WPF异步MVVM等待窗体

WPF异步MVVM等待窗体

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 ：https://www.wendangku.net/doc/777189843.html,/

等待控件

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1

2

3 Grid.Column="0"

4 Width="100"

5 Height="100"

6 Margin="0,0,0,0"

7 HorizontalAlignment="Center"

8 VerticalAlignment="Center"

9 Background="Transparent"

10 Interval="60"

11 IsIndeterminate="True"

12 StartAngle="-90"

13 TickColor="{DynamicResource MaskForegroundColor}"

14 TickCount="16"

15 TickWidth="5" />

16

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等待效果

定义MVVM 中的ViewModel 的状态

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///

[Flags]

public enum ViewModelStatus

{

///

None = 0x0,

///

Initializing = 0x1,

///

Initialized = 0x2,

///

Loading = 0x4,

///

Loaded = 0x8,

///

Saving = 0x16,

///

Saved = 0x32

}

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ViewModel 状态转变为控件状态

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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 #endregion

37 }

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使UserControl 支持异步显示

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1

x:Key="StatusToAnimationVisibilityConverter" />

2

3

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应用Style 至UserControl

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1

2 xmlns="https://www.wendangku.net/doc/777189843.html,/winfx/2006/xaml/presentation"

3 xmlns:x="https://www.wendangku.net/doc/777189843.html,/winfx/2006/xaml"

4 xmlns:d="https://www.wendangku.net/doc/777189843.html,/expression/blend/2008"

5 xmlns:mc="https://www.wendangku.net/doc/777189843.html,/markup-compatibility/2006"

6 d:DesignHeight="318"

7 d:DesignWidth="632"

8 Style="{DynamicResource AsyncWorkUserControlStyle}"

9 mc:Ignorable="d">

10

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定义基础ViewModel

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1 ///

4 public abstract class ViewModelResponsive : ViewModelBase, IViewModelResponsive

5 {

6 #region Fields

7

8 private ViewModelStatus _status = ViewModelStatus.None;

9

10 #endregion

11

12 #region ViewModel Status

13

14 ///

17 public virtual void Refresh()

18 {

19

20 }

21

22 ///

25 public ViewModelStatus Status

26 {

27 get

28 {

29 return _status;

30 }

31 protected set

32 {

33 if (_status != value)

34 {

35 _status = value;

36 RaisePropertyChanged(@"Status");

37 }

38 }

39 }

40

41 #endregion

42 }

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ViewModel 应用

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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 }

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