Slide 1

Slide 1 text

Crazy Fancy Android Text DevFest MN (2019) @danlew42

Slide 2

Slide 2 text

No content

Slide 3

Slide 3 text

The Trouble with Trello (Markdown) • Basic nesting of elements would fail • Image loading was iffy at best • Endless URL parsing issues • Code blocks would fail to render due to cool wind breezes • HTML-escaped entities would scramble text • Russian text crashes the app

Slide 4

Slide 4 text

Text -> Abstract Syntax Tree -> Fancy TextView

Slide 5

Slide 5 text

Simple Styles

Slide 6

Slide 6 text

Styling an Entire TextView

Slide 7

Slide 7 text

Styling an Entire TextView

Slide 8

Slide 8 text

No content

Slide 9

Slide 9 text

No content

Slide 10

Slide 10 text

Spannable Span Span Span Span Span Span

Slide 11

Slide 11 text

Definitions Span - markup objects that can style text Spannable - text with mutable spans Spanned - text with spans

Slide 12

Slide 12 text

Constructing Spannables

Slide 13

Slide 13 text

Easy Mode: HTML Whoa this is wild! \n\n How did you do that? \n\n I cheated Spans! ==

Slide 14

Slide 14 text

Easy Mode: HTML Whoa this is wild! \n\n How did you do that? \n\n I cheated Spans!

Slide 15

Slide 15 text

Easy Mode: HTML textView.text = HtmlCompat.fromHtml( "Whoa this is wild!" + "\n\n" + "How did you do that?" + "\n\n" + "I cheated Spans!”, 0 )

Slide 16

Slide 16 text

Easy Mode: HTML == textView.text = HtmlCompat.fromHtml( "Whoa this is wild!" + "\n\n" + "How did you do that?" + "\n\n" + "I cheated Spans!”, 0 )

Slide 17

Slide 17 text

Easy Mode: HTML !=

Slide 18

Slide 18 text

Easy Mode: HTML != Whoa this is wild! \n\n How did you do that? \n\n I cheated Spans! textView.text = HtmlCompat.fromHtml( "Whoa this is wild!" + "\n\n" + "How did you do that?" + "\n\n" + "I cheated Spans!”, 0 )

Slide 19

Slide 19 text

HTML Drawbacks • Limited tag support • Strings support different tags than Html.fromHtml() • Details: https://blog.danlew.net/2011/04/13/html_in_text_views/

Slide 20

Slide 20 text

Hard Mode: Build Your Own • Code only • Verbose • Flexible & powerful

Slide 21

Slide 21 text

Hard Mode: Build Your Own == val text = SpannableString("Whoa this is wild!\n\nHow did you do that?\n\nI cheated Spans!") text.setSpan(SuperscriptSpan(), 0, 4, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.ITALIC), 5, 9, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(SubscriptSpan(), 10, 12, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.BOLD), 13, 17, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(ForegroundColorSpan(Color.RED), 20, 40, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StrikethroughSpan(), 42, 51, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)

Slide 22

Slide 22 text

Hard Mode: Build Your Own val text = SpannableString("Whoa this is wild!\n\nHow did you do that?\n\nI cheated Spans!") text.setSpan(SuperscriptSpan(), 0, 4, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.ITALIC), 5, 9, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(SubscriptSpan(), 10, 12, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.BOLD), 13, 17, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(ForegroundColorSpan(Color.RED), 20, 40, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StrikethroughSpan(), 42, 51, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)

Slide 23

Slide 23 text

Hard Mode: Build Your Own val text = SpannableString("Whoa this is wild!\n\nHow did you do that?\n\nI cheated Spans!") text.setSpan(SuperscriptSpan(), 0, 4, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.ITALIC), 5, 9, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(SubscriptSpan(), 10, 12, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.BOLD), 13, 17, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(ForegroundColorSpan(Color.RED), 20, 40, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StrikethroughSpan(), 42, 51, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)

Slide 24

Slide 24 text

Hard Mode: Build Your Own Class Mutable Text Mutable Markup SpannedString No No SpannableString No Yes SpannableStringBuilder Yes Yes

