WPF异步MVVM等待窗体-白红宇

需求描述

在 ViewModel 中处理 Model 中的数据需要一定时间的等待；

ViewModel 或 Model 在获取数据或访问同步服务时有一定延迟需要等待；

ViewModel 操作 View 加载数据需要一段时间；

解决办法

显示一个等待 UI，当数据处理完毕或服务接口返回后等待UI消失

转动齿轮控件

参考开源实现 SprocketControl ：

等待控件

等待效果

定义 MVVM 中的 ViewModel 的状态

///   /// 在MVVM模式中ViewModel的状态  /// 
  [Flags]  public enum ViewModelStatus  {    ///     /// ViewModel无状态    /// 
    None = 0x0,    ///     /// ViewModel正在初始化    /// 
    Initializing = 0x1,    ///     /// ViewModel初始化完毕    /// 
    Initialized = 0x2,    ///     /// ViewModel正在加载    /// 
    Loading = 0x4,    ///     /// ViewModel加载完毕    /// 
    Loaded = 0x8,    ///     /// ViewModel正在保存    /// 
    Saving = 0x16,    ///     /// ViewModel保存完毕    /// 
    Saved = 0x32  }

ViewModel 状态转变为控件状态

1   public class StatusToAnimationVisibilityConverter : IValueConverter 2   { 3     #region IValueConverter Members 4  5     public object Convert( 6       object value, Type targetType, object parameter, CultureInfo culture) 7     { 8       try 9       {10         string status = value.ToString();11 12         switch (status)13         {14           case "Initializing":15           case "Loading":16           case "Saving":17             return Visibility.Visible;18           case "Loaded":19           case "Saved":20           default:21             return Visibility.Collapsed;22         }23       }24       catch (Exception)25       {26         return Visibility.Collapsed;27       }28     }29 30     public object ConvertBack(31       object value, Type targetType, object parameter, CultureInfo culture)32     {33       return DependencyProperty.UnsetValue;34     }35 36     #endregion37   }

使 UserControl 支持异步显示

1   
       2  3

应用 Style 至 UserControl

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       10

定义基础 ViewModel

1   ///  2   /// 响应式的ViewModel模型 3   /// 
 4   public abstract class ViewModelResponsive : ViewModelBase, IViewModelResponsive 5   { 6     #region Fields 7  8     private ViewModelStatus _status = ViewModelStatus.None; 9 10     #endregion11     12     #region ViewModel Status13 14     /// 15     /// 刷新UI数据16     /// 
17     public virtual void Refresh()18     {19 20     }21 22     /// 23     /// ViewModel状态24     /// 
25     public ViewModelStatus Status26     {27       get28       {29         return _status;30       }31       protected set32       {33         if (_status != value)34         {35           _status = value;36           RaisePropertyChanged(@"Status");37         }38       }39     }40 41     #endregion42   }

ViewModel 应用

1   public class CameraManagementViewModel : ViewModelResponsive 2   { 3     protected override void BindCommands() 4     { 5       RefreshCommand = new RelayCommand(() => 6       { 7         Refresh(); 8       }); 9     }10     11     public override void Refresh()12     {13       base.Refresh();14 15       Status = ViewModelStatus.Initializing;16       CameraCollection.Clear();17       Model.GetCameras(GetCamerasCallback);18     }19     20     private void GetCamerasCallback(object sender, AsyncWorkerCallbackEventArgs
      
       
        > args)21     {22       CameraCollection.Clear();23       Status = ViewModelStatus.Loaded;24 25       if (result)26       {27         foreach (var item in (args.Data as IList
        
         ))28         {29           CameraCollection.Add(item);30         }31       }32     }33   }

实现效果

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