鸿蒙应用开发：数据持久化

最近在搞公司项目用到了鸿蒙端的数据持久化，特来跟大家分享一下。

在鸿蒙开发中，可以使用以下几个包来实现数据的持久化处理：

Data Ability

通过数据能力组件，开发者可以实现复杂的数据操作，包括增、删、改、查等功能。它允许不同的应用共享数据，并提供了统一的数据访问接口。

SQLite

这是一个轻量级的关系型数据库，适用于本地存储。开发者可以使用 SQL 语句进行数据管理，支持事务处理，适合需要复杂查询的场景。

Preferences

适合存储简单的配置信息和用户偏好。通过键值对的方式存取数据，非常方便，尤其是在需要保存少量数据时。

File System

直接操作文件系统，允许读写文件。这种方法灵活性高，适合存储大文件或非结构化数据，比如图片、音频等。

本次分享主要以用户首选项为例：在登陆页面输入个人信息后，点击“配置”后保存输入数据并且跳转到下一个页面，在第二个页面显示用户在登陆页输入的信息，并且支持登录页与显示页的数据同步。此外，登录页“退出”按钮绑定了应用关闭功能。

PreferenceModel.ets

import dataPreferences from '@ohos.data.preferences';
import promptAction from '@ohos.promptAction';
import { BusinessError } from '@ohos.base';
import showToast from './ShowToast';let context = getContext(this);let TAG:string = 'preference';// 自定义用户首选项类
export class PreferenceModel {static preferences: dataPreferences.Preferences | null = null;/*** 初始化用户首选项类*/public static initPre(){let options: dataPreferences.Options = { name: 'myStore.db' };PreferenceModel.preferences = dataPreferences.getPreferencesSync(context, options);}/*** 写入并保存数据* @param name - 键名* @param data - 键值*/public static async writeData(name:string,data:string) {// Check whether the data is null.let isDataNull = PreferenceModel.checkData(data);if (isDataNull) {return;}// The data is inserted into the preferences database if it is not empty.PreferenceModel.preferences.putSync(name,data);// 使用flush方法将preferences实例的数据存储到持久化文件，调用用户首选项实例的flush接口await PreferenceModel.preferences.flush();// PreferenceModel.putPreference(name,data);showToast('保存成功！');}/*** 获取数据，返回字符串类型结果* @param name - 键名*/public static getPreference(name:string) {let isExist: boolean = PreferenceModel.preferences.hasSync(name);if (isExist) {console.info(TAG + "The key 'startup' is contained.");let value: dataPreferences.ValueType = PreferenceModel.preferences.getSync(name, 'default');return value.toString().replace(/^"|"$/g, '');} else {console.info(TAG + "The key 'startup' dose not contain.");showToast('该值不存在！');}}}

