I'm using QR Code Scanner in Xamarin App, when it scans the qr code, there are some operation it does which takes about a minute, while it's performing operation, I want to show a loading dialog on the screen. But, it isn't showing on the screen, and elsewhere in the app, it's working perfectly.
Code
var expectedFormat = ZXing.BarcodeFormat.QR_CODE;
var opts = new ZXing.Mobile.MobileBarcodeScanningOptions { PossibleFormats = new List<ZXing.BarcodeFormat> { expectedFormat } };
var scanner = new ZXing.Mobile.MobileBarcodeScanner();
var result = await scanner.Scan(opts);
if (result == null)
{
// code
return null;
}
else
{
using (UserDialogs.Instance.Loading("Processing"))
{
// code
}
}
UPDATE CODE SAMPLE
public async Task Verification(object sender, EventArgs e)
{
try
{
var expectedFormat = ZXing.BarcodeFormat.QR_CODE;
var opts = new ZXing.Mobile.MobileBarcodeScanningOptions { PossibleFormats = new List<ZXing.BarcodeFormat> { expectedFormat } };
var scanner = new ZXing.Mobile.MobileBarcodeScanner();
var result = await scanner.Scan(opts);
if (result == null)
{
// Code
return null;
}
else
{
try
{
// QR Scan Result
string qr_scan = result.Response;
var result = JsonConvert.DeserializeObject<QRScan>(qr_scan);
await CreateConnection();
}
catch (Exception error)
{ }
finally
{
// navigate to next page
await NavigationService.NavigateToAsync<NextViewModel>();
}
}
}
catch (Exception error)
{ }
return null;
}
public async Task CreateConnection()
{
UserDialogs.Instance.Loading("Processing");
if ()
{
try
{
// Code
}
catch (Exception error)
{
// Code
}
finally
{
await CreateFolder(default, default);
}
}
}
public async Task CreateFolder(object sender, EventArgs e)
{
UserDialogs.Instance.Loading("Processing");
try
{
// Code
}
catch (Exception error)
{
// Code
}
return null;
}
Try something like this
Device.BeginInvokeOnMainThread(async () =>
{
try
{
using (UserDialogs.Instance.Loading(("Processing")))
{
await Task.Delay(300);
//Your Service code
}
}
catch (Exception ex)
{
var val = ex.Message;
UserDialogs.Instance.Alert("Test", val.ToString(), "Ok");
}
});
You can use Xamarin.Essentials' MainThread class and more specifically - the InvokeOnMainThreadAsync method. The idea of this method is to not only execute a code on the UI/main thread, but to also to await it's code. This way you can have both async/await logic and main thread execution.
try
{
// QR Scan Result
string qr_scan = result.Response;
var result = JsonConvert.DeserializeObject<QRScan>(qr_scan);
await MainThread.InvokeOnMainThreadAsync(() => CreateConnection());
}
catch (Exception error)
{ }
finally
{
// navigate to next page
await NavigationService.NavigateToAsync<NextViewModel>();
}
Keep in mind that if the method CreateConnection takes a long time to execute, then it would be better to execute on the main thread only the dialog presentation (UserDialogs.Instance.Loading("")).