Feature Request: Download Files

[jrahma]

Hi,

Please add a feature to download files in Xamarin Forms platform, for example, photoz, documents, etc..

Thanks,
Jassim

[gsmental]

File download with downloaded percentage so that developer can easily display in progress bar.

[mattleibow]

This can already be done with WebClient which is available in .NET Standard 2.0: https://docs.microsoft.com/en-us/dotnet/api/system.net.webclient?view=netstandard-2.0

And then if you really want to go hardcore, you can have a look at the source for this baby: https://github.com/dotnet/corefx/blob/master/src/System.Net.WebClient/src/System/Net/WebClient.cs

[Redth]

Yeah I'm not sure what value we can add to HttpClient or WebClient.

If you think there's something missing, please elaborate.

[Redth]

One thing that has come to my attention is that we might want to enable background downloading of files such as with NSUrlSession on iOS, and perhaps just generic background tasks on Android/UWP.

This might be interesting. Need to research more details on how NSUrlSession works and how that influences what the xplat API will look like.

[gsmental]

property and methods
FileUrl --string or URI
IsUrlExistsOnServer --bool
ClientAppFilePath --string
DeleteIfAlreadyExists --bool

and event which will fire during downloading of file and provide information as below
TotalSizeInBytes --double
DownloadedSizeInBytes --double
Percentage -- decimal (it is option otherwise we have to calculate manually)

[mattleibow]

For Android: https://developer.android.com/reference/android/app/DownloadManager
For UWP: https://docs.microsoft.com/en-us/uwp/api/Windows.Networking.BackgroundTransfer.BackgroundDownloader / https://docs.microsoft.com/en-us/windows/uwp/networking/background-transfers

[Redth]

As we've discussed in another issue around background tasks, we can't really work with events for this situation, since we aren't really guaranteed to have that context kept around for us. Android for instance simply sends a broadcast when the file is done downloading, and we must handle that with a broadcast receiver which may be called after our application has been terminated and restarted (even something as simple as a reboot).

I think this one is going to depend on us working out the pattern for #409 first

[DanielCauser]

@jrahma I'm using this lib for exactly what you want.
https://github.com/aritchie/httptransfertasks

[Redth]

I think we can come up with an event that can be subscribed to while the app is in the foreground, but of course it is possible the event will stop firing once the app enters the background.

[newky2k]

As there is a library that provides this functionality already we are going to close this off.