Question

Sometimes we need a hamburger- less page. We do that with the IsFullScreen property. Additional we want to use this IsFullScreen property for switching the visibility of always available common controls.

<UserControl  Visibility="{Binding IsVisible, Converter={StaticResource BooleanToVisibilityConverter}}">
</UserControl>

public class MyViewModel : ViewModelBase
{
  public bool IsVisible
  {
    get
    {
      return !SettingsService.IsFullScreen;
    }
  }
}

How could we attach the propertychanged event for the IsFullScreen property.

Thanks for your efforts

Answer 1

您需要在INotifyPropertyChanged课程中实施SettingsService。和RaisePropertyChanged();（这是Binding所必需的。或者你可以使用依赖属性）

像这样：在SettingsService类

中

public class SettingsService : INotifyPropertyChanged
{
    public static SettingsService Instance { get; } = new SettingsService();

    bool _IsFullScreen;
    public event EventHandler IsFullScreenChanged;
    public bool IsFullScreen
    {
        get { return _IsFullScreen; }
        set
        {
            if (_IsFullScreen != value)
            {
                _IsFullScreen = value;
                //
                RaisePropertyChanged(); //uses CallerMemberName
                IsFullScreenChanged?.Invoke(this, EventArgs.Empty);
            }
        }
    }

    #region INotifyPropertyChanged

    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged([CallerMemberName] string propertyName = null) =>
       PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

    #endregion
}

在MyViewModel课程中，只需添加属性Settings。

public class MyViewModel : ViewModelBase
{
    public SettingsService Settings => SettingsService.Instance;
    //
}

在XAML文件中：在Binding路径中写入属性路径，如Settings.IsFullScreen（我使用ValueWhenConverter将bool转换为可见性）

<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:converter="using:Template10.Converters"
mc:Ignorable="d">

<Page.DataContext>
    <vm:MyViewModel x:Name="MyViewModel " />
</Page.DataContext>

<Page.Resources>
    <converter:ValueWhenConverter x:Key="VisibleWhenTrueConverter">
        <converter:ValueWhenConverter.When>
            <x:Boolean>True</x:Boolean>
        </converter:ValueWhenConverter.When>
        <converter:ValueWhenConverter.Value>
            <Visibility>Visible</Visibility>
        </converter:ValueWhenConverter.Value>
        <converter:ValueWhenConverter.Otherwise>
            <Visibility>Collapsed</Visibility>
        </converter:ValueWhenConverter.Otherwise>
    </converter:ValueWhenConverter>
    <converter:ValueWhenConverter x:Key="VisibleWhenFalseConverter">
        <converter:ValueWhenConverter.When>
            <x:Boolean>False</x:Boolean>
        </converter:ValueWhenConverter.When>
        <converter:ValueWhenConverter.Value>
            <Visibility>Visible</Visibility>
        </converter:ValueWhenConverter.Value>
        <converter:ValueWhenConverter.Otherwise>
            <Visibility>Collapsed</Visibility>
        </converter:ValueWhenConverter.Otherwise>
    </converter:ValueWhenConverter>
</Page.Resources>

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <UserControl  Visibility="{Binding Settings.IsFullScreen, Converter={StaticResource VisibleWhenFalseConverter}}">
    </UserControl>
</Grid>

Answer 2

感谢您的回答。我们解决了这个问题如下。我们的SettingsService类是Template10 uwp extension的一部分。对于数据绑定，我们使用MVVM Light工具包。我们广播了一个ScreenSizeChangedArgs

public class ScreenSizeChangedArgs : MessageBase
{
  public bool IsFullScreen
  {
    get; set;
  }
  public ScreenSizeChangedArgs(bool isFullScreen)
  {
    IsFullScreen = isFullScreen;
  }
}

IsFullScreen属性发生更改时的

消息。

public class SettingsService
{
  public static SettingsService Instance { get; } = new SettingsService();
  public bool IsFullScreen
  {
    get
    {
      return m_settingsHelper.Read<bool>(nameof(IsFullScreen), false);
    }
    set
    {
      m_settingsHelper.Write(nameof(IsFullScreen), value);
      Views.Shell.HamburgerMenu.IsFullScreen = value;
      Messenger.Default.Send(new ScreenSizeChangedArgs(value));
    }
  }
}

在相关的视图模型中，我们注册了ScreenSizeChangedArgs消息并处理新的IsFullScreen值。

public class MyViewModel : ViewModelBase
{
  public bool IsVisible
  {
    get
    {
      return m_isVisible;
    }
    set
    {
      m_isVisible = value;
      RaisePropertyChanged("IsVisible");
    }
  }
  public MyViewModel()
  {
    //The event when the IsFullScreen property has changed.
    Messenger.Default.Register<ScreenSizeChangedArgs>(this, args =>
    {
      IsVisible = !args.IsFullScreen;
    });
  }
}

对于bool到可见性转换，我们使用类似于http://blogs.u2u.be/diederik/post/2011/11/14/null.aspx的IValueConverter

IsFullScreen propertychanged event in Template10 uwp apps

2 个答案: