WPF实现Element UI风格的日期时间选择器

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摘要

业务开发过程中遇到一个日期范围选择的需求，和Element UI的DateTimePicker组件比较类似，由两个日历控件组成，联动选择起始时间和结束时间。
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背景

业务开发过程中遇到一个日期范围选择的需求，和Element UI的DateTimePicker组件比较类似，由两个日历控件组成，联动选择起始时间和结束时间。

问题

WPF中提供了一个DatePicker的控件，主要由DatePickerTextBox、Button和一个Calendar组成，其中Calendar是后台代码动态添加的，因此不能直接通过自定义DatePicker的控件模板实现需求。这里通过实现自定义DateTimePicker控件来满足需求。

技术要点与实现

由于Calendar结构比较复杂，本文通过控件组合的方式简单实现自定义DateTimePicker。先来看下实现效果。
WPF实现Element UI风格的日期时间选择器

首先创建一个名为DateTimePicker的UserControl,添加依赖属性HoverStart和HoverEnd用于控制日历中的开始日期和结束日期，添加依赖属性DateTimeRangeStart和DateTimeRangeEnd用于设置外部设置/获取起始时间和结束时间。

然后在XAML中添加两个WatermarkTextBox用于输入起始时间和结束时间（增加校验规则验证时间的合法性，这里不再详细说明如何写校验规则，具体可参考ValidationRule实现参数绑定）。接着添加一个Popup(默认关闭)，并在其中添加两个Calendar用于筛选日期，以及四个ComboBox用于筛选小时和分钟。当WatermarkTextBox捕获到鼠标时触发Popup打开。

