wpf c# backgroundworker 等到完成

Question

我的 wpf 应用程序中有几个文本框。每个文本框的 LostFocus-Event 都会启动后台程序将数据发送到连接的串行端口。

private readonly BackgroundWorker online_mode_send_worker = new BackgroundWorker();
online_mode_send_worker.DoWork += online_mode_send_worker_DoWork;
online_mode_send_worker.RunWorkerCompleted += online_mode_send_worker_RunWorkerCompleted;

private void TextBox_LostFocus(object sender, RoutedEventArgs e)
{
    online_mode_send_worker.RunWorkerAsync(data);
}

private void online_mode_send_worker_DoWork(object sender, DoWorkEventArgs e)
{
    List<object> data = (List<object>)e.Argument;
    Port.WriteLine(STARTCHARACTER + XMLSET + XML_TAG_START + data[0] + XML_TAG_STOP + data[1] + ENDCHARACTER);
    string received = Port.ReadLine();
}

private void online_mode_send_worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    //do some things after worker completed
}

至此，一切正常。

但有时我必须一个接一个地发送两个数据点，这时我遇到了问题。

private void TextBox_LostFocus(object sender, RoutedEventArgs e)
{
    online_mode_send_worker.RunWorkerAsync(data1);
    //wait until backgroundworker has finished 
    online_mode_send_worker.RunWorkerAsync(data2);
}

Backgroundworker 仍然是运行，我抛出了一个异常。是否可以等到第一个 online_mode_send_worker.RunWorkerAsync(data) 完成后再开始第二个 online_mode_send_worker.RunWorkerAsync(data)?

while(online_mode_send_worker.isBusy); 不工作，因为主线程正在阻塞并且 RunWorkerCompleted() 没有被抛出，所以 Backgroundwoker 总是很忙。

我找到了类似的东西，但是 Application.DoEvents() 在 wpf 中不可用。

while (online_mode_send_worker.IsBusy)
{
    Application.DoEvents();
    System.Threading.Thread.Sleep(100);
}

Answer 1

看来我错过了连载的东西。所以你要做的是同步你的异步调用：

private void Button_Click(object sender, RoutedEventArgs e)
{
    Task.Run(() => mySerialDevice1.WriteData(data1));
    Task.Run(() => mySerialDevice1.WriteData(data2));
}

public class SerialDevice
{
    public Port Port { get; set; }
    public object _LockWriteData = new object();
    public void WriteData(string data)
    {
        lock(_LockWriteData)
        {
            Port.WriteLine(data);
        }
    }
}

另见：

原始答案

您可以使用 Task 而不是 Backgroundworker。

private void Button_Click(object sender, RoutedEventArgs e)
{   
    Task.Run(() => OnlineModeSendData(data1));
    Task.Run(() => OnlineModeSendData(data2));
}
private void OnlineModeSendData(List<string> data)
{
    Port.WriteLine(STARTCHARACTER + XMLSET + XML_TAG_START + data[0]+ XML_TAG_STOP + data[1] + ENDCHARACTER);
    string received = Port.ReadLine();
}

我还想建议您制作真实的对象，而不是将字符串数组作为参数传递。

例如发送 BlinkLedRequest:

public class BlinkLedRequest
{
     public int LedId{get;set;}
     public int DurationInMilliseconds {get;set}
}

和相应的方法：

public void SendBlinkLed(BlickLedRequest request)
{
....
}

Answer 2

这是我在评论中提到的粗略想法。

public class Messenger {
    private readonly BackgroundWorker online_mode_send_worker = new BackgroundWorker();
    private readonly ConcurrentQueue<object> messages;

    public Messenger() {
        messages = new ConcurrentQueue<object>();
        online_mode_send_worker.DoWork += online_mode_send_worker_DoWork;
        online_mode_send_worker.RunWorkerCompleted += online_mode_send_worker_RunWorkerCompleted;
    }

    public void SendAsync(object message) {
        if (online_mode_send_worker.IsBusy) {
            messages.Enqueue(message);
        } else {
            online_mode_send_worker.RunWorkerAsync(message);
        }
    }

    public Action<object> MessageHandler = delegate { };

    private void online_mode_send_worker_DoWork(object sender, DoWorkEventArgs e) {
        if (MessageHandler != null)
            MessageHandler(e.Argument);
    }

    private void online_mode_send_worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {
        object nextMessage = null;
        if (messages.Count > 0 && messages.TryDequeue(out nextMessage)) {
            online_mode_send_worker.RunWorkerAsync(nextMessage);
        }
    }

