.NET Core 3 WPF MVVM框架 Prism系列之區域管理器-有解無憂

本文將介紹如何在.NET Core3環境下使用MVVM框架Prism的使用區域管理器對于View的管理

一.區域管理器

我們在之前的Prism系列構建了一個標準式Prism專案，這篇文章將會講解之前專案中用到的利用區域管理器更好的對我們的View進行管理，同樣的我們來看看官方給出的模型圖：

現在我們可以知道的是，大致一個區域管理器RegionMannager對一個控制元件創建區域的要點：

創建Region的控制元件必須包含一個RegionAdapter配接器
region是依賴在具有RegionAdapter控制元件身上的

其實后來我去看了下官方的介紹和原始碼，默認RegionAdapter是有三個，且還支持自定義RegionAdapter，因此在官方的模型圖之間我做了點補充：

二.區域創建與視圖的注入

我們先來看看我們之前專案的區域的劃分，以及如何創建區域并且把View注入到區域中：

我們把整個主表單劃分了四個區域：

ShowSearchPatientRegion：注入了ShowSearchPatient視圖
PatientListRegion：注入了PatientList視圖
FlyoutRegion：注入了PatientDetail和SearchMedicine視圖
ShowSearchPatientRegion：注入了ShowSearchPatient視圖

在Prism中，我們有兩種方式去實作區域創建和視圖注入：

ViewDiscovery
ViewInjection

1.ViewDiscovery

我們截取其中PatientListRegion的創建和視圖注入的代碼(更仔細的可以去觀看demo原始碼)：

MainWindow.xaml：

<ContentControl Grid.Row="2" prism:RegionManager.RegionName="PatientListRegion" Margin="10"/>

這里相當于在后臺MainWindow.cs：

RegionManager.SetRegionName(ContentControl, "PatientListRegion");

PatientModule.cs：

 public class PatientModule : IModule
 {
    public void OnInitialized(IContainerProvider containerProvider)
    {
         var regionManager = containerProvider.Resolve<IRegionManager>();
         //PatientList
         regionManager.RegisterViewWithRegion(RegionNames.PatientListRegion, typeof(PatientList));
         //PatientDetail-Flyout
         regionManager.RegisterViewWithRegion(RegionNames.FlyoutRegion, typeof(PatientDetail));
           
     }

    public void RegisterTypes(IContainerRegistry containerRegistry)
    {
           
    }
 }

2.ViewInjection

我們在MainWindow表單的Loaded事件中使用ViewInjection方式注入視圖PatientList

MainWindow.xaml：

  <i:Interaction.Triggers>
      <i:EventTrigger EventName="Loaded">
          <i:InvokeCommandAction Command="{Binding LoadingCommand}"/>
       /i:EventTrigger>
  </i:Interaction.Triggers>

MainWindowViewModel.cs:

      
private IRegionManager _regionManager;
private IRegion _paientListRegion;        
private PatientList _patientListView;

private DelegateCommand _loadingCommand;
public DelegateCommand LoadingCommand =>
     _loadingCommand ?? (_loadingCommand = new DelegateCommand(ExecuteLoadingCommand));

void ExecuteLoadingCommand()
{
     _regionManager = CommonServiceLocator.ServiceLocator.Current.GetInstance<IRegionManager>();
     _paientListRegion = _regionManager.Regions[RegionNames.PatientListRegion];
     _patientListView = CommonServiceLocator.ServiceLocator.Current.GetInstance<PatientList>();
     _paientListRegion.Add(_patientListView);

 }

我們可以明顯的感覺到兩種方式的不同，ViewDiscovery方式是自動地實體化視圖并且加載出來，而ViewInjection方式則是可以手動控制注入視圖和加載視圖的時機(上述例子是通過Loaded事件)，官方對于兩者的推薦使用場景如下：

ViewDiscovery：

需要或要求自動加載視圖
視圖的單個實體將加載到該區域中

ViewInjection：

需要顯式或編程控制何時創建和顯示視圖，或者您需要從區域中洗掉視圖
需要在區域中顯示相同視圖的多個實體，其中每個視圖實體都系結到不同的資料
需要控制添加視圖的區域的哪個實體
應用程式使用導航API(后面會講到)