<Grid>     <Border Height="30" Width="320" BorderBrush="#c4c4c4" BorderThickness="1" CornerRadius="2">         <StackPanel x:Name="datetimeSelected" Orientation="Horizontal" Height="30">             <local:WatermarkTextBox x:Name="DateStartWTextBox" Style="{StaticResource DateWatermarkTextBoxStyle}" GotMouseCapture="WatermarkTextBox_GotMouseCapture">                 <local:WatermarkTextBox.Resources>                     <helper:BindingProxy x:Key="dateRangeCeiling" Data="{Binding Text,ElementName=DateEndWTextBox}"/>                 </local:WatermarkTextBox.Resources>                 <local:WatermarkTextBox.Text>                     <Binding Path="DateTimeRangeStart" ElementName="self" StringFormat="{}{0:yyyy-MM-dd HH:mm}" UpdateSourceTrigger="PropertyChanged">                         <Binding.ValidationRules>                             <helper:DateTimeValidationRule Type="Range">                                 <helper:ValidationParams Param1="{x:Static System:DateTime.Today}" Param2="{Binding Data,Source={StaticResource dateRangeCeiling}}"/>                             </helper:DateTimeValidationRule>                         </Binding.ValidationRules>                     </Binding>                 </local:WatermarkTextBox.Text>             </local:WatermarkTextBox>             <TextBlock Text="~"/>             <local:WatermarkTextBox x:Name="DateEndWTextBox" Style="{StaticResource DateWatermarkTextBoxStyle}" GotMouseCapture="WatermarkTextBox_GotMouseCapture">                 <local:WatermarkTextBox.Resources>                     <helper:BindingProxy x:Key="dateRangeFloor" Data="{Binding Text,ElementName=DateStartWTextBox}"/>                 </local:WatermarkTextBox.Resources>                 <local:WatermarkTextBox.Text>                     <Binding Path="DateTimeRangeEnd" ElementName="self" StringFormat="{}{0:yyyy-MM-dd HH:mm}" UpdateSourceTrigger="PropertyChanged">                         <Binding.ValidationRules>                             <helper:DateTimeValidationRule Type="Floor">                                 <helper:ValidationParams Param1="{Binding Data,Source={StaticResource dateRangeFloor}}"/>                             </helper:DateTimeValidationRule>                         </Binding.ValidationRules>                     </Binding>                 </local:WatermarkTextBox.Text>             </local:WatermarkTextBox>             <local:ImageButton Width="18" Height="18" Click="ImageButton_Click"                 HoverImage="/LBD_CLP_WPFControl;component/Images/calendar_hover.png"                 NormalImage="/LBD_CLP_WPFControl;component/Images/calendar.png" />         </StackPanel>     </Border>     <Popup x:Name="DatetimePopup" AllowsTransparency="True" StaysOpen="False" Placement="Top" VerticalOffset="-10" HorizontalOffset="-300" PlacementTarget="{Binding ElementName=datetimeSelected}" PopupAnimation="Slide">         <Grid Background="White" Margin="3">             <Grid.Effect>                 <DropShadowEffect Color="Gray"  BlurRadius="16"  ShadowDepth="3" Opacity="0.2" Direction="0" />             </Grid.Effect>             <Grid.RowDefinitions>                 <RowDefinition Height="*"/>                 <RowDefinition Height="42"/>                 <RowDefinition Height="42"/>             </Grid.RowDefinitions>             <StackPanel Orientation="Horizontal">                 <Calendar x:Name="startCalendar" DockPanel.Dock="Left"                             Style="{DynamicResource CalendarStyle}" SelectionMode="SingleRange" SelectedDatesChanged="Calendar_SelectedDatesChanged"/>                 <Line Y1="0" Y2="{Binding ActualHeight ,ElementName=startCalendar}" Stroke="#e4e4e4"/>                 <Calendar x:Name="endCalendar" DockPanel.Dock="Right"                             Style="{DynamicResource CalendarStyle}" SelectionMode="SingleRange" SelectedDatesChanged="Calendar_SelectedDatesChanged" DisplayDate="{Binding DisplayDate,ElementName=startCalendar,Converter={StaticResource DateTimeAddtionConverter},ConverterParameter=1}"/>             </StackPanel>             <Border Grid.Row="1" BorderThickness="0 0 0 1" BorderBrush="#e4e4e4">                 <StackPanel Orientation="Horizontal" TextElement.Foreground="#999999" TextElement.FontSize="14">                     <TextBlock Text="开始时间:" Margin="15 0 7 0"/>                     <ComboBox x:Name="startHours" Width="64" ItemStringFormat="{}{0:D2}" SelectionChanged="startHours_SelectionChanged"/>                     <TextBlock Text=":" Margin="5 0 5 0"/>                     <ComboBox x:Name="startMins" ItemStringFormat="{}{0:D2}" Width="64"/>                     <TextBlock Text="截止时间:" Margin="40 0 7 0"/>                     <ComboBox x:Name="endHours" ItemStringFormat="{}{0:D2}" Width="64"/>                     <TextBlock Text=":" Margin="5 0 5 0"/>                     <ComboBox x:Name="endMins" ItemStringFormat="{}{0:D2}" Width="64"/>                 </StackPanel>             </Border>             <StackPanel Grid.Row="2" Orientation="Horizontal" HorizontalAlignment="Right" Margin="0 0 11 0">                 <local:ImageButton x:Name="clearBtn" Style="{StaticResource ImageLinkButton}" Content="清空" FontSize="14" Foreground="#0099ff"                                     Click="clearBtn_Click"                                     NormalImage="{x:Null}"                                     HoverImage="{x:Null}"                                     DownImage="{x:Null}"                                     />                 <Button x:Name="yesBtn" Content="确定" Width="56" Height="28" Margin="12 0 0 0" Click="yesBtn_Click">                     <Button.Style>                         <Style TargetType="{x:Type Button}" BasedOn="{StaticResource BaseButtonStyle}">                             <Setter Property="BorderThickness" Value="1"/>                             <Setter Property="BorderBrush" Value="#dcdfe6"/>                             <Setter Property="Foreground" Value="#333333"/>                             <Setter Property="OverridesDefaultStyle" Value="True"/>                             <Setter Property="Template">                                 <Setter.Value>                                     <ControlTemplate TargetType="{x:Type Button}">                                         <Border x:Name="border" Background="Transparent" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="3" ClipToBounds="True">                                             <ContentPresenter                                              RecognizesAccessKey="True"                                             Margin="{TemplateBinding Padding}"                                             SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"                                             HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"                                              VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>                                         </Border>                                         <ControlTemplate.Triggers>                                             <MultiTrigger>                                                 <MultiTrigger.Conditions>                                                     <Condition Property="IsPressed" Value="false"/>                                                     <Condition Property="IsMouseOver" Value="true"/>                                                 </MultiTrigger.Conditions>                                                 <Setter Property="BorderBrush" Value="#409eff"/>                                                 <Setter Property="Foreground" Value="#409eff"/>                                             </MultiTrigger>                                         </ControlTemplate.Triggers>                                     </ControlTemplate>                                 </Setter.Value>                             </Setter>                         </Style>                     </Button.Style>                 </Button>             </StackPanel>         </Grid>     </Popup> </Grid>

