Advanced ConstraintLayout

ConstraintLayout 1.0 made building flexible UI easy, with a deep integration in the Android Studio layout editor. The recently introduced 1.1 version is bringing even more flexibility, with new capabilities like barriers or groups. This talk will take a deeper look at the current state of the library, why you should use it and when: architecture, performance behavior, examples of complex UI, animation capabilities and discussing some upcoming features.

presented at 360 AnDev 2017

1. ConstraintLayout Nicolas Roard
2. What is it • Expressive Layout Manager • Flat Layouts • Deep integration with Android Studio + Layout Editor • Unbundled Library • Compatible with 99% of devices
3. Once upon a time
4. <RelativeLayout > <ImageView /> <ImageView /> <RelativeLayout > <TextView /> <LinearLayout > <TextView /> <RelativeLayout > <EditText /> </RelativeLayout> </LinearLayout> <LinearLayout > <TextView /> <RelativeLayout > <EditText /> </RelativeLayout> </LinearLayout> <TextView /> </RelativeLayout> <LinearLayout > <Button /> <Button /> </LinearLayout> </RelativeLayout>
5. <RelativeLayout > <ImageView /> <ImageView /> <RelativeLayout > <TextView /> <LinearLayout > <TextView /> <RelativeLayout > <EditText /> </RelativeLayout> </LinearLayout> <LinearLayout > <TextView /> <RelativeLayout > <EditText /> </RelativeLayout> </LinearLayout> <TextView /> </RelativeLayout> <LinearLayout > <Button /> <Button /> </LinearLayout> </RelativeLayout>
7. The Tetris Model
8. The Tetris Model • Relatively easy at first
9. The Tetris Model • Relatively easy at first • Can get very complex very quickly
10. The Tetris Model • Change is hard • Impose limits for animation / transitions • Not conductive to a great design tool experience • Performance can become an issue
16. Layout != Views
17. Flat Layouts
18. Flat Layouts • Layout definition is not mixed with the view hierarchy • Easy to manipulate in a graphical editor • Easy to change • Animation friendly • Keep layout computation in a single place
19. <RelativeLayout > <ImageView /> <ImageView /> <RelativeLayout > <TextView /> <LinearLayout > <TextView /> <RelativeLayout > <EditText /> </RelativeLayout> </LinearLayout> <LinearLayout > <TextView /> <RelativeLayout > <EditText /> </RelativeLayout> </LinearLayout> <TextView /> </RelativeLayout> <LinearLayout > <Button /> <Button /> </LinearLayout> </RelativeLayout> <android.support.constraint.ConstraintLayout> <ImageView /> <ImageView /> <TextView /> <EditText /> <TextView /> <TextView /> <EditText /> <Button /> <Button /> <TextView /> </android.support.constraint.ConstraintLayout>
20. $ANDROID_HOME/platform-tools/systrace/systrace.py —time=10 -o ~/trace.html gfx view res CL 1.0.2, Nexus 5X
21. Expressivity
22. Solver
23. Simplex • Linear Programming • Invented by Georges Dantzig in 1947 • Large, empty matrices representing the equations
24. Example Minimize Constrained by Z x y z s t = Basic Feasible Solution (BFS) Matrix representation (plus slack variables s & t) Pivot on z, row 2 BFS Objective row
25. Cassowary • https://constraints.cs.washington.edu/cassowary/ • Constraints for User Interface Applications • Alan Borning, Kim Marriott, Peter Stuckey, and Yi Xiao, Solving Linear Arithmetic, Proceedings of the 1997 ACM Symposium on User Interface Software and Technology, October 1997, pages 87-96.
26. Cassowary • Incremental resolution and construction of the system • Handles positive and negative variables • Goal function and error representation
27. Pros / Cons • Very flexible, can represent any type of layout situation • But “relatively” heavy computation compared to simple layouts • Can be more memory intensive • Specifying layout via equations?…
28. ConstraintLayout solver • Pure java • Represents the system matrix as rows of sparse arrays • Memory Efficient • Efficient incremental construction • Has to have good performances on both Dalvik and Art
29. Constraints Model
30. Constraints Model • Simple model — relative positioning, centering • No Equations exposed • Evolving (bias, new dimension constraints, etc.)
