更改 WindowsForms UI 在一个 Task 中 c#

huangapple
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英文:

Changing WindowsForms UI in a Task c#

问题

I wrote a windows forms application where I receive messages with MQTTNet from the broker. I want to change the UI according to the received message. But I couldn't make it happen. I took the client code from the MQTTNet github page. When I receive the message, I want to change a label. Because it is a task, I had to call the invoke function, but it never executes. The function to change the label is called, but the change statement is never reached.

  1. public Form1()
  2. {
  3.     InitializeComponent();
  4.     trainCount = 1;
  5.     tagCount = 2;
  6.     trains = new Train[trainCount];
  7.     tags = new Tag[tagCount];
  8.     InitializeTrains();
  9.     InitializeTags();
  10.     control = this;
  11.     Task task = Handle_Received_Application_Message();
  12. }
  1. public async Task Handle_Received_Application_Message()
  2. {
  3.     var mqttFactory = new MqttFactory();
  5.     using (var mqttClient = mqttFactory.CreateMqttClient())
  6.     {
  7.         var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer("127.0.0.1").Build();
  9.         mqttClient.ApplicationMessageReceivedAsync += async e =>
  10.         {
  11.             Console.WriteLine("Received application message.");
  12.             Console.WriteLine(e.ApplicationMessage.ConvertPayloadToString());
  13.             for (int i = 0; i < tagCount; i++)
  14.             {
  15.                 if (tags[i].code.CompareTo(e.ApplicationMessage.ConvertPayloadToString()) == 0)
  16.                 {
  17.                     for (int k = 0; k < trainCount; k++)
  18.                     {
  19.                         if (e.ApplicationMessage.ConvertPayloadToString().Substring(0, 2).CompareTo(trains[k].code) == 0)
  20.                         {
  21.                             Console.WriteLine("In Tag Event");
  22.                             trains[k].currentTag = tags[i];
  23.                             var message = e.ApplicationMessage.ConvertPayloadToString();
  24.                             await ChangeUI(); // Change UI is called here.
  25.                         }
  26.                     }
  27.                 }
  28.             }
  29.         };
  31.         await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
  33.         var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
  34.             .WithTopicFilter(
  35.                 f =>
  36.                 {
  37.                     f.WithTopic("anten/main");
  38.                 })
  39.             .Build();
  41.         await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
  43.         Console.WriteLine("MQTT client subscribed to topic.");
  44.         Console.ReadKey();
  45.     }
  46. }
  1. public async Task ChangeUI()
  2. {
  3.     if (InvokeRequired)
  4.         BeginInvoke(new MethodInvoker(
  5.             delegate
  6.             {
  7.                 ChangeUI().Wait();
  8.             }
  9.         ));
  10.     else
  11.     {
  12.         label1.Text = "sadasdasd";  // Code never reaches here.
  13.     }
  14. }

I tried creating a different thread when a message is received, but it didn't work neither.

Any help would be appreciated. I got stuck on this for 10 hours.

英文:

I wrote a windows forms application where I receive messages with MQTTNet from the broker. I want to change the UI according to the received message. But I couldn't make it happen. I took the client code from the MQTTNet github page. When I receive the message, I want to change a label. Because it is a task, I had to call the invoke function, but it never executes. The function to change the label is called, but the change statement is never reached.

  1. public Form1()
  2.         {
  3.             InitializeComponent();
  4.             trainCount = 1;
  5.             tagCount = 2;
  6.             trains = new Train[trainCount];
  7.             tags = new Tag[tagCount];
  8.             InitializeTrains();
  9.             InitializeTags();
  10.             control = this;
  11.             Task task = Handle_Received_Application_Message();
  12.         }
  1. public async Task Handle_Received_Application_Message()
  2.         {
  4.             var mqttFactory = new MqttFactory();
  6.             using (var mqttClient = mqttFactory.CreateMqttClient())
  7.             {
  8.                 var mqttClientOptions = new MqttClientOptionsBuilder().WithTcpServer(&quot;127.0.0.1&quot;).Build();
  10.                 mqttClient.ApplicationMessageReceivedAsync += e =&gt;
  11.                 {
  12.                     Console.WriteLine(&quot;Received application message.&quot;);
  13.                     Console.WriteLine(e.ApplicationMessage.ConvertPayloadToString());
  14.                     for (int i = 0; i &lt; tagCount; i++)
  15.                     {
  16.                         if (tags[i].code.CompareTo(e.ApplicationMessage.ConvertPayloadToString()) == 0)
  17.                         {
  18.                             for (int k = 0; k &lt; trainCount; k++)
  19.                             {
  20.                                 if (e.ApplicationMessage.ConvertPayloadToString().Substring(0, 2).CompareTo(trains[k].code) == 0)
  21.                                 {
  22.                                     Console.WriteLine(&quot;In Tag Event&quot;);
  24.                                     trains[k].currentTag = tags[i];
  25.                                     var message = e.ApplicationMessage.ConvertPayloadToString();
  26.                                     ChangeUI(); //Change UI is called here.
  27.                                     
  28.                                 }
  29.                             }
  30.                         }
  31.                     }
  32.                     
  33.                     return Task.CompletedTask;
  34.                 };
  36.                 await mqttClient.ConnectAsync(mqttClientOptions, CancellationToken.None);
  38.                 var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
  39.                     .WithTopicFilter(
  40.                         f =&gt;
  41.                         {
  42.                             f.WithTopic(&quot;anten/main&quot;);
  43.                         })
  44.                     .Build();
  46.                 await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);
  48.                 Console.WriteLine(&quot;MQTT client subscribed to topic.&quot;);
  49.                 Console.ReadKey();
  50.             }
  53.         }
  1. public void ChangeUI()
  2.         {
  3.             if (InvokeRequired)
  4.                 BeginInvoke(new MethodInvoker(
  5.                     delegate
  6.                     {
  7.                 ChangeUI();
  8.                     }
  9.                     ));
  10.             else
  11.             {
  12.                 label1.Text = &quot;sadasdasd&quot;;  // Code never reaches here.
  13.             }
  14.         }

I tried creating a different thread when a message is received, but it didn't work neither.

Any help would be appreciated. I got stuck on this for 10 hours.

答案1

得分: 2

Console.ReadKey 会阻止 Windows 消息循环执行，从而阻止任何 UI 更新。

我建议移除 Console.ReadKey，并且还要移除 Handle_Received_Application_Message 中的 using，以便不销毁客户端。而是在 Handle_Received_Application_Message 中创建一个成员变量来持有客户端，在应用程序开始关闭时进行销毁。

英文:

Console.ReadKey will prevent the Windows message loop from executing, which prevents any UI updates.

I recommend removing Console.ReadKey and also removing the using in Handle_Received_Application_Message so the client is not disposed. Instead of disposing the client in Handle_Received_Application_Message, create a member variable to hold the client and dispose it when your application begins to shut down.

huangapple
  • 本文由 发表于 2023年3月7日 21:32:31
  • 转载请务必保留本文链接：https://go.coder-hub.com/75662639.html
  • c#
  • invoke
  • mqttnet
  • multithreading
  • task
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