在 Android、Xamarin.forms 上的整个应用程序中保持沉浸式模式

Question

我想使用 Xamarin.forms 在 Android 上的应用程序中保持沉浸式模式。我读过一些博客和帖子。这个有效，但只有当我按下输入文本框或滚动屏幕时才有效。我想避免这种情况。这个问题争论了我的担忧，但我不明白解决方案。也许它已经过时了。我的 Android 设备是7.1，这是我的.Android MainActivity, ,上的代码void OnCreate：void OnCreate

public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity{
    protected override void OnCreate(Bundle savedInstanceState){
        Xamarin.Essentials.Platform.Init(this, savedInstanceState);
        global::Xamarin.Forms.Forms.Init(this, savedInstanceState);

        TabLayoutResource = Resource.Layout.Tabbar;
        ToolbarResource = Resource.Layout.Toolbar;
        base.OnCreate(savedInstanceState);
        LoadApplication(new App());

        ImmersiveMode();
    }

    public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults){
        Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

        base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
    }

    public void ImmersiveMode() {
        int uiOptions = (int)(Forms.Context as Activity).Window.DecorView.SystemUiVisibility;
        uiOptions |= (int)SystemUiFlags.Fullscreen;
        uiOptions |= (int)SystemUiFlags.HideNavigation;
        uiOptions |= (int)SystemUiFlags.ImmersiveSticky;
        (Forms.Context as Activity).Window.DecorView.SystemUiVisibility = (StatusBarVisibility)uiOptions;
    }
}

我该如何解决这个问题？您能具体说明我应该在哪里放置新代码吗？我是 Xamarin.Forms 新手，这对我来说看起来很棘手。谢谢

编辑：这段代码：

this.Window.AddFlags(WindowManagerFlags.Fullscreen);上面.Android MainActivity隐藏了 Android 栏，其中包含 wifi 信号、时间、蓝牙等。

有没有类似的一行来隐藏这个 Android 按钮？

Answer 1

Window.DecorView.SystemUiVisibility自 起已弃用Android R (11)。在此 API 版本中提供了一种新方法来执行此操作。

下面是我在我的一个应用程序中使用的代码。我必须重写 MainActivity 类中的一堆方法。

using System;

using Android.App;
using Android.Content.PM;
using Android.Runtime;
using Android.OS;
using Android.Views;

namespace SampleApp.Droid
{
    [Activity(Label = "SampleApp", Icon = "@mipmap/icon", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation | ConfigChanges.UiMode | ConfigChanges.ScreenLayout | ConfigChanges.SmallestScreenSize )]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);

            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
            LoadApplication(new App());
            SetFullscreenFlags();
        }

        protected override void OnResume()
        {
            base.OnResume();
            SetFullscreenFlags();
        }

        public override void OnWindowFocusChanged(bool hasFocus)
        {
            base.OnWindowFocusChanged(hasFocus);
            SetFullscreenFlags();
        }

        protected void SetFullscreenFlags()
        {
            var attrs = Window.Attributes;
            attrs.Flags |= WindowManagerFlags.Fullscreen;
            Window.Attributes = attrs;

            // BuildVersionCodes has a wrong value for Android R (1000 instead of 30)
            // https://github.com/xamarin/xamarin-android/issues/5723
            // if (Build.VERSION.SdkInt >= BuildVersionCodes.R)
            if ((int)Build.VERSION.SdkInt >= 30)
            {
                Window.SetDecorFitsSystemWindows(false);

                if (Window.InsetsController != null)
                {
                    Window.InsetsController.Hide(WindowInsets.Type.NavigationBars());
                    Window.InsetsController.Hide(WindowInsets.Type.StatusBars());
                    Window.InsetsController.Hide(WindowInsets.Type.SystemBars());
                    Window.InsetsController.Show(WindowInsets.Type.Ime());
                }
            }
            else
            {
                var uiOptions = (int)Window.DecorView.SystemUiVisibility;
                var newUiOptions = (int)uiOptions;

                newUiOptions |=
                    (int)SystemUiFlags.LayoutStable |
                    (int)SystemUiFlags.LayoutHideNavigation |
                    (int)SystemUiFlags.LayoutFullscreen |
                    (int)SystemUiFlags.HideNavigation |
                    (int)SystemUiFlags.Fullscreen |
                    (int)SystemUiFlags.ImmersiveSticky;

                Window.DecorView.SystemUiVisibility = (StatusBarVisibility)newUiOptions;
            }
        }

        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }

    }
}

之前我也实现过这个View.IOnSystemUiVisibilityChangeListener接口。但它也已被弃用，并将在未来的版本中删除：

public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity, View.IOnSystemUiVisibilityChangeListener
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        // omitted code

        Window.DecorView.SetOnSystemUiVisibilityChangeListener(this);
    }

    public void OnSystemUiVisibilityChange([GeneratedEnum] StatusBarVisibility visibility)
    {
        SetFullscreenFlags();
    }
}

编辑：

如果您想在用户将某些输入控件集中在屏幕上后保持沉浸式模式，您可以实现ViewTreeObserver.IOnGlobalFocusChangeListener界面。我是这样做的：

public class MainActivity : 
    global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity, 
    ViewTreeObserver.IOnGlobalFocusChangeListener
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        // ommited code
    }

    public override void SetContentView(View view)
    {
        base.SetContentView(view);

        if (view?.ViewTreeObserver != null)
            view.ViewTreeObserver.AddOnGlobalFocusChangeListener(this);
    }

    public override void SetContentView(View view, ViewGroup.LayoutParams @params)
    {
        base.SetContentView(view, @params);

        if (view?.ViewTreeObserver != null)
            view.ViewTreeObserver.AddOnGlobalFocusChangeListener(this);
    }

    public void OnGlobalFocusChanged(View oldFocus, View newFocus)
    {
        SetFullscreenFlags();
    }
}