31. Constraints Model
32. Constraints Model
33. Constraints Model
34. Constraints Model
35. Constraint Layout Solver Constraints Model
36. Constraint Layout Solver Constraints Model Optimizer
37. Optimizer
38. Optimizer • Constraints which can be resolved unambiguously • app:layout_optimizationLevel=“none|all|basic|chains” • multiple steps: • wrap content computation • direct resolution of simple dependency • chains on parent
39. Optimizer • match_constraint is more costly, as we need to remeasure • wrap_content, fixed dimension are cheap on a widget (end up as a value in the solver)
40. Optimizer - wrap content • If widgets contain match_constraint, no optimizations: • if ratio is specified • if percent is specified (for dimension, guideline) • if wrap_content is specified in the other dimension
41. Optimizer - Direct resolution • Only if the container is not in wrap_content • Only for widgets that are not match_constraints • Will resolve as much as it can before handing the system to the full solver
42. Optimizer - Chains • Only for chains that are connected to the container (stable endpoints) • Only for widgets in a chain that are not match_constraints / ratio • Right now, only for chains in spread mode
43. Functionalities
44. 1.0 • Relative positioning • Center positioning & bias • Guidelines - helper objects • Chains • Dimension constraints: min/max, Ratio • ConstraintSet
45. Gone Behavior
46. Gone Behavior
47. Inadapted Margin
48. Inadapted Margin
49. Gone Margins
50. Gone Margins
51. Example
52. Example
53. beta 1 1.1.0
54. • Barriers beta 1 1.1.0
55. • Barriers beta 1 1.1.0
56. • Barriers beta 1 1.1.0
57. Barriers
58. Barriers
59. Barriers
60. Barriers
61. Barriers <android.support.constraint.Barrier android:id="@+id/barrier" android:layout_width="wrap_content" android:layout_height="wrap_content" app:barrierDirection="right" app:constraint_referenced_ids="textView1,textView2,textView3" />
62. • Barriers • Group - apply visibility to a set of widgets beta 1 1.1.0
63. Groups textview2 textview3
64. Groups <android.support.constraint.Group android:id="@+id/group2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:visibility="visible" app:constraint_referenced_ids="textView2,textView3" />
65. Groups Invisible Gone
66. • Barriers • Group • Placeholder beta 1 1.1.0 ?
67. class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) } fun select(v: View) { TransitionManager.beginDelayedTransition(main_layout) placeholder.setContentId(v.id) main_title.text= v.tag as CharSequence?;""; } } Placeholder
68. class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) } fun select(v: View) { TransitionManager.beginDelayedTransition(main_layout) placeholder.setContentId(v.id) main_title.text= v.tag as CharSequence?;""; } } Placeholder
69. • Barriers • Group • Placeholder • Percent dimensions beta 1 1.1.0
70. Dimension Constraints • width|height set to 0dp (“match_constraint”) • control behavior with • app:layout_constraintWidth_default=“spread|wrap|percent” • spread matches endpoints • wrap behave like wrap_content, but respect constraints
72. default=wrap
73. default=wrap
74. default=wrap
75. Percent Dimension • As a percentage of the parent container • Not bounded by the container • value from 0 to 1 android:layout_width="0dp" app:layout_constraintWidth_default="percent" app:layout_constraintWidth_percent="0.5"
76. beta 1 1.1.0 maven { url "https://maven.google.com" } dependencies { ... compile 'com.android.support.constraint:constraint-layout:1.1.0-beta1' }
77. ConstraintSet
78. Layout != Views
79. ConstraintLayout Views
80. ConstraintLayout Views ConstraintSet
81. ConstraintLayout Views ConstraintSet
82. ConstraintLayout Views ConstraintSet
83. ConstraintSet
84. ConstraintSet • Separate views from how we layout them
85. ConstraintSet • Separate views from how we layout them • Encapsulate all constraints in an object
86. ConstraintSet • Separate views from how we layout them • Encapsulate all constraints in an object • You can apply a ConstraintSet to an existing ConstraintLayout
87. ConstraintSet • Separate views from how we layout them • Encapsulate all constraints in an object • You can apply a ConstraintSet to an existing ConstraintLayout • Switch between multiple ConstraintSet
