1. 前言

最近突然想要個(gè)BusyIndicator。做過(guò)WPF開(kāi)發(fā)的程序員對(duì)BusyIndicator應(yīng)該不陌生，Extended WPF Toolkit 提供了BusyIndicator的開(kāi)源實(shí)現(xiàn)，Silverlight Toolkit也有一個(gè)，這次想要把這個(gè)控件移植到UWP中。

2. 先說(shuō)點(diǎn)正經(jīng)的

2.1 BusyIndicator的功能

BusyIndicator的功能很簡(jiǎn)單，就是提示正在執(zhí)行操作并遮擋不能被修改的內(nèi)容。通常它派生自ContentControl并提供public bool IsBusy{ get; set; }屬性，當(dāng)設(shè)置IsBusy=True時(shí)將Content.IsEnabled設(shè)置成False，并顯示Overlay、BusyContent和一個(gè)ProgressBar。在Silverlight中，它的UI如下：

2.2 移植

Extended WPF Toolkit和Silverlight Toolkit中的BusyIndicator實(shí)現(xiàn)基本一致，由于Silverlight和各個(gè)XAML平臺(tái)的兼容性都比較好，我選擇了Silverlight Toolkit中的BusyIndicator用于移植。事實(shí)證明這是個(gè)正確的選擇，只改動(dòng)了幾行代碼就完美移植成功了。

2.3 改進(jìn)

既然UWP有ProgressRing，我就不想用ProgressBar來(lái)展示Busy的狀態(tài)。另外，雖然BusyIndicator的ControlTemplate已經(jīng)夠精簡(jiǎn)了，為了方便將來(lái)修改我再進(jìn)一步簡(jiǎn)化了XAML，結(jié)果如下：

<ContentControl x:Name="content"Content="{TemplateBinding Content}"ContentTemplate="{TemplateBinding ContentTemplate}"ContentTransitions="{TemplateBinding ContentTransitions}"HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" /> <Rectangle x:Name="overlay"Style="{TemplateBinding OverlayStyle}" /> <ContentPresenter x:Name="busycontent"><Grid HorizontalAlignment="Center"VerticalAlignment="Center"><Grid.RowDefinitions><RowDefinition /><RowDefinition Height="Auto" /></Grid.RowDefinitions><ProgressRing x:Name="ProgressRing"IsActive="True"Style="{TemplateBinding ProgressRingStyle}" /><ContentPresenter Content="{TemplateBinding BusyContent}"ContentTemplate="{TemplateBinding BusyContentTemplate}"Grid.Row="1"FontSize="15"HorizontalAlignment="Center"Foreground="{ThemeResource SystemControlHighlightAccentBrush}" /></Grid> </ContentPresenter>

和Silverlight/WPF不同的是，需要在ContentControl上綁定ContentTransitions屬性。

UWP可以使用VisualState.Setters代替VisualState.Storyboard，這簡(jiǎn)化了大量XAML，為什么微軟早十年沒(méi)想到這個(gè)做法。

Silverlight的BusyIndicator：

<VisualStateManager.VisualStateGroups><VisualStateGroup x:Name="VisibilityStates"><VisualState x:Name="Hidden"><Storyboard><ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.001" Storyboard.TargetName="busycontent" Storyboard.TargetProperty="(UIElement.Visibility)"><DiscreteObjectKeyFrame KeyTime="00:00:00"><DiscreteObjectKeyFrame.Value><Visibility>Collapsed</Visibility></DiscreteObjectKeyFrame.Value></DiscreteObjectKeyFrame></ObjectAnimationUsingKeyFrames><ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.001" Storyboard.TargetName="overlay" Storyboard.TargetProperty="(UIElement.Visibility)"><DiscreteObjectKeyFrame KeyTime="00:00:00"><DiscreteObjectKeyFrame.Value><Visibility>Collapsed</Visibility></DiscreteObjectKeyFrame.Value></DiscreteObjectKeyFrame></ObjectAnimationUsingKeyFrames></Storyboard></VisualState><VisualState x:Name="Visible"><Storyboard><ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.001" Storyboard.TargetName="busycontent" Storyboard.TargetProperty="(UIElement.Visibility)"><DiscreteObjectKeyFrame KeyTime="00:00:00"><DiscreteObjectKeyFrame.Value><Visibility>Visible</Visibility></DiscreteObjectKeyFrame.Value></DiscreteObjectKeyFrame></ObjectAnimationUsingKeyFrames><ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.001" Storyboard.TargetName="overlay" Storyboard.TargetProperty="(UIElement.Visibility)"><DiscreteObjectKeyFrame KeyTime="00:00:00"><DiscreteObjectKeyFrame.Value><Visibility>Visible</Visibility></DiscreteObjectKeyFrame.Value></DiscreteObjectKeyFrame></ObjectAnimationUsingKeyFrames></Storyboard></VisualState></VisualStateGroup><VisualStateGroup x:Name="BusyStatusStates"><VisualState x:Name="Idle"><Storyboard><ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.001" Storyboard.TargetName="content" Storyboard.TargetProperty="(Control.IsEnabled)"><DiscreteObjectKeyFrame KeyTime="00:00:00"><DiscreteObjectKeyFrame.Value><sys:Boolean>True</sys:Boolean></DiscreteObjectKeyFrame.Value></DiscreteObjectKeyFrame></ObjectAnimationUsingKeyFrames></Storyboard></VisualState><VisualState x:Name="Busy"><Storyboard><ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.001" Storyboard.TargetName="content" Storyboard.TargetProperty="(Control.IsEnabled)"><DiscreteObjectKeyFrame KeyTime="00:00:00"><DiscreteObjectKeyFrame.Value><sys:Boolean>False</sys:Boolean></DiscreteObjectKeyFrame.Value></DiscreteObjectKeyFrame></ObjectAnimationUsingKeyFrames></Storyboard></VisualState></VisualStateGroup> </VisualStateManager.VisualStateGroups>