Slide 25

Slide 25 text

Hard Mode: Build Your Own val text = SpannableString("Whoa this is wild!\n\nHow did you do that?\n\nI cheated Spans!") text.setSpan(SuperscriptSpan(), 0, 4, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.ITALIC), 5, 9, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(SubscriptSpan(), 10, 12, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.BOLD), 13, 17, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(ForegroundColorSpan(Color.RED), 20, 40, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StrikethroughSpan(), 42, 51, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)

Slide 26

Slide 26 text

Hard Mode: Build Your Own val text = SpannableString("Whoa this is wild!\n\nHow did you do that?\n\nI cheated Spans!") text.setSpan(SuperscriptSpan(), 0, 4, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.ITALIC), 5, 9, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(SubscriptSpan(), 10, 12, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StyleSpan(Typeface.BOLD), 13, 17, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(ForegroundColorSpan(Color.RED), 20, 40, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(StrikethroughSpan(), 42, 51, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)

Slide 27

Slide 27 text

Hard Mode: Build Your Own text.setSpan( SuperscriptSpan(), 0, 4, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE ) Span Start End WTF?

Slide 28

Slide 28 text

Span Flags • Flags define behavior • Can control precise behavior… • …But just use 0 or SPAN_EXCLUSIVE_EXCLUSIVE

Slide 29

Slide 29 text

Multiple Spans

Slide 30

Slide 30 text

Built-In Spans N

Slide 31

Slide 31 text

Span Types • Appearance-only spans • Metric-affecting spans • Paragraph-affecting spans

Slide 32

Slide 32 text

Appearance-only Spans • StyleSpan • UnderlineSpan • ForegroundColorSpan • BackgroundColorSpan • URLSpan

Slide 33

Slide 33 text

Metric-affecting Spans • SuperscriptSpan • RelativeSizeSpan • ImageSpan

Slide 34

Slide 34 text

Paragraph-affecting Spans • LeadingMarginSpan • DrawableMarginSpan • BulletSpan • QuoteSpan

Slide 35

Slide 35 text

Bad Spans • BulletSpan - Sucks until API 28! • QuoteSpan - Sucks until API 28! • URLSpan - Crashes when there’s no intent handler!

Slide 36

Slide 36 text

Custom Spans

Slide 37

Slide 37 text

Custom Span Process • Pick a Span to extend • Decipher how it works • Get frustrated by limited Span API

Slide 38

Slide 38 text

Thematic Break Span

Slide 39

Slide 39 text

Thematic Break Span ≈ ≈ ReplacementSpan

Slide 40

Slide 40 text

Thematic Break Span ReplacementSpan

Slide 41

Slide 41 text

Thematic Break Span ReplacementSpan

Slide 42

Slide 42 text

Thematic Break Span ReplacementSpan

Slide 43

Slide 43 text

Thematic Break Span ReplacementSpan

Slide 44

Slide 44 text

Thematic Break Span class ThematicBreakSpan(val lineColor: Int, val lineHeight: Int, val verticalPadding: Int) : ReplacementSpan() { override fun getSize(paint: Paint, text: CharSequence?, start: Int, end: Int, fm: Paint.FontMetricsInt?): Int { if (fm != null) { fm.ascent = -lineHeight - (2 * verticalPadding) fm.descent = 0 fm.top = fm.ascent fm.bottom = 0 } return 1 } ... }

Slide 45

Slide 45 text

Thematic Break Span class ThematicBreakSpan(val lineColor: Int, val lineHeight: Int, val verticalPadding: Int) : ReplacementSpan() { override fun getSize(paint: Paint, text: CharSequence?, start: Int, end: Int, fm: Paint.FontMetricsInt?): Int { if (fm != null) { fm.ascent = -lineHeight - (2 * verticalPadding) fm.descent = 0 fm.top = fm.ascent fm.bottom = 0 } return 1 } ... }

Slide 46

Slide 46 text

Thematic Break Span class ThematicBreakSpan(val lineColor: Int, val lineHeight: Int, val verticalPadding: Int) : ReplacementSpan() { override fun draw(canvas: Canvas, text: CharSequence?, start: Int, end: Int, x: Float, top: Int, y: Int, bottom: Int, paint: Paint) { val color = paint.color val style = paint.style paint.color = lineColor paint.style = Paint.Style.FILL canvas.drawRect(etc etc etc) paint.color = color paint.style = style } }

