不幸的是，MyApp.Android已经停止。与ContentPage.Resource在XAML文件中

Question

我开始在Android上使用Xamarin Forms构建UI。我的XAML文件在下面给出。

<?xml version="1.0" encoding="utf-8" ?> 
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
      xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
      xmlns:PortableViews="clr-namespace:MyApp.Portable.Views" 
      x:Class="MyApp.Portable.Views.MainPage3"> 

    <ContentPage.Resources> 
    <PortableViews:NullVisibilityConverter x:Key="NullVisibilityConverter"/> 
    </ContentPage.Resources> 
<Grid> 
</Grid> 
</ContentPage> 

我能够编译和部署到device.When我运行与设备的应用程序，我得到的错误说 Unfortunately, MyApp.Android has stopped.

如果我注释掉<ContentPage.Resources>标签它运行并显示我一个空白屏幕。为什么不对

<ContentPage.Resources> 
     <PortableViews:NullVisibilityConverter x:Key="NullVisibilityConverter"/> 
</ContentPage.Resources> 

logcat显示以下消息。

11-10 14:01:39.675 I/DEBUG (2131): [OnPurpose Redunant in void preset_info(aed_report_record*, int, int)] pid: 2058, tid: -1361051648, name: UNKNOWN >>> MyApp.Android.MyApp.Android

如果我的logcat看Android Runtime我收到以下错误。

11-10 14:42:18.554 E/AndroidRuntime(4487): FATAL EXCEPTION: main 
11-10 14:42:18.554 E/AndroidRuntime(4487): Process: MyApp.Android.MyApp.Android, PID: 4487 
11-10 14:42:18.554 E/AndroidRuntime(4487): java.lang.RuntimeException: java.lang.reflect.InvocationTargetException 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:750) 
11-10 14:42:18.554 E/AndroidRuntime(4487): Caused by: java.lang.reflect.InvocationTargetException 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at java.lang.reflect.Method.invoke(Native Method) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at java.lang.reflect.Method.invoke(Method.java:372) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:955) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  ... 1 more 
11-10 14:42:18.554 E/AndroidRuntime(4487): Caused by: android.runtime.JavaProxyThrowable: Xamarin.Forms.Xaml.XamlParseException: Position 13:6. Type Window not found in xmlns http://xamarin.com/schemas/2014/forms 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Xamarin.Forms.Xaml.ApplyPropertiesVisitor.GetRealNameAndType (System.Type& elementType, System.String namespaceURI, System.String& localname, Xamarin.Forms.Xaml.HydratationContext context, IXmlLineInfo lineInfo) <0x7f59f99ac0 + 0x0013c> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Xamarin.Forms.Xaml.ApplyPropertiesVisitor.SetPropertyValue (System.Object xamlelement, XmlName propertyName, System.Object value, Xamarin.Forms.BindableObject rootElement, INode node, Xamarin.Forms.Xaml.HydratationContext context, IXmlLineInfo lineInfo) <0x7f59fb3160 + 0x0013b> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Xamarin.Forms.Xaml.ApplyPropertiesVisitor.Visit (Xamarin.Forms.Xaml.ElementNode node, INode parentNode) <0x7f59f9e048 + 0x005eb> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Xamarin.Forms.Xaml.ElementNode.Accept (IXamlNodeVisitor visitor, INode parentNode) <0x7f59fc4658 + 0x00277> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Xamarin.Forms.Xaml.RootNode.Accept (IXamlNodeVisitor visitor, INode parentNode) <0x7f59fc3ed8 + 0x000ff> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Xamarin.Forms.Xaml.XamlLoader.Load (Xamarin.Forms.BindableObject view, System.String xaml) <0x7f5a924650 + 0x00387> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Xamarin.Forms.Xaml.XamlLoader.Load (Xamarin.Forms.BindableObject view, System.Type callingType) <0x7f5a99ba20 + 0x00053> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Xamarin.Forms.Xaml.Extensions.LoadFromXaml[TView] (Xamarin.Forms.Xaml.TView view, System.Type callingType) <0x7f5a99b9d8 + 0x00023> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at MyApp.Portable.Views.MainPage3.InitializeComponent() <0x7f5a99b950 + 0x0002b> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at MyApp.Portable.Views.MainPage3..ctor() <0x7f5a9bf0d0 + 0x0001f> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at MyApp.Portable.App..ctor() <0x7f5b4276f8 + 0x0002f> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at MyApp.Android.MainActivity.OnCreate (Android.OS.Bundle bundle) <0x7f5b457370 + 0x00043> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (IntPtr jnienv, IntPtr native__this, IntPtr native_savedInstanceState) <0x7f5b457080 + 0x00063> in <filename unknown>:0 
11-10 14:42:18.554 E/AndroidRuntime(4487): at (wrapper dynamic-method) System.Object:5c4437ec-ddbf-41de-b890-3c31365af092 (intptr,intptr,intptr) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at md5b10bea1896ca4a98de5581931a9e1765.MainActivity.n_onCreate(Native Method) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at md5b10bea1896ca4a98de5581931a9e1765.MainActivity.onCreate(MainActivity.java:29) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.app.Activity.performCreate(Activity.java:5971) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1111) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2413) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2522) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.app.ActivityThread.access$800(ActivityThread.java:167) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1417) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.os.Handler.dispatchMessage(Handler.java:111) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.os.Looper.loop(Looper.java:194) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  at android.app.ActivityThread.main(ActivityThread.java:5534) 
11-10 14:42:18.554 E/AndroidRuntime(4487):  ... 4 more 

Answer 1

ContentPage.Resources需要一个ResourceDictionary实例，但是xaml会提供一个NullVisibilityConverter的实例，导致类型不匹配。

修复它通过包装资源字典里面的NullVisibilityConverter：

<ContentPage.Resources> 
    <ResourceDictionary> 
     <PortableViews:NullVisibilityConverter x:Key="NullVisibilityConverter"/> 
    </ResourceDictionary> 
</ContentPage.Resources> 

Answer 2

问题是InvocationTargetException引起的（我猜测）：

<PortableViews:NullVisibilityConverter x:Key="NullVisibilityConverter"/> 

什么是NullVisibilityConverter？它在你的代码中的位置？我的猜测和第一个实例将是PortableViews文件夹和NullVisibilityConverter类（只是一个猜测）。

哪个元素使用NullVisibilityConverter可能是一个很好的观点。