tencent cloud

    // The advanced download API supports checkpoint restart. Therefore, a HEAD request will be sent before the download to obtain the file information.
    // If you are using a temporary key or accessing with a sub-account, ensure that your permission list includes HeadObject.

    // `TransferManager` supports checkpoint restart for download. You only need to ensure the consistency of parameters `bucket`, `cosPath`, and `savePath`.
    // Then the SDK will resume the download from where interrupted.

    // Get the `TransferManager`
    CosTransferManger transferManager = Cos().getDefaultTransferManger();
    //CosTransferManger transferManager = Cos().getTransferManger("newRegion");
    // Bucket name in the format of `BucketName-APPID` (`APPID` is required), which can be viewed in the COS console at https://console.tencentcloud.com/cos5/bucket.
    String bucket = "examplebucket-1250000000";
    String cosPath = "exampleobject"; // Location identifier of the object in the bucket, i.e., the object key
    String downliadPath = "Absolute path of the local file"; // Absolute path of the local file

    // Callback for successful download
    successCallBack(result) {
      // TODO: Logic after successful download
    }
    // Callback for failed download
    failCallBack(clientException, serviceException) {
      // TODO: Logic after failed download
      if (clientException != null) {
        print(clientException);
      }
      if (serviceException != null) {
        print(serviceException);
      }
    }
    // Callback for the download status, through which you can check the task process
    stateCallback(state) {
      // todo notify transfer state
    }
    // Callback for the download progress
    progressCallBack(complete, target) {
      // todo Do something to download progress...
    }
    // Start the download
    TransferTask transferTask = await transferManager.download(bucket, cosPath, downliadPath, 
        resultListener: ResultListener(successCallBack, failCallBack),
        stateCallback: stateCallback,
        progressCallBack: progressCallBack
    );
    // Pause the task
    transferTask.pause();
    // Resume the task
    transferTask.resume();
    // Cancel the task
    transferTask.cancel();