Xamarin Forms Label - Justify?

问题

I just wanted to ask if there is any way to justify text in a Label. I am using Xamarin Forms Xaml.

Thanks.

UPDATE: As for now, it is not possible to justify text. Most of the answers were about centering the text, but it is not what I asked. One way could be to use Renderer as by Timothy.

回答1:

Though you can't stretch label's text to a full width using Xamarin.Forms features, it's easily achieved with a platform renderer.

Most Xamarin platforms have the text justification feature available in corresponding native elements, and it's just a matter of setting a single attribute of a native element. I suppose the reason for not adding this feature to standard Xamarin.Forms label is lagging of platforms in that capability, e.g. Android had Android.Text.JustificationMode.InterWord flag added only in version 8.1

Below you can see Android renderer implementation:

using Android.Content;
using Saplin.CPDT.UICore.Controls;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[assembly: ExportRenderer(typeof(Saplin.CPDT.UICore.Controls.ExtendedLabel), typeof(Saplin.CPDT.Droid.ExtnededLabelRenderer))]
namespace Saplin.CPDT.Droid
{
    public class ExtnededLabelRenderer : Xamarin.Forms.Platform.Android.LabelRenderer
    {
        public ExtnededLabelRenderer(Context context) : base(context)
        {
        }

        protected override void OnElementChanged(ElementChangedEventArgs<Label> e)
        {
            base.OnElementChanged(e);

            var el = (Element as ExtendedLabel);

            if (el != null && el.JustifyText)
            {
                if (Android.OS.Build.VERSION.SdkInt >= Android.OS.BuildVersionCodes.O)
                {
                    Control.JustificationMode = Android.Text.JustificationMode.InterWord;
                }

            }
        }
    }
}

Your create renderer class in native project
You add assembly: ExportRenderer attribute
You set TextView's JustificationMode

In my example I used ExtenedLabel subclass of Xamarin.Forms.Label with extra property JustifyText to let setting the justification of the text. That's how the subclassed control can be declared:

using System;
using Xamarin.Forms;

namespace Saplin.CPDT.UICore.Controls
{
    public class ExtendedLabel : Label
    {
        public static readonly BindableProperty JustifyTextProperty =
            BindableProperty.Create(
                propertyName: nameof(JustifyText),
                returnType: typeof(Boolean),
                declaringType: typeof(ExtendedLabel),
                defaultValue: false,
                defaultBindingMode: BindingMode.OneWay
         );

        public bool JustifyText
        {
            get { return (Boolean)GetValue(JustifyTextProperty); }
            set { SetValue(JustifyTextProperty, value); }
        }
    }
}

Examples of platform renderers for WPF and macOS.

回答2:

The current way to do this is by using HorizontalTextAlignment and the values for the TextAlignment enumeration are:

Center = Center-aligned text
Start = Left-aligned
End = Right-aligned

Center a label and its text example:

<Label x:Name="Description" HorizontalTextAlignment="Center" VerticalOptions="Center" HorizontalOptions="Center" />

回答3:

Use the XAlign property

Label lbl = new Label();
lbl.Text = "I'm a Label!";
lbl.XAlign = TextAligntment.Start; // Start, Center, End are valid

回答4:

What sort of container are you using to hold the text? Having a StackLayout with HorizontalOptions of FillAndExpand, along with the XAlign, might do it, but only if your text is only one line long per control.

回答5:

Try this:

<StackLayout HorizontalOptions="FillAndExpand" Padding="0, 10, 0, 10" Spacing="0">
      <Label Text="Test message" XAlign="Center"/>
      <Label FontSize="Small" Text="Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat." LineBreakMode="WordWrap"
XAlign="Center" />
</StackLayout>

回答6:

If you use the Label under relativeLayout you can justify the label..

The trick is you must fill the width & height as per parent..

So I use HeightConstraint,WidthConstraint with factor=1.. so it take full width & height of the parent..

  <RelativeLayout >

    <Label Text="My text"
           FontSize="20" 
           HorizontalOptions="Center" 
           VerticalOptions="Center"
           RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent,Property=Height,Factor=1,Constant=0}"
           RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent,Property=Width,Factor=1,Constant=0}" />
  </RelativeLayout>

回答7:

As it can't be done directly within a label, a workaround is to use the new FlexLayout from Xamarin.Forms 3. The idea is to split the text at space character and insert corresponding label in the FlexLayout with JustifyContent set to SpaceBetween.

Example :

XAML

<Frame
    HorizontalOptions="Center"
    Margin="20,50,20,0"
    Padding="10"
    WidthRequest="300"
    HasShadow="true">
    <FlexLayout
        x:Name="TextContainer"
        Direction="Row"
        AlignItems="End"
        JustifyContent="SpaceBetween"
        Wrap="Wrap"/>
</Frame>

Code behind

var textparts = "This is a long text to be justified"
                .Split(' ', StringSplitOptions.RemoveEmptyEntries)
                .Select(x => new Label
                {
                    Text = x,
                    FontSize = 12,
                    TextColor = Color.FromHex("#555555"),
                    Margin = new Thickness(1, 0)
                });

            foreach (var textpart in textparts)
                TextContainer.Children.Add(textpart);

来源：https://stackoverflow.com/questions/30062368/xamarin-forms-label-justify

标签

xaml

Xamarin

label

text-alignment

justify