如何在 Xamarin.Forms 中设置 ContentPage 方向

Question

我正在使用 Xamarin.Forms 创建一个跨平台应用程序，我所有的 ContentPages 都位于 PCL 内。

我正在寻找一种方法来设置和锁定单个ContentPage 的orientation 到Landscape，最好不必在每个平台特定项目中创建另一个活动。

由于我的ContentPage.Content 设置为ScrollView，我尝试将ScrollOrientation 设置为Horizontal，但这不起作用。

我也尝试过使用RelativeLayout，但我在这上面看不到Orientation 属性。

public class PlanningBoardView : ContentPage //Container Class.
    {
        public PlanningBoardView()
        {
            scroller = new ScrollView ();

            Board = new PlanningBoard();

            scroller.Orientation = ScrollOrientation.Horizontal;
            scroller.WidthRequest = Board.BoardWidth;
            scroller.Content = Board;

            Content = scroller;
        }
    }

我尝试的最后一件事是使用 Xamarin Studio 的 Intellisense 版本和 Xamarin Forms API Doc's 查看可供我使用的不同布局，其中没有一个具有 Orientation 属性。

我担心这样做的唯一方法是为这个ContentPage 创建第二个特定于平台的Activity 并将方向设置为横向。

虽然这种方法可行，但它使屏幕之间的导航更加复杂。

目前正在 Android 中进行测试。

Answer 1

不想这么说，但这只能使用custom renderers 或特定于平台的代码来完成

在android中，可以将MainActivity的RequestedOrientation属性设置为ScreenOrientation.Landscape。

在 iOS 中，当 Xamarin.Forms.Application.Current.MainPage 是您感兴趣的 ContentPage 时，您可以覆盖 AppDelegate 类中的 GetSupportedInterfaceOrientations 以返回 UIInterfaceOrientationMask 值之一。

安卓

[assembly: Xamarin.Forms.ExportRenderer(typeof(MyCustomContentPage), typeof(CustomContentPageRenderer))]

public class CustomContentPageRenderer : Xamarin.Forms.Platform.Android.PageRenderer
{
    private ScreenOrientation _previousOrientation = ScreenOrientation.Unspecified;

    protected override void OnWindowVisibilityChanged(ViewStates visibility)
    {
        base.OnWindowVisibilityChanged(visibility);

        var activity = (Activity)Context;

        if (visibility == ViewStates.Gone)
        {
            // Revert to previous orientation
            activity.RequestedOrientation = _previousOrientation == ScreenOrientation.Unspecified ? ScreenOrientation.Portrait : _previousOrientation;
        }
        else if (visibility == ViewStates.Visible)
        {
            if (_previousOrientation == ScreenOrientation.Unspecified)
            {
                _previousOrientation = activity.RequestedOrientation;
            }

            activity.RequestedOrientation = ScreenOrientation.Landscape;
        }
    }
}

iOS

public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
{
    public override UIInterfaceOrientationMask GetSupportedInterfaceOrientations(UIApplication application, UIWindow forWindow)
    {
        if (Xamarin.Forms.Application.Current == null || Xamarin.Forms.Application.Current.MainPage == null)
        {
            return UIInterfaceOrientationMask.Portrait;
        }

        var mainPage = Xamarin.Forms.Application.Current.MainPage;

        if (mainPage is MyCustomContentPage ||
           (mainPage is NavigationPage && ((NavigationPage)mainPage).CurrentPage is MyCustomContentPage) ||
           (mainPage.Navigation != null && mainPage.Navigation.ModalStack.LastOrDefault() is MyCustomContentPage))
        {
            return UIInterfaceOrientationMask.Landscape;
        }

        return UIInterfaceOrientationMask.Portrait;
    }
}

Answer 2

这也可以通过使用 MessagingCenter 类将消息从表单项目发送到宿主项目来完成。不使用自定义渲染器或依赖服务如下，

public partial class ThirdPage : ContentPage
  {
      protected override void OnAppearing()
      { 
          base.OnAppearing(); 
         MessagingCenter.Send(this, "allowLandScapePortrait");
      }
       //during page close setting back to portrait
      protected override void OnDisappearing()
      {
          base.OnDisappearing(); 
          MessagingCenter.Send(this, "preventLandScape");
      }
  }

更改 mainactivity 以接收消息并设置 RequestedOrientation

[Activity(Label = "Main", ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation,ScreenOrientation = ScreenOrientation.Portrait)]
 public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsApplicationActivity
  {        
  //allowing the device to change the screen orientation based on the rotation
  MessagingCenter.Subscribe<ThirdPage>(this, "allowLandScapePortrait", sender =>
  { 
   RequestedOrientation = ScreenOrientation.Unspecified;
  });
 //during page close setting back to portrait
 MessagingCenter.Subscribe<ThirdPage>(this, "preventLandScape", sender =>
  { 
   RequestedOrientation = ScreenOrientation.Portrait;
  });
 }

在我的博文中查看更多信息：http://www.appliedcodelog.com/2017/05/force-landscape-or-portrait-for-single.html

Answer 3

如果您在 Android 上也遇到问题，设备轮换返回提示用户电子邮件，您可以在此处跟进 ADAL 和 MSAL 的修复进度：

https://github.com/AzureAD/azure-activedirectory-library-for-dotnet/issues/1622https://github.com/xamarin/xamarin-android/issues/3326

Answer 4

Dealdiane 的代码对我来说效果很好，只需稍作改动：

protected override void OnWindowVisibilityChanged(ViewStates visibility) {
    base.OnWindowVisibilityChanged( visibility );

    IRotationLock page = Element as IRotationLock;
    if ( page == null )
        return;

    var activity = (Activity) Context;

    if ( visibility == ViewStates.Gone ) {
        // Revert to previous orientation
        activity.RequestedOrientation = _previousOrientation;
    } else if ( visibility == ViewStates.Visible ) {
        if ( _previousOrientation == ScreenOrientation.Unspecified ) {
            _previousOrientation = activity.RequestedOrientation;
        }

        switch ( page.AllowRotation() ) {
            case RotationLock.Landscape:
                activity.RequestedOrientation = ScreenOrientation.SensorLandscape;
                break;
            case RotationLock.Portrait:
                activity.RequestedOrientation = ScreenOrientation.SensorPortrait;
                break;
        }
    }
}