[UWP]做个调皮的BusyIndicator

2018-03-01 07:47:33来源:cnblogs.com作者:dino.c人点击

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1. 前言

最近突然想要个BusyIndicator。做过WPF开发的程序员对BusyIndicator应该不陌生,Extended WPF Toolkit 提供了BusyIndicator的开源实现,Silverlight Toolkit也有一个,这次想要把这个控件移植到UWP中。

2. 先说点正经的

2.1 BusyIndicator的功能

BusyIndicator的功能很简单,就是提示正在执行操作并遮挡不能被修改的内容。通常它派生自ContentControl并提供public bool IsBusy{ get; set; }属性,当设置IsBusy=True时将Content.IsEnabled设置成False,并显示Overlay、BusyContent和一个ProgressBar。在Silverlight中,它的UI如下:

2.2 移植

Extended WPF Toolkit和Silverlight Toolkit中的BusyIndicator实现基本一致,由于Silverlight和各个XAML平台的兼容性都比较好,我选择了Silverlight Toolkit中的BusyIndicator用于移植。事实证明这是个正确的选择,只改动了几行代码就完美移植成功了。

2.3 改进

既然UWP有ProgressRing,我就不想用ProgressBar来展示Busy的状态。另外,虽然BusyIndicator的ControlTemplate已经够精简了,为了方便将来修改我再进一步简化了XAML,结果如下:

<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上绑定ContentTransitions属性。

UWP可以使用VisualState.Setters代替VisualState.Storyboard,这简化了大量XAML,为什么微软早十年没想到这个做法。

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 其它细节

<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,有一些细节是实现模板化控件需要注意的:

BusyContent
BusyContent没有在依赖属性定义中的PropertyMetadata给出默认值,而是在Setter中给出,这是模板化控件中依赖属性的最佳做法。PropertyMetadata的默认值应该尽量做到:值类型使用值类型的默认值,引用类型使用Null。

IsTabStop
已经不厌其烦地提醒过复合类型控件要将IsTabStop设置为False,以便在使用键盘导航时其内容可以直接获得焦点。

OverlayStyle和ProgressRingStyle
复合类型控件通常都会像这样为里面某个元素提供Style的属性,代替提供一大堆OverlayBackground,OverlayOpacity等属性。为了使用户清楚这两个Style属性对应的TargetType,可以在BusyIndicator的类型声明上使用StyleTypedPropertyAttribute:

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

IsTabStop和StyleTypedPropertyAttribute的介绍都可见我另一篇文章:了解模板化控件(9):UI指南

HorizontalContentAlignment和VerticalContentAlignment
使用ContentControl时几乎每次都要设置HorizontalContentAlignment和VerticalContentAlignment为Stretch,SilverlightToolkit中BusyIndicator的作者就很清楚这点。

这两个属性和BusyContent不同,并不是BusyIndicator定义的,而是从父类继承而来。像这种从父类继承而来的属性通常不会在构造函数中设置默认值,而是在DefaultStyle的Setter中设置默认值。

2.4 运行效果

就这样一个BusyIndicator就移植成功了。由于代码部分基本没有改变(除了ProgressBarStyle改成ProgressRingStyle),应该不会出什么大问题。运行效果如下:

<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. 来点调皮的

突然来了点兴致,于是就派生出新的控件ExtendBusyIndicator并新增public object BusyInformation{ get; set; }public object IdleInformation{ get; set; }两个属性,运行效果如下:

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="这个网页终于加载完了"                       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. 结语

BusyIndicator十分实用,毕竟已经经过多年的考验而代码基本没有更改,应该可以使用在UWP的实际项目中。

其实我个人不是很喜欢IsBusy就将Content.IsEnabled设置成False这么简单粗暴,因为这样内容会变成灰色。而且busyContent显示的过程应该是个透明度渐变的过程。这两个点使得执行很快的操作会令UI闪烁一下。而且ControlTemplate中ProgressRing和Overlay的父元素是一个叫busyContent的Grid,但BusyContent(注意大小些)是BusyIndicator的一个属性,内容是Busy状态下显示的文字内容,这样很容易让人混淆。幸运的是模板化控件最大的特色就是对修改UI是开放的,将来可以想办法修改。

ExtendBusyIndicator就算了,闹着玩的。

6. 参考

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

7. 源码

BusyIndicatorSample

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