三.激活與失效視圖

Activate和Deactivate

首先我們需要控制PatientList和MedicineMainContent兩個視圖的激活情況，上代碼：

MainWindow.xaml：

<StackPanel Grid.Row="1">
    <Button  Content="Load MedicineModule" FontSize="25"  Margin="5" Command="{Binding LoadMedicineModuleCommand}"/>
     <UniformGrid Margin="5">
         <Button Content="ActivePaientList" Margin="5" Command="{Binding ActivePaientListCommand}"/>
         <Button Content="DeactivePaientList" Margin="5" Command="{Binding DeactivePaientListCommand}"/>
         <Button Content="ActiveMedicineList" Margin="5" Command="{Binding ActiveMedicineListCommand}"/>
         <Button Content="DeactiveMedicineList" Margin="5" Command="{Binding DeactiveMedicineListCommand}"/>
     </UniformGrid>
</StackPanel>

<ContentControl Grid.Row="2" prism:RegionManager.RegionName="PatientListRegion" Margin="10"/>
<ContentControl Grid.Row="3" prism:RegionManager.RegionName="MedicineMainContentRegion"/>

MainWindowViewModel.cs：

  private IRegionManager _regionManager;
  private IRegion _paientListRegion;
  private IRegion _medicineListRegion;
  private PatientList _patientListView;
  private MedicineMainContent _medicineMainContentView;

  private bool _isCanExcute = false;
  public bool IsCanExcute
  {
     get { return _isCanExcute; }
     set { SetProperty(ref _isCanExcute, value); }
  }

  private DelegateCommand _loadingCommand;
  public DelegateCommand LoadingCommand =>
      _loadingCommand ?? (_loadingCommand = new DelegateCommand(ExecuteLoadingCommand));

  private DelegateCommand _activePaientListCommand;
  public DelegateCommand ActivePaientListCommand =>
      _activePaientListCommand ?? (_activePaientListCommand = new DelegateCommand(ExecuteActivePaientListCommand));

  private DelegateCommand _deactivePaientListCommand;
  public DelegateCommand DeactivePaientListCommand =>
      _deactivePaientListCommand ?? (_deactivePaientListCommand = new DelegateCommand(ExecuteDeactivePaientListCommand));

   private DelegateCommand _activeMedicineListCommand;
   public DelegateCommand ActiveMedicineListCommand =>
      _activeMedicineListCommand ?? (_activeMedicineListCommand = new DelegateCommand(ExecuteActiveMedicineListCommand)
      .ObservesCanExecute(() => IsCanExcute));

   private DelegateCommand _deactiveMedicineListCommand;
   public DelegateCommand DeactiveMedicineListCommand =>
       _deactiveMedicineListCommand ?? (_deactiveMedicineListCommand = new DelegateCommand(ExecuteDeactiveMedicineListCommand)
      .ObservesCanExecute(() => IsCanExcute));

   private DelegateCommand _loadMedicineModuleCommand;
   public DelegateCommand LoadMedicineModuleCommand =>
       _loadMedicineModuleCommand ?? (_loadMedicineModuleCommand = new DelegateCommand(ExecuteLoadMedicineModuleCommand));

 /// <summary>
 /// 表單加載事件
 /// </summary>
 void ExecuteLoadingCommand()
 {
      _regionManager = CommonServiceLocator.ServiceLocator.Current.GetInstance<IRegionManager>();
      _paientListRegion = _regionManager.Regions[RegionNames.PatientListRegion];
      _patientListView = CommonServiceLocator.ServiceLocator.Current.GetInstance<PatientList>();
      _paientListRegion.Add(_patientListView);
      _medicineListRegion = _regionManager.Regions[RegionNames.MedicineMainContentRegion];
 }

  /// <summary>
  /// 失效medicineMainContent視圖
  /// </summary>
  void ExecuteDeactiveMedicineListCommand()
  {
      _medicineListRegion.Deactivate(_medicineMainContentView);
  }

  /// <summary>
  /// 激活medicineMainContent視圖
  /// </summary>
  void ExecuteActiveMedicineListCommand()
  {
      _medicineListRegion.Activate(_medicineMainContentView);
  }

  /// <summary>
  /// 失效patientList視圖
  /// </summary>
  void ExecuteDeactivePaientListCommand()
  {
       _paientListRegion.Deactivate(_patientListView);
  }

  /// <summary>
  /// 激活patientList視圖
  /// </summary>
  void ExecuteActivePaientListCommand()
  {
       _paientListRegion.Activate(_patientListView);
  }
  
  /// <summary>
  /// 加載MedicineModule
  /// </summary>
  void ExecuteLoadMedicineModuleCommand()
  {
       _moduleManager.LoadModule("MedicineModule");
       _medicineMainContentView = (MedicineMainContent)_medicineListRegion.Views
            .Where(t => t.GetType() == typeof(MedicineMainContent)).FirstOrDefault();
       this.IsCanExcute = true;
   }

效果如下：

監控視圖激活狀態

Prism其中還支持監控視圖的激活狀態，是通過在View中繼承IActiveAware來實作的，我們以監控其中MedicineMainContent視圖的激活狀態為例子：