Slide 47

Slide 47 text

Thematic Break Span class ThematicBreakSpan(val lineColor: Int, val lineHeight: Int, val verticalPadding: Int) : ReplacementSpan() { override fun draw(canvas: Canvas, text: CharSequence?, start: Int, end: Int, x: Float, top: Int, y: Int, bottom: Int, paint: Paint) { val color = paint.color val style = paint.style paint.color = lineColor paint.style = Paint.Style.FILL canvas.drawRect(etc etc etc) paint.color = color paint.style = style } }

Slide 48

Slide 48 text

Custom Span Limitations • Bound by API limitations • Cannot Parcelable custom spans • Cannot copy/paste your custom span • Choose wisely what you extend

Slide 49

Slide 49 text

Example Custom Spans • BetterURLSpan : URLSpan • BulletSpanCompat : BulletSpan • QuoteSpanCompat : QuoteSpan • CodeBackgroundSpan : LineBackgroundSpan • ListItemSpan : BulletSpan • ThematicBreakSpan : ReplacementSpan

Slide 50

Slide 50 text

Odds & Ends

Slide 51

Slide 51 text

Reusing Spans? val boldSpan = StyleSpan(Typeface.BOLD) val text = SpannableString("Alice threw the ball to Bob") text.setSpan(boldSpan, 0, 5, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(boldSpan, 24, 27, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE)

Slide 52

Slide 52 text

Reusing Spans? val boldSpan = StyleSpan(Typeface.BOLD) val text = SpannableString("Alice threw the ball to Bob") text.setSpan(boldSpan, 0, 5, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) text.setSpan(boldSpan, 24, 27, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE) ==

Slide 53

Slide 53 text

Spacing Newlines Newlines Newlines w/ RelativeSizeSpan

Slide 54

Slide 54 text

Construction Optimization Class Mutable Text Mutable Markup SpannableString No Yes SpannableStringBuilder Yes Yes

Slide 55

Slide 55 text

Construction Optimization • SpannableStringBuilder was taking 98% of construction time • Faster method: val sb = StringBuilder() val spans = mutableListOf() data class SpanInfo(val what: Any, val start: Int, val end: Int, val flags: Int)

Slide 56

Slide 56 text

Construction Optimization Construction Layout SpannableStringBuilder 51.3ms 9.4ms StringBuilder + SpannableString 1.5ms 16.4ms https://blog.danlew.net/2018/08/30/exploring-spannable-performance/

Slide 57

Slide 57 text

Replacement Spans • Cannot attach to empty space • Options • Invisible character • Fallback text if replacement span fails • Space character

Slide 58

Slide 58 text

Testing Spans • Comparing two Spannables is difficult because… • Span API is weird • Spans do not implement equals() • Not all Span attributes are public

Slide 59

Slide 59 text

Testing Spans val spanObjects = spanned.getSpans(0, spanned.length, Any::class.java) spanObjects.forEach { span -> val start = expected.getSpanStart(span) val end = expected.getSpanEnd(span) val flags = expected.getSpanFlags(span) }

Slide 60

Slide 60 text

Testing Spans val spanObjects = spanned.getSpans(0, spanned.length, Any::class.java) spanObjects.forEach { span -> val start = spanned.getSpanStart(span) val end = spanned.getSpanEnd(span) val flags = spanned.getSpanFlags(span) }

Slide 61

Slide 61 text

Testing Spans fun assertSpanEquals(expected: RelativeSizeSpan, actual: RelativeSizeSpan) { assertEquals(expected.sizeChange, actual.sizeChange) } fun assertSpanEquals(expected: LeadingMarginSpan.Standard, actual:LeadingMarginSpan.Standard) { assertEquals(expected.getLeadingMargin(true), actual.getLeadingMargin(true)) assertEquals(expected.getLeadingMargin(false), actual.getLeadingMargin(false)) }

Slide 62

Slide 62 text

Resources • Florina Muntenescu: https://medium.com/@florina.muntenescu • Optimizing spans • Styling internationalized text • …And more! • Google IO Talk: https://youtu.be/x-FcOX6ErdI

Slide 63

Slide 63 text

Questions? @danlew42