xamarin.forms - 当 Android 9 中 xamarin.forms 中的设备方向发生变化时，我收到 NullReferenceException

问题描述

在我使用 Xamarin.forms 开发的 android 应用程序中，每当我更改设备的方向时，我都会收到 NullReferenceException 并且应用程序在 Android 9 中崩溃。但在以前的 android 版本中，应用程序运行良好。没有崩溃。

这是 MainActivity.cs

namespace RSMapp.Droid
{
    [Activity(Label = "FIRE", Icon = "@drawable/launcherIcon", Theme = "@style/splashscreen", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation, ScreenOrientation = ScreenOrientation.Portrait)]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        internal static MainActivity Instance { get; private set; }

        protected async override void OnCreate(Bundle savedInstanceState)
        {

            TryToGetPermissions();

            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.Window.RequestFeature(WindowFeatures.ActionBar);
            base.SetTheme(Resource.Style.MainTheme);
            UserDialogs.Init(this);
            base.OnCreate(savedInstanceState);
            Instance = this;
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            CrossCurrentActivity.Current.Init(this, savedInstanceState);
            Plugin.InputKit.Platforms.Droid.Config.Init(this, savedInstanceState);
            UltimateXFSettup.Initialize(this);
            LoadApplication(new App());

        }


}

}

我尝试删除 ScreenOrientation = ScreenOrientation.Portrait，但存在问题。

在将方向纵向更改为横向后，在“输出”窗口中获取此信息

10-18 11:52:37.366 I/MultiWindowDecorSupport(19021): updateCaptionType >> DecorView@3acb272[MainActivity], isFloating: false, isApplication: true, hasWindowDecorCaption: false, hasWindowControllerCallback: true
10-18 11:52:37.366 D/MultiWindowDecorSupport(19021): setCaptionType = 0, DecorView = DecorView@3acb272[MainActivity]
10-18 11:52:37.373 D/ViewRootImpl@403bf69[MainActivity](19021): MSG_RESIZED_REPORT: frame=[0,0][2048,1536] ci=[0,48][0,0] vi=[0,48][0,0] or=2
10-18 11:52:37.399 D/ViewRootImpl@403bf69[MainActivity](19021): Relayout returned: old=[0,0][2048,1536] new=[0,0][2048,1536] result=0x23 surface={true 490213163008} changed=false
10-18 11:52:37.401 D/OpenGLRenderer(19021): eglDestroySurface = 0x7222da2700, 0x7222fb4000
10-18 11:52:37.402 D/OpenGLRenderer(19021): eglCreateWindowSurface = 0x7222da2700, 0x7222fb4010
Unhandled Exception:

System.NullReferenceException: Object reference not set to an instance of an object.

此代码中存在问题。

public override Resources Resources
{
    get
    {
        if ((int)Build.VERSION.SdkInt >= 25)
        {
            Configuration config = new Configuration();
            config.SetToDefaults();
            Context context = CreateConfigurationContext(config);
            Resources resources = context.Resources;
            return resources;
        }
        else
        {
            Resources res = base.Resources;
            Configuration config = new Configuration();
            config.SetToDefaults();
            res.UpdateConfiguration(config, res.DisplayMetrics);
            return res;
        }

    }
}

我正在使用它来省略用户的系统级字体大小更改为应用程序。这给出了 Android 9 中的错误

标签： xamarin.formsxamarin.android

xamarin.forms - 当 Android 9 中 xamarin.forms 中的设备方向发生变化时，我收到 NullReferenceException

问题描述

解决方案

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