WPF - 模板

模板描述了控件的整体外观和视觉呈现。每个控件都与其关联的默认模板，该模板赋予控件其外观。在 WPF 应用程序中，当您想要自定义控件的视觉行为和视觉外观时，可以轻松创建自己的模板。

逻辑和模板之间的连接可以通过数据绑定来实现。样式和模板之间的主要区别如下所示：

样式只能使用该控件的默认属性更改控件的外观。
使用模板，您可以访问比样式中更多控件的部件。您还可以指定控件的现有行为和新行为。

最常用的模板类型有两种：

控件模板
数据模板

控件模板

控件模板定义控件的视觉外观。所有 UI 元素都具有一定的外观和行为，例如，按钮具有外观和行为。单击事件或鼠标悬停事件是响应单击和悬停而触发的行为，并且按钮还有一个默认外观，可以通过控件模板更改。

示例

让我们来看一个简单的例子。我们将创建两个按钮（一个带模板，另一个是默认按钮）并使用一些属性初始化它们。

<Window x:Class = "TemplateDemo.MainWindow" 
   xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
   xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml" 
   Title = "MainWindow" Height = "350" Width = "604"> 
	
   <Window.Resources> 
      <ControlTemplate x:Key = "ButtonTemplate" TargetType = "Button">
		
         <Grid> 
            <Ellipse x:Name = "ButtonEllipse" Height = "100" Width = "150" > 
               <Ellipse.Fill> 
                  <LinearGradientBrush StartPoint = "0,0.2" EndPoint = "0.2,1.4"> 
                     <GradientStop Offset = "0" Color = "Red" /> 
                     <GradientStop Offset = "1" Color = "Orange" /> 
                  </LinearGradientBrush> 
               </Ellipse.Fill> 
            </Ellipse> 
				
            <ContentPresenter Content = "{TemplateBinding Content}" 
               HorizontalAlignment = "Center" VerticalAlignment = "Center" /> 
         </Grid> 
			
         <ControlTemplate.Triggers> 
			
            <Trigger Property = "IsMouseOver" Value = "True"> 
               <Setter TargetName = "ButtonEllipse" Property = "Fill" > 
                  <Setter.Value> 
                     <LinearGradientBrush StartPoint = "0,0.2" EndPoint = "0.2,1.4"> 
                        <GradientStop Offset = "0" Color = "YellowGreen" /> 
                        <GradientStop Offset = "1" Color = "Gold" /> 
                     </LinearGradientBrush> 
                  </Setter.Value> 
               </Setter> 
            </Trigger> 
				
            <Trigger Property = "IsPressed" Value = "True"> 
               <Setter Property = "RenderTransform"> 
                  <Setter.Value> 
                     <ScaleTransform ScaleX = "0.8" ScaleY = "0.8" 
                        CenterX = "0" CenterY = "0"  /> 
                  </Setter.Value> 
               </Setter> 
               <Setter Property = "RenderTransformOrigin" Value = "0.5,0.5" /> 
            </Trigger> 
				
         </ControlTemplate.Triggers> 
			
      </ControlTemplate> 
   </Window.Resources> 
	
   <StackPanel> 
      <Button Content = "Round Button!"
         Template = "{StaticResource ButtonTemplate}" 
         Width = "150" Margin = "50" /> 
      <Button Content = "Default Button!" Height = "40" 
         Width = "150" Margin = "5" />
   </StackPanel> 
	
</Window>

编译并执行上述代码后，将显示以下 MainWindow。

当您将鼠标悬停在具有自定义模板的按钮上时，它将更改其颜色，如下所示。

数据模板

数据模板定义并指定数据集合的外观和结构。它提供了在任何 UI 元素上格式化和定义数据呈现的灵活性。它主要用于与数据相关的项控件，例如 ComboBox、ListBox 等。

示例

让我们来看一个简单的示例，以了解数据模板的概念。创建一个名为WPFDataTemplates的新 WPF 项目。
在下面的 XAML 代码中，我们将创建一个作为资源的数据模板来保存标签和文本框。还有一个按钮和一个列表框用于显示数据。

<Window x:Class = "WPFDataTemplates.MainWindow" 
   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:local = "clr-namespace:WPFDataTemplates" 
   xmlns:loc = "clr-namespace:WPFDataTemplates" 
   mc:Ignorable = "d" Title = "MainWindow" Height = "350" Width = "525"> 
	
   <Window.Resources> 
      <DataTemplate DataType = "{x:Type loc:Person}"> 
		
         <Grid> 
            <Grid.RowDefinitions> 
               <RowDefinition Height = "Auto" /> 
               <RowDefinition Height = "Auto" /> 
            </Grid.RowDefinitions> 
				
            <Grid.ColumnDefinitions> 
               <ColumnDefinition Width = "Auto" /> 
               <ColumnDefinition Width = "200" /> 
            </Grid.ColumnDefinitions>
				
            <Label Name = "nameLabel" Margin = "10"/> 
            <TextBox Name = "nameText" Grid.Column = "1" Margin = "10" 
               Text = "{Binding Name}"/>  
            <Label Name = "ageLabel" Margin = "10" Grid.Row = "1"/> 
            <TextBox Name = "ageText" Grid.Column = "1" Grid.Row = "1" Margin = "10" 
               Text = "{Binding Age}"/> 
         </Grid> 
			
      </DataTemplate> 
   </Window.Resources> 
	
   <Grid> 
      <Grid.RowDefinitions> 
         <RowDefinition Height = "Auto" /> 
         <RowDefinition Height = "*" /> 
      </Grid.RowDefinitions> 
		
      <ListBox ItemsSource = "{Binding}" />  
      <StackPanel Grid.Row = "1" > 
         <Button Content = "_Show..." Click = "Button_Click" Width = "80" HorizontalAlignment = "Left" Margin = "10"/> 
      </StackPanel> 
		
   </Grid> 
	
</Window>

以下是C# 实现，其中将 Person 对象列表分配给 DataContext，Person 类的实现和按钮单击事件。

using System.Collections.Generic; 
using System.Windows;
  
namespace WPFDataTemplates { 

   public partial class MainWindow : Window { 
	
      Person src = new Person { Name = "Ali", Age = 27 }; 
      List<Person> people = new List<Person>(); 
		
      public MainWindow() { 
         InitializeComponent(); 
         people.Add(src); 
         people.Add(new Person { Name = "Mike", Age = 62 }); 
         people.Add(new Person { Name = "Brian", Age = 12 });  
         this.DataContext = people; 
      } 
		
      private void Button_Click(object sender, RoutedEventArgs e) { 
         string message = src.Name + " is " + src.Age; 
         MessageBox.Show(message); 
      } 
   } 
	
   public class Person { 
      private string nameValue; 
		
      public string Name { 
         get { return nameValue; } 
         set { nameValue = value; } 
      }  
		
      private double ageValue; 
		
      public double Age { 
         get { return ageValue; } 
         set { 
            if (value != ageValue) { 
            ageValue = value; 
            } 
         } 
      } 
   } 
	
}

编译并执行上述代码后，将生成以下窗口。它包含一个列表，在列表框内，每个列表框项都包含 Person 类对象数据，这些数据显示在标签和文本框上。

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