Reactjs 此.setState不适用于我的React本机项目
在我正在开发的react本机应用程序上,this.setState不起作用,并且未更新构造函数中的值。但是这个.state({})正在工作。但是当我使用它重置构造函数时,请指出代码中的错误Reactjs 此.setState不适用于我的React本机项目,reactjs,react-native,setstate,Reactjs,React Native,Setstate,在我正在开发的react本机应用程序上,this.setState不起作用,并且未更新构造函数中的值。但是这个.state({})正在工作。但是当我使用它重置构造函数时,请指出代码中的错误 import React from 'react'; import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native'; import { RkTextInput, RkButton } from
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
从“React”导入React;
从“react native”导入{样式表、文本、视图、TouchableOpacity、TextInput、图像};
从“react native ui kitten”导入{RkTextInput,RkButton};
从“firebase”导入*作为firebase;
导出默认类Home扩展React.Component{
建造师(道具){
超级(道具)
此.state={
uType:'正常',
AdminNavbutton:“”
}
}
ProfileSubmithandler=()=>{
警报(this.state.uType+“”+this.state.AdminNavbutton)
}
componentDidMount(){
此参数为.readUserData();
}
readUserData=()=>{
userstype='users/'+firebase.auth().currentUser.uid+'/userType'
firebase.database().ref(userstype).once('value')。然后(snapshot=>{
this.setState({uType:snapshot.val()})//不工作且不更新uType
警报(snapshot.val())//工作正常
})
}
emailid=()=>{
}
render(){
返回(
塔姆斯
开发者版
家
阿尔法0.0.0.1
this.ProfileSubmithandler()}>
提交
this.props.navigation.navigate(this.state.AdminNavbutton)}>Profile
);
}
}
此.setState()
是异步的,您的更新值在调用后立即可用
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
当setState()
完成值更新后,您将能够在this.state.uType
下的render
函数中访问更新的数据
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
如果要立即在函数中使用值,则应将其放入其他变量中:
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
const uType = snapshot.val()
this.setState({ uType }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
alert(uType) // Also working
})
}
this.setState()
是异步的,您的更新值现在在调用它后立即可用
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
当setState()
完成值更新后,您将能够在this.state.uType
下的render
函数中访问更新的数据
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
如果要立即在函数中使用值,则应将其放入其他变量中:
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
const uType = snapshot.val()
this.setState({ uType }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
alert(uType) // Also working
})
}
这是因为SetState中存在异步问题。设置从firebase提取的数据和状态时,显示按钮。给你:
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import {RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props){
super(props)
this.state={
uType:'normal',
AdminNavbutton:false,
}
}
ProfileSubmithandler=()=>{
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
};
readUserData=()=> {
userstype= 'users/'+ firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid=()=>{
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
{
this.state.AdminNavbutton &&
<RkButton onPress = {()=>this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={()=>this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
}
</View>
);
}
}
从“React”导入React;
从“react native”导入{样式表、文本、视图、TouchableOpacity、TextInput、图像};
从“react native ui kitten”导入{RkTextInput,RkButton};
从“firebase”导入*作为firebase;
导出默认类Home扩展React.Component{
建造师(道具){
超级(道具)
这个州={
uType:“正常”,
AdminNavbutton:false,
}
}
ProfileSubmithandler=()=>{
警报(this.state.uType+“”+this.state.AdminNavbutton)
}
componentDidMount(){
此参数为.readUserData();
};
readUserData=()=>{
userstype='users/'+firebase.auth().currentUser.uid+'/userType'
firebase.database().ref(userstype).once('value')。然后(snapshot=>{
this.setState({uType:snapshot.val()})//不工作且不更新uType
警报(snapshot.val())//工作正常
})
}
emailid=()=>{
}
render(){
返回(
塔姆斯
开发者版
家
阿尔法0.0.0.1
{
this.state.AdminNavbutton&&
this.ProfileSubmithandler()}>
提交
this.props.navigation.navigate(this.state.AdminNavbutton)}>Profile
}
);
}
}
这是因为SetState中存在异步问题。设置从firebase提取的数据和状态时,显示按钮。给你:
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import { RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props) {
super(props)
this.state = {
uType: 'normal',
AdminNavbutton: ''
}
}
ProfileSubmithandler = () => {
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
}
readUserData = () => {
userstype = 'users/' + firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid = () => {
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
<RkButton onPress={() => this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={() => this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
</View>
);
}
}
import React from 'react';
import { StyleSheet, Text, View, TouchableOpacity, TextInput, Image } from 'react-native';
import {RkTextInput, RkButton } from 'react-native-ui-kitten';
import * as firebase from 'firebase';
export default class Home extends React.Component {
constructor(props){
super(props)
this.state={
uType:'normal',
AdminNavbutton:false,
}
}
ProfileSubmithandler=()=>{
alert(this.state.uType + " " + this.state.AdminNavbutton)
}
componentDidMount() {
this.readUserData();
};
readUserData=()=> {
userstype= 'users/'+ firebase.auth().currentUser.uid + '/userType'
firebase.database().ref(userstype).once('value').then(snapshot => {
this.setState({ uType: snapshot.val() }) // notworking and not updating uType
alert(snapshot.val()) //working Properly
})
}
emailid=()=>{
}
render() {
return (
<View style={styles.container}>
<Text style={styles.titleText}>Taams</Text>
<Text style={styles.edition}>Developer's Edition</Text>
<Text style={styles.titleText}>Home</Text>
<Text>Alpha 0.0.0.1</Text>
{
this.state.AdminNavbutton &&
<RkButton onPress = {()=>this.ProfileSubmithandler()}>
<Text style={styles.LoginButtonText}>Submit</Text>
</RkButton>
<TouchableOpacity onPress={()=>this.props.navigation.navigate(this.state.AdminNavbutton)}><Text style={styles.signinButton}>Profile</Text></TouchableOpacity>
}
</View>
);
}
}
从“React”导入React;
从“react native”导入{样式表、文本、视图、TouchableOpacity、TextInput、图像};
从“react native ui kitten”导入{RkTextInput,RkButton};
从“firebase”导入*作为firebase;
导出默认类Home扩展React.Component{
建造师(道具){
超级(道具)
这个州={
uType:“正常”,
AdminNavbutton:false,
}
}
ProfileSubmithandler=()=>{
警报(this.state.uType+“”+this.state.AdminNavbutton)
}
componentDidMount(){
此参数为.readUserData();
};
readUserData=()=>{
userstype='users/'+firebase.auth().currentUser.uid+'/userType'
firebase.database().ref(userstype).once('value')。然后(snapshot=>{