c# - 不确定进度条

Question

当前，我有一个按钮，当用户单击它时，它会寻找已准备就绪且包含文件的特定CD-ROM驱动器。有时，当用户单击一个按钮时，鼠标单击将使按钮单击，并且程序将挂起一段不确定的时间，直到计算机读取CD-ROM驱动器。

我进入了进度栏，但发现了一些问题:

1)在调用检查CD驱动器的方法之前，程序会挂起/冻结。因此，我无法设置进度条在调用该方法时显示。似乎在单击按钮时以及用户同时放入CD时程序挂起。单击按钮并且鼠标仍然向下/直到系统检测到CD驱动器后，如何显示进度栏？

2)我对如何实现后台工作程序感到困惑。我看了喜欢的示例，但没有一个示例具有使用MVVM(不确定代码)方法的不确定进度条。

3)操作完成后如何使窗口消失？目前，我有一个取消按钮(绝对没有用)。

到目前为止，这是我设置的内容。不确定如何继续:

进度条:

<Grid>
        <Border BorderBrush="Black" BorderThickness="2" CornerRadius="4" Background="#EEEEEE" HorizontalAlignment="Left" Height="110" VerticalAlignment="Top" Width="295" />
        <StackPanel>
            <Label x:Name="lblProgress"/>
            <ProgressBar x:Name="progress" Height="25" Width="270"  IsIndeterminate="True" Foreground="Green"></ProgressBar>
            <StackPanel Orientation="Horizontal" HorizontalAlignment="Left" Margin="225,10,0,0" RenderTransformOrigin="0.083,0.526">
                <Button x:Name="btnCancel" Width="60" Content="Cancel" Command="{Binding CloseCommand}"/>
            </StackPanel>
        </StackPanel>
    </Grid>

我有一个ProgressBarViewModel，其中包含允许用户取消进度窗口的命令。此外，我还有另一个ViewModel需要在内部调用progressBar对话框，但是我不确定在哪里调用它，因为如果我在内部调用它方法，按钮仍然挂起而不显示进度条。

我注意到是否在codebehind中使用Button_PreviewMouseDown方法，但是，当鼠标按下时进度条会正确显示，并且系统的确显示了进度条，但是我不想使用codebehind，因为我在另一个 View 中都有进度条。

当前，对于我的导入按钮，所有附加的命令是调用一种方法，该方法在驱动器中搜索CD-ROM驱动器。

MainViewModel:

 public ICommand ImportCDFilePathCommand
        {
            get
            {
                return new RelayCommand(ImportCDFilePath, null);
            }

        }

private void ImportCDFilePath()
        {
           // dialogService.ShowDialog("Progress", progressBarWindow); <---Does not get called until the operation is done


            //Gets all the drives 
            DriveInfo[] allDrives = DriveInfo.GetDrives();

            //checks if any CD-Rom exists in the drives
            var cdRomExists = allDrives.Any(x => x.DriveType == DriveType.CDRom);

            // Get all the cd roms
            var cdRoms = allDrives.Where(x=>x.DriveType==DriveType.CDRom && allDrives.Any(y=>y.IsReady));

 //.... There is other code that is commented out too long and not necessary 

}

编辑:

使用BackgroundWorker的一些尝试:

static BackgroundWorker _bw = new BackgroundWorker();

//constructor
MainViewModel() {


            _bw.DoWork += bw_DoWork;
            _bw.RunWorkerAsync("Message to worker");
}

 void bw_DoWork(object sender, DoWorkEventArgs e)
        {
            // This is called on the worker thread
            Console.WriteLine(e.Argument);        // writes "Message to worker"
            // Perform time-consuming task...
            ImportCDFilePath();
        }

错误我得到:

The calling thread must be STA, because many UI components require this.

