OpenHarmony应用如何获取媒体文件的标准化数据类型及其图标文件

简介：

媒体文件如图片，音频，视频等类型文件的标准话数据类型获取可以使用@ohos.data.uniformTypeDescriptor。

文档环境：

• 开发环境：Windows 10专业版
• DevEco Studio版本：DevEco Studio 4.0Release (4.0.0.600)
• SDK版本：4.1.3.3 (full sdk)
• API版本：Version 11
• 开发板型号：DAYU200(RK3568)
• 系统版本：OpenHarmony 4.1.3.5

演示demo：

• 新建一个 Stage 框架的 demo 工程，在page/Index.ets中通过 let context = getContext(this) as common.UIAbilityContext;filePath = context.filesDir; 拿到应用的沙箱files路径信息，通过文件操作接口在files下创建文件夹utdType并分别创建以png，mp3，mp4为后缀的文件。
• 通过接口fs.listFileSync(filesPath)获取utdType_test文件夹下的所有文件，由字符串接口index = fileName.lastIndexOf('.')和fileExtension = fileName.substring(index)拿到文件的后缀。
• 通过接口getUniformDataTypeByFilenameExtension(fileExtension)获得文件标准化数据类型，再通过接口getTypeDescriptor和belongsTo判断文件是否归属与标准化数据类型xxx demo运行效果： 核心代码如下：

import utdDesc from '@ohos.data.uniformTypeDescriptor';
import fs from '@ohos.file.fs';
import common from '@ohos.app.ability.common';
import hilog from '@ohos.hilog';

let context = getContext(this) as common.UIAbilityContext;
let baseDir = context.filesDir;
let filesPath = baseDir + '/utdType';

class FileInfo {
  filename: string;
  utdType: string;
  iconFile: string;

  constructor(fileName: string, utdType: string, iconFile: string) {
    this.filename = fileName;
    this.utdType = utdType;
    this.iconFile = iconFile;
  }
}

let class2UTD = new Map([
  ["Images", "general.image"],
  ["Audios", "general.audio"],
  ["Videos", "general.video"]
]);

let precastFiles: string[] = [
  "imagePng.png",
  "audioMp3.mp3",
  "videoMp4.mp4",
];

function CreatePrecastFile(): void {
  try {
    let res = fs.accessSync(filesPath);
    if (res) {
      hilog.info(0, `file path: ${filesPath} exists`);
    } else {
      hilog.info(0, `file path: ${filesPath} not exists`);
      fs.mkdirSync(filesPath);
    }
  } catch (error) {
    let err: BusinessError = error as BusinessError;
    hilog.error(0, "accessSync failed with error message: " + err.message + ", error code: " + err.code);
  }

  for (let i = 0; i < precastFiles.length; i++) {
    let fileName = filesPath + "/" + precastFiles[i];
    hilog.info(0, `The file name: ${fileName}`);
    try {
      let res = fs.accessSync(fileName);
      if (res) {
        hilog.info(0, `file: ${fileName} exists!.`);
      } else {
        hilog.info(0, `file: ${fileName} not exists, will create it!.`);
        let file = fs.openSync(fileName, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
        hilog.info(0, "file fd: " + file.fd);
        fs.closeSync(file);
      }
    } catch (error) {
      let err: BusinessError = error as BusinessError;
      hilog.error(0, "accessSync failed with error message: " + err.message + ", error code: " + err.code);
    }
  }
}

@Entry
@Component
struct selectMediaType {
  @State text: string = "Images";
  @State index: number = 1;
  @State space: number = 12;
  @State arrowPosition: ArrowPosition = ArrowPosition.END;
  @State fileNames: string[] = [];
  @State selectedFilesInfos: FileInfo[] = [];
  private routerBackUrl: string = 'pages/Index';
  private routerNextUrl: string = 'pages/displayMediaFile';

  getListFile(): string[] {
    let files = fs.listFileSync(filesPath);
    for (let i = 0; i < files.length; i++) {
      hilog.info(0, `The name of file: ${files[i]}`);
    }
    return files;
  }

