Probably a simple question but:
可能是一个简单的问题,但是
How do I programmatically change the color of an ellipse that is defined in XAML based on a variable?
如何以编程方式更改基于变量在XAML中定义的椭圆的颜色?
Everything I've read on binding is based on collections and lists -can't I set it simply (and literally) based on the value of a string variable? string color = "red" color = "#FF0000"
我在绑定上读到的所有内容都是基于集合和列表的——难道我不能简单地(从字面上)基于字符串变量的值来设置它吗?string color = "red" color = "#FF0000"
3 个解决方案
#1
16
It's worth pointing out that the converter the other posts reference already exists, which is why you can do <Ellipse Fill="red">
in xaml in the first place. The converter is System.Windows.Media.BrushConverter
:
值得指出的是,其他post引用的转换器已经存在,这就是为什么您可以首先在xaml中执行
BrushConverter bc = new BrushConverter();
Brush brush = (Brush) bc.ConvertFrom("Red");
The more efficient way is to use the full syntax:
更有效的方法是使用完整的语法:
myEllipse.Fill = new SolidColorBrush(Colors.Red);
EDIT in response to -1 and comments:
编辑回应-1和评论:
The code above works perfectly fine in code, which is what the original question was asking about. You also don't want an IValueConverter
- these are typically used for binding scenarios. A TypeConverter
is the right solution here (because you're one-way converting a string to a brush). See this article for details.
上面的代码在代码中工作得非常好,这正是最初的问题所在。您也不需要IValueConverter——这些通常用于绑定场景。TypeConverter是正确的解决方案(因为您是单向的将字符串转换为画笔)。有关细节,请参阅本文。
Further edit (having reread Aviad's comment): you don't need to explicitly use the TypeConverter
in Xaml - it's used for you. If I write this in Xaml:
进一步编辑(重读Aviad的评论):您不需要在Xaml中显式地使用TypeConverter——它是为您使用的。如果我用Xaml写:
<Ellipse Fill="red">
... then the runtime automagically uses a BrushConverter
to turn the string literal into a brush. That Xaml is essentially converted into the equivalent longhand:
…然后运行时自动使用笔刷转换器将字符串文字转换为笔刷。Xaml本质上被转化为等价的longhand:
<Ellipse>
<Ellipse.Fill>
<SolidColorBrush Color="#FFFF0000" />
</Ellipse.Fill>
</Ellipse>
So you're right - you can't use it in Xaml - but you don't need to.
你是对的,你不能在Xaml中使用它,但你不需要。
Even if you had a string value that you wanted to bind in as the fill, you don't need to specify the converter manually. This test from Kaxaml:
即使您想要将一个字符串值绑定到填充,也不需要手动指定转换器。Kaxaml这个测试:
<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:s="clr-namespace:System;assembly=mscorlib">
<Page.Resources>
<s:String x:Key="col">Red</s:String>
</Page.Resources>
<StackPanel>
<Ellipse Width="20" Height="20" Fill="{Binding Source={StaticResource col}}" />
</StackPanel>
</Page>
Strangely, you can't just use the StaticResource col
and still have this work - but with the binding it and automatically uses the ValueConverter
to turn the string into a brush.
奇怪的是,您不能仅仅使用StaticResource col,而且仍然有这个工作——但是绑定它并自动使用ValueConverter将字符串转换成画笔。
#2
6
what you will need to do is implement a custom converter to convert the colour to the brush object. Something like this...
