Android Spannable in kotlin

Kotlin wrappers around SpannableStringBuilder. Inspired by binaryfork's Spanny.

SpannableStringBuilder API is attractive, it's a nice way to styling text without split your text into multiple views, but the usage of the raw API is awful.

Let's say a simple example: Spans are ~~hard~~?

The raw SpannableStringBuilder API:

val builder = SpannableStringBuilder()
builder.append("Spans ")
var str = "are "
builder.append(str)
builder.setSpan(StyleSpan(Typeface.BOLD), builder.length - str.length, builder.length,
    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)
str = "hard"
builder.append(str)
builder.setSpan(StyleSpan(Typeface.BOLD), builder.length - str.length, builder.length,
    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)
builder.setSpan(StrikethroughSpan(), builder.length - str.length, builder.length,
    Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)
builder.append("?")

The Spanny helper API:

val spanny = Spanny("Spans ")
    .append("are ", StyleSpan(Typeface.BOLD))
    .append("hard", StyleSpan(Typeface.BOLD), StrikethroughSpan())
    .append("?")

That is cool in Java, but I was using kotlin, and it's not cool enough, it's verbose and limited. Kotlin allows to type-check builders, which is the best way to build spans, so I make it happen:

val text = span {
  +"Spans "
  span {
    textStyle = "bold"
    +"are "
    span("hard") {
      textDecorationLine = "line-through"
    }
  }
  +"?"
}

Download

You can grab it via Gradle:

implementation 'me.gujun.android:span:1.7'

Usage

val text = span {
  textColor = Color.BLACK
  backgroundColor = Color.WHITE
  textSize = dp(13)
  fontFamily = "monospace"
  typeface = getFont(R.font.pacifico)
  textStyle = "bold"
  alignment = "normal"
  textDecorationLine = "underline"
  lineSpacing = dp(3)
  verticalPadding = dp(5)
  paddingTop = dp(5)
  paddingBottom = dp(5)
  onClick = {
  }
  addSpan(TextAppearanceSpan(context, R.style.TextAppearance))
  
  span {
    text = "Hi"
  }
  
  span("Hi")
  
  +"Hi"
  
  link("http://google.com", "Text")
  
  quote(Color.RED, "Text")
  
  subscript("Text")
  
  superscript("Text")
  
  image(getDrawable(R.drawable.ic_fun))
}

Caution: Avoid nested text in spans

The following code will cause RuntimeException: Can't nest "World" in spans. This is because you try to nest span with text "World" in its parent span with text "Hello", it does not make any sense.

val text = span {
  text = "Hello"
  span("World")
}

Overwrite styles

Styles can be overwrite in nested spans, inner span overwrite the outer span.

val text = span {
  textColor = Color.BLUE
  textSize = dp(20)
  +"Simple text"
  +"\n"
  span("Overwrite foreground") {
    textColor = Color.RED
  }
  +"\n"
  span("Overwrite text size") {
    textSize = dp(10)
  }
}

Reusable style

You can create reusable styles and use them in multiple spans.

val headerStyle = style {
  textColor = Color.BLACK
  textStyle = "bold"
  textSize = dp(20)
  verticalPadding = dp(3)
}
val content = span {
  span("Header1") {
    style = headerStyle
  }
  span {
    text = "\n...\n"
  }
  span("Header2") {
    style = headerStyle
  }
}

or you can declare an extension function and apply styles as you wish:

fun Span.header(text: CharSequence): Span = span(text) {
  textColor = Color.BLACK
  textStyle = "bold"
  textSize = dp(20)
  verticalPadding = dp(3)
}

val content = span {
  header("Header1\n")
  span {
    text = "..."
  }
}

Global style

You can set global style by create a style and pass it to the companion object Span.globalStyle.

For example, if your project using a custom typeface, you can apply styles with custom typeface, then you will no need to specify typeface each time you using spans.

Span.globalStyle = style {
  typeface = getFont(R.font.pacifico)
}

Reference

Supported attributes

text
textColor
backgroundColor
textSize
typeface
lineSpacing
verticalPadding
paddingTop
paddingBottom
onClick
fontFamily: include "monospace", "serif", and "sans-serif"
textStyle: include "normal", "bold", "italic", and "bold_italic"
alignment: include "normal", "opposite", and "center"
textDecorationLine: include "none", "underline", "line-through", and "underline line-through"

Extended spans

link: URLSpan
quote: QuoteSpan
superscript: SuperscriptSpan
subscript: SubscriptSpan
image: ImageSpan, include "bottom" and "baseline" alignment
addSpan: Add custom span

License

Copyright 2018 Jun Gu

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.

2dxgujun/Kpan