}

您有一个队列来保留在后台工作人员忙碌时发送的消息，并让工作人员在完成工作后检查队列中是否有任何待处理的消息。

信使可以这样用

private Messenger messenger = new Messenger();

private void Initialize() { //I would expect this to be in the constructor
    messenger.MessageHandler = MessageHandler;
}

private void TextBox_LostFocus(object sender, RoutedEventArgs e)
{
    messenger.SendAsync(data);
}

private void MessageHandler(object message)
{
    List<object> data = (List<object>)message;
    Port.WriteLine(STARTCHARACTER + XMLSET + XML_TAG_START + data[0] + XML_TAG_STOP + data[1] + ENDCHARACTER);
    string received = Port.ReadLine();
}

Answer 3

我认为你应该使用 RunWorkerCompleted 事件并添加一个委托：

      online_mode_send_worker.RunWorkerCompleted += (s, ev) =>
                {
                    if (ev.Error != null)
                    {
                        //log Exception
                    }
                    //if(conditionToBrake)
                    //    return;
                    online_mode_send_worker.RunWorkerAsync(data2);
                };
 online_mode_send_worker.RunWorkerCompleted(data1);

确保你设置了条件以避免无限循环。

Answer 4

更新：

bw.RunWorkerAsync(data1);
//wait here
bw.RunWorkerAsync(data2);

不是一个好的方法，因为UI会在等待的时候被阻塞。更好：

bw.RunWorkerAsync(new object[] { data1, data2 }); //or new object[] { data1 } if no data2

原回答：

我建议不要使用构造：while (bw.Busy) { ... }（它会消耗cpu时间），使用同步对象，例如ManualResetEvent

BackgroundWorker 很棒class，但不支持等待。只需创建等待的添加对象：

var bw = new BackgroundWorker();
bw.DoWork += Bw_DoWork;
bw.RunWorkerCompleted += Bw_RunWorkerCompleted;
bool wasError;
ManualResetEvent e = null;

private void TextBox_LostFocus(object sender, RoutedEventArgs e)
{
    if (e != null)
        return;
    wasError = false;
    e = new ManualResetEvent(false); //not signaled
    bw.RunWorkerAsync(data1);
    e.Wait(); //much better than while(bw.Busy())
    if (!wasError)
       bw.RunWorkerAsync(data2);
    e = null;
}

private void Bw_DoWork(object sender, DoWorkEventArgs e)
{
    //background work in another thread
}

private void Bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    if (e.Error != null)
    {
        //catch exception here
        wasError = true;
    }
    e.Set(); //switch to signaled
}

Answer 5

我想说的是，如果您必须等到第一个 "job" 完成之后，您想要的是 Task.ContinueWith() 并相应地更改您的界面。 IMO 的 msdn page is good，但请注意您正在等待 "correct" 任务对象。提示：您应该在 Wait() 上调用 ContinueWith() 的 return 值。这是启动 Task 然后等待它的好模式，只要你可以保留 returned 的 Task，这样你就可以等待它。

对于更通用的 "I only want one background thread doing things in the order they're added, and I want to wait until they're ALL done and I know when I'm done adding."，我建议使用只有一个线程使用它们的 BlockingCollection<Action>。 in this other answer.

提供了如何执行此操作的示例

Answer 6

如果您只需要调用两次，您可以这样做：

 bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);

    void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        online_mode_send_worker.RunWorkerAsync(data2);
    }

但是，如果您需要对命令进行排队，则需要使用任务以另一种方式重写。一个任务，在其中你将有一个 for 循环，你将在其中通过串行端口顺序发送数据。

https://msdn.microsoft.com/pt-br/library/system.threading.tasks.task(v=vs.110).aspx

wpf c# backgroundworker 等到完成

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