Register.ets

import router from '@ohos.router';
import { PreferenceModel } from '../common/PreferenceModel';
import { BusinessError } from '@ohos.base';
import common from '@ohos.app.ability.common';
import window from '@ohos.window';@Entry
@Component
struct Register {@State ip:string = '';@State port:string = '';@State username:string = '';@State password:string = '';@State port_ftp:string = '';@State isFocused: boolean = false;context: common.UIAbilityContext = getContext(this) as common.UIAbilityContextaboutToAppear(): void {// 设置不显示导航栏和状态栏window.getLastWindow(this.context).then((data) => {data.setWindowSystemBarEnable([]).then(() => {console.debug('Succeeded in setting the system bar to be invisible.');});});PreferenceModel.initPre()this.ip = PreferenceModel.hasPreference('register-ip')? (PreferenceModel.getPreference('register-ip')).toString(): '10.0.1.182';this.port = PreferenceModel.hasPreference('register-port')? (PreferenceModel.getPreference('register-port')).toString(): '1883';this.username = PreferenceModel.hasPreference('register-username')? (PreferenceModel.getPreference('register-username')).toString(): 'username';this.password = PreferenceModel.hasPreference('register-password')? (PreferenceModel.getPreference('register-password')).toString(): 'password';this.port_ftp = PreferenceModel.hasPreference('register-port-ftp')? (PreferenceModel.getPreference('register-port-ftp')).toString(): '21';}build() {Stack({ alignContent: Alignment.TopStart }) {// 中间的内容部分Column({  }) {Column({ space:20 }){TextInput({text: this.ip}).backgroundColor('#FFFFFF').focusable(this.isFocused).textAlign(TextAlign.Center).onChange((value:string)=>{this.ip = value}).onClick(()=>{this.isFocused = true})Divider().margin({top:-25})TextInput({text: this.port}).backgroundColor('#FFFFFF').focusable(this.isFocused).textAlign(TextAlign.Center).onChange((value:string)=>{this.port = value}).onClick(()=>{this.isFocused = true})Divider().margin({top:-25})TextInput({text: this.username}).backgroundColor('#FFFFFF').focusable(this.isFocused).textAlign(TextAlign.Center).onChange((value:string)=>{this.username = value}).onClick(()=>{this.isFocused = true})Divider().margin({top:-25})TextInput({text: this.password}).backgroundColor('#FFFFFF').focusable(this.isFocused).textAlign(TextAlign.Center).onChange((value:string)=>{this.password = value}).onClick(()=>{this.isFocused = true})Divider().margin({top:-25})TextInput({text: this.port_ftp}).backgroundColor('#FFFFFF').focusable(this.isFocused).textAlign(TextAlign.Center).expandSafeArea([SafeAreaType.KEYBOARD], [SafeAreaEdge.TOP, SafeAreaEdge.BOTTOM]).onChange((value:string)=>{this.port_ftp = value}).onClick(()=>{this.isFocused = true})Divider().margin({top:-25})}.width('40%').height('60%').margin({top:px2vp(200)})Row({space:80}){Text("配置").fontFamily('Source Han Sans CN-Regular').fontSize(24).fontColor('#262B2F').fontWeight(400).textAlign(TextAlign.Center).width(130).height(60).borderRadius(10).backgroundColor('#c1e6c6').onClick(()=>{PreferenceModel.writeData('register-ip',JSON.stringify(this.ip))PreferenceModel.writeData('register-port',JSON.stringify(this.port))PreferenceModel.writeData('register-username',JSON.stringify(this.username))PreferenceModel.writeData('register-password',JSON.stringify(this.password))PreferenceModel.writeData('register-port-ftp',JSON.stringify(this.port_ftp))router.pushUrl({url: 'pages/Index'}).then(()=>{}).catch((err: BusinessError) => {})})Text("退出").fontFamily('Source Han Sans CN-Regular').fontSize(24).fontColor('#262B2F').fontWeight(400).textAlign(TextAlign.Center).width(130).height(60).borderRadius(10).backgroundColor('#c1e6c6').onClick(async ()=>{this.context.terminateSelf()})}.width(500).height('30%').justifyContent(FlexAlign.Center)}.width('94.6%').height('92.2%').backgroundColor('#FFFFFF').borderRadius(30).margin({left:"2.7%",top:"7.8%"}).alignItems(HorizontalAlign.Center)}.width('100%').height('100%').backgroundColor('#2d2736')}
}

Index.ets

import { PreferenceModel } from '../common/PreferenceModel';@Entry
@Component
struct Index {@State message: string[] = [];aboutToAppear(): void {PreferenceModel.initPre()this.message.push(PreferenceModel.getPreference('register-ip').toString());this.message.push(PreferenceModel.getPreference('register-port').toString());this.message.push(PreferenceModel.getPreference('register-username').toString());this.message.push(PreferenceModel.getPreference('register-password').toString());this.message.push(PreferenceModel.getPreference('register-port-ftp').toString());}build() {Row() {Column() {ForEach(this.message, (item, index)=>{Text(item).fontSize(50).fontWeight(FontWeight.Bold)})}.width('100%')}.height('100%')}
}