元服务——json文件处理

先创建元服务

需要手动登录，打开浏览器后同意登录

1、json权限获取

找到string.json添加一段代码

entry\src\main\resources\base\element\string.json

找到module.json5添加一段代码

entry\src\main\module.json5

2、写入文件操作

需要的包：

import { fileIo } from '@kit.CoreFileKit';
import { common } from '@kit.AbilityKit';
import { buffer, List } from '@kit.ArkTS';

写入函数：

createFile(){
  // 获取应用文件路径
  let context = getContext(this) as common.UIAbilityContext;
  let filesDir = context.filesDir;
  // 新建并打开文件
  let file = fileIo.openSync(filesDir + this.fileName, fileIo.OpenMode.WRITE_ONLY | fileIo.OpenMode.CREATE);
  // 将集合转换成json序列化对象存储到文件中
  let writeLen = fileIo.writeSync(file.fd, "写入的信息");
  console.info("字符串长度: " + writeLen);
  // 从文件读取一段内容
  console.info(filesDir)
  // 关闭文件
  fileIo.closeSync(file);
}

完整Index:

import { authentication } from '@kit.AccountKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { hilog } from '@kit.PerformanceAnalysisKit';
import { fileIo } from '@kit.CoreFileKit';
import { common } from '@kit.AbilityKit';
import { buffer, List } from '@kit.ArkTS';

@Entry
@Component
struct Index {
  @State message: string = 'Hello World';
  @State fileName:string="/test.txt";
  aboutToAppear(): void {
    this.createFile();
    console.info("初始化完毕")
  }
  createFile(){
    // 获取应用文件路径
    let context = getContext(this) as common.UIAbilityContext;
    let filesDir = context.filesDir;
    // 新建并打开文件
    let file = fileIo.openSync(filesDir + this.fileName, fileIo.OpenMode.WRITE_ONLY | fileIo.OpenMode.CREATE);
    // 将集合转换成json序列化对象存储到文件中
    let writeLen = fileIo.writeSync(file.fd, "写入的信息");
    console.info("字符串长度: " + writeLen);
    // 从文件读取一段内容
    console.info(filesDir)
    // 关闭文件
    fileIo.closeSync(file);
  }
  build() {
    RelativeContainer() {
      Text(this.message)
        .id('HelloWorld')
        .fontSize(50)
        .fontWeight(FontWeight.Bold)
        .alignRules({
          center: { anchor: '__container__', align: VerticalAlign.Center },
          middle: { anchor: '__container__', align: HorizontalAlign.Center }
        })
    }
    .height('100%')
    .width('100%')
  }

}

运行之后，会在log日志中看到初始化完毕

并且在根目录（我的在D盘）会自动创建test.txt写入信息

3、读取文件操作

Index中添加代码：

readFile():string{
    let context = getContext(this) as common.UIAbilityContext;
    if (!context) {
      console.info("无法获取有效的上下文");
      return "";
    }
    let filesDir = context.filesDir;
    // 新建并打开文件
    let file = fileIo.openSync(filesDir + this.fileName, fileIo.OpenMode.READ_ONLY|fileIo.OpenMode.CREATE);

    let bufferSize = 1024;
    let arrayBuffer = new ArrayBuffer(bufferSize);
    class Option {
      public offset: number = 0;
      public length: number = bufferSize;
    }
    let option = new Option();
    let content: string = "";
    let readLen: number=0;
    do {
      // 读取文件内容到数组缓冲区
      readLen = fileIo.readSync(file.fd, arrayBuffer, option);
      if (readLen > 0) {
        let buf = buffer.from(arrayBuffer, 0, readLen);
        content += buf.toString();
        // 更新下一次读取的偏移量，继续从文件后续位置读取
        option.offset += readLen;
      }
    } while (readLen === bufferSize);//判断+赋值
    console.info("内容是："+content)
    // 关闭文件
    fileIo.closeSync(file);
    return content;
  }

可以将build中文本标签改成按钮

build() {
    RelativeContainer() {
      Button(this.message)
        .id('HelloWorld')
        .fontSize(50)
        .fontWeight(FontWeight.Bold)
        .alignRules({
          center: { anchor: '__container__', align: VerticalAlign.Center },
          middle: { anchor: '__container__', align: HorizontalAlign.Center }
        }).onClick(()=>{
          console.info(this.readFile())
      })
    }
    .height('100%')
    .width('100%')
  }

