Xamarin Forms Await/Async Task on Main Thread - xamarin.forms

Question

I am downloading images from my app to phone gallery for both iOS and android successfully. Below is my code:
public void DownloadImages_Clicked(System.Object sender, System.EventArgs e)
{
CarDetailLoader.IsVisible = true;
CarDetailLoader.IsRunning = true;
foreach (var imgurl in car.CarImages)
{
var webClient = new WebClient();
byte[] imageBytes = webClient.DownloadData(imgurl);
DependencyService.Get<IMediaServices>().SaveImageFromByte(imageBytes, "DINImage");
}
CarDetailLoader.IsVisible = false;
CarDetailLoader.IsRunning = false;
}
However, the ActivityLoader doesn't work when this method runs, even though it takes a few seconds. I tried using some:
Task.Run(() => )
methods that I read online, however,
"SaveImageFromByte()" method can only run on the main thread.
So how do I approach this issue?

Answer 1

You can use Task.Run() to await the Task and use Device.BeginInvokeOnMainThread to run method in Main thread, here is an example:
public async void DownloadImages_Clicked()
{
Device.BeginInvokeOnMainThread(() => {
CarDetailLoader.IsVisible = true;
CarDetailLoader.IsRunning = true;
});
await Task.Run(async () =>
{
for (int i = 0; i< 3;i++)
{
//var webClient = new WebClient();
//byte[] imageBytes = webClient.DownloadData((string)imgurl);
Console.WriteLine("before delay");
await Task.Delay(3000);
Console.WriteLine("after delay");
Device.BeginInvokeOnMainThread(() =>
{
//DependencyService.Get<IMediaServices>().SaveImageFromByte(imageBytes, "DINImage");
Console.WriteLine("BeginInvokeOnMainThread");
});
}
});
Device.BeginInvokeOnMainThread(() => {
CarDetailLoader.IsVisible = false;
CarDetailLoader.IsRunning = false;
});
}