[Bug] HttpClient crashes on Android

[gviddy]

Description

The app crashes on Android when I try to make an HttpClient call. It works fine on Windows.

Steps to Reproduce

1, private readonly HttpClient _httpClient = new HttpClient();
2. var response = await _httpClient.GetAsync("https://www.google.com.au");
3. The above line causes the app to crash with no exceptions/errors. Just a clean crash.
4. Nothing interesting can be seen in the logs.

Expected Behavior

Expect it to work like it does for Windows. The same code works fine on WinUI3.

Actual Behavior

Crashes on Android Emulator.

Basic Information

.NET MAUI Preview 4
maui-check (Everything is OK)

Please note I created the project from Visual Studio 2019 Preview. No other code/xml has been changed.

[GaryGormley]

I can also confirm this behaviour, but I can't get it to work on WinUI3 either though.
.Net MAUI Preview 4

[gviddy]

My hope is that preview 5 will support being able to use and access remote APIs. I saw that they demonstrated a weather app at Build 2021, however when I looked at the code I discovered it was all fake. They were not making http client calls either so for whatever reason it appears network functionality is yet to exist. Odd that after 4 previews this isn't something that can be done.

[GaryGormley]

So, good news and bad news.

Good news is that I successfully downloaded and installed .net maui preview 5, so maui-check reports all is well.
Updated VS 2019 to 16.11.0 preview 2

Bad news is that the same behaviour is observed when trying to make a call to a remote API using HttpClient(checked and it's from .net 6).

[steaward]

I get crashes all the time from HttpClient as well, but only in release mode:
My error message:

My current work around to hit my own APIs through http requests:

1. Add this android manifest file:
   <uses-permission android:name="android.permission.INTERNET"></uses-permission>

2. Use the deprecated System.Net.WebRequest and stream the response back from the server.

[titarenko-alexander]

Any updates here?

[scheidtdav]

Unfortunately the release of preview 10 does not seem to fix this.
Since the debug mode is working fine, my best guess is that there is something wrong with linking.

I found a corresponding issue in dotnet/runtime#60896 which suggests (dotnet/runtime#60896 (comment)) to instantiate your HttpClient like this as a workaround: new HttpClient(new Xamarin.Android.Net.AndroidMessageHandler()).

I can confirm that this works (make sure to have the INTERNET permission set in your manifest)!

This should be fixed by this commit, but I am not sure when it will be available.

[jsuarezruiz]

@jonathanpeppers Would dotnet/android@ff202f2 fix this issue?. Can include a related sample test in the .NET MAUI Gallery to validate it.

[jonathanpeppers]

Yes, that commit should fix this -- looks like the same issue.

@jsuarezruiz if you added a test that loads an image from a URL on the web -- and then validate it is displayed? Maybe it could just assert there wasn't an error coming through the log.

You'd also need to build the app in Release mode.

[wuyuansushen]

Unfortunately the release of preview 10 does not seem to fix this. Since the debug mode is working fine, my best guess is that there is something wrong with linking.

I found a corresponding issue in dotnet/runtime#60896 which suggests (dotnet/runtime#60896 (comment)) to instantiate your HttpClient like this as a workaround: new HttpClient(new Xamarin.Android.Net.AndroidMessageHandler()).

I can confirm that this works (make sure to have the INTERNET permission set in your manifest)!

This should be fixed by this commit, but I am not sure when it will be available.

@scheidtdav Could you illustrate how to import the reference to Xamarin.Android.Net.AndroidMessageHandler Class?
I try to use it directly but MAUI said Xamarin is not found...

[scheidtdav]

@wuyuansushen For me it was simply just a matter of calling the constructor of the message handler.
Since this is Android specific you will need to wrap it in a condition, like so:

public HttpClient CreateClient() 
{
#if __ANDROID__
  return new HttpClient(new Xamarin.Android.Net.AndroidMessageHandler());
#else
  return new HttpClient();
#endif
}

Hope that helps!