Wpf 简明教程
WPF - Triggers
触发器基本上使您可以根据属性的值更改属性值或执行操作。因此，它允许您动态更改控件的外观和/或行为，而无需创建新控件。
触发器用于在满足某些条件时更改任何给定属性的值。触发器通常在样式中或文档根部中定义，并应用于该特定控件。有三种类型的触发器：
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Property Triggers
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Data Triggers
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Event Triggers
Property Triggers
在属性触发器中，当一个属性发生变化时，它将立即或以动画形式更改另一个属性。例如，您可以使用属性触发器来更改按钮外观，当鼠标悬停在按钮上时。
以下示例代码展示了如何在鼠标悬停在按钮上时更改按钮的前景色。
<Window x:Class = "WPFPropertyTriggers.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>
<Style x:Key = "TriggerStyle" TargetType = "Button">
<Setter Property = "Foreground" Value = "Blue" />
<Style.Triggers>
<Trigger Property = "IsMouseOver" Value = "True">
<Setter Property = "Foreground" Value = "Green" />
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid>
<Button Width = "100" Height = "70"
Style = "{StaticResource TriggerStyle}" Content = "Trigger"/>
</Grid>
</Window>当你编译并执行以上代码时，它将产生以下窗口：
当鼠标悬停在按钮上时，其前景色将变为绿色。
Data Triggers
数据触发器在绑定数据满足某些条件时执行某些操作。让我们来看一下以下 XAML 代码，其中创建了一个具有某些属性的复选框和一个文本块。当选中复选框时，它会将其前景色变为红色。
<Window x:Class = "WPFDataTrigger.MainWindow"
xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml"
Title = "Data Trigger" Height = "350" Width = "604">
<StackPanel HorizontalAlignment = "Center">
<CheckBox x:Name = "redColorCheckBox"
Content = "Set red as foreground color" Margin = "20"/>
<TextBlock Name = "txtblock" VerticalAlignment = "Center"
Text = "Event Trigger" FontSize = "24" Margin = "20">
<TextBlock.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding = "{Binding ElementName = redColorCheckBox, Path = IsChecked}"
Value = "true">
<Setter Property = "TextBlock.Foreground" Value = "Red"/>
<Setter Property = "TextBlock.Cursor" Value = "Hand" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</StackPanel>
</Window>编译并执行上述代码时，将产生以下输出 -
当您勾选复选框时，文本块将将其前景色更改为红色。
Event Triggers
事件触发器在触发特定事件时执行某些操作。它通常用于在控件上完成某些动画，例如 DoubleAnumatio、ColorAnimation 等。在以下示例中，我们将创建一个简单的按钮。当触发单击事件时，它将扩展按钮的宽度和高度。
<Window x:Class = "WPFEventTrigger.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">
<Grid>
<Button Content = "Click Me" Width = "60" Height = "30">
<Button.Triggers>
<EventTrigger RoutedEvent = "Button.Click">
<EventTrigger.Actions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty =
"Width" Duration = "0:0:4">
<LinearDoubleKeyFrame Value = "60" KeyTime = "0:0:0"/>
<LinearDoubleKeyFrame Value = "120" KeyTime = "0:0:1"/>
<LinearDoubleKeyFrame Value = "200" KeyTime = "0:0:2"/>
<LinearDoubleKeyFrame Value = "300" KeyTime = "0:0:3"/>
</DoubleAnimationUsingKeyFrames>
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty = "Height"
Duration = "0:0:4">
<LinearDoubleKeyFrame Value = "30" KeyTime = "0:0:0"/>
<LinearDoubleKeyFrame Value = "40" KeyTime = "0:0:1"/>
<LinearDoubleKeyFrame Value = "80" KeyTime = "0:0:2"/>
<LinearDoubleKeyFrame Value = "150" KeyTime = "0:0:3"/>
</DoubleAnimationUsingKeyFrames>
</Storyboard>
</BeginStoryboard>
</EventTrigger.Actions>
</EventTrigger>
</Button.Triggers>
</Button>
</Grid>
</Window>当你编译并执行以上代码时，它将产生以下窗口：
点击此按钮后，您将观察到它将开始按两个维度展开。
我们建议您编译并执行以上示例，并且将触发器应用于其他属性。