紧接着就是修改Calendar的样式了。通常情况下，自定义控件模板只需要在Visual Studio的设计窗口或者Blend中选中控件，然后右键菜单中编辑模板即可。可能由于Calendar中的部分元素（CalendarButton和CalendarDayButton）是后台代码生成，这个方法编辑Calendar模板副本生成的CalendarStyle不包含完整的可视化树结构，无法对样式进一步修改。幸运的是微软官方文档公开了控件的默认样式和模板，在此基础上进行修改即可。通过官方文档可以发现Calendar完整的可视化树中包含了四个类型控件Calendar、CalendarItem、CalendarButton、CalendarDayButton。其中CalendarDayButton对应的就是日历中具体的“天”，管理着具体的“天”的状态，比如选中状态、不可选状态等，这也是我们主要修改的地方，接下来看下CalendarDayButton的样式。（其他几个元素的样式和模板参照官方文档修改即可）

<Style x:Key="CalendarDayButtonStyle" TargetType="{x:Type CalendarDayButton}">     <Setter Property="MinWidth" Value="5" />     <Setter Property="MinHeight" Value="5" />     <Setter Property="Width" Value="42"/>     <Setter Property="Height" Value="42"/>     <Setter Property="FontSize" Value="12" />     <Setter Property="HorizontalContentAlignment" Value="Center" />     <Setter Property="VerticalContentAlignment" Value="Center" />     <Setter Property="BorderThickness" Value="0"/>     <Setter Property="Template">         <Setter.Value>             <ControlTemplate TargetType="{x:Type CalendarDayButton}">                 <Grid Height="26" MouseUp="Grid_MouseUp">                     <Border x:Name="SelectedBackground" Background="#f2f6fc" Visibility="Collapsed">                         <Border.CornerRadius>                             <MultiBinding Converter="{StaticResource SelectedDatesConverter}">                                 <Binding/>                                 <Binding Path="HoverStart" RelativeSource="{RelativeSource AncestorType={x:Type local:DateTimePicker}}"/>                                 <Binding Path="HoverEnd" RelativeSource="{RelativeSource AncestorType={x:Type local:DateTimePicker}}"/>                             </MultiBinding>                         </Border.CornerRadius>                     </Border>                     <Grid Width="22" Height="22">                         <Rectangle x:Name="StartStopBackground" Fill="#409eff" RadiusX="11" RadiusY="11" >                             <Rectangle.Visibility>                                 <MultiBinding Converter="{StaticResource SelectedDatesConverter}">                                     <Binding/>                                     <Binding Path="HoverStart" RelativeSource="{RelativeSource AncestorType={x:Type local:DateTimePicker}}"/>                                     <Binding Path="HoverEnd" RelativeSource="{RelativeSource AncestorType={x:Type local:DateTimePicker}}"/>                                     <Binding Path="IsInactive" RelativeSource="{RelativeSource AncestorType={x:Type CalendarDayButton}}"/>                                 </MultiBinding>                             </Rectangle.Visibility>                         </Rectangle>                         <Border                         Background="{TemplateBinding Background}"                         BorderBrush="{TemplateBinding BorderBrush}"                         BorderThickness="{TemplateBinding BorderThickness}" />                         <Rectangle                         x:Name="HighlightBackground"                         Grid.ColumnSpan="2"                         Fill="#FFBADDE9"                         Opacity="0"                         RadiusX="11"                         RadiusY="11" />                         <ContentPresenter                         x:Name="NormalText"                         HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"                         VerticalAlignment="{TemplateBinding VerticalContentAlignment}"                         TextElement.Foreground="#FF333333" />                         <Path                         x:Name="Blackout"                         Grid.ColumnSpan="2"                         Margin="3"                         HorizontalAlignment="Stretch"                         VerticalAlignment="Stretch"                         Data="M8.1772461,11.029181 L10.433105,11.029181 L11.700684,12.801641 L12.973633,11.029181 L15.191895,11.029181 L12.844727,13.999395 L15.21875,17.060919 L12.962891,17.060919 L11.673828,15.256231 L10.352539,17.060919 L8.1396484,17.060919 