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WPF日常开发,经常遇到默认的控件功能不满足需求,怎么办?
No1. 自定义控件模板
平时开发中,经常遇到比较”俗“的需求,嫌弃控件默认的样子。怎么办?哈哈,那就整个容呗..... !
还记得心灵深处的Button吗?是不是第一印象就是规规矩矩的长方形,好了,这次我们俗一下,把它变成圆形!
上代码:
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<Button Content= "Test1" Width= "80" Height= "80" FocusVisualStyle= "{x:Null}" Background= "LightSeaGreen" BorderBrush= "DarkBlue" > <Button.Template> <ControlTemplate TargetType= "ButtonBase" > <Grid> <Ellipse x:Name= "ellipseBorder" StrokeThickness= "1" Stroke= "{TemplateBinding BorderBrush}" Fill= "{TemplateBinding Background}" /> <ContentPresenter HorizontalAlignment= "Center" VerticalAlignment= "Center" Content= "{TemplateBinding Content}" /> </Grid> <ControlTemplate.Triggers> <Trigger Property= "IsMouseOver" Value= "True" > <Setter Property= "Stroke" Value= "Orange" TargetName= "ellipseBorder" /> </Trigger> <Trigger Property= "IsPressed" Value= "True" > <Setter Property= "Stroke" Value= "OrangeRed" TargetName= "ellipseBorder" /> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </Button.Template> </Button> |
上外表:
No2. 重写控件
很多情况下,并不是把控件换个外貌就可以解决的,我们不仅要改变外貌,还要改变控件的功能,比如说我们经常用的TextBox控件,正常的功能就是用来输入的,但更人性化点,我们想要TextBox能告诉我们当前的文本框应该输入用户名呢,还是地址呢等等。其实这个就是我们经常看到的水印功能,水印文字肯定要能按需设置,那我们不可能简单的通过改变下控件模板就可以解决的。
通过需求我们知道,新的带水印的文本框,至少有个水印这么个依赖属性,供外部设置。当然新的带水印文本框和TextBox大概的样子差不多,但我们也要为新的控件定义外貌。
所以第一步,先定义控件的功能,上代码:
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public class WaterMarkTextBox : TextBox { static WaterMarkTextBox() { DefaultStyleKeyProperty.OverrideMetadata( typeof (WaterMarkTextBox), new FrameworkPropertyMetadata( typeof (WaterMarkTextBox))); } public string WaterMark { get { return ( string )GetValue(WaterMarkProperty); } set { SetValue(WaterMarkProperty, value); } } // Using a DependencyProperty as the backing store for WaterMark. This enables animation, styling, binding, etc... public static readonly DependencyProperty WaterMarkProperty = DependencyProperty.Register( "WaterMark" , typeof ( string ), typeof (WaterMarkTextBox), new PropertyMetadata( null )); } |
第二步,再定义控件的样子,上代码:
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<Style TargetType= "{x:Type local:WaterMarkTextBox}" > <Setter Property= "BorderBrush" Value= "Black" /> <Setter Property= "BorderThickness" Value= "1" /> <Setter Property= "VerticalContentAlignment" Value= "Center" /> <Setter Property= "Template" > <Setter.Value> <ControlTemplate TargetType= "{x:Type local:WaterMarkTextBox}" > <Grid> <Border Background= "{TemplateBinding Background}" BorderBrush= "{TemplateBinding BorderBrush}" BorderThickness= "{TemplateBinding BorderThickness}" > </Border> <ScrollViewer x:Name= "PART_ContentHost" Grid.Column= "0" Margin= "0" Padding= "{TemplateBinding Padding}" VerticalAlignment= "Stretch" Background= "{x:Null}" BorderThickness= "0" IsTabStop= "False" SnapsToDevicePixels= "{TemplateBinding SnapsToDevicePixels}" /> <TextBlock x:Name= "PART_Message" Margin= "4 0" Padding= "{TemplateBinding Padding}" HorizontalAlignment= "{TemplateBinding HorizontalContentAlignment}" VerticalAlignment= "Center" Foreground= "Gray" Text= "{TemplateBinding WaterMark}" Visibility= "Collapsed" /> </Grid> <ControlTemplate.Triggers> <DataTrigger Binding= "{Binding RelativeSource={RelativeSource Self}, Path=Text}" Value= "" > <Setter TargetName= "PART_Message" Property= "Visibility" Value= "Visible" /> </DataTrigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter> </Style> |
请注意Name为PART_Message的TextBlock就是用来呈现水印提示消息的,同时加了个触发器,实现这样的功能:如果未输入任何内容,则显示水印,否则就隐藏水印。
控件使用,上代码:
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<local:WaterMarkTextBox Margin= "20,0,0,0" Width= "200" Height= "50" WaterMark= "Please Input your name" /> |
上效果:
No3. 附加属性来试试
重写控件看似很完美了,真的是这样吗?
