request主要给应用提供上传下载文件、后台传输代理的基础能力。

场景一：上传下载进度回调。

方式一：使用request.agent.create下载文件开启进度回调，当前规格是约1s一次回调。

//进度回调的Callback
let progressCallback = (progress: request.agent.Progress) => {
  console.info('download task progress：'+progress.sizes+'/'+progress.processed);  };
request.agent.create(context, config1).then((task: request.agent.Task) => {
  console.log(task.tid)
  //开启进度回调监听
  task.on('progress', progressCallback);
  console.info(`Succeeded in creating a download task. result: ${task.tid}`);
  task.on('completed', createOnCallback);
  task.start((err: BusinessError) => {
    if (err) {
      console.error(`Failed to start the download task, Code: ${err.code}, message: ${err.message}`);
      return;
    }
    console.info(`Succeeded in starting a download task.`);
  });
  console.info(`Succeeded in creating a download task. result: ${task.tid}`);
}).catch((err: BusinessError) => {
  console.error(`Failed to create a download task, Code: ${err.code}, message: ${err.message}`);
});

方式二：使用request.downloadFile下载文件，传入context和DownloadConfig，开启进度回调。

request.downloadFile(context.getApplicationContext(), {
  url: 'xxxxx',
  filePath: filesDir + '/文件路径',
  enableMetered: true
}).then((downloadTask: request.DownloadTask) => {
  let progresCallback = (receivedSize: number, totalSize: number) => {
    console.info("download receivedSize:" + receivedSize + " totalSize:" + totalSize);
  };
  //开启进度回调
  downloadTask.on('progress', progresCallback);
})

场景二：暂停恢复下载。

要实现按钮点击暂停/恢复下载，需要先将Task传入，然后调用pause()暂停/resume()恢复下载任务。

request.agent.create(getContext(), config).then((task: request.agent.Task) => {
  // pause暂停任务
  task.pause((err: BusinessError) => {
    if (err) {
      console.error(`Failed to pause the download task, Code: ${err.code}, message:    ${err.message}`);
      return;
    }
    console.info(`Succeeded in pausing a download task. `);
  });
  console.info(`Succeeded in creating a download task. result: ${task.tid}`);
}).catch((err: BusinessError) => {
  console.error(`Failed to create a download task, Code: ${err.code}, message: ${err.message}`);
});

request.agent.create(getContext(), config).then((task: request.agent.Task) => {
  // resume恢复下载任务
  task.resume((err: BusinessError) => {
    if (err) {
      console.error(`Failed to resume the download task, Code: ${err.code}, message:   ${err.message}`);
      return;
    }
    console.info(`Succeeded in resuming a download task. `);
  });
  console.info(`Succeeded in creating a download task. result: ${task.tid}`);
}).catch((err: BusinessError) => {
  console.error(`Failed to create a download task, Code: ${err.code}, message: ${err.message}`);
});

场景三：后台上传下载，应用长时任务。

requestdownload接口默认是后台任务，支持应用长时任务。

request.agent需要配置为BACKGROUND模式，后台任务默认会有系统通知。

gauge：后台任务的过程进度通知策略，仅应用于后台任务，默认值为false。

• false：代表仅完成或失败的通知。
• true：发出每个进度，已完成或失败的通知。

上传任务配置：

let attachments: Array<request.agent.FormItem> = [{
  name: "createTest",
  value: {
    filename: "createTest.mp4",
    mimeType: "application/octet-stream",
    path: "./createTest.mp4",
  }
}];
let config: request.agent.Config = {
  //任务操作选项。UPLOAD表示上传任务。DOWNLOAD表示下载任务。
  action: request.agent.Action.UPLOAD,
  url: 'http://127.0.0.1',
  title: 'createTest',
  description: 'Sample code for create task',
  //下载的模式，FOREGROUND表示前台任务；BACKGROUND表示后台任务。
  mode: request.agent.Mode.BACKGROUND,
  //覆写配置true，覆盖已存在的文件。 false，下载失败。
  overwrite: false,
  method: "PUT",
  data: attachments,
  saveas: "./",
  network: request.agent.Network.CELLULAR,
  //是否允许在按流量计费的网络中工作，默认为false。
  metered: false,
  roaming: true,
  //是否为后台任务启用自动重试，仅应用于后台任务，默认为true。
  retry: true,
  //是否允许重定向，默认为true。
  redirect: true,
  index: 0,
  gauge: true,
  //如果设置为true，在上传/下载无法获取文件大小时任务失败。
  precise: false,
  token: "it is a secret"，
  //任务的优先级。任务模式相同的情况下，该配置项的数字越小优先级越高，默认值为0。
  priority:0
};
request.agent.create(getContext(), config, (err: BusinessError, task: request.agent.Task) => {
  if (err) {
    console.error(`Failed to create a download task, Code: ${err.code}, message: ${err.message}`);
    return;
  }
  console.info(`Succeeded in creating a download task. result: ${task.config}`);
});

下载任务配置：

let config1: request.agent.Config  =  {
  action: request.agent.Action.DOWNLOAD,
  url: "https://fe-static.xhscdn.com/mp/red/bc446184a0c84aa785ea3cada920f6ac.zip",
  overwrite: true,
  method: 'GET',
  //保存的地址，默认为cache目录下，如果需要保存在子目录下需要提前手动创建。
  saveas: './',
  mode: request.agent.Mode.BACKGROUND,
  gauge: true,
  priority:0
}
let createOnCallback2 = (progress: request.agent.Progress) => {
  console.info('download task pro.'+progress.sizes+'/'+progress.processed);
};
let createOnCallback = (progress: request.agent.Progress) => {
 
  console.info('downloadTask complete,filesDir:' );
 
};
let createOnCallback1 = (progress: request.agent.Progress) => {
  console.info('download task failed.'+progress);
};
request.agent.create(context, config1).then((task: request.agent.Task) => {
  console.log(task.tid)
  task.on('progress', createOnCallback2);
  task.on('failed', createOnCallback1);
  console.info(`Succeeded in creating a download task. result: ${task.tid}`);
  task.on('completed', createOnCallback);
  task.start((err: BusinessError) => {
    if (err) {
      console.error(`Failed to start the download task, Code: ${err.code}, message: ${err.message}`);
      return;
    }
    console.info(`Succeeded in starting a download task.`);
  });
  console.info(`Succeeded in creating a download task. result: ${task.tid}`);
}).catch((err: BusinessError) => {
  console.error(`Failed to create a download task, Code: ${err.code}, message: ${err.message}`);
});

场景四：断点续传。

断点续传的场景，如果是因网络等问题导致的任务失败，用户可以改为使用api10后台任务设置retry属性为true，这样内部会有自动暂停，网络恢复时自动重试，内部能续传时自动续传。on('pause') 回调会监听到它的暂停状态。

场景五：获取服务端返回的headers信息，用于后续处理。

订阅on('response')事件返回的headers中包含有header和body，可以通过解析返回的headers来进行后续处理。

let responseCallback = (response: request.agent.HttpResponse) => {
  console.info('download task response.'+JSON.stringify(response)+JSON.stringify(response.headers));
};
task.on('response',responseCallback)