UWP的BusyIndicator

<VisualStateManager.VisualStateGroups><VisualStateGroup x:Name="VisibilityStates"><VisualState x:Name="Hidden"><VisualState.Setters><Setter Target="overlay.(UIElement.Visibility)"Value="Collapsed" /><Setter Target="busycontent.(UIElement.Visibility)"Value="Collapsed" /></VisualState.Setters></VisualState><VisualState x:Name="Visible" /></VisualStateGroup><VisualStateGroup x:Name="BusyStatusStates"><VisualState x:Name="Idle" /><VisualState x:Name="Busy"><VisualState.Setters><Setter Target="content.(Control.IsEnabled)"Value="False" /></VisualState.Setters></VisualState></VisualStateGroup> </VisualStateManager.VisualStateGroups>

2.3 其它細(xì)節(jié)

<Setter Property="BusyContent"Value="Please wait..." /> <Setter Property="IsTabStop"Value="False" /> <Setter Property="OverlayStyle"><Setter.Value><Style TargetType="Rectangle"><Setter Property="Fill"Value="{ThemeResource ApplicationForegroundThemeBrush}" /><Setter Property="Opacity"Value="0.2" /></Style></Setter.Value> </Setter> <Setter Property="ProgressRingStyle"><Setter.Value><Style TargetType="ProgressRing"><Setter Property="Height"Value="50" /><Setter Property="Width"Value="50" /><Setter Property="Margin"Value="8,8,8,0" /></Style></Setter.Value> </Setter> <Setter Property="DisplayAfter"Value="00:00:00.1" /> <Setter Property="HorizontalAlignment"Value="Stretch" /> <Setter Property="VerticalAlignment"Value="Stretch" /> <Setter Property="HorizontalContentAlignment"Value="Stretch" /> <Setter Property="VerticalContentAlignment"Value="Stretch" />

上面是BusyIndicator DefaultStyle的Setters，有一些細(xì)節(jié)是實(shí)現(xiàn)模板化控件需要注意的：

BusyContent
BusyContent沒(méi)有在依賴屬性定義中的PropertyMetadata給出默認(rèn)值，而是在Setter中給出，這是模板化控件中依賴屬性的最佳做法。PropertyMetadata的默認(rèn)值應(yīng)該盡量做到：值類型使用值類型的默認(rèn)值，引用類型使用Null。

IsTabStop
已經(jīng)不厭其煩地提醒過(guò)復(fù)合類型控件要將IsTabStop設(shè)置為False，以便在使用鍵盤導(dǎo)航時(shí)其內(nèi)容可以直接獲得焦點(diǎn)。

OverlayStyle和ProgressRingStyle
復(fù)合類型控件通常都會(huì)像這樣為里面某個(gè)元素提供Style的屬性，代替提供一大堆OverlayBackground，OverlayOpacity等屬性。為了使用戶清楚這兩個(gè)Style屬性對(duì)應(yīng)的TargetType，可以在BusyIndicator的類型聲明上使用StyleTypedPropertyAttribute：

[StyleTypedProperty(Property = "OverlayStyle", StyleTargetType = typeof(Rectangle))] [StyleTypedProperty(Property = "ProgressRingStyle", StyleTargetType = typeof(ProgressRing))]