89. ConstraintSet mConstraintSet1 = new ConstraintSet(); ConstraintSet mConstraintSet2 = new ConstraintSet();
90. ConstraintSet mConstraintSet1 = new ConstraintSet(); ConstraintSet mConstraintSet2 = new ConstraintSet(); // get constraints from layout mConstraintSet2.clone(context, R.layout.state2); setContentView(R.layout.state1); mConstraintLayout = (ConstraintLayout) findViewById(R.id.activity_main); // get constraints from ConstraintSet mConstraintSet1.clone(mConstraintLayout);
91. ConstraintSet mConstraintSet1 = new ConstraintSet(); ConstraintSet mConstraintSet2 = new ConstraintSet(); // get constraints from layout mConstraintSet2.clone(context, R.layout.state2); setContentView(R.layout.state1); mConstraintLayout = (ConstraintLayout) findViewById(R.id.activity_main); // get constraints from ConstraintSet mConstraintSet1.clone(mConstraintLayout); mConstraintSet1.applyTo(mConstraintLayout);
92. Landscape
93. Rotation
94. Rotation
95. Motion
96. Motion • Flat Hierarchy == No clipping issues
97. Motion • Flat Hierarchy == No clipping issues • Scene Graph
98. Motion • Flat Hierarchy == No clipping issues • Scene Graph • ConstraintSet == Keyframe
99. ConstraintSet mConstraintSet1 = new ConstraintSet(); ConstraintSet mConstraintSet2 = new ConstraintSet(); // get constraints from layout mConstraintSet2.clone(context, R.layout.state2); setContentView(R.layout.state1); mConstraintLayout = (ConstraintLayout) findViewById(R.id.activity_main); // get constraints from ConstraintSet mConstraintSet1.clone(mConstraintLayout); mConstraintSet1.applyTo(mConstraintLayout);
100. ConstraintSet mConstraintSet1 = new ConstraintSet(); ConstraintSet mConstraintSet2 = new ConstraintSet(); // get constraints from layout mConstraintSet2.clone(context, R.layout.state2); setContentView(R.layout.state1); mConstraintLayout = (ConstraintLayout) findViewById(R.id.activity_main); // get constraints from ConstraintSet mConstraintSet1.clone(mConstraintLayout); mConstraintSet1.applyTo(mConstraintLayout);
101. TransitionManager.beginDelayedTransition(mConstraintLayout); ConstraintSet mConstraintSet1 = new ConstraintSet(); ConstraintSet mConstraintSet2 = new ConstraintSet(); // get constraints from layout mConstraintSet2.clone(context, R.layout.state2); setContentView(R.layout.state1); mConstraintLayout = (ConstraintLayout) findViewById(R.id.activity_main); // get constraints from ConstraintSet mConstraintSet1.clone(mConstraintLayout); mConstraintSet1.applyTo(mConstraintLayout);
104. ConstraintLayout : choreographer • What you can do with widgets, you can do with components • Everything is still the same • Flexible • Easy to build and test
105. NavigationView
106. NavigationView
109. • |
110. • |
111. Custom Transitions • ConstraintSet • Custom TransitionSet • Support library physics TransitionManager.beginDelayedTransition(cl, new MyCustomAnimationSet())
112. Custom Transitions • ConstraintSet • Custom TransitionSet • Support library physics TransitionManager.beginDelayedTransition(cl, new MyCustomAnimationSet())
113. What’s next
114. What’s next • More performance optimizations • experimental background resolution • segmentation of constraints • broadening the optimizer surface
115. What’s next • ConstraintHelper • Chains • Layers • Custom • Motion • better motion control • gesture support
116. Documentation • http://www.constraintlayout.com • https://developer.android.com/reference/android/support/ constraint/package-summary.html • https://developer.android.com/training/constraint-layout/ index.html • https://codelabs.developers.google.com/codelabs/constraint-layout • https://medium.com/google-developers/building-interfaces-with- constraintlayout-3958fa38a9f7
117. Documentation • http://www.constraintlayout.com • https://developer.android.com/reference/android/support/ constraint/package-summary.html • https://developer.android.com/training/constraint-layout/ index.html • https://codelabs.developers.google.com/codelabs/constraint-layout • https://medium.com/google-developers/building-interfaces-with- constraintlayout-3958fa38a9f7
118. Thank you! +NicolasRoard @camaelon http://b.android.com File bugs & requests on: