A simple Kotlin builder for creating SpannableStrings. Original idea from https://gist.github.com/JakeWharton/11274467.

example.kt

val span = spannable {
  +"'spannable' makes it "
 
  typeface(android.graphics.Typeface.ITALIC) {
    +" easy "
  }
 
  +" to build a "
 
  typeface(android.graphics.Typeface.BOLD) {
    +" SpannableString "
  }
 
  +" without needing to touch SpannableStringBuilder."
  +"\n\n"
  +"It supports any type of span, and they can be nested!"
  +"\n\n"
 
  span(android.text.style.URLSpan("http://www.google.com")) {
    +"www."
    typeface(android.graphics.Typeface.BOLD) {
      +"google"
    }
    +".com"
  }
}
 
val textView = findViewById(R.id.text) as TextView
textView.setText(span.toCharSequence())

Spannable.kt

// Copyright 2014 Robert Carr
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import java.util.ArrayList
import android.text.SpannableStringBuilder
import android.text.style.StyleSpan
import android.text.Spanned

fun spannable(init: SpanWithChildren.() -> Unit) : SpanWithChildren {
  val spanWithChildren = SpanWithChildren()
  spanWithChildren.init()
  return spanWithChildren
}

trait Span {
  fun render(builder: SpannableStringBuilder)

  fun toCharSequence() : SpannableStringBuilder {
    val builder = SpannableStringBuilder()
    render(builder)
    return builder
  }
}

class SpanWithChildren(val what : Any? = null) : Span {
  val children = ArrayList<Span>()

  fun typeface(typeface: Int, init: SpanWithChildren.() -> Unit) : SpanWithChildren =
    span(StyleSpan(typeface), init)

  fun span(what: Any, init: SpanWithChildren.() -> Unit) : SpanWithChildren {
    var child = SpanWithChildren(what)
    child.init()
    children.add(child)
    return this
  }

  fun String.plus() {
    children.add(SpanWithText(this))
  }

  override fun render(builder: SpannableStringBuilder) {
    val start = builder.length()

    for (c in children) {
      c.render(builder)
    }

    if (what != null) {
      builder.setSpan(what, start, builder.length(), Spanned.SPAN_INCLUSIVE_EXCLUSIVE)
    }
  }
}

class SpanWithText(val content: String) : Span {
  override fun render(builder: SpannableStringBuilder) {
    builder.append(content)
  }
}

thx, add to class SpanWithCildren the size too

fun size(size: Float, init: SpanWithChildren.()-> Unit): SpanWithChildren =
span(RelativeSizeSpan(size), init)