  UpdateSelectedFiles(): void {
    this.fileNames = this.getListFile();
    for (let i = this.selectedFilesInfos.length - 1; i >= 0; i--) {
      this.selectedFilesInfos.pop();
    }
    this.selectedFilesInfos = [];
    hilog.info(0, "selectText: " + this.text)
    for (let i = 0; i < this.fileNames.length; i++) {
      let fileName = this.fileNames[i];
      hilog.info(0, `fileNames file: ${fileName}`);
      let index = fileName.lastIndexOf('.');
      if (index < 0) {
        continue;
      } else {
        let fileExtension = fileName.substring(index);
        hilog.info(0, `fileNames file extension: ${fileExtension}`);
        let utd = utdDesc.getUniformDataTypeByFilenameExtension(fileExtension);
        try {
          if (utd != null) {
            let typeObj: utdDesc.TypeDescriptor = utdDesc.getTypeDescriptor(utd);
            let utdType: string = "";
            if (typeObj.belongsTo("general.image")) {
              utdType = "general.image"
              
            } else if (typeObj.belongsTo("general.audio")) {
              utdType = "general.audio"
            } else if (typeObj.belongsTo("general.video")) {
              utdType = "general.video"
            } else {
              continue;
            }
            hilog.info(0, `typeObj.belongsTo: ${fileName}, utdType: ${utdType}`);
            let fileInfo = new FileInfo(fileName, utdType, typeObj.iconFile);
            this.selectedFilesInfos.push(fileInfo);
          }
        }
        catch (e) {
          let error: BusinessError = e as BusinessError;
          hilog.error(0, `belongsTo throws an exception. code is ${error.code}, message is ${error.message} `);
        }
      }
    }
  }

  aboutToAppear() {
    CreatePrecastFile();
    this.UpdateSelectedFiles();
  }

  aboutToDisappear() {
    for (let i = this.selectedFilesInfos.length - 1; i >= 0; i--) {
      this.selectedFilesInfos.pop();
    }
  }

  build() {
    Column() {
      Column() {
        List({ space: 2, initialIndex: 0 }) {
          ForEach(this.selectedFilesInfos, (item: FileInfo, no: Number) => {
            ListItem() {
              Row() {
                Image(item.iconFile)
                  .id('imageBack')
                  .width(24)
                  .height(24)
                  .objectFit(ImageFit.Fill)
                  .alignSelf(ItemAlign.Auto)
                  .margin({ left: 12, right: 12 })
                Text(item.filename)
                  .fontSize(16)
                  .textAlign(TextAlign.Start)
                  .margin({ left: 12, right: 12 })
                  .fontWeight(500)
                  .id("textFilename_" + no)
                  .visibility(Visibility.Visible)
                Text(item.utdType)
                  .fontSize(16)
                  .textAlign(TextAlign.Start)
                  .margin({ left: 12, right: 12 })
                  .fontWeight(500)
                  .id("textFilename_" + no)
                  .visibility(Visibility.Visible)
              }
              .width('100%')
              .height(48)
              .alignItems(VerticalAlign.Center)
            }
            .id("listItem_" + no)
          })
        }
        .listDirection(Axis.Vertical)
        .scrollBar(BarState.Auto)
        .friction(0.6)
        .margin({ left: 12, right: 12 })
        .borderRadius(24)
        .edgeEffect(EdgeEffect.Spring)
        .backgroundColor(0xFFFFFF)
      }
      .width('100%')
      .height(680)
      .alignItems(HorizontalAlign.Start)
      .justifyContent(FlexAlign.Start)
    }
    .width('100%')
    .height('100%')
    .backgroundColor(#F1F3F5)
    .alignItems(HorizontalAlign.Start)
    .justifyContent(FlexAlign.Center)
  }
}

sample仓地址：

本功能的sample仓地址：https://gitee.com/openharmony/applications_app_samples/tree/master/code/BasicFeature/DataManagement/UDMF/UniformTypeDescriptor/UTDType