About Xamarin Camera permission - xamarin.android

Question

I'm making Android app with Xamarin, This use zxing.
When user click a button, It show QrScan page and dialog for asking allow camera permission.
I want to show dialog asking permission by user allow permission every time clicked button.
Now, If user click deny, permission dialog ever don't shown, before restart application.
Have you any idea?
This is my source.
Android --- MainActivity.cs
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
global::Xamarin.Forms.Forms.Init(this, bundle);
ZXing.Net.Mobile.Forms.Android.Platform.Init();
LoadApplication(new App { OSVersion = "Android Version " + "2.0" });
}
public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Permission[] grantResults)
{
// If this is not be, occur unexpected exception when user click deny
if(grantResults[0] == Permission.Denied)
{
return;
}
global::ZXing.Net.Mobile.Android.PermissionsHandler.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}
}
And this is my Executing QrScan Method In PCL project which called clicked button.
public async void ImgQrScan_Clicked(object sender, EventArgs e)
{
this.TappedEvent?.Invoke(sender, e);
CustomScanViewMaker();
await Navigation.PushModalAsync(oCustomQrScanPage);
zxingPage.IsScanning = true;
string sScanResult = "";
zxingPage.OnScanResult += (result) =>
{
sScanResult = result.Text;
zxingPage.IsScanning = false;
Device.BeginInvokeOnMainThread(async () =>
{
this.OnClicked?.Invoke(sender, new QrScannerClickEventArgs(sScanResult));
await Navigation.PopModalAsync();
});
};
this.OnClicked?.Invoke(sender, new QrScannerClickEventArgs(sScanResult));
}
Thank you.

Answer 1

I want to show dialog asking permission by user allow permission every time clicked button.
You could try using shouldShowRequestPermissionRationale method to implement this feature, as the document said :
To help find situations where the user might need an explanation, Android provides a utiltity method, shouldShowRequestPermissionRationale(). This method returns true if the app has requested this permission previously and the user denied the request.
For its usage, you could refer to the official document Requesting Permissions at Run Time, in C#, it's something like this :
// Here, this is the current activity
if (ContextCompat.CheckSelfPermission(this, Manifest.Permission.Camera) != Permission.Granted)
{
// Should we show an explanation?
if (ActivityCompat.ShouldShowRequestPermissionRationale(this, Manifest.Permission.Camera))
{
// Provide an additional rationale to the user if the permission was not granted
// and the user would benefit from additional context for the use of the permission.
// For example if the user has previously denied the permission.
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
Log.Info(TAG, "Displaying camera permission rationale to provide additional context.");
}
else
{
// No explanation needed, we can request the permission.
ActivityCompat.RequestPermissions(this, new string[] { Manifest.Permission.Camera }, REQUEST_CAMERA);
// REQUEST_CAMERA is an app-defined int constant. The callback method gets the
// result of the request.
}
}
else
{
System.Diagnostics.Debug.WriteLine("Permission Granted!!!");
}