
yesSelected: false,
helper
};
}
_accept = () => {
this.setState({ yesSelected: true, noSelected: false }, () => {
this.props.onPress(true);
});
};
_decline = () => {
this.setState({ noSelected: true, yesSelected: false }, () => {
this.props.onPress(false);
});
};
with:
this.state = {
// noSelected: false,
// yesSelected: false,
// helper
cardSelectedStatus: []
};
with the idea of then implementing cardSelectedStatus in my mapStateToProps
function mapStateToProps(state) {
return {cardSelectedStatus: state.};
}
但后来我意识到我不确定我传入了什么,因为这个组件中没有动作创建者,因此没有减速器,所以如果这个组件中没有动作创建者/减速器,我可以使用mapStateToProps
吗?
使用 mapStateToProps 是我知道的唯一方法,或者是我最有经验的方法,将来自应用程序 state 的用户输入作为道具传递并基于该道具进行渲染,而不是内部 state。
我能猜到问题所在。 问题是您使用的是FlatList
类的东西。 每次您在屏幕上滚动时,它都会重新创建卡片,然后向后滚动。
所以有两种方法可以解决它:
ScrollView
。 它不会重新创建卡片 this.state = {
cardSelectedStatus: [], // array [true, false, true, ...]. Mean card 0: selected, card 1: no selected,...
...
};
然后你可以将 state 传递给每张卡
因此,经过几周的努力并发布了上述问题,这就是我最终磨练出来的内容:
isSelected: false
。isSelected
更改为true
。isSelected: true
。 因此,基于此,因为isSelected
没有中性值,即以false
开头,这相当于No ,我不能依靠 Redux state 来呈现选择,这可以解决这个问题。
相反,为了节省时间,我能想到的唯一解决方案是设置<FlatList windowSize={500} />
。
这不是一个优雅的解决方案,但它会使FlatList
的行为更像ScrollView
,因为它保留了所有组件,因此当用户滚动到远离它时,我的组件 state 不会被清除。 这无需实际将其替换为ScrollView
即可工作,因为FlatList
的某些属性和方法仅通过将其放入ScrollView
就无法正常工作,就像在FlatList
中一样,例如,在ScrollView
中没有renderItem
属性。
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