解决Xamarin Forms中Android 12的启动页重复显示问题

问题根源分析 #

1. SplashActivity生命周期方法重载错误：原代码使用带PersistableBundle参数的OnCreate重载，默认启动流程不会触发该方法，导致页面初始化逻辑缺失，引发生命周期异常。
2. Android 12启动页规范未适配：API 31+引入了全新的Splash Screen API，旧的windowBackground方式会与系统默认启动页叠加，造成重复显示。
3. 主题配置矛盾：原启动页主题父类为Theme.AppCompat.Light.NoActionBar，却又设置android:windowActionBar="true"，引发主题冲突。
4. 页面跳转逻辑不严谨：启动MainActivity时未设置正确的Intent Flags，也未主动销毁SplashActivity，导致页面残留。

具体修复步骤 #

1. 修正SplashActivity代码 #

namespace Splash12.Droid
{
    [Activity(Theme = "@style/MyTheme.Splash", MainLauncher = true, NoHistory = true, LaunchMode = LaunchMode.SingleTop)]
    public class SplashActivity : AppCompatActivity
    {
        static readonly string TAG = "X:" + typeof(SplashActivity).Name;

        // 使用默认的OnCreate重载，确保启动时触发
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            Log.Debug(TAG, "SplashActivity.OnCreate");
        }

        protected override void OnResume()
        {
            base.OnResume();
            _ = Task.Run(async () => await SimulateStartup());
        }

        async Task SimulateStartup()
        {
            Log.Debug(TAG, "Performing startup work.");
            await Task.Delay(2000); // 替换为真实初始化逻辑
            Log.Debug(TAG, "Startup work finished - launching MainActivity.");
            
            var intent = new Intent(Application.Context, typeof(MainActivity));
            // 清除栈顶，避免重复实例化
            intent.AddFlags(ActivityFlags.ClearTop | ActivityFlags.SingleTop);
            StartActivity(intent);
            Finish(); // 主动销毁SplashActivity，防止残留
        }
    }
}

2. 适配Android 12启动页主题 #

低版本兼容主题（res/values/styles.xml）

<style name="MyTheme.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>
</style>

Android 12专属主题（res/values-v31/styles.xml）

<style name="MyTheme.Splash" parent="Theme.SplashScreen">
    <!-- 启动页背景色 -->
    <item name="windowSplashScreenBackground">@color/splash_background</item>
    <!-- 启动页图标 -->
    <item name="windowSplashScreenAnimatedIcon">@drawable/splash_screen</item>
    <!-- 图标动画时长（无需动画可设为0） -->
    <item name="windowSplashScreenAnimationDuration">200</item>
    <!-- 指定跳转后的Activity主题 -->
    <item name="postSplashScreenTheme">@style/MainTheme</item>
</style>

3. 更新MainActivity适配系统启动页 #

[Activity(Label = "Splash12", Theme = "@style/MainTheme", Icon = "@mipmap/icon", MainLauncher = false, 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)
    {
        // 适配Android 12系统启动页，完成初始化后自动隐藏
        if (Build.VERSION.SdkInt >= BuildVersionCodes.S)
        {
            var splashScreen = SplashScreen.InstallSplashScreen(this);
            splashScreen.SetKeepOnScreenCondition(() => false);
        }

        base.OnCreate(savedInstanceState);

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

    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);
    }
}

4. 规范splash_screen.xml结构（示例） #

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@color/splash_background"/>
    <item>
        <bitmap
            android:gravity="center"
            android:src="@mipmap/ic_launcher"/>
    </item>
</layer-list>

内容的提问来源于stack exchange，提问作者nike