MedicineMainContentViewModel.cs:

 public class MedicineMainContentViewModel : BindableBase,IActiveAware
 {
     public event EventHandler IsActiveChanged;

     bool _isActive;
     public bool IsActive
     {
         get { return _isActive; }
         set
         {
             _isActive = value;
             if (_isActive)
             {
                 MessageBox.Show("視圖被激活了");
             }
             else
             {
                 MessageBox.Show("視圖失效了");
             }
             IsActiveChanged?.Invoke(this, new EventArgs());
          }
      }

  }

Add和Remove

上述例子用的是ContentControl，我們再用一個ItemsControl的例子，代碼如下：

MainWindow.xaml:

  <metro:MetroWindow.RightWindowCommands>
      <metro:WindowCommands x:Name="rightWindowCommandsRegion" />
  </metro:MetroWindow.RightWindowCommands>

MainWindow.cs:

 public MainWindow()
 {
    InitializeComponent();
    var regionManager= ServiceLocator.Current.GetInstance<IRegionManager>();
    if (regionManager != null)
    {
       SetRegionManager(regionManager, this.flyoutsControlRegion, RegionNames.FlyoutRegion);
       //創建WindowCommands控制元件區域
       SetRegionManager(regionManager, this.rightWindowCommandsRegion, RegionNames.ShowSearchPatientRegion);
    }
 }

 void SetRegionManager(IRegionManager regionManager, DependencyObject regionTarget, string regionName)
 {
     RegionManager.SetRegionName(regionTarget, regionName);
     RegionManager.SetRegionManager(regionTarget, regionManager);
 }

ShowSearchPatient.xaml：

<StackPanel x:Class="PrismMetroSample.MedicineModule.Views.ShowSearchPatient"
       xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
       xmlns:prism="http://prismlibrary.com/"  
       xmlns:const="clr-namespace:PrismMetroSample.Infrastructure.Constants;assembly=PrismMetroSample.Infrastructure"
       Orientation="Horizontal"    
       xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
       prism:ViewModelLocator.AutoWireViewModel="True">
   <i:Interaction.Triggers>
       <i:EventTrigger EventName="Loaded">
           <i:InvokeCommandAction Command="{Binding ShowSearchLoadingCommand}"/>
       </i:EventTrigger>
   </i:Interaction.Triggers>
   <CheckBox IsChecked="{Binding IsShow}"/>
   <Button Command="{Binding ApplicationCommands.ShowCommand}" CommandParameter="{x:Static const:FlyoutNames.SearchMedicineFlyout}">
       <StackPanel Orientation="Horizontal">
           <Image Height="20" Source="pack://application:,,,/PrismMetroSample.Infrastructure;Component/Assets/Photos/按鈕.png"/>
           <TextBlock Text="Show" FontWeight="Bold" FontSize="15" VerticalAlignment="Center"/>
       </StackPanel>
   </Button>
</StackPanel>

ShowSearchPatientViewModel.cs:

 private IApplicationCommands _applicationCommands;
 private readonly IRegionManager _regionManager;
 private ShowSearchPatient _showSearchPatientView;
 private IRegion _region;

 public IApplicationCommands ApplicationCommands
 {
      get { return _applicationCommands; }
      set { SetProperty(ref _applicationCommands, value); }
 }

 private bool _isShow=true;
 public bool IsShow
 {
      get { return _isShow=true; }
      set 
      { 
          SetProperty(ref _isShow, value);
          if (_isShow)
          {
               ActiveShowSearchPatient();
          }
          else
          {
               DeactiveShowSearchPaitent();
          }
      }
 }

 private DelegateCommand _showSearchLoadingCommand;
 public DelegateCommand ShowSearchLoadingCommand =>
         _showSearchLoadingCommand ?? (_showSearchLoadingCommand = new DelegateCommand(ExecuteShowSearchLoadingCommand));

 void ExecuteShowSearchLoadingCommand()
 {
        _region = _regionManager.Regions[RegionNames.ShowSearchPatientRegion];
        _showSearchPatientView = (ShowSearchPatient)_region.Views
            .Where(t => t.GetType() == typeof(ShowSearchPatient)).FirstOrDefault();
 }


  public ShowSearchPatientViewModel(IApplicationCommands applicationCommands,IRegionManager regionManager)
  {
        this.ApplicationCommands = applicationCommands;
        _regionManager = regionManager;
  }

  /// <summary>
  /// 激活視圖
  /// </summary>
  private void ActiveShowSearchPatient()
  {
       if (!_region.ActiveViews.Contains(_showSearchPatientView))
       {
           _region.Add(_showSearchPatientView);
       }         
  }
   
