这一节了解一下鸿蒙中常用存储API，主要有LocalStorage ，AppStorage，PersistentStorage，LocalStorage 是一种页面级UI状态存储机制，主要用于在UIAbility内和页面间共享状态数据。通过使用特定的装饰器，LocalStorage能够实现组件内部变量与LocalStorage中属性的单向或双向同步。
LocalStorage的装饰器器
@LocalStorageProp：此装饰器用于建立组件内部变量与LocalStorage中指定属性的单向同步关系。当LocalStorage中的属性变化时，会同步到组件的变量，但本地修改不会同步回LocalStorage。
@LocalStorageLink：此装饰器用于建立组件内部变量与LocalStorage中指定属性的双向同步关系。本地和LocalStorage中的修改都会互相同步。
栗子:
EntryAbility.ts import UIAbility from '@ohos.app.ability.UIAbility';
import hilog from '@ohos.hilog';
import window from '@ohos.window';export default class EntryAbility extends UIAbility {onCreate(want, launchParam) {hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onCreate');}onDestroy() {hilog.info(0x0000, 'testTag', '%{public}s', 'Ability onDestroy');}storage = new LocalStorage({user: {name: 'jack',age: 20}})onWindowStageCreate(windowStage: window.WindowStage) {// Main window is created, set main page for this abilityhilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageCreate');windowStage.loadContent('pages/Index', this.storage, (err, data) => {if (err.code) {hilog.error(0x0000, 'testTag', 'Failed to load the content. Cause: %{public}s', JSON.stringify(err) ?? '');return;}hilog.info(0x0000, 'testTag', 'Succeeded in loading the content. Data: %{public}s', JSON.stringify(data) ?? '');});}onWindowStageDestroy() {// Main window is destroyed, release UI related resourceshilog.info(0x0000, 'testTag', '%{public}s', 'Ability onWindowStageDestroy');}onForeground() {// Ability has brought to foregroundhilog.info(0x0000, 'testTag', '%{public}s', 'Ability onForeground');}onBackground() {// Ability has back to backgroundhilog.info(0x0000, 'testTag', '%{public}s', 'Ability onBackground');}
}Index.ets
import { User } from '../models'const storage = LocalStorage.GetShared()@Entry(storage)
@Component
struct Index {@LocalStorageProp('user')user: User = {}build() {Column({ space: 30 }) {Text(this.user.name + this.user.age).onClick(() => {this.user.age ++})Child()Navigator({target: 'pages/OtherPage',}){Text('Jump Other Page')}}.height('100%')}
}@Component
struct Child {@LocalStorageLink('user')user: User = {}build() {Text(this.user.name + this.user.age).onClick(() => {this.user.age ++})}
}OtherPage.ets
import { User } from '../models'const storage = LocalStorage.GetShared()@Entry(storage)
@Component
struct OtherPage {@LocalStorageLink('user')user: User = {}build() {Column(){Text(' Other Page ')Text(this.user.name + this.user.age).onClick(() => {this.user.age ++})}}
}bean类:
Index.ets
export class User {name?: stringage?: number
}AppStorage为应用程序的UI状态属性提供中央存储，并且由UI框架在应用程序启动时创建。与LocalStorage不同，LocalStorage是页面级的存储，通常用于单个页面或页面间的数据共享，而AppStorage则是全局的状态共享，相当于整个应用的“中枢”。
AppStorage的装饰器
@StorageProp：此装饰器用于建立组件内部变量与AppStorage中指定属性的单向同步关系。当AppStorage中的属性变化时，会同步到组件的变量，但本地修改不会同步回AppStorage。
@StorageLink：此装饰器用于建立组件内部变量与AppStorage中指定属性的双向同步关系。本地和AppStorage中的修改都会互相同步。
栗子:
Index.etsimport promptAction from '@ohos.promptAction'
import { User } from '../models'
AppStorage.SetOrCreate('user', { name: 'jack', age: 16 })@Entry
@Component
struct Index {@StorageLink('user')user: User = {}build() {Column({ space: 15 }) {Text(this.user.name + this.user.age).onClick(() => {this.user.age ++})Divider()Child()Divider()ChildB()}.height('100%').width('100%').justifyContent(FlexAlign.Center)}
}@Component
struct Child {@StorageLink('user')user: User = {}build() {Text(this.user.name + this.user.age).onClick(() => {this.user.age ++})}
}@Component
struct ChildB {build() {Column(){Text('获取 AppStorage').onClick(() => {const user = AppStorage.Get<User>('user')promptAction.showToast({ message: user.name + user.age })})Text('修改 AppStorage').onClick(() => {AppStorage.Set<User>('user', { name: 'tom', age: 20 })})Text('Link 修改 AppStorage').onClick(() => {const link: SubscribedAbstractProperty<User> = AppStorage.Link('user')// promptAction.showToast({ message: link.get().name + link.get().age })link.set({name: link.get().name,age: link.get().age + 1})})}}
}PersistentStorage 是一个用于实现数据持久化的存储机制，其主要作用是确保选定的 AppStorage 属性在应用程序重新启动时的值与应用程序关闭时的值相同。PersistentStorage 将选定的 AppStorage 属性保留在设备磁盘上，通过 API 来决定哪些 AppStorage 属性应借助 PersistentStorage 进行持久化。所有属性访问都是对 AppStorage 的访问，AppStorage 中的更改会自动同步到 PersistentStorage。
PersistentStorage的装饰器
@persistProp：此装饰器用于将指定的 AppStorage 属性持久化到设备磁盘上。例如，使用 PersistentStorage.persistProp('aProp', 47) 将 'aProp' 属性持久化。
@StorageLink：此装饰器用于建立组件内部变量与 AppStorage 中指定属性的双向同步关系，所有同步也会反映到 PersistentStorage 中。
栗子:
Index.ets
import { User } from '../models'
PersistentStorage.PersistProp('count', 100)
PersistentStorage.PersistProp('user', `{ "name": "jack", "age": 17 }`)@Entry
@Component
struct Index {@StorageLink('count')count: number = 0@StorageLink('user')userJson: string = ''@Stateuser: User = JSON.parse(this.userJson)build() {Column({ space: 15 }) {Text(this.count.toString()).onClick(() => {this.count ++})Text(this.user.name + this.user.age).onClick(() => {this.user.age ++// this.userJson = JSON.stringify(this.user)AppStorage.Set('user', JSON.stringify(this.user))})Divider()ChildA()}.height('100%').width('100%').justifyContent(FlexAlign.Center)}
}@Component
struct ChildA {@StorageLink('count')count: number = 0@StorageLink('user')userJson: string = ''build() {Column(){Text(this.count.toString()).onClick(() => {this.count ++})Text(this.userJson)}}
}
)