您需要做的是实现一个自定义转换器来将颜色转换为画笔对象。是这样的……
public class ColorToBrushConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
System.Drawing.Color col = (System.Drawing.Color)value;
Color c = Color.FromArgb(col.A, col.R, col.G, col.B);
return new System.Windows.Media.SolidColorBrush(c);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
SolidColorBrush c = (SolidColorBrush)value;
System.Drawing.Color col = System.Drawing.Color.FromArgb(c.Color.A, c.Color.R, c.Color.G, c.Color.B);
return col;
}
}
And then specify that converter in your binding
然后在绑定中指定该转换器
Fill="{Binding Colors.Red, Converter={StaticResource ColorToBrushConverter }"
#3
1
use
使用
"System.Windows.Media"
if the 'Name' of of your ellipse in your xaml is "my_ellipse", in your code something like this:
如果xaml中椭圆的“名称”是“my_ellipse”,那么在代码中应该是这样的:
my_ellipse.Fill = System.Windows.Media.Brushes.Red;
or this:
或:
my_ellipse.Fill = (SolidColorBrush)new BrushConverter().ConvertFromString("#F4F4F5")
#1
16
It's worth pointing out that the converter the other posts reference already exists, which is why you can do <Ellipse Fill="red">
in xaml in the first place. The converter is System.Windows.Media.BrushConverter
:
值得指出的是,其他post引用的转换器已经存在,这就是为什么您可以首先在xaml中执行
BrushConverter bc = new BrushConverter();
Brush brush = (Brush) bc.ConvertFrom("Red");
The more efficient way is to use the full syntax:
更有效的方法是使用完整的语法:
myEllipse.Fill = new SolidColorBrush(Colors.Red);
EDIT in response to -1 and comments:
编辑回应-1和评论:
The code above works perfectly fine in code, which is what the original question was asking about. You also don't want an IValueConverter
- these are typically used for binding scenarios. A TypeConverter
is the right solution here (because you're one-way converting a string to a brush). See this article for details.
上面的代码在代码中工作得非常好,这正是最初的问题所在。您也不需要IValueConverter——这些通常用于绑定场景。TypeConverter是正确的解决方案(因为您是单向的将字符串转换为画笔)。有关细节,请参阅本文。
Further edit (having reread Aviad's comment): you don't need to explicitly use the TypeConverter
in Xaml - it's used for you. If I write this in Xaml:
进一步编辑(重读Aviad的评论):您不需要在Xaml中显式地使用TypeConverter——它是为您使用的。如果我用Xaml写:
<Ellipse Fill="red">
... then the runtime automagically uses a BrushConverter
to turn the string literal into a brush. That Xaml is essentially converted into the equivalent longhand:
…然后运行时自动使用笔刷转换器将字符串文字转换为笔刷。Xaml本质上被转化为等价的longhand:
<Ellipse>
<Ellipse.Fill>
<SolidColorBrush Color="#FFFF0000" />
</Ellipse.Fill>
</Ellipse>
So you're right - you can't use it in Xaml - but you don't need to.
你是对的,你不能在Xaml中使用它,但你不需要。
Even if you had a string value that you wanted to bind in as the fill, you don't need to specify the converter manually. This test from Kaxaml:
即使您想要将一个字符串值绑定到填充,也不需要手动指定转换器。Kaxaml这个测试:
<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:s="clr-namespace:System;assembly=mscorlib">
<Page.Resources>
<s:String x:Key="col">Red</s:String>
</Page.Resources>
<StackPanel>
<Ellipse Width="20" Height="20" Fill="{Binding Source={StaticResource col}}" />
</StackPanel>
</Page>
Strangely, you can't just use the StaticResource col
and still have this work - but with the binding it and automatically uses the ValueConverter
to turn the string into a brush.
奇怪的是,您不能仅仅使用StaticResource col,而且仍然有这个工作——但是绑定它并自动使用ValueConverter将字符串转换成画笔。
#2
6
what you will need to do is implement a custom converter to convert the colour to the brush object. Something like this...
您需要做的是实现一个自定义转换器来将颜色转换为画笔对象。是这样的……
public class ColorToBrushConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
System.Drawing.Color col = (System.Drawing.Color)value;
Color c = Color.FromArgb(col.A, col.R, col.G, col.B);
return new System.Windows.Media.SolidColorBrush(c);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
SolidColorBrush c = (SolidColorBrush)value;
System.Drawing.Color col = System.Drawing.Color.FromArgb(c.Color.A, c.Color.R, c.Color.G, c.Color.B);
return col;
}
}
And then specify that converter in your binding
然后在绑定中指定该转换器
Fill="{Binding Colors.Red, Converter={StaticResource ColorToBrushConverter }"
#3
1
use
使用
"System.Windows.Media"
if the 'Name' of of your ellipse in your xaml is "my_ellipse", in your code something like this:
如果xaml中椭圆的“名称”是“my_ellipse”,那么在代码中应该是这样的:
my_ellipse.Fill = System.Windows.Media.Brushes.Red;
or this:
或:
my_ellipse.Fill = (SolidColorBrush)new BrushConverter().ConvertFromString("#F4F4F5")