  /// <summary>
  /// 失效視圖
  /// </summary>
   private async void DeactiveShowSearchPaitent()
   {
        _region.Remove(_showSearchPatientView);
        await Task.Delay(2000);
        IsShow = true;
   }

效果如下：

這里的WindowCommands 的繼承鏈為：WindowCommands <-- ToolBar <-- HeaderedItemsControl <--ItemsControl，因此由于Prism默認的配接器有ItemsControlRegionAdapter,因此其子類也繼承了其行為

這里重點歸納一下：

當進行模塊化時，加載完模塊才會去注入視圖到區域(可參考MedicineModule視圖加載順序)
ContentControl控制元件由于Content只能顯示一個，在其區域中可以通過Activate和Deactivate方法來控制顯示哪個視圖，其行為是由ContentControlRegionAdapter配接器控制
ItemsControl控制元件及其子控制元件由于顯示一個集合視圖，默認全部集合視圖是激活的，這時候不能通過Activate和Deactivate方式來控制(會報錯),通過Add和Remove來控制要顯示哪些視圖，其行為是由ItemsControlRegionAdapter配接器控制
這里沒講到Selector控制元件，因為也是繼承自ItemsControl，因此其SelectorRegionAdapter配接器和ItemsControlRegionAdapter配接器異曲同工
可以通過繼承IActiveAware介面來監控視圖激活狀態

四.自定義區域配接器

我們在介紹整個區域管理器模型圖中說過，Prism有三個默認的區域配接器：ItemsControlRegionAdapter，ContentControlRegionAdapter，SelectorRegionAdapter，且支持自定義區域配接器，現在我們來自定義一下配接器

1.創建自定義配接器

新建類UniformGridRegionAdapter.cs：

public class UniformGridRegionAdapter : RegionAdapterBase<UniformGrid>
{
    public UniformGridRegionAdapter(IRegionBehaviorFactory regionBehaviorFactory) : base(regionBehaviorFactory)
    {

    }

    protected override void Adapt(IRegion region, UniformGrid regionTarget)
    {
        region.Views.CollectionChanged += (s, e) =>
        {
          if (e.Action==System.Collections.Specialized.NotifyCollectionChangedAction.Add)
          {
              foreach (FrameworkElement element in e.NewItems)
              {
                   regionTarget.Children.Add(element);
              }
          }
        };
    }

    protected override IRegion CreateRegion()
    {
        return new AllActiveRegion();
    }
 }

2.注冊映射

App.cs:

protected override void ConfigureRegionAdapterMappings(RegionAdapterMappings regionAdapterMappings)
{
    base.ConfigureRegionAdapterMappings(regionAdapterMappings);
    //為UniformGrid控制元件注冊配接器映射
    regionAdapterMappings.RegisterMapping(typeof(UniformGrid),Container.Resolve<UniformGridRegionAdapter>());
}

3.為控制元件創建區域

MainWindow.xaml:

    <UniformGrid Margin="5" prism:RegionManager.RegionName="UniformContentRegion" Columns="2">
        <Button Content="ActivePaientList" Margin="5" Command="{Binding ActivePaientListCommand}"/>
        <Button Content="DeactivePaientList" Margin="5" Command="{Binding DeactivePaientListCommand}"/>
        <Button Content="ActiveMedicineList" Margin="5" Command="{Binding ActiveMedicineListCommand}"/>
        <Button Content="DeactiveMedicineList" Margin="5" Command="{Binding DeactiveMedicineListCommand}"/>
     </UniformGrid>

4.為區域注入視圖

這里用的是ViewInjection方式：

MainWindowViewModel.cs

  void ExecuteLoadingCommand()
  {
         _regionManager = CommonServiceLocator.ServiceLocator.Current.GetInstance<IRegionManager>();

         var uniformContentRegion = _regionManager.Regions["UniformContentRegion"];
         var regionAdapterView1 = CommonServiceLocator.ServiceLocator.Current.GetInstance<RegionAdapterView1>();
         uniformContentRegion.Add(regionAdapterView1);
         var regionAdapterView2 = CommonServiceLocator.ServiceLocator.Current.GetInstance<RegionAdapterView2>();
         uniformContentRegion.Add(regionAdapterView2); 
  }

效果如圖：

我們可以看到我們為UniformGrid創建區域配接器，并且注冊后，也能夠為UniformGrid控制元件創建區域，并且注入視圖顯示，如果沒有該區域配接器，則是會報錯，下一篇我們將會講解基于區域Region的prism導航系統，

五.原始碼

?最后，附上整個demo的源代碼：PrismDemo原始碼

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