如何使用 Xamarin Forms 更改导航页面标题的字体? [英] How can I change the font for the header of a Navigation page with Xamarin Forms?

问题描述

我可以像这样更改字体颜色:

I can change the font color like this:

var homePage = new NavigationPage(new HomePage())
{ 
   Title = "Home",
   Icon = "ionicons_2_0_1_home_outline_25.png",
   BarTextColor = Color.Gray,
};

但是有没有办法改变标题的字体.我只想为 iOS 和 Android 平台更改它.希望有人知道可以帮助我做到这一点的自定义渲染器代码.

But is there a way to change the font for the Title. I would like to change it for the iOS and Android platforms only. Hoping that someone knows of custom renderer code that can help me to do this.

推荐答案

你需要 Custom Renderer ，参考 此示例

You need Custom Renderer , refer to this sample

[assembly: ExportRenderer(typeof(CustomNavigationPage), typeof(CustomNavigationPageRenderer))]
namespace CustomFontsNavigationPage.iOS.Renderers
{
public class CustomNavigationPageRenderer : NavigationRenderer
{
    protected override void OnElementChanged(VisualElementChangedEventArgs e)
    {
        base.OnElementChanged(e);

        if (e.NewElement != null)
        {
            var att = new UITextAttributes();
            UIFont customFont = UIFont.FromName("Trashtalk", 20);
            UIFont systemFont = UIFont.SystemFontOfSize(20.0);
            UIFont systemBoldFont = UIFont.SystemFontOfSize(20.0 , FontAttributes.Bold);
            att.Font = font;
            UINavigationBar.Appearance.SetTitleTextAttributes(att);
        }
    }
}
}

安卓

[assembly: ExportRenderer(typeof(CustomNavigationPage), typeof(CustomNavigationPageRenderer))]
namespace CustomFontsNavigationPage.Droid.Renderers
{
public class CustomNavigationPageRenderer : NavigationPageRenderer
{
    private Android.Support.V7.Widget.Toolbar _toolbar;

    public override void OnViewAdded(Android.Views.View child)
    {
        base.OnViewAdded(child);

        if (child.GetType() == typeof(Android.Support.V7.Widget.Toolbar))
        {
            _toolbar = (Android.Support.V7.Widget.Toolbar)child;
            _toolbar.ChildViewAdded += Toolbar_ChildViewAdded;
        }
    }

    protected override void Dispose(bool disposing)
    {
        base.Dispose(disposing);

        if(disposing)
        {
            _toolbar.ChildViewAdded -= Toolbar_ChildViewAdded;
        }
    }

    private void Toolbar_ChildViewAdded(object sender, ChildViewAddedEventArgs e)
    {
        var view = e.Child.GetType();

        if (e.Child.GetType() == typeof(Android.Widget.TextView))
        {
            var textView = (Android.Widget.TextView)e.Child;
            var spaceFont = Typeface.CreateFromAsset(Forms.Context.ApplicationContext.Assets, "Trashtalk.ttf");
            var systemFont = Typeface.DEFAULT;
            var systemBoldFont = Typeface.DEFAULT_BOLD;
            textView.Typeface = spaceFont;
            _toolbar.ChildViewAdded -= Toolbar_ChildViewAdded;
        }
    }
}
}

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