Xamarin Forms 在 iOS 上强制页面特定方向

Question

我的 XF 应用程序中有几个页面需要纵向或横向，具体取决于它显示的内容。在 Android 上，这没有问题，在 iOS 16 发布之前，在 iOS 上也从来没有问题。

iOS 16 显然删除了使用 UIDevice UIInterfaceOrientation 方法的能力，该方法位于我的 AppDelegate 中，如下所示。

MessagingCenter.Subscribe<MainPage>(this, "SetLandscapeModeOff", sender =>
            {
                UIDevice.CurrentDevice.SetValueForKey(new NSNumber((int)UIInterfaceOrientation.Portrait), new NSString("orientation"));
            });

这工作得很好，我可以简单地在我试图以特定方向加载的页面上的 OnAppearing 方法中调用下面的代码。

MessagingCenter.Send(this, "SetLandscapeModeOff");

我在这里看到 1 或 2 篇帖子谈论新方法（还有很多关于 iOS 16 之前的方法）但它们都不够完整，不足以让我的技能水平的人理解如何实现它们。除了上面发布的内容外，我没有任何起点。

编辑

我根据回复尝试了以下解决方案。

界面：

using System;
using System.Collections.Generic;
using System.Text;

namespace MyApp
{
    public interface InterfaceOrientationService
    {
        void SetLandscape();
        void SetPortrait();
    }
}

AppDelegate.cs

[assembly: Xamarin.Forms.Dependency(typeof(MyApp.iOS.InterfaceOrientationServiceiOS))]

namespace MyApp.iOS
{
    public class InterfaceOrientationServiceiOS : InterfaceOrientationService
    {
        public InterfaceOrientationServiceiOS() { }

        public void SetLandscape()
        {
            if (UIDevice.CurrentDevice.CheckSystemVersion(16, 0))
            {
                var windowScene = (UIApplication.SharedApplication.ConnectedScenes.ToArray()[0] as UIWindowScene);

                if (windowScene != null)
                {
                    var nav = UIApplication.SharedApplication.KeyWindow?.RootViewController;
                    if (nav != null)
                    {
                        nav.SetNeedsUpdateOfSupportedInterfaceOrientations();
                        windowScene.RequestGeometryUpdate(
                            new UIWindowSceneGeometryPreferencesIOS(UIInterfaceOrientationMask.Portrait),
                            error => { }
                        );
                    }
                }
            }
            else
            {
                UIDevice.CurrentDevice.SetValueForKey(new NSNumber((int)UIInterfaceOrientation.Portrait), new NSString("orientation"));
            }
        }
        public void SetPortrait()
        {

            if (UIDevice.CurrentDevice.CheckSystemVersion(16, 0))
            {
                var windowScene = (UIApplication.SharedApplication.ConnectedScenes.ToArray()[0] as UIWindowScene);
                if (windowScene != null)
                {
                    var nav = UIApplication.SharedApplication.KeyWindow?.RootViewController;
                    if (nav != null)
                    {
                        nav.SetNeedsUpdateOfSupportedInterfaceOrientations();
                        windowScene.RequestGeometryUpdate(
                            new UIWindowSceneGeometryPreferencesIOS(UIInterfaceOrientationMask.Portrait),
                            error => { }
                        );
                    }
                }
            }
            else
            {
                UIDevice.CurrentDevice.SetValueForKey(new NSNumber((int)UIInterfaceOrientation.Portrait), new NSString("orientation"));
            }
        }
    }

    [Register("AppDelegate")]
    public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
    {
        public override bool FinishedLaunching(UIApplication app, NSDictionary options)
        {
            LoadApplication(new App());
            return base.FinishedLaunching(app, options);
        }
    }
}

我在需要横向的页面上的 OnAppearing 方法：

protected override void OnAppearing()
        {
            base.OnAppearing();
            DependencyService.Get <InterfaceOrientationService>().SetLandscape();
        }

Answer 1

iOS16改变了换页的方式，可以使用DependencyService来实现，参考如下代码：

在 Forms 中创建一个界面：

public interface InterfaceOrientationService    {        
void SetLandscape();        
void SetPortrait();    
}

iOS 项目：

using Foundation;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using UIKit;
using Xamarin.Forms;
using XamarinFormsOne;
using XamarinFormsOne.iOS;

[assembly: Xamarin.Forms.Dependency(typeof(InterfaceOrientationServiceiOS))]   
namespace XamarinFormsOne.iOS    
{
    public class InterfaceOrientationServiceiOS: InterfaceOrientationService 
    {
        public InterfaceOrientationServiceiOS() { }

        public void SetLandscape() {
            if (UIDevice.CurrentDevice.CheckSystemVersion(16, 0))    
            {    
                var windowScene = (UIApplication.SharedApplication.ConnectedScenes.ToArray()[0] as UIWindowScene);

                if (windowScene != null)    
                {    
                    var nav = UIApplication.SharedApplication.KeyWindow?.RootViewController;   
                    if (nav != null)  
                    {
                   nav.SetNeedsUpdateOfSupportedInterfaceOrientations();   
                        windowScene.RequestGeometryUpdate( 
                            new UIWindowSceneGeometryPreferencesIOS(UIInterfaceOrientationMask.Portrait),
                            error => { }    
                        );
                    }
               }
            }
            else
            {
                UIDevice.CurrentDevice.SetValueForKey(new NSNumber((int)UIInterfaceOrientation.Portrait), new NSString("orientation"));
            }
        }
            public void SetPortrait() {
    
                if (UIDevice.CurrentDevice.CheckSystemVersion(16, 0))
                {
                    var windowScene = (UIApplication.SharedApplication.ConnectedScenes.ToArray()[0] as UIWindowScene);
                    if (windowScene != null)
                    {
                        var nav = UIApplication.SharedApplication.KeyWindow?.RootViewController;
                        if (nav != null)
                        {
                       nav.SetNeedsUpdateOfSupportedInterfaceOrientations();
                            windowScene.RequestGeometryUpdate(
                                new UIWindowSceneGeometryPreferencesIOS(UIInterfaceOrientationMask.Portrait),
                                error => { }
                            );
                        }
                    }
                }
                else
                {
                    UIDevice.CurrentDevice.SetValueForKey(new NSNumber((int)UIInterfaceOrientation.Portrait), new NSString("orientation"));
                }
            }
        }
    }

在 Xamarin.Forms 中调用接口：

protected override void OnAppearing()        
{            
base.OnAppearing();            
//SetLandscape            
DependencyService.Get<InterfaceOrientationService().SetLandscape();            
//SetPortrait            
DependencyService.Get<InterfaceOrientationService>().SetPortrait();        
}

更新: 在 AppDelegate 中

public override UIInterfaceOrientationMask GetSupportedInterfaceOrientations(UIApplication application, [Transient] UIWindow forWindow)        
{            
   var mainPage = Xamarin.Forms.Application.Current.MainPage;            
   if (mainPage.Navigation.NavigationStack.Last() is PageOne)            
{            
 return UIInterfaceOrientationMask.Landscape;            
}            
return UIInterfaceOrientationMask.Portrait;       
}