Question

以下是我编写的代码段。

Task.Factory.StartNew(() =>
{
  BeginInvokeOnMainThread(() => scannerView.StartScanning(result =>
  {

      if (!ContinuousScanning)
      {
          Console.WriteLine("Stopping scan...");
          scannerView.StopScanning();
      }

      var evt = this.OnScannedResult;
      if (evt != null)
          evt(result);


    try
    {
        this.NavigationController.PushViewController(product, true);
    }
    catch(Exception e)
    {
        throw new Exception("Unable to push to the product page", e);   
    }

  }, this.ScanningOptions));

});

但是当我尝试运行PushViewController时，我收到以下错误消息：

DECODE FAILED：System.Exception：尝试重定向到产品屏幕时发生错误---＆gt; System.Exception：无法推送到产品页面---＆gt; UIKit.UIKitThreadAccessException：UIKit一致性错误：您正在调用只能从UI线程调用的UIKit方法。

我如何从lambda中运行这样的东西？

Answer 1

Task.Factory.StartNew(() => // <-- This starts a task which may or may not be on a 
                            // separate thread. It is non-blocking, and as such, code 
                            // after it is likely to execute before the task starts
{
  BeginInvokeOnMainThread(() => scannerView.StartScanning(result =>
  // This invokes a method on the main thread, which may or may not be the current thread
  // Again, it's non-blocking, and it's very likely code after this will execute first

  {

      if (!ContinuousScanning)
      {
          Console.WriteLine("Stopping scan...");
          scannerView.StopScanning();
      }

      var evt = this.OnScannedResult;
      if (evt != null)
          evt(result);

      Console.WriteLine("Some output 1"); // <-- This output is executed once the entire
                                          // task has been completed, which is I believe
                                          // what you're looking for
  }, this.ScanningOptions));

  Console.WriteLine("Some output 2");
});

Console.WriteLine("lambda finished...");

Answer 2

对于那些正在努力解决这个问题的人，我设法通过将我的代码包装在InvokeOnMainThread（）中来实现它的工作

                    InvokeOnMainThread(() =>
                    {
                         this.NavigationController.PushViewController(product, true);
                    });

C＃Lambda将无法完成执行

2 个答案: