[英]Windows Phone 8.1 SmartCard app with background task crashing
我遇到了一个问题,现在要解决一个多星期,但我无法解决。 我正在尝试使用nfc和智能卡的东西制作一个非常简单的Windows Phone 8.1应用程序。 稍后,我尝试使用由类SmartCardEmulator提供的智能卡仿真,但是现在,我只希望有一个后台任务,当接近nfc标签/智能卡时,该任务就会执行操作。 对于这个问题,我做了一个完整的新项目,其中仅包含基础知识。 当我按下按钮时,程序不断崩溃。
开始时,我制作了一个空白的Windows Phone App项目和一个Windows运行时组件 ,并将它们添加到解决方案中。 Phone App Project引用了Windows Runtime Component Project。
在MainPage.xaml中,我只放置了一个按钮和一个文本框。
Windows Server应用程序项目中有BackgroundTaskManager类,运行时组件项目中有TaskOne类。
在文件Package.appxmanifest中,我在声明中添加了后台任务,其中BackgroundTasks.TaskOne作为EntryPoint , 系统事件作为支持任务类型
在需求中,我启用了NFC
按下按钮时出现的错误如下:
A first chance exception of type 'System.ArgumentException' occurred in mscorlib.ni.dll
A first chance exception of type 'System.ArgumentException' occurred in mscorlib.ni.dll
A first chance exception of type 'System.UnauthorizedAccessException' occurred in SimpleNfcApp.exe
A first chance exception of type 'System.UnauthorizedAccessException' occurred in mscorlib.ni.dll
A first chance exception of type 'System.UnauthorizedAccessException' occurred in mscorlib.ni.dll
我尝试调试 ,并将中断点放在BackgroundTaskManager.cs中的RegisterBackgroundTask方法的开头,然后在MainPage.xaml.cs中的doSomething结束时崩溃
以下是源代码:
MainPage.xaml.cs
namespace SimpleNfcApp
{
public sealed partial class MainPage : Page
{
public MainPage() {
this.InitializeComponent();
this.NavigationCacheMode = NavigationCacheMode.Required;
}
protected override void OnNavigatedTo(NavigationEventArgs e) {
}
// method put on a button
private async void doSomething(object sender, TappedRoutedEventArgs e)
{
String taskName = BackgroundTaskManager.TaskOneName;
bool isActive = isTaskActive(taskName);
if(isActive == false) {
startTask();
} else {
myTextBox.Text = "Task already active";
}
}
// starts a task
private async void startTask()
{
var trigger = new SmartCardTrigger(SmartCardTriggerType.EmulatorNearFieldEntry);
var task = BackgroundTaskManager.RegisterBackgroundTask(BackgroundTaskManager.TaskOneEntryPoint,
BackgroundTaskManager.TaskOneName,
trigger,
null);
await task;
myTextBox.Text += task.Result.ToString();
}
// checks if the task is already active
private static bool isTaskActive(String name)
{
foreach (var task in BackgroundTaskRegistration.AllTasks)
{
if (task.Value.Name == name)
return true;
}
return false;
}
}
}
BackgroundTaskManager.cs
namespace SimpleNfcApp
{
class BackgroundTaskManager
{
public const string TaskOneEntryPoint = "BackgroundTasks.TaskOne";
public const string TaskOneName = "TaskOne";
public static string TaskOneProgress = "";
public static bool TaskOneRegistered = false;
// creates and registers the task
public static async Task<BackgroundTaskRegistration> RegisterBackgroundTask(String taskEntryPoint, String taskName, IBackgroundTrigger taskTrigger, IBackgroundCondition taskCondition)
{
if (TaskRequiresBackgroundAccess(taskName))
await BackgroundExecutionManager.RequestAccessAsync();
var builder = new BackgroundTaskBuilder();
builder.Name = taskName;
builder.TaskEntryPoint = taskEntryPoint;
builder.SetTrigger(taskTrigger);
BackgroundTaskRegistration task = builder.Register();
var settings = ApplicationData.Current.LocalSettings;
settings.Values.Remove(taskName);
return task;
}
// checks if it is a windows phone app or a simple windows app
public static bool TaskRequiresBackgroundAccess(String name)
{
#if WINDOWS_PHONE_APP
return true;
#else
#endif
}
}
}
TaskOne.cs
namespace BackgroundTasks
{
public sealed class TaskOne
{
IBackgroundTaskInstance _taskInstance;
BackgroundTaskDeferral _deferral;
public async void Run(IBackgroundTaskInstance taskInstance)
{
_taskInstance = taskInstance;
_deferral = taskInstance.GetDeferral();
int x;
x = 2 + 2;
_deferral.Complete();
}
}
}
有人看到我在做什么错吗? 谢谢阅读。 格里茨,斯基皮
编辑:
我在MainPage.xaml.cs的doSomething方法周围添加了一个try catch块 ,并得到了一个新的更具说服力的错误消息。
A first chance exception of type 'System.UnauthorizedAccessException' occurred in mscorlib.ni.dll
System.UnauthorizedAccessException: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
at Windows.ApplicationModel.Background.BackgroundTaskBuilder.Register()
at SimpleNfcApp.BackgroundTaskManager.<RegisterBackgroundTask>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at SimpleNfcApp.MainPage.<startTask>d__0.MoveNext() Second exception caught.
另外,当我在注册任务之前在doSomething中更改触发器时,它可以工作。 我尝试了这个:
//var trigger = new SmartCardTrigger(SmartCardTriggerType.EmulatorNearFieldEntry);
var trigger = new SystemTrigger(SystemTriggerType.ServicingComplete, false);
你在那里有错误代码
var settings = ApplicationData.Current.LocalSettings;
settings.Values.Remove(taskName);
ApplicationData.Current.LocalSettings-对此文件的访问被拒绝。
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