constraint-layout.md

ConstraintLayout

• should be nested when listing CardView.
  • https://stackoverflow.com/questions/37938767/designing-cardview-while-its-parent-is-constraintlayout
• If a view has an attribute related to ConstraintLayout, the innermost ViewGroup that contains the view must be ConstraintLayout to interpret the attribute. For example, If the ViewGroup is a CardView, the attribute will not be understood.

<MotionScene>

• must contain at least one <Transition>.
• When using MotionLayout, all the constraints of animated views must be specified in <MotionScene>. The constraints of non-animated views can be specified in <MotionLayout>.

<Transition>

• is one animation.
• contains the following attributes
  • constraintSetStart
  • constraintSetEnd
  • duration
  • Optionally, <KeyFrameSet>

<KeyFrameSet>

• contains at least one <KeyPosition>.

At framePosition modify the path of motionTarget by moving it by percentX or percentY according to the coordinates determined by keyPositionType.

• https://codelabs.developers.google.com/codelabs/motion-layout/index.html?index=..%2F..advanced-android-kotlin-training#4

<KeyPosition>

• never affects start and end constraints.
• never affects other views that are constained to the view associated with <KeyPosition>.

<ConstraintSet>

• is the start and the end constraints of a motion.
• contains <Constraint>(s).
• contains only constraints or layout information such as width, height, alpha, or visibility, but not views.
• whose constraints override constraints in a layout file.

RelativeLayout vs. ConstraintLayout

RelativeLayout	ConstraintLayout
android:layout_centerInParent="true"	app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintTop_toTopOf=""parent"
android:layout_centerVertical="true"	app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintTop_toTopOf="parent"
android:layout_centerHorizontal="true""	app:layout_constraintStart_toStartOf="parent" app:layout_constraintEnd_toEndOf="parent"
android:layout_alignParentTop="true"	app:layout_constraintTop_toTopOf="parent"
android:layout_alignParentBottom="true"	app:layout_constraintBottom_toBottomOf="parent"
android:layout_alignParentStart="true"	app:layout_constraintStart_toStartOf="parent"
android:layout_alignParentEnd="true"	app:layout_constraintