将方法从视图移动到viewmodel - WPF MVVM

Question

我的代码背后有以下代码:

public partial class MainWindow
{
    private Track _movieSkipSliderTrack;
    private Slider sMovieSkipSlider = null;
    private Label lbTimeTooltip = null;
    private MediaElement Player = null;

    public VideoPlayerViewModel ViewModel
    {
        get { return DataContext as VideoPlayerViewModel; }
    }

    public MainWindow()
    {
        InitializeComponent();
    }

    private void SMovieSkipSlider_OnLoaded(object sender, RoutedEventArgs e)
    {
        _movieSkipSliderTrack = (Track)sMovieSkipSlider.Template.FindName("PART_Track", sMovieSkipSlider);
        _movieSkipSliderTrack.Thumb.DragDelta += Thumb_DragDelta;
        _movieSkipSliderTrack.Thumb.MouseEnter += Thumb_MouseEnter;
    }

    private void Thumb_MouseEnter(object sender, MouseEventArgs e)
    {
        if (e.LeftButton == MouseButtonState.Pressed && e.MouseDevice.Captured == null)
        {
            var args = new MouseButtonEventArgs(e.MouseDevice, e.Timestamp, MouseButton.Left)
            {
                RoutedEvent = MouseLeftButtonDownEvent
            };
            SetPlayerPositionToCursor();
            _movieSkipSliderTrack.Thumb.RaiseEvent(args);
        }
    }

    private void Thumb_DragDelta(object sender, DragDeltaEventArgs e)
    {
        SetPlayerPositionToCursor();
    }

    private void SMovieSkipSlider_OnMouseEnter(object sender, MouseEventArgs e)
    {
        lbTimeTooltip.Visibility = Visibility.Visible;
        lbTimeTooltip.SetLeftMargin(Mouse.GetPosition(sMovieSkipSlider).X);
    }

    private void SMovieSkipSlider_OnPreviewMouseMove(object sender, MouseEventArgs e)
    {
        double simulatedPosition = SimulateTrackPosition(e.GetPosition(sMovieSkipSlider), _movieSkipSliderTrack);
        lbTimeTooltip.AddToLeftMargin(Mouse.GetPosition(sMovieSkipSlider).X - lbTimeTooltip.Margin.Left + 35);
        lbTimeTooltip.Content = TimeSpan.FromSeconds(simulatedPosition);
    }

    private void SMovieSkipSlider_OnMouseLeave(object sender, MouseEventArgs e)
    {
        lbTimeTooltip.Visibility = Visibility.Hidden;
    }

    private void SetPlayerPositionToCursor()
    {
        Point mousePosition = new Point(Mouse.GetPosition(sMovieSkipSlider).X, 0);
        double simulatedValue = SimulateTrackPosition(mousePosition, _movieSkipSliderTrack);
        SetNewPlayerPosition(TimeSpan.FromSeconds(simulatedValue));
    }

    private double CalculateTrackDensity(Track track)
    {
        double effectivePoints = Math.Max(0, track.Maximum - track.Minimum);
        double effectiveLength = track.Orientation == Orientation.Horizontal
            ? track.ActualWidth - track.Thumb.DesiredSize.Width
            : track.ActualHeight - track.Thumb.DesiredSize.Height;
        return effectivePoints / effectiveLength;
    }

    private double SimulateTrackPosition(Point point, Track track)
    {
        var simulatedPosition = (point.X - track.Thumb.DesiredSize.Width / 2) * CalculateTrackDensity(track);
        return Math.Min(Math.Max(simulatedPosition, 0), sMovieSkipSlider.Maximum);
    }

    private void SetNewPlayerPosition(TimeSpan newPosition)
    {
        Player.Position = newPosition;
        ViewModel.AlignTimersWithSource(Player.Position, Player);
    }
}

我想遵循MVVM模式,并将此代码移至我的ViewModel,目前只有少数属性.我已经在这里和StackOverflow之外阅读了很多关于这个主题的答案,我已经下载了一些github项目,以查看经验丰富的程序员如何处理特定的情况,但这些似乎都没有让我感到困惑.我想看看如何重构我的案例以遵循MVVM模式.

这些是额外的扩展方法,也是ViewModel本身:

static class Extensions
{
    public static void SetLeftMargin(this FrameworkElement target, double value)
    {
        target.Margin = new Thickness(value, target.Margin.Top, target.Margin.Right, target.Margin.Bottom);
    }

    public static void AddToLeftMargin(this FrameworkElement target, double valueToAdd)
    {
        SetLeftMargin(target, target.Margin.Left + valueToAdd);
    }
}

public class VideoPlayerViewModel : ViewModelBase
{
    private TimeSpan _movieElapsedTime = default(TimeSpan);
    public TimeSpan MovieElapsedTime
    {
        get { return _movieElapsedTime; }
        set
        {
            if (value != _movieElapsedTime)
            {
                _movieElapsedTime = value;
                OnPropertyChanged();
            }
        }
    }

    private TimeSpan _movieLeftTime = default(TimeSpan);
    public TimeSpan MovieLeftTime
    {
        get { return _movieLeftTime; }
        set
        {
            if (value != _movieLeftTime)
            {
                _movieLeftTime = value;
                OnPropertyChanged();
            }
        }
    }

    public void AlignTimersWithSource(TimeSpan currentPosition, MediaElement media)
    {
        MovieLeftTime = media.NaturalDuration.TimeSpan - currentPosition;
        MovieElapsedTime = currentPosition;
    }
}

public class ViewModelBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string propName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
    }
}

我已经尝试按照注释中的要求准备好代码复制/粘贴,如果要完全复制它,则在XAML中创建View后面代码中的所有控件.

Answer 1

我建议使用 Caliburn Micro。如果您使用该库，您可以绑定如下事件：

<Button cal:Message.Attach="Save">

或者像这样

<Button cal:Message.Attach="[Event MouseEnter] = [Action Save]">

查看他们的网站以了解更高级的可能性：

https://caliburnmicro.codeplex.com/wikipage?title=Cheat%20Sheet