Xamarin Android 上出现重复的启动画面

Question

我使用 MS 的这篇文章创建了一个启动屏幕：

https://learn.microsoft.com/en-us/xamarin/android/user-interface/splash-screen

问题是，当应用程序启动时：

1. 它以红色背景开始
2. 然后加载 SplashScreen 图像
3. 然后加载MainActivity

如何摆脱第一步？我想直接显示启动画面。

在 MainActivity 中，我设置 MainLauncher = false 和 Theme = "@style/MainTheme"：

[Activity(Label = "S", Icon = "@mipmap/icon", Theme = "@style/MainTheme", MainLauncher = false, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]

splash_screen.xml：

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" android:opacity="opaque">
  <item>
    <color android:color="@color/splash_background"/>
  </item>
  <item>
    <bitmap
        android:src="@drawable/splash_logo"
        android:tileMode="disabled" 
        /><!--deleted android:gravity="center" to get a fullscreen image-->
  </item>
</layer-list>

style.xml：

<?xml version="1.0" encoding="utf-8" ?>
<resources>
  <!-- Base theme applied no matter what API -->
  <style name="MainTheme.Base" parent="Theme.AppCompat.Light.DarkActionBar">
    <!--If you are using revision 22.1 please use just windowNoTitle. Without android:-->
    <item name="windowNoTitle">true</item>
    <!--We will be using the toolbar so no need to show ActionBar-->
    <item name="windowActionBar">false</item>
    <!-- Set theme colors from http://www.google.com/design/spec/style/color.html#color-color-palette -->
    <!-- colorPrimary is used for the default action bar background -->
    <item name="colorPrimary">#2196F3</item>
    <!-- colorPrimaryDark is used for the status bar -->
    <item name="colorPrimaryDark">#1976D2</item>
    <!-- colorAccent is used as the default value for colorControlActivated
         which is used to tint widgets -->
    <item name="colorAccent">#FF4081</item>
    <!-- You can also set colorControlNormal, colorControlActivated
         colorControlHighlight and colorSwitchThumbNormal. -->
    <item name="windowActionModeOverlay">true</item>

    <item name="android:datePickerDialogTheme">@style/AppCompatDialogStyle</item>
  </style>

  <style name="MainTheme.Splash" parent ="Theme.AppCompat.Light.NoActionBar">
    <item name="android:windowBackground">@drawable/splash_screen</item>
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowFullscreen">true</item>
    <item name="android:windowContentOverlay">@null</item>
    <item name="android:windowActionBar">true</item>
  </style>
  <style name="MainTheme" parent="MainTheme.Base">
  </style>
  <style name="AppCompatDialogStyle" parent="Theme.AppCompat.Light.Dialog">
    <item name="colorAccent">#FF4081</item>
  </style>
</resources>

SplashActivity.cs：

    [Activity(Theme = "@style/MainTheme.Splash", MainLauncher = true, NoHistory = true, ScreenOrientation = ScreenOrientation.Portrait) ]
    public class SplashActivity : AppCompatActivity
    {
        static readonly string TAG = "X:" + typeof(SplashActivity).Name;

        public override void OnCreate(Bundle savedInstanceState, PersistableBundle persistentState)
        {
            
            base.OnCreate(savedInstanceState, persistentState);
            
        }

        // Launches the startup task
        protected override void OnResume()
        {
            base.OnResume();

            Task startupWork = new Task(() => { SimulateStartup(); });
            startupWork.Start();
            SimulateStartup();
        }

        // Simulates background work that happens behind the splash screen
       async void SimulateStartup()
        {
            //Log.Debug(TAG, "Performing some startup work that takes a bit of time.");
            await Task.Delay(5000); // Simulate a bit of startup work.

            //Log.Debug(TAG, "Startup work is finished - starting MainActivity.");
            StartActivity(new Intent(Application.Context, typeof(MainActivity)));
        }

        public override void OnBackPressed() { }
    }
}

Answer 1

在 Android 12 中更改了启动屏幕要求。推荐的方式已经改变。以下是在现代 Xamarin.Android 应用程序中执行此操作的方法：

1. 添加对

   Xamarin.AndroidX.Core.SplashScreen

的 NuGet 引用
2. 在活动 OnCreate 中使用新的 Splash Screen API 安装启动屏幕。
3. 创建保持屏幕状态以确定启动画面何时消失。
4. 在

   [Activity]

   或 AndroidManifest.xml 中更新您的主题。

MainActivity.cs：

protected override void OnCreate(Bundle bundle)
{
    var splashScreen = AndroidX.Core.SplashScreen.SplashScreen.InstallSplashScreen(this);
    splashScreen.SetKeepOnScreenCondition(new TrueKeepOnScreenCondition());
    ....
    base.OnCreate(bundle);
}

TrueKeepOnScreenCondition.cs：

public class TrueKeepOnScreenCondition : Java.Lang.Object, SplashScreen.IKeepOnScreenCondition
{
    [Preserve(Conditional = true)]
    public TrueKeepOnScreenCondition(IntPtr handle, JniHandleOwnership transfer) : base(handle, transfer)
    {
    }

    public TrueKeepOnScreenCondition()
    {
    }

    [Preserve(Conditional = true)]
    public bool ShouldKeepOnScreen()
    {
        return true;
    }
}

我总是返回 true，因为我正在使用 MvvmCross，并且有一个单独的进程将在 MvvmCross 完成加载时完成启动活动。

AndroidManifest.xml：

<application android:theme="@style/Theme.App.Starting">
    ...
</application>

资源值 hemes.xml：

<resources xmlns:tools="http://schemas.android.com/tools">
  <style name="Theme.App" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
    <item name="colorPrimary">@color/your_primary_color</item>
    ...
  </style>
  <style name="Theme.App.Starting" parent="Theme.SplashScreen.IconBackground">
    <item name="windowSplashScreenBackground">#165cab</item>
    <item name="windowSplashScreenAnimatedIcon">@mipmap/ic_launcher_foreground</item>
    <item name="postSplashScreenTheme">@style/Theme.App</item>
  </style>

</resources>

Answer 2

@TrevorBacom 你是如何更新

ShouldKeepOnScreen

的返回值的？ 谢谢