IsTabStop和StyleTypedPropertyAttribute的介紹都可見(jiàn)我另一篇文章：了解模板化控件(9)：UI指南

HorizontalContentAlignment和VerticalContentAlignment
使用ContentControl時(shí)幾乎每次都要設(shè)置HorizontalContentAlignment和VerticalContentAlignment為Stretch，SilverlightToolkit中BusyIndicator的作者就很清楚這點(diǎn)。

這兩個(gè)屬性和BusyContent不同，并不是BusyIndicator定義的，而是從父類繼承而來(lái)。像這種從父類繼承而來(lái)的屬性通常不會(huì)在構(gòu)造函數(shù)中設(shè)置默認(rèn)值，而是在DefaultStyle的Setter中設(shè)置默認(rèn)值。

2.4 運(yùn)行效果

就這樣一個(gè)BusyIndicator就移植成功了。由于代碼部分基本沒(méi)有改變（除了ProgressBarStyle改成ProgressRingStyle），應(yīng)該不會(huì)出什么大問(wèn)題。運(yùn)行效果如下：

<busyIndicatorSample:BusyIndicator x:Name="BusyIndicator"><Button HorizontalAlignment="Center"VerticalAlignment="Center"Content="Login"Click="Button_Click"Margin="0,0,0,150" /> </busyIndicatorSample:BusyIndicator> private async void Button_Click(object sender, RoutedEventArgs e) {BusyIndicator.IsBusy = true;await Task.Delay(TimeSpan.FromSeconds(3));BusyIndicator.IsBusy = false; }

3. 來(lái)點(diǎn)調(diào)皮的

突然來(lái)了點(diǎn)興致，于是就派生出新的控件ExtendBusyIndicator并新增public object BusyInformation{ get; set; }和public object IdleInformation{ get; set; }兩個(gè)屬性，運(yùn)行效果如下：

XAML:

<busyIndicatorSample:ExtendBusyIndicator x:Name="BusyIndicator"Background="White"><busyIndicatorSample:ExtendBusyIndicator.BusyInformation><StackPanel><TextBlock Text="十年后"HorizontalAlignment="Center" /><TextBlock Text="10 years later"HorizontalAlignment="Center"Margin="0,2,0,0" /></StackPanel></busyIndicatorSample:ExtendBusyIndicator.BusyInformation><busyIndicatorSample:ExtendBusyIndicator.IdleInformation><StackPanel><TextBlock Text="這個(gè)網(wǎng)頁(yè)終于加載完了"HorizontalAlignment="Center" /><TextBlock Text="the Web page finally finished loading."HorizontalAlignment="Center"Margin="0,2,0,0" /></StackPanel></busyIndicatorSample:ExtendBusyIndicator.IdleInformation><Button Style="{StaticResource ButtonRevealStyle}"Padding="0"HorizontalAlignment="Center"Background="Transparent"Margin="0,0,0,150"Click="Button_Click"><Image Source="logo1.png"Width="80" /></Button> </busyIndicatorSample:ExtendBusyIndicator>

4. 莓良心的

5. 結(jié)語(yǔ)

BusyIndicator十分實(shí)用，畢竟已經(jīng)經(jīng)過(guò)多年的考驗(yàn)而代碼基本沒(méi)有更改，應(yīng)該可以使用在UWP的實(shí)際項(xiàng)目中。

其實(shí)我個(gè)人不是很喜歡IsBusy就將Content.IsEnabled設(shè)置成False這么簡(jiǎn)單粗暴，因?yàn)檫@樣內(nèi)容會(huì)變成灰色。而且busyContent顯示的過(guò)程應(yīng)該是個(gè)透明度漸變的過(guò)程。這兩個(gè)點(diǎn)使得執(zhí)行很快的操作會(huì)令UI閃爍一下。而且ControlTemplate中ProgressRing和Overlay的父元素是一個(gè)叫busyContent的Grid，但BusyContent（注意大小些）是BusyIndicator的一個(gè)屬性，內(nèi)容是Busy狀態(tài)下顯示的文字內(nèi)容，這樣很容易讓人混淆。幸運(yùn)的是模板化控件最大的特色就是對(duì)修改UI是開(kāi)放的，將來(lái)可以想辦法修改。

ExtendBusyIndicator就算了，鬧著玩的。

6. 參考

Extended WPF Toolkit
Silverlight Toolkit - CodePlex Archive
UWP BusyIndicator · telerik UI For UWP

7. 源碼

BusyIndicatorSample

轉(zhuǎn)載于:https://www.cnblogs.com/dino623/p/BusyIndicator.html

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