L10.519043,14.042364 z"                         Fill="#FF000000"                         Opacity="0"                         RenderTransformOrigin="0.5,0.5"                         Stretch="Fill" />                         <Rectangle                         x:Name="DayButtonFocusVisual"                         Grid.ColumnSpan="2"                         IsHitTestVisible="false"                         RadiusX="11"                         RadiusY="1"                         Stroke="#FF45D6FA"                         Visibility="Collapsed" />                     </Grid>                 </Grid>                 <ControlTemplate.Triggers>                     <Trigger Property="IsInactive" Value="True">                         <Setter Property="Visibility" Value="Collapsed" TargetName="SelectedBackground"/>                         <Setter Property="TextElement.Foreground" Value="#c0c4cc" TargetName="NormalText"/>                     </Trigger>                     <Trigger Property="IsBlackedOut" Value="true">                         <Setter Property="Visibility" Value="Collapsed" TargetName="SelectedBackground"/>                         <Setter Property="TextElement.Foreground" Value="#c0c4cc" TargetName="NormalText"/>                     </Trigger>                     <MultiTrigger>                         <MultiTrigger.Conditions>                             <Condition Property="IsInactive" Value="false"/>                             <Condition Property="IsSelected" Value="true"/>                         </MultiTrigger.Conditions>                         <MultiTrigger.Setters>                             <Setter Property="Visibility" Value="Visible" TargetName="SelectedBackground"/>                         </MultiTrigger.Setters>                     </MultiTrigger>                     <MultiTrigger>                         <MultiTrigger.Conditions>                             <Condition Property="IsInactive" Value="false"/>                             <Condition Property="IsBlackedOut" Value="false"/>                             <Condition Property="IsMouseOver" Value="true"/>                         </MultiTrigger.Conditions>                         <MultiTrigger.Setters>                             <Setter Property="Opacity" Value="0.5" TargetName="HighlightBackground"/>                         </MultiTrigger.Setters>                     </MultiTrigger>                     <MultiTrigger>                         <MultiTrigger.Conditions>                             <Condition Property="IsInactive" Value="false"/>                             <Condition Property="IsToday" Value="true"/>                         </MultiTrigger.Conditions>                         <MultiTrigger.Setters>                             <Setter Property="TextElement.Foreground" Value="#409eff" TargetName="NormalText"/>                         </MultiTrigger.Setters>                     </MultiTrigger>                     <MultiTrigger>                         <MultiTrigger.Conditions>                             <Condition Property="IsInactive" Value="false"/>                             <Condition Property="Visibility" Value="Visible" SourceName="StartStopBackground"/>                         </MultiTrigger.Conditions>                         <MultiTrigger.Setters>                             <Setter Property="TextElement.Foreground" Value="#ffffff" TargetName="NormalText"/>                         </MultiTrigger.Setters>                     </MultiTrigger>                 </ControlTemplate.Triggers>             </ControlTemplate>         </Setter.Value>     </Setter> </Style>

样式中用到一个MultiBinding绑定CalendarDayButton以及前边提到的两个依赖属性：HoverStart和HoverEnd，然后通过MultiValueConverter转换器比较CalendarDayButton是否处于选中的日期范围，根据不同的状态设置其背景色和字体颜色。

最后就是在后台代码中根据日历的SelectedDatesChanged事件设置HoverStart和HoverEnd的值，以此来控制DateTimePicker中选中日期的样式。

总结

本文分享了一种简单实现自定义DateTimePicker控件的方式，同时也介绍了另外一种查看原生控件默认样式和模板的方法：查看微软官方文档。这种方法虽然不如在Visual Studio的设计窗口或者Blend中编辑模板副本方便，但提供了完整的结构、每个元素的组成部分以及可视化状态，方便开发人员清晰的了解控件全貌，可以应对修改复杂的原生控件样式和模板的需求。

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