按钮水平和垂直文本对齐答案

【问题标题】：Button Horizontal and Vertical Text Alignment按钮水平和垂直文本对齐
【发布时间】：2020-09-29 11:30:37
【问题描述】：

请帮我制作 VerticalTextAlignment 和 HorisontalTextAlignment 我使用这个网站，但我不知道如何添加 VerticalTextAlignment

https://forums.xamarin.com/discussion/58774/button-horizontal-text-alignment

这个例子没有用

How to change Text Alignment of button on Android (Xamarin Forms)?

我使用 1 个站点，它可以工作，请帮助将 VerticalTextAlignment 添加到第一个代码

public class ExtendedButton : Xamarin.Forms.Button
{
    public static BindableProperty HorizontalTextAlignmentProperty = BindableProperty.Create<ExtendedButton, Xamarin.Forms.TextAlignment>(x => x.HorizontalTextAlignment, Xamarin.Forms.TextAlignment.Center);
    public Xamarin.Forms.TextAlignment HorizontalTextAlignment
    {
        get
        {
            return (Xamarin.Forms.TextAlignment)GetValue(HorizontalTextAlignmentProperty);
        }
        set
        {
            SetValue(HorizontalTextAlignmentProperty, value);
        }
    }
}

安卓

[assembly:ExportRenderer(typeof(ExtendedButton), typeof(ExtendedButtonRenderer)]
namespace SomeNamespace.Droid
{
    public class ExtendedButtonRenderer : Xamarin.Forms.Platform.Android.AppCompat.ButtonRenderer
    {
        public new ExtendedButton Element
        {
            get
            {
                return (ExtendedButton)base.Element;
            }
        }

        protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
        {
            base.OnElementChanged(e);

            if (e.NewElement == null)
            {
                return;
            }

            SetTextAlignment();
        }

        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);

            if (e.PropertyName == ExtendedButton.HorizontalTextAlignmentProperty.PropertyName)
            {
                SetTextAlignment();
            }
        }

        public void SetTextAlignment()
        {
            Control.Gravity = Element.HorizontalTextAlignment.ToHorizontalGravityFlags();
        }
    }

    public static class AlignmentHelper
    {
        public static GravityFlags ToHorizontalGravityFlags(this Xamarin.Forms.TextAlignment alignment)
        {
            if (alignment == Xamarin.Forms.TextAlignment.Center)
                return GravityFlags.AxisSpecified;
            return alignment == Xamarin.Forms.TextAlignment.End ? GravityFlags.Right : GravityFlags.Left;
        }
    }
}

【问题讨论】：

我添加了我的问题
如果您不向我们展示您的代码，我们将无法帮助您
我添加了有问题的代码

标签： c# xaml xamarin xamarin.forms xamarin.android

【解决方案1】：

您也可以使用这种方式为ExtendedButton添加VerticalTextAlignmentProperty，如下：

public class ExtendedButton:Button
{
  
    public static BindableProperty HorizontalTextAlignmentProperty = BindableProperty.Create<ExtendedButton, Xamarin.Forms.TextAlignment>(x => x.HorizontalTextAlignment, Xamarin.Forms.TextAlignment.Center);
    public Xamarin.Forms.TextAlignment HorizontalTextAlignment
    {
        get
        {
            return (Xamarin.Forms.TextAlignment)GetValue(HorizontalTextAlignmentProperty);
        }
        set
        {
            SetValue(HorizontalTextAlignmentProperty, value);
        }
    }


    public static BindableProperty VerticalTextAlignmentProperty = BindableProperty.Create<ExtendedButton, Xamarin.Forms.TextAlignment>(x => x.VerticalTextAlignment, Xamarin.Forms.TextAlignment.Center);
    public Xamarin.Forms.TextAlignment VerticalTextAlignment
    {
        get
        {
            return (Xamarin.Forms.TextAlignment)GetValue(VerticalTextAlignmentProperty);
        }
        set
        {
            SetValue(VerticalTextAlignmentProperty, value);
        }
    }
}

然后ExtendedButtonRenderer修改如下：

[assembly: ExportRenderer(typeof(ExtendedButton), typeof(ExtendedButtonRenderer))]
namespace XamrinTemp.Droid
{
    [Obsolete]
    public class ExtendedButtonRenderer : ButtonRenderer
    {
        public new ExtendedButton Element
        {
            get
            {
                return (ExtendedButton)base.Element;
            }
        }

        protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
        {
            base.OnElementChanged(e);
            if (e.NewElement == null)
            {
                return;
            }

            SetHorizonalTextAlignment();
            SetVerticalTextAlignment();
        }

        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);
            if (e.PropertyName == ExtendedButton.HorizontalTextAlignmentProperty.PropertyName)
            {
                SetHorizonalTextAlignment();
            }

            if (e.PropertyName == ExtendedButton.VerticalTextAlignmentProperty.PropertyName)
            {
                SetVerticalTextAlignment();
            }
        }

        private void SetHorizonalTextAlignment()
        {
            Control.Gravity = Element.HorizontalTextAlignment.ToHorizontalGravityFlags() | Element.VerticalTextAlignment.ToVerticalGravityFlags();
        }

        private void SetVerticalTextAlignment()
        {
            Control.Gravity = Element.VerticalTextAlignment.ToVerticalGravityFlags() | Element.HorizontalTextAlignment.ToHorizontalGravityFlags();
        }
    }

    public static class AlignmentHelper
    {
        public static GravityFlags ToHorizontalGravityFlags(this Xamarin.Forms.TextAlignment alignment)
        {
            if (alignment == Xamarin.Forms.TextAlignment.Center)
                return GravityFlags.CenterHorizontal;
            return alignment == Xamarin.Forms.TextAlignment.End ? GravityFlags.Right : GravityFlags.Left;
        }

        public static GravityFlags ToVerticalGravityFlags(this Xamarin.Forms.TextAlignment alignment)
        {
            if (alignment == Xamarin.Forms.TextAlignment.Center)
                return GravityFlags.CenterVertical;
            return alignment == Xamarin.Forms.TextAlignment.End ? GravityFlags.Top : GravityFlags.Bottom;
        }
    }
}

现在如果在 Xaml 中设置属性如下：

<local:ExtendedButton Text="Here is the Text of Extended Button" 
                        WidthRequest="300"
                        HeightRequest="200"
                        HorizontalTextAlignment="Start"
                        VerticalTextAlignment="End"/>

效果会显示：

【讨论】：