views-dsl-constraintlayout

Views DSL ConstraintLayout

ConstraintLayout extension of Views DSL.

Supported platforms: Android.

Table of contents

• ConstraintLayout tailored lParams extension
• ConstraintLayout.LayoutParams extensions for safe and readable usage
• Download

ConstraintLayout tailored lParams extension

The lParams() extension function on ConstraintLayout looks to be similar to the similarly named extensions on LinearLayout and FrameLayout, but there are two key differences:

• Since ConstraintLayout children are meant to have constraints, their default width and height are matchConstraints, not wrapContent. That means that you'll often have to specify height = wrapContent for things like TextViews and Buttons.
• In xml, match_parent is not supported for ConstraintLayout and can decrease performance (the alternative being adding 0dp + 2 parent relative constraints). This is not the case here as matchParent is rewritten as matchConstraints with the appropriate parent relative constraints. The result is a more readable UI code, without performance compromises.

ConstraintLayout.LayoutParams extensions for safe and readable usage

With this split also comes a set of extension functions to use in lParams(…) { … }. Almost all of them have optional margin and goneMargin parameters.

Center relatively to parent:

• centerHorizontally(…)
• centerVertically(…)
• centerInParent(…)

Parent relative constraints:

• topOfParent(…)
• bottomOfParent(…)
• startOfParent(…)
• endOfParent(…)
• leftOfParent(…)
• rightOfParent(…)

Center relatively to another View:

• alignVerticallyOn(…)
• alignHorizontallyOn(…)
• centerOn(…)

View relative constraints:

• above(…) (alias to bottomToTopOf(…))
• below(…) (alias to topToBottomOf(…))
• before(…) (alias to endToStartOf(…))
• after(…) (alias to startToEndOf(…))
• topToTopOf(…)
• topToBottomOf(…)
• bottomToTopOf(…)
• bottomToBottomOf(…)
• baselineToBaselineOf(…)
• startToStartOf(…)
• startToEndOf(…)
• endToStartOf(…)
• endToEndOf(…)
• leftToLeftOf(…)
• leftToRightOf(…)
• rightToRightOf(…)
• rightToLeftOf(…)

Chains:

• horizontalChain(…) { … } and its companion horizontalMargin extension for List<View>.
• verticalChain(…) { … } and its companion verticalMargin extension for List<View>.

Barriers:

• barrier(…) which takes a BarrierType (inline class) and a list or vararg of Views.
• startBarrier(…), leftBarrier(…), topBarrier(…), endBarrier(…), rightBarrier(…) and bottomBarrier(…)

Guidelines:

• verticalGuideline(…) and horizontalGuideline(…) which take a begin offset (pixels), an end offset, or a ratio (between 0 and 1).

Groups:

• group(…) which takes the views to group.

These methods come with a great bonus feature:

If a View involved in a constraint has no valid id, then a generated one is automatically assigned to it!

These generated ids can't clash with aapt/xml ids, so it's safe to put xml defined ids on some views that need to have their state saved (e.g. a RecyclerView, an EditText or a CheckBox) in the same layout.

Note that View ids are crucial to ConstraintLayout machinery.

Download

implementation("com.louiscad.splitties:splitties-views-dsl-constraintlayout:$splitties_version")