[转]WPF 构建无外观（Lookless）控件

构建一个用户可以使用Template属性设置外观的WPF控件需要以下几步

1. 1、继承自System.Windows.Controls.Control 
   2、设置DefaultStyleKeyProperty 
   3、实现控件功能
2. 4、定义默认Sytle
3. 5、添加ThemeInfo 
   我借用一个时钟的控件例子，讲解以下每一个步骤

4. 第1步 继承自System.Windows.Controls.Control

我们的自定义控件继承自System.Windows.Controls.Control，如果有更特别的控件，也可以继承自更复杂的控件。

类声明

   1: public class Clock : Control

   2: {

   3: }

第2步 设置DefaultStyleKeyProperty

无外观的控件需要在静态构造函数中设置DefaultStyleKeyProperty,这样它会去在themes/generic.xaml的文件获取默认的样式。

   1: static Clock()

   2: {

   3:     DefaultStyleKeyProperty.OverrideMetadata(typeof(Clock), new FrameworkPropertyMetadata(typeof(Clock)));

   4: }

第3步 实现控件功能

这一步没什么特别的，就是内部有个DateTime类型和一个DispatcherTimer，完成一个时钟的功能

   1: public class Clock : Control

   2: {

   3:     private DispatcherTimer timer;

   4:  

   5:     static Clock()

   6:     {

   7:         DefaultStyleKeyProperty.OverrideMetadata(typeof(Clock), new FrameworkPropertyMetadata(typeof(Clock)));

   8:     }

   9:  

  10:     protected override void OnInitialized(EventArgs e)

  11:     {

  12:         base.OnInitialized(e);

  13:  

  14:         UpdateDateTime();

  15:  

  16:         timer = new DispatcherTimer();

  17:         timer.Interval = TimeSpan.FromMilliseconds(1000 - DateTime.Now.Millisecond);

  18:         timer.Tick += new EventHandler(Timer_Tick);

  19:         timer.Start();

  20:     }

  21:  

  22:     private void Timer_Tick(object sender, EventArgs e)

  23:     {

  24:         UpdateDateTime();

  25:  

  26:         timer.Interval = TimeSpan.FromMilliseconds(1000 - DateTime.Now.Millisecond);

  27:         timer.Start();

  28:     }

  29:  

  30:     private void UpdateDateTime()

  31:     {

  32:         this.DateTime = System.DateTime.Now;

  33:     }

  34:  

  35:     public DateTime DateTime

  36:     {

  37:         get

  38:         {

  39:             return (DateTime)GetValue(DateTimeProperty);

  40:         }

  41:         private set

  42:         {

  43:             SetValue(DateTimeProperty, value);

  44:         }

  45:     }

  46:  

  47:     public static DependencyProperty DateTimeProperty = DependencyProperty.Register(

  48:             "DateTime",

  49:             typeof(DateTime),

  50:             typeof(Clock),

  51:             new PropertyMetadata(DateTime.Now, new PropertyChangedCallback(OnDateTimeInvalidated)));

  52:  

  53:     public static readonly RoutedEvent DateTimeChangedEvent =

  54:         EventManager.RegisterRoutedEvent("DateTimeChanged", RoutingStrategy.Bubble, typeof(RoutedPropertyChangedEventHandler<DateTime>), typeof(Clock));

  55:  

  56:     protected virtual void OnDateTimeChanged(DateTime oldValue, DateTime newValue)

  57:     {

  58:         RoutedPropertyChangedEventArgs<DateTime> args = new RoutedPropertyChangedEventArgs<DateTime>(oldValue, newValue);

  59:         args.RoutedEvent = Clock.DateTimeChangedEvent;

  60:         RaiseEvent(args);

  61:     }

  62:  

  63:     private static void OnDateTimeInvalidated(DependencyObject d, DependencyPropertyChangedEventArgs e)

  64:     {

  65:         Clock clock = (Clock)d;

  66:  

  67:         DateTime oldValue = (DateTime)e.OldValue;

  68:         DateTime newValue = (DateTime)e.NewValue;

  69:  

  70:         clock.OnDateTimeChanged(oldValue, newValue);

  71:     }

  72: }

第4步 定义默认Sytle

如上所述，我们还需要一个默认的Template，它写在themes/generic.xaml文件中，这个文件可能需要自己创建

   1: <ResourceDictionary

   2:     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

   3:     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

   4:     xmlns:local="clr-namespace:CustomControlLibrary"

   5:     >

   6:  

   7:     <Style TargetType="{x:Type local:Clock}">

   8:         <Setter Property="Template">

   9:             <Setter.Value>

  10:                 <ControlTemplate TargetType="{x:Type local:Clock}">

  11:                     <TextBlock Text="{Binding Path=DateTime, RelativeSource={RelativeSource TemplatedParent}}" />

  12:                 </ControlTemplate>

  13:             </Setter.Value>

  14:         </Setter>

  15:     </Style>

  16: </ResourceDictionary>

这里要注意TargetType的使用。到这里控件还是不能找到默认的模板，还需要下面的最后一步

1. 第5步 添加ThemeInfo

最后还需要在AssemblyInfo.cs文件中加入ThemeInfo信息，在文件中加入以下特性

   1: [assembly: ThemeInfo(

   2:     ResourceDictionaryLocation.None,

   3:     ResourceDictionaryLocation.SourceAssembly

   4: )]

1. 附注

如果需要在模板中使用特定的元素名，来或许模板中的某个特定控件，还有几个地方需要注意。

1、模板内的Name最好以PART开头，好的名称类似于PART_TextBox

2、获取Template中控件的代码，需要重载OnApplyTemplate（）方法，可以使用GetTemplateChild方法获取，如下

   1: public override void OnApplyTemplate()

   2: {

   3:     base.OnApplyTemplate();

   4:  

   5:     //从模板中获取名称为PART_PresentationTextBox的TextBox

   6:     _presentationTextBox = GetTemplateChild("PART_PresentationTextBox") as TextBox;

   7:     if(_presentationTextBox != null)

   8:     {

   9:         //对_presentationTextBox进行操作

  10:     }

  11: }

3、在控件类添加TemplatePart

   1: [TemplatePart(Name = "PART_PresentationTextBox", Type = typeof(TextBox))]

   2: public class TimeSpanPicker:Control

这个内容可以参考https://gitcafe.com/atskyline/WPFTimeSpanPickerControl

1. 参考资料

http://www.codeproject.com/Articles/14340/Creating-a-look-less-custom-control-in-WPF

http://www.codeproject.com/Articles/35444/Defining-the-Default-Style-for-a-Lookless-Control