After months of intensive development, we are delighted to announce the 1.0 release of the ConstraintLayout library. It's available as a small unbundled library, in the Android Studio SDK Manager (under the "Support Repository" section), compatible with API level 9 (Gingerbread and above). We recommend updating to this version, particularly if used in production.

Note: with Android Studio 2.3 reaching release candidate status, we also encourage people to switch to it for editing layouts (ConstraintLayout included). Many improvements have been made since 2.2, providing a smoother experience.

The ConstraintLayout library allows you to create complex layouts easily, avoiding deep nested hierarchies and providing many powerful features for designing UIs:

• Relative positioning of widgets to parent or siblings

• Centering positioning and bias control

• Flexible size control (min/max/wrap/constrained)

• Per axis group behavior (chains, weights)

• Advanced visibility behavior (gone handling and margins)

• Horizontal and Vertical virtual guidelines (fixed positions or percentage-based)

• Aspect Ratio support

• Advanced API to set constraints programmatically, allowing easy animations between layouts

A code lab is available as an introduction to ConstraintLayout as well as a developer guide. A complete online documentation is also available. Many excellent tutorials have also been created by the developers’ community; you can find them on YouTube, Medium, or your favorite search engine.  

We just published ConstraintLayout beta 5. As always, it's available in the SDK Manager (under the "Support Repository" section). We recommend to update to this version -- it will be the last beta before 1.0 and is considered as the release candidate.

Key Changes:

• Use of MATCH_PARENT now throws exception

• Improved performance in wrap_content use cases (30-40%)

• Better view dimension control (6 new attributes)

• Improved behaviour of gone in chains

• Aspect ratio enhancements

• Increased coverage of apis in ConstraintSet (chains, transforms, etc.). See documentation.

Note: if you are using Android Studio 2.2, you might have to do File->Invalidate Caches & restart studio after installing this version (the editor behavior may not be correct, with widgets temporarily snapping to the top left corner or not shown). Using Android Studio 2.3 is strongly encouraged.

MATCH_PARENT

MATCH_PARENT is not valid in ConstraintLayout when set on its children, and its behavior undefined. To reduce the risk of errors we now throws an exception if we encounter it.

Improved performance

This release fixes a few issues and performance improvements (notably, wrap_content measure on the layout got a ~30-40% speed bump).

Better view dimension controls

The new available behaviors when a dimension is set to 0dp (MATCH_CONSTRAINT). As before, both endpoints (left/right or top/bottom) need to be connected to targets.

• layout_constraintWidth_default = spread (default, similar to the previous behavior)

• layout_constraintWidth_default = wrap

• layout_constraintHeight_default = spread

• layout_constraintHeight_default = wrap

Additionally, minimum and maximum dimensions can be specified (they will only apply to MATCH_CONSTRAINT widgets):

• layout_constraintWidth_min = [dimension]

• layout_constraintWidth_max = [dimension]

• layout_constraintHeight_min = [dimension]

• layout_constraintHeight_max = [dimension]

Spread provides the previous behaviour of expanding to fill the area defined by the constraints.