好了,我的需求又来了,现在文本框提示很perfect,可是我的密码框PasswordBox也要搞个水印啊?怎么办?再重写个带水印的密码框?此时有没有做相同事情的感觉?作为合格的码农,我们还是要牢记码农界的警世名言:Don't Repeat Yourself!
此时请回忆下WPF的经典知识点:
控件A放到Grid中,A要支持设置行和列,控件B放到Grid中,B也要支持设置行和列。教程中已经告诉我们不要傻不拉几在A和B中都去定义行和列的属性,否则后续C、D......没完没了。
此时就是我们应用附加属性的时候了,在Grid中定义统一的行和列的附加属性,然后附加应用到A、B上就可以了。
反过来看看我们现在的需求,是不是一样的套路?我是不是在个公共的地方定义个水印WaterMark附加属性,然后分别应用到文本框和密码框就可以了?说对了一半,因为我们文本框和密码框老的外表没有显示水印的地方,所以我们同时还要重新定义下他们的新外表。
话不多说,先上附加属性定义的代码:
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public class WaterMarkHelper { public static string GetWaterMark(DependencyObject obj) { return ( string )obj.GetValue(WaterMarkProperty); } public static void SetWaterMark(DependencyObject obj, string value) { obj.SetValue(WaterMarkProperty, value); } public static readonly DependencyProperty WaterMarkProperty = DependencyProperty.RegisterAttached( "WaterMark" , typeof ( string ), typeof (WaterMarkHelper), new PropertyMetadata( null )); } |
上TextBox新的样式:
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<Style x:Key= "TextBoxWithWaterMark" TargetType= "{x:Type TextBox}" > <Setter Property= "BorderBrush" Value= "Black" /> <Setter Property= "BorderThickness" Value= "1" /> <Setter Property= "VerticalContentAlignment" Value= "Center" /> <Setter Property= "Template" > <Setter.Value> <ControlTemplate TargetType= "{x:Type TextBox}" > <Grid> <Border Background= "{TemplateBinding Background}" BorderBrush= "{TemplateBinding BorderBrush}" BorderThickness= "{TemplateBinding BorderThickness}" > </Border> <ScrollViewer x:Name= "PART_ContentHost" Grid.Column= "0" Margin= "0" Padding= "{TemplateBinding Padding}" VerticalAlignment= "Stretch" Background= "{x:Null}" BorderThickness= "0" IsTabStop= "False" SnapsToDevicePixels= "{TemplateBinding SnapsToDevicePixels}" /> <TextBlock x:Name= "PART_Message" Margin= "4 0" Padding= "{TemplateBinding Padding}" HorizontalAlignment= "{TemplateBinding HorizontalContentAlignment}" VerticalAlignment= "Center" Foreground= "Gray" Text= "{TemplateBinding local:WaterMarkHelper.WaterMark}" Visibility= "Collapsed" /> </Grid> <ControlTemplate.Triggers> <DataTrigger Binding= "{Binding RelativeSource={RelativeSource Self}, Path=Text}" Value= "" > <Setter TargetName= "PART_Message" Property= "Visibility" Value= "Visible" /> </DataTrigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter> </Style> |
请和自定义控件中的样式对比下,其实就是PART_Message对应控件的Text绑定的不一样了,这样绑定的是TextBox的附加属性WaterMarkHelper.WaterMark
上应用代码:
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<TextBox Style= "{StaticResource TextBoxWithWaterMark}" Margin= "20,0,0,0" Width= "200" Height= "50" local:WaterMarkHelper.WaterMark= "Please Input your name" /> |
请注意,这样要手动明确应用定义的样式资源!
上效果:
课后作业:请依葫芦画瓢,实现PasswordBox的水印功能
总结
除了这里列举的三种方式,其实还可以通过Behavior行为功能,扩展一个控件的功能,比如著名的拖拽功能!写到这里,我想总结的是:工欲善其事必先利其器!
当我们基础扎实之后,我们真的可以跳出栅栏,灵活应用!
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原文链接:https://www.cnblogs.com/liuww/p/15021857.html