How can I block rotation to only allow portrait mode in xamarin forms?

Question

I need to block rotation on a specific page and this has to work both for Android and iOS.

I tried using NuGet Plugin.DeviceOrientation and adding the following code

protected override void OnAppearing()
        {
            base.OnAppearing();
            if (CrossDeviceOrientation.IsSupported) 
                CrossDeviceOrientation.Current.LockOrientation(Plugin.DeviceOrientation.Abstractions.DeviceOrientations.Portrait);
        }


protected override void OnDisappearing()
        {
            base.OnDisappearing();
            if (CrossDeviceOrientation.IsSupported) 
                CrossDeviceOrientation.Current.UnlockOrientation();
        }

but throws exception: System.NullReferenceException: 'Object reference not set to an instance of an object.'

Answer 1

For Xamarin.Forms, you could dependency service.

Create a interface:

 public interface IRotate
{
    void ForcePortrait();
}

Android:

[assembly: Xamarin.Forms.Dependency(typeof(RoateHandler))]
namespace RotatePage.Droid
{
class RoateHandler : IRotate
{
    public void ForcePortrait()
    {
        ((Activity)Forms.Context).RequestedOrientation = ScreenOrientation.Portrait;
    }
}
}

iOS:

[assembly: Xamarin.Forms.Dependency(typeof(RoateImplementation))]
namespace RotatePage.iOS
{
class RoateImplementation : IRotate
{
    public void ForcePortrait()
    {
        UIDevice.CurrentDevice.SetValueForKey(new NSNumber((int)UIInterfaceOrientation.Portrait), new NSString("orientation"));
    }
}
}

Usage:

DependencyService.Get().ForcePortrait();

Screenshot: