如何阻止旋转以仅允许 xamarin 表单中的纵向模式？

Question

我需要在 特定页面 上阻止旋转，这对 Android 和 iOS 都有效。

我尝试使用 NuGet Plugin.DeviceOrientation 并添加以下代码

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();
        }

但抛出异常： System.NullReferenceException: 'Object reference not set to an instance of an object.'

Answer 1

对于Xamarin.Forms，您可以依赖服务。

创建接口：

 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"));
    }
}
}

用法：

DependencyService.Get().ForcePortrait();

截图：

如何阻止旋转以仅允许 xamarin 表单中的纵向模式？

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

c#

xamarin.forms

device-orientation