[Harmony]大文件持久化

1.添加权限

在module.json5文件中添加权限

"requestPermissions": [{"name": "ohos.permission.READ_WRITE_USER_FILE", // 读写用户数据"reason": "$string:read_write_user_file_reason","usedScene": {"abilities": ["MFLargeDataStorage"],"when": "always"}}
]

string.json

{"string": [{"name": "read_write_user_file_reason","value": "读写用户文件"}]
}

2.封装大文件数据持久工具

import fs from '@ohos.file.fs';
import { BusinessError } from '@ohos.base';
import common from '@ohos.app.ability.common';
import ConsoleLog from '../extension/ConsoleLog';
import { buffer } from '@kit.ArkTS';class MFLargeDataStorage {private static readonly FILE_NAME = 'user_data.json';private static _context: common.UIAbilityContext;static setContext(abilityContext: common.UIAbilityContext): void {MFLargeDataStorage._context = abilityContext;}private static getFilePath(): string {if (!MFLargeDataStorage._context) {throw new Error('Context not initialized');}return `${MFLargeDataStorage._context.filesDir}/${MFLargeDataStorage.FILE_NAME}`;}static async saveUserJson(data: object): Promise<void> {const filePath = MFLargeDataStorage.getFilePath();const jsonStr = JSON.stringify(data);try {const file = await fs.open(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);await fs.write(file.fd, jsonStr);await fs.close(file.fd);} catch (err) {ConsoleLog.error(`[MFLargeDataStorage] save error: ${(err as BusinessError).message}`);}}static async saveUserJsonString(jsonStr: string): Promise<void> {const filePath = MFLargeDataStorage.getFilePath();try {const file = await fs.open(filePath, fs.OpenMode.CREATE | fs.OpenMode.READ_WRITE);await fs.write(file.fd, jsonStr);await fs.close(file.fd);} catch (err) {ConsoleLog.error(`[MFLargeDataStorage] save error: ${(err as BusinessError).message}`);}}static async loadUserJson(): Promise<string> {const filePath = MFLargeDataStorage.getFilePath();try {if (!await fs.access(filePath)) {return "";}const file = await fs.open(filePath, fs.OpenMode.READ_ONLY);const stat = await fs.stat(filePath);const buf = new ArrayBuffer(stat.size);await fs.read(file.fd, buf);await fs.close(file.fd);// 使用buffer模块的from和toString方法const str = buffer.from(buf).toString('utf-8');return str;} catch (err) {ConsoleLog.error(`[MFLargeDataStorage] load error: ${(err as BusinessError).message}`);return "";}}
}export default MFLargeDataStorage;

3.使用示例

import common from '@ohos.app.ability.common';
import ConsoleLog from '../support/extension/ConsoleLog';
import MFLargeDataStorage from '../support/data/MFLargeDataStorage';interface UserItem {name: string;age: number;
}@Entry
@Component
struct Index {private context = getContext(this) as common.UIAbilityContext;aboutToAppear() {if (!this.context) {ConsoleLog.error('无效的上下文对象');return;}MFLargeDataStorage.setContext(this.context);}build() {RelativeContainer() {Column() {Button('保存大文件').onClick(async () => {const userData: UserItem = { name: "张三", age: 25 };try {await MFLargeDataStorage.saveUserJson(userData);} catch (err) {ConsoleLog.error('保存失败:', err);}})Button('获取大文件').onClick(async () => {const loadedData = await MFLargeDataStorage.loadUserJson();ConsoleLog.log(loadedData); // 输出: {name: "张三", age: 25}})}}.height('100%').width('100%')}
}