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如何读取本地/预制数据库

解决措施

1. 将db文件推到数据存储沙箱路径：/data/app/el2/100/database/(bundleName)/entry/rdb/下,实现方式为用文件管理的接口打开本地数据库，读取本地数据库内容并写入沙箱路径下的db文件中。

   import { fileIo, ReadOptions } from '@kit.CoreFileKit';
   import { resourceManager } from '@kit.LocalizationKit';
   import { relationalStore } from '@kit.ArkData';
   
   let context = getContext(this);
   let RDBDirectory = getContext(this).getApplicationContext().databaseDir;
   let resource = getContext(this).resourceManager;
   
   function saveFileToCache(file: resourceManager.RawFileDescriptor, dbName: string) {
     // 创建缓存文件(当前是覆盖式创建)
     let cFile = RDBDirectory + '/entry/rdb/' + dbName;
     let cacheFile = fileIo.openSync(cFile, fileIo.OpenMode.READ_WRITE | fileIo.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
     let currentOffset = file.offset;
   
     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
     };
   
     // 后面len会一直减，直到没有
     while (true) {
       // 读取buffer容量的内容
       let readLength = fileIo.readSync(file.fd, buffer, readOption);
       // 写入buffer容量的内容
       fileIo.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 != undefined) {
         readOption.offset += readLength;
       }
     }
     console.log('Copy Success!!!')
     fileIo.close(cacheFile);
   }
   
   function INIT() {
     // 创建数据库沙箱目录
     try {
       let dirPath = RDBDirectory + '/entry';
       fileIo.mkdirSync(dirPath);
       dirPath = dirPath + '/rdb';
       fileIo.mkdirSync(dirPath);
     } catch (error) {
       console.error(`mkdir rdbPath failed, error code: ${error.code}, message: ${error.message}.`);
     }
   
     //数据库名称
     let dbName: string = 'Company.db';
   
     //读取rawfile目录下db文件
     try {
       resource.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());
           saveFileToCache(value, dbName);
         }
       });
     } catch (error) {
       console.error(`callback getRawFd failed, error code: ${error.code}, message: ${error.message}.`);
     }
   }

2. 通过getRdbStore获取保存在沙箱路径下的db文件

   function getRDB(): relationalStore.RdbStore | undefined {
     let result: relationalStore.RdbStore | undefined = undefined;
     const STORE_CONFIG: relationalStore.StoreConfig = {
       name: 'Company.db',
       securityLevel: relationalStore.SecurityLevel.S1
     };
   
     relationalStore.getRdbStore(context, STORE_CONFIG, (err, store) => {
       if (err) {
         console.error(`Failed to get RdbStore. Code:${err.code}, message:${err.message}`);
         return;
       } else {
         console.info(`Succeeded in getting RdbStore.`);
       }
       result = store;
     })
     return result;
   }

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