Xamarin.Forms 中主从页面的母版页有多宽？

根据屏幕尺寸（和设备习惯？），母版页的宽度会有所不同：在手机上，它约为屏幕宽度的 80%，而在平板电脑上，它似乎是一个恒定尺寸，如 320 dp。

有人知道这个值的一般公式吗？我想用它在施工期间布置一些元素，当Width属性尚未设置。

Edit: I know 如何获取当前屏幕尺寸 http://xforms-kickstarter.com/#referring-to-the-screen-size。但是 Xamarin.Form 的主从页面所呈现的母版页的宽度与它有何关系？它不会覆盖整个屏幕，而是根据设备填充屏幕的不同部分。

您可以请求设备的实际屏幕宽度、高度和比例因子。

(From https://github.com/mattregul/Xamarin_GetDeviceScreensize https://github.com/mattregul/Xamarin_GetDeviceScreensize)

iOS AppDelegate.cs

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

            // Store off the device sizes, so we can access them within Xamarin Forms
            App.DisplayScreenWidth  = (double)UIScreen.MainScreen.Bounds.Width;
            App.DisplayScreenHeight = (double)UIScreen.MainScreen.Bounds.Height;
            App.DisplayScaleFactor  = (double)UIScreen.MainScreen.Scale;

            LoadApplication(new App());

            return base.FinishedLaunching(app, options);
        }
    }

Android MainActivity.cs

[Activity(Label = "Xamarin_GetDeviceScreensize.Droid", Icon = "@drawable/icon", Theme = "@style/MyTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle bundle)
        {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(bundle);

            // Store off the device sizes, so we can access them within Xamarin Forms
            App.DisplayScreenWidth  = (double)Resources.DisplayMetrics.WidthPixels  / (double)Resources.DisplayMetrics.Density; // Width = WidthPixels / Density
            App.DisplayScreenHeight = (double)Resources.DisplayMetrics.HeightPixels / (double)Resources.DisplayMetrics.Density; // Height = HeightPixels / Density
            App.DisplayScaleFactor  = (double)Resources.DisplayMetrics.Density;

            global::Xamarin.Forms.Forms.Init(this, bundle);

            LoadApplication(new App());
        }
    }

Xamarin 表单 App.cs

public class App : Application
    {
        public static double DisplayScreenWidth;
        public static double DisplayScreenHeight;
        public static double DisplayScaleFactor;

        public App()
        {

            string ScreenDetails =  Device.OS.ToString() + " Device Screen Size:\n" +
                                    $"Width: {DisplayScreenWidth}\n" +
                                    $"Height: {DisplayScreenHeight}\n" +
                                    $"Scale Factor: {DisplayScaleFactor}";

            // The root page of your application
            var content = new ContentPage
            {
                Title = "Xamarin_GetDeviceScreensize",
                Content = new StackLayout
                {
                    VerticalOptions = LayoutOptions.Center,
                    Children = {
                        new Label {
                            HorizontalTextAlignment = TextAlignment.Center,
                            FontSize = Device.GetNamedSize (NamedSize.Large, typeof(Label)),
                            Text = ScreenDetails
                        }
                    }
                }
            };

            MainPage = new NavigationPage(content);
        }

    }