这是我的代码:
<StackLayout>
<Label x:Name="emptyLabel1" FontSize="18" XAlign="Start" TextColor="Gray" />
<Label x:Name="emptyLabel2" FontSize="18" XAlign="Center" TextColor="Gray" />
<Label x:Name="emptyLabel3" FontSize="18" XAlign="Center" TextColor="Gray" />
</StackLayout>
第一个多行标签从左侧开始,但在右侧的某些行上有空格。第2和第3个多行标签居中,左右两侧各有空格。
有没有什么方法可以让所有标签行完全填满从左到右完全填充的行o每行的第一个字符总是在左边排列,每个行的最后一个字符的最后一个字符行总是排在右边?请注意,这将需要每行中的一些单词在它们之间具有不同的间隙。
答案 0 :(得分:19)
使用对齐支持实现标签有点棘手,但可以通过平台渲染器实现。
第一步是在表单项目中声明自定义控件。
public class JustifiedLabel : Label { }
下一步是在iOS中定义和注册平台渲染器。这个很简单,因为我们只是将formatted-string和paragraph-style结合起来得到我们想要的东西。
[assembly: ExportRenderer(typeof(JustifiedLabel), typeof(JustifiedLabelRenderer))]
namespace SomeAppNamespace.iOS
{
public class JustifiedLabelRenderer : LabelRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
{
base.OnElementChanged(e);
//if we have a new forms element, we want to update text with font style (as specified in forms-pcl) on native control
if (e.NewElement != null)
UpdateTextOnControl();
}
protected override void OnElementPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
//if there is change in text or font-style, trigger update to redraw control
if(e.PropertyName == nameof(Label.Text)
|| e.PropertyName == nameof(Label.FontFamily)
|| e.PropertyName == nameof(Label.FontSize)
|| e.PropertyName == nameof(Label.TextColor)
|| e.PropertyName == nameof(Label.FontAttributes))
{
UpdateTextOnControl();
}
}
void UpdateTextOnControl()
{
if (Control == null)
return;
//define paragraph-style
var style = new NSMutableParagraphStyle()
{
Alignment = UITextAlignment.Justified,
FirstLineHeadIndent = 0.001f,
};
//define attributes that use both paragraph-style, and font-style
var uiAttr = new UIStringAttributes()
{
ParagraphStyle = style,
BaselineOffset = 0,
Font = Control.Font
};
//define frame to ensure justify alignment is applied
Control.Frame = new RectangleF(0, 0, (float)Element.Width, (float)Element.Height);
//set new text with ui-style-attributes to native control (UILabel)
var stringToJustify = Control.Text ?? string.Empty;
var attributedString = new Foundation.NSAttributedString(stringToJustify, uiAttr.Dictionary);
Control.AttributedText = attributedString;
Control.Lines = 0;
}
}
}
在android平台上,它有点棘手 - 因为android不支持TextView
的对齐 - 所以我们需要使用WebView
代替它来渲染文本。
(注意:您也可以alternatively use an android library使用它代替WebView
)
[assembly: ExportRenderer(typeof(JustifiedLabel), typeof(JustifiedLabelRenderer))]
namespace SomeAppNamespace.Droid
{
//We don't extend from LabelRenderer on purpose as we want to set
// our own native control (which is not TextView)
public class JustifiedLabelRenderer : ViewRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<View> e)
{
base.OnElementChanged(e);
//if we have a new forms element, we want to update text with font style (as specified in forms-pcl) on native control
if (e.NewElement != null)
{
if (Control == null)
{
//register webview as native control
var webView = new Android.Webkit.WebView(Context);
webView.VerticalScrollBarEnabled = false;
webView.HorizontalScrollBarEnabled = false;
webView.LoadData("<html><body> </body></html>", "text/html; charset=utf-8", "utf-8");
SetNativeControl(webView);
}
//if we have a new forms element, we want to update text with font style (as specified in forms-pcl) on native control
UpdateTextOnControl();
}
}
protected override void OnElementPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
//if there is change in text or font-style, trigger update to redraw control
if (e.PropertyName == nameof(Label.Text)
|| e.PropertyName == nameof(Label.FontFamily)
|| e.PropertyName == nameof(Label.FontSize)
|| e.PropertyName == nameof(Label.TextColor)
|| e.PropertyName == nameof(Label.FontAttributes))
{
UpdateTextOnControl();
}
}
void UpdateTextOnControl()
{
var webView = Control as Android.Webkit.WebView;
var formsLabel = Element as Label;
// create css style from font-style as specified
var cssStyle = $"margin: 0px; padding: 0px; text-align: justify; color: {ToHexColor(formsLabel.TextColor)}; background-color: {ToHexColor(formsLabel.BackgroundColor)}; font-family: {formsLabel.FontFamily}; font-size: {formsLabel.FontSize}; font-weight: {formsLabel.FontAttributes}";
// apply that to text
var strData =
$"<html><body style=\"{cssStyle}\">{formsLabel?.Text}</body></html>";
// and, refresh webview
webView.LoadData(strData, "text/html; charset=utf-8", "utf-8");
webView.Reload();
}
// helper method to convert forms-color to css-color
string ToHexColor(Color color)
{
var red = (int)(color.R * 255);
var green = (int)(color.G * 255);
var blue = (int)(color.B * 255);
var alpha = (int)(color.A * 255);
var hex = $"#{red:X2}{green:X2}{blue:X2}";
return hex;
}
}
}
<StackLayout Margin="20">
<Entry x:Name="InputEntry" />
<Label Margin="0,10,0,0" BackgroundColor="Navy" TextColor="White" Text="Normal Text Label" FontSize="15" HorizontalOptions="CenterAndExpand" />
<Label
FontSize="20"
FontAttributes="Bold"
Text="{Binding Text, Source={x:Reference InputEntry}}" />
<Label Margin="0,10,0,0" BackgroundColor="Navy" TextColor="White" Text="Justified Text Label" FontSize="15" HorizontalOptions="CenterAndExpand" />
<local:JustifiedLabel
FontSize="20"
FontAttributes="Bold"
Text="{Binding Text, Source={x:Reference InputEntry}}"
TextColor="Green"
BackgroundColor="Yellow"
VerticalOptions="FillAndExpand"
HorizontalOptions="FillAndExpand" />
</StackLayout>
答案 1 :(得分:3)
答案 2 :(得分:0)
我从未见过任何简单的解决方案,只提到了here提及的解决方法。
您需要使用组件或为每个平台创建自己的解决方案。
答案 3 :(得分:0)
我很惊讶还没有人提出这个问题...
实现此效果的一种非常简单的方法是将标签封装在自己的StackLayout中,如下所示:
<StackLayout Orientation="Vertical" >
<Label Text="My Label" />
</StackLayout>