}

点击按钮后，可以将信息显示在log中

序列化

先在entry\src\main\etc下创建 “model” 文件夹 创建Orders模型：

export class Orders{
    /**
     * 排名
     */
   public getTime:string = "";
    public no :number = 0;
    public score :number = 0;
    public name:string = "";
}

将以下代码替换Index.json中部分

createFile(){
    // 获取应用文件路径
    let context = getContext(this) as common.UIAbilityContext;
    let filesDir = context.filesDir;
    // 新建并打开文件
    let file = fileIo.openSync(filesDir + this.fileName, fileIo.OpenMode.WRITE_ONLY | fileIo.OpenMode.CREATE);
    //字符串序列化
    let o :Orders = new Orders()
    o.no = 1;
    o.name = "刘德华";
    o.getTime = "1998-10-10 06:06:06"
    o.score = 98 ;
    //反序列化
    let writeLen = fileIo.writeSync(file.fd,JSON.stringify(o));
    console.info("字符串长度: " + writeLen);
    // 从文件读取一段内容
    console.info(filesDir)
    // 关闭文件
    fileIo.closeSync(file);
  }

会看到编译完成后，点击 “Hello World” 按钮，log更新的日志 效果：

同样test.txt中日志也会更新

反序列化

示例一

Index上方添加调用语句： @State info : Orders|null = null;

读取代码下方单独写一下反序列化代码：

//将字符串反序列化
  backModel(){
    this.info = JSON.parse(this.readFile())
  }

在build中添加文本：

Text(){
        Span(this.info?.no.toString())
        Span(this.info?.name.toString())
        Span(this.info?.getTime.toString())
        Span(this.info?.score.toString())

      }

完整Index

import { authentication } from '@kit.AccountKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { hilog } from '@kit.PerformanceAnalysisKit';
import { fileIo } from '@kit.CoreFileKit';
import { common } from '@kit.AbilityKit';
import { buffer, List } from '@kit.ArkTS';
import { Orders } from '../model/Orders';

@Entry
@Component
struct Index {
  @State message: string = 'Hello World';
  @State fileName:string="/test.txt";
  @State info : Orders|null = null;
  aboutToAppear(): void {
    this.createFile();
    console.info("初始化完毕")
    this.backModel()
  }
  createFile(){
    // 获取应用文件路径
    let context = getContext(this) as common.UIAbilityContext;
    let filesDir = context.filesDir;
    // 新建并打开文件
    let file = fileIo.openSync(filesDir + this.fileName, fileIo.OpenMode.WRITE_ONLY | fileIo.OpenMode.CREATE);
    //字符串序列化
    let o :Orders = new Orders()
    o.no = 1;
    o.name = "刘德华";
    o.getTime = "1998-10-10 06:06:06"
    o.score = 98 ;
    //反序列化
    let writeLen = fileIo.writeSync(file.fd,JSON.stringify(o));
    console.info("字符串长度: " + writeLen);
    // 从文件读取一段内容
    console.info(filesDir)
    // 关闭文件
    fileIo.closeSync(file);
  }

  readFile():string{
    let context = getContext(this) as common.UIAbilityContext;
    if (!context) {
      console.info("无法获取有效的上下文");
      return "";
    }
    let filesDir = context.filesDir;
    // 新建并打开文件
    let file = fileIo.openSync(filesDir + this.fileName, fileIo.OpenMode.READ_ONLY|fileIo.OpenMode.CREATE);

    let bufferSize = 1024;
    let arrayBuffer = new ArrayBuffer(bufferSize);
    class Option {
      public offset: number = 0;
      public length: number = bufferSize;
    }
    let option = new Option();
    let content: string = "";
    let readLen: number=0;
    do {
      // 读取文件内容到数组缓冲区
      readLen = fileIo.readSync(file.fd, arrayBuffer, option);
      if (readLen > 0) {
        let buf = buffer.from(arrayBuffer, 0, readLen);
        content += buf.toString();
        // 更新下一次读取的偏移量，继续从文件后续位置读取
        option.offset += readLen;
      }
    } while (readLen === bufferSize);//判断+赋值
    console.info("内容是："+content)
    // 关闭文件
    fileIo.closeSync(file);
    return content;
  }
  //将字符串反序列化
  backModel(){
    this.info = JSON.parse(this.readFile())
  }

  build() {
    RelativeContainer() {
      Text(){
        Span(this.info?.no.toString())
        Span(this.info?.name.toString())
        Span(this.info?.getTime.toString())
        Span(this.info?.score.toString())

