我的初始状态为component:
constructor(props) {
super(props)
this.state = {
currentId: 0,
pause: true,
count: 0,
storiesDone: 0
}
this.defaultInterval = 4000
this.width = props.width || 360
this.height = props.height || 640
}
我必须从currentId = 0开始,然后即使在刷新页面后也要更新组件的状态.
我要在保持值1之后恢复currentId = 1.
当我尝试在上面的代码中替换currentId = localStorage.getItem(‘currentId’)时,出现了属性无法更改的错误.
var currentId = this.state.currentId;
localStorage.setItem( 'currentId', 1);
console.log(currentId);
localStorage.getItem('currentId');
我也尝试过:
_this.setState((state) => {
return {currentId: localStorage.getItem('currentId')};
});
解决方法:
值类型坚持到localStorage must be a string.
考虑修改与localStorage交互的代码,以便在将状态值currentId传递给localStorage.setItem()之前先将其转换为字符串.
还要注意,当存在键时,由localStorage.getItem()表示string values are returned,这意味着您应该解析返回的值以获得currentId作为数字.
与此类似的东西应该起作用:
const saveCurrentId = () => {
const { currentId } = this.state;
/* Format string from value of currentId and persist */
localStorage.setItem( 'currentId', `${ currentId }`);
}
const loadCurrentId = (fallbackValue) => {
/* Load currentId value from localStorage and parse to integer */
const currentId = Number.parseInt(localStorage.getItem('currentId'));
/* Return currentId if valid, otherwise return fallback value */
return Number.isNaN(currentId) ? fallbackValue : currentId;
}
使用上面的代码,然后可以更新组件构造函数以自动加载和应用持久化的currentId,如下所示:
constructor(props) {
super(props)
this.state = {
/* Use 0 as fallback if no persisted value present */
currentId: this.loadCurrentId( 0 ),
pause: true,
count: 0,
storiesDone: 0
}
this.defaultInterval = 4000
this.width = props.width || 360
this.height = props.height || 640
}