Answer 1

嗨，我在这里有点快，您所使用的方法没有任何异步等待重载。因此，您可以使用旧的BackgroundWorker。我在这里为您提供了一个非常简单的示例，可以快速制作(制作食物)。 (未运行的)示例将仅报告进度0或100，但不会冻结UI。报告进度时，您发送一个int(进度)和一个userstate对象，这可能是您想要发送的任何对象。只需将其转换，然后执行您想要的操作即可:)

public class TestViewModel : INotifyPropertyChanged
{
    private int progress;
    private BackgroundWorker bgWorker;
    private bool isBusy;
    private readonly Dispatcher dispatcher;
    private ObservableCollection<DriveInfo> cdRoms;

    public Int32 Progress
    {
        get { return progress; }
        set
        {
            if (value == progress) return;
            progress = value;
            OnPropertyChanged();
        }
    }

    public bool IsBusy
    {
        get { return isBusy; }
        set
        {
            if (value.Equals(isBusy)) return;
            isBusy = value;
            OnPropertyChanged();
        }
    }

    public ICommand ImportCDFilePathCommand
    {
        get
        {
            return new RelayCommand(ImportReagentLotFilePath);
        }
    }


    public ObservableCollection<DriveInfo> CdRoms
    {
        get { return cdRoms; }
        set
        {
            if (Equals(value, cdRoms)) return;
            cdRoms = value;
            OnPropertyChanged();
        }
    }

    // This one made your app crash if you defined it directly in the xaml as datacontext and not were using a viewmodellocator
    public TestViewModel(Dispatcher dispatcher) // ugh I'm sure there is an interface for this, feed your UI dispatcher here
    {
        this.dispatcher = dispatcher;
    }

    // Add this one!
    public TestViewModel()
    {
        this.dispatcher = App.Current.Dispatcher; // Bad pie
    }


    private void ImportReagentLotFilePath()
    {

        IsBusy = true;
        Progress = 0;
        bgWorker = new BackgroundWorker { WorkerReportsProgress = true, WorkerSupportsCancellation = true };
        bgWorker.DoWork += bgWorker_DoWork;
        bgWorker.ProgressChanged += bgWorker_ProgressChanged;
        bgWorker.RunWorkerCompleted += bgWorker_RunWorkerCompleted;
        bgWorker.RunWorkerAsync(/*whatever parameter you want goes here*/);
    }

    void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        // you are done! 
        Progress = 100;
        CdRoms =  new ObservableCollection<DriveInfo>(e.UserState as IEnumerable<DriveInfo>);
    }

    void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        // Notifty your gui changes here forinstance, this method will be called on the gui thread. Just cast/parse what you feed
        Progress = e.ProgressPercentage;
        if (Progress == 100)
            IsBusy = false;
    }

    void bgWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        try
        {
            DriveInfo[] allDrives = DriveInfo.GetDrives();                
            bool cdRomExists = allDrives.Any(x => x.DriveType == DriveType.CDRom);
            IEnumerable<DriveInfo> cdroms = allDrives.Where(x => x.DriveType == DriveType.CDRom && allDrives.Any(y => y.IsReady));

            // reports the progress on the ui thread.... 
            bgWorker.ReportProgress(Progress,cdroms);
        }
        catch (Exception ex)
        {
            // errror handling + cancel run
            dispatcher.BeginInvoke((Action) (() => { IsBusy = false; Progress = 0; }));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator] // remove if you are not using R#
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
    }
}

使用任务:

    // Alternatively use a task.....

    public ICommand TaskTestCommand
    {
        get
        {
            return new RelayCommand(DoStuffAsync);
        }
    }


    public Task DoStuffAsync()
    {
        Task tcs = Task.Factory.StartNew(() =>
        {
            try
            {
                // No awaits...  please note that anything bound in the gui must be changed on the dispatcher
                DriveInfo[] allDrives = DriveInfo.GetDrives();
                bool cdRomExists = allDrives.Any(x => x.DriveType == DriveType.CDRom);
                IEnumerable<DriveInfo> cdroms = allDrives.Where(x => x.DriveType == DriveType.CDRom && allDrives.Any(y => y.IsReady));
            }
            catch (Exception ex)
            {
                // handle your errors here. Note that you must check the innerexception for the real fault
                System.Diagnostics.Trace.WriteLine(ex.ToString());
            }
        }).ContinueWith((e) => { // this code is run when the task is completed...
            if(e.Exception!=null)
            {
                // hande error.. / 
            }
            else
            {
                // complete.. do whatever here
            }
        });     
        return tcs;       
    }

希望它能帮助您朝正确的方向前进!我实际上对您使用的方法没有async-await重载感到有些惊讶，因为它将允许您使用漂亮的async-await“statemachine-auto footer”。

干杯，

施蒂安