Xamarin Android在同一textview中使用多种字体

Question

我使用Xamarin作为Android应用，我创建了一个自定义TypeFace，如下所示：

Typeface weatherFont = Typeface.CreateFromAsset(Assets, "Weather.ttf");

我的问题是我必须将string分配给TextView，我需要将前3个字符的字体设置为默认的android字体，剩下的字体设置为weatherFont {1}}字体。我怎么能这样做？

Answer 1

在API-27之前，您需要一个自定义CharacterStyle子类才能将自定义Typeface应用于Spannable。

实施例

var sushiFont = Typeface.CreateFromAsset(Assets, "Tastysushi.ttf");
var spannable = new SpannableString("123 = SushiHangover");
spannable.SetSpan (new CustomTypefaceSpan(sushiFont), 3, spannable.Length(), SpanTypes.ExclusiveInclusive);
button.SetText(spannable, TextView.BufferType.Spannable);

或者在API-21（+）中，您可以使用SetSpan来避免SpannableStringBuilder.Append char开始/结束索引：

var sushiFont = Typeface.CreateFromAsset(Assets, "Tastysushi.ttf");
var spannableString = new SpannableStringBuilder("123");
var spannable = new SpannableString(" = SushiHangover");
spannableString.Append(spannable, new CustomTypefaceSpan(sushiFont), SpanTypes.ExclusiveInclusive);
button.SetText(spannableString, TextView.BufferType.Spannable);

在API-28 +中，您可以直接创建直接包含不同Typeface的跨度，而无需使用CharacterStyle子类：

spannableString.Append(spannable, new TypefaceSpan(sushiFont), SpanTypes.ExclusiveInclusive);

CustomTypefaceSpan类

public class CustomTypefaceSpan : MetricAffectingSpan
{
    readonly Typeface typeFace;

    public CustomTypefaceSpan(Typeface typeFace)
    {
        this.typeFace = typeFace;
    }

    public override void UpdateDrawState(TextPaint tp)
    {
        tp.SetTypeface(typeFace);
    }

    public override void UpdateMeasureState(TextPaint p)
    {
        p.SetTypeface(typeFace);
    }
}