      }
      Button(this.message)
        .id('HelloWorld')
        .fontSize(50)
        .fontWeight(FontWeight.Bold)
        .alignRules({
          center: { anchor: '__container__', align: VerticalAlign.Center },
          middle: { anchor: '__container__', align: HorizontalAlign.Center }
        }).onClick(()=>{
          console.info(this.readFile())
      })
    }
    .height('100%')
    .width('100%')
  }

}

效果：

示例二

将以下代码替换build后文本部分：

Column() {
      ForEach(this.info,(o:Orders,Index)=> {
        Column() {
          Text(o.no.toString())
          Text(o.name.toString())
          Text(o.getTime.toString())
          Text(o.score.toString())
        }
      })

将以下代码替换示例一调用语句： @State info : Array<Orders>|null = null;

示例一的createFile部分的反序列化代码中 “o” 替换为 “arr” ： let writeLen = fileIo.writeSync(file.fd,JSON.stringify(arr)); 完整Index:

import { authentication } from '@kit.AccountKit';
import { BusinessError } from '@kit.BasicServicesKit';
import { hilog } from '@kit.PerformanceAnalysisKit';
import { fileIo } from '@kit.CoreFileKit';
import { common } from '@kit.AbilityKit';
import { buffer, List } from '@kit.ArkTS';
import { Orders } from '../model/Orders';

@Entry
@Component
struct Index {
  @State message: string = 'Hello World';
  @State fileName:string="/test.txt";
  @State info : Array<Orders>|null = null;
  aboutToAppear(): void {
    this.createFile();
    console.info("初始化完毕")
    this.backModel()
  }
  createFile(){
    // 获取应用文件路径
    let context = getContext(this) as common.UIAbilityContext;
    let filesDir = context.filesDir;
    // 新建并打开文件
    let file = fileIo.openSync(filesDir + this.fileName, fileIo.OpenMode.WRITE_ONLY | fileIo.OpenMode.CREATE);
    //字符串序列化
    let arr: Array<Orders> = new Array<Orders>();
    for (let index = 0; index < 10; index++) {
      let o:Orders = new Orders();
      o.no = index + 1;
      o.name = "刘德华"+index;
      o.getTime = "1998-10-10 06:06:0"+index;
      o.score = 80+index;
      arr.push(o)

    }
    //反序列化
    let writeLen = fileIo.writeSync(file.fd,JSON.stringify(arr));
    console.info("字符串长度: " + writeLen);
    // 从文件读取一段内容
    console.info(filesDir)
    // 关闭文件
    fileIo.closeSync(file);
  }

  readFile():string{
    let context = getContext(this) as common.UIAbilityContext;
    if (!context) {
      console.info("无法获取有效的上下文");
      return "";
    }
    let filesDir = context.filesDir;
    // 新建并打开文件
    let file = fileIo.openSync(filesDir + this.fileName, fileIo.OpenMode.READ_ONLY|fileIo.OpenMode.CREATE);

    let bufferSize = 1024;
    let arrayBuffer = new ArrayBuffer(bufferSize);
    class Option {
      public offset: number = 0;
      public length: number = bufferSize;
    }
    let option = new Option();
    let content: string = "";
    let readLen: number=0;
    do {
      // 读取文件内容到数组缓冲区
      readLen = fileIo.readSync(file.fd, arrayBuffer, option);
      if (readLen > 0) {
        let buf = buffer.from(arrayBuffer, 0, readLen);
        content += buf.toString();
        // 更新下一次读取的偏移量，继续从文件后续位置读取
        option.offset += readLen;
      }
    } while (readLen === bufferSize);//判断+赋值
    console.info("内容是："+content)
    // 关闭文件
    fileIo.closeSync(file);
    return content;
  }
  //将字符串反序列化
  backModel(){
    this.info = JSON.parse(this.readFile())
  }

  build() {
    Column() {
      ForEach(this.info,(o:Orders,Index)=> {
        Column() {
          Text(o.no.toString())
          Text(o.name.toString())
          Text(o.getTime.toString())
          Text(o.score.toString())
        }
      })
      Button(this.message)
        .id('HelloWorld')
        .fontSize(50)
        .fontWeight(FontWeight.Bold)
        .alignRules({
          center: { anchor: '__container__', align: VerticalAlign.Center },
          middle: { anchor: '__container__', align: HorizontalAlign.Center }
        }).onClick(()=>{
          console.info(this.readFile())
      })
    }
    .height('100%')
    .width('100%')
  }

}

效果：