#HarmonyOS NEXT 体验官#本地数据库实现《菜谱大全》app（一） 原创

export class Constant {
    //数据库名称
    static readonly DB_NAME = "menu.db"
 }

import { common } from '@kit.AbilityKit';
import { Constant } from '../constant/Constant';
import fs, { ReadOptions } from '@ohos.file.fs';
/**
 * 将rawfile下的menu.db 写入到手机本地文件中
 * @param context
 */
export async function saveDB2LocalFile(context: common.UIAbilityContext, copyCallback: (isSuccess: boolean) => void) {
  let dirPath = context.getApplicationContext().databaseDir + "/entry"
  if (!fs.accessSync(dirPath)) {
    fs.mkdirSync(dirPath);
  }
  dirPath = dirPath + "/rdb"
  if (!fs.accessSync(dirPath)) {
    fs.mkdirSync(dirPath);
  }
  //数据库名称
  let dbName: string = Constant.DB_NAME
  if (!fs.accessSync(dirPath + "/" + dbName)) {
    try {
      context.resourceManager.getRawFd('rdb/' + dbName, (error, value) => {
        if (error != null) {
          console.log(`callback getRawFd failed error code: ${error.code}, message: ${error.message}.`);
        } else {
          console.info(value.length.toString() + "DWSD")
          // saveFileToCache(context,value, dbName)
          let cFile = context.getApplicationContext().databaseDir + "/entry/rdb/" + dbName
          let cacheFile = fs.openSync(cFile, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE)
          // 读取缓冲区大小
          let bufferSize = 30000
          let buffer = new ArrayBuffer(bufferSize); //创建buffer缓冲区
          // 要copy的文件的offset和length
          let currentOffset = value.offset;
          let lengthNeedToReed = value.length;

          let readOption: ReadOptions = {
            offset: currentOffset, //期望读取文件的位置。可选，默认从当前位置开始读
            length: bufferSize //每次期望读取数据的长度。可选，默认缓冲区长度
          }
          while (true) {
            // 读取buffer容量的内容
            let readLength = fs.readSync(value.fd, buffer, readOption);
            // 写入buffer容量的内容
            fs.writeSync(cacheFile.fd, buffer, { length: readLength }) //写到cacheFile里
            // 判断后续内容 修改读文件的参数
            // buffer没读满代表文件读完了
            if (readLength < bufferSize) {
              break;
            }
            if (readOption.offset) {
              readOption.offset += readLength
            }
          }
          console.log("Copy Success!!!")
          fs.close(cacheFile);
          copyCallback(true)
        }
      });
    } catch (error) {
      console.error(`callback getRawFd failed, error code: ${error.code}, message: ${error.message}.`)
    }
  }else {
    copyCallback(true)
  }
}

@Entry
@Component
struct Index {
  build() {
    Stack() {
        Column() {
          Tabs() {
            TabContent() {
            }
            .tabBar(this.tabBuilder("菜谱", 0, $r("app.media.tab_menu_selected"), $r("app.media.tab_menu_normal")))

            TabContent() {
            }
            .tabBar(this.tabBuilder("初级", 1, $r("app.media.tab_chuji_selected"), $r("app.media.tab_chuji_normal")))
            TabContent() {
            }
            .tabBar(this.tabBuilder("高级", 2, $r("app.media.tab_gaoji_selected"), $r("app.media.tab_gaoji_normal")))
          }
          .onChange((index: number) => {
            this.currentIndex = index
          })
          .onTabBarClick((index) => {
            this.currentIndex = index
          })
          .barPosition(BarPosition.End)
          .barHeight(50)
          .layoutWeight(1)
        }.height("100%")

      }
  }
  @State currentIndex: number = 0

  @Builder
  tabBuilder(title: string, targetIndex: number, selectedImg: Resource, normalImg: Resource) {
    Column() {
      Image(this.currentIndex === targetIndex ? selectedImg : normalImg)
        .size({ width: 25, height: 25 })
      Text(title)
        .fontColor(this.currentIndex === targetIndex ? $r("app.color.primary") : $r("app.color._bfbfbf"))
    }
    .width('100%')
    .height(50)
    .justifyContent(FlexAlign.Center)
    .clickEffect({ level: ClickEffectLevel.HEAVY, scale: 0.6 })
  }
}

{
  "app": {
    "bundleName": "com.lingmou.lovecook",
    "vendor": "example",
    "versionCode": 1000000,
    "versionName": "1.0.0",
    "icon": "$media:app_icon",
    "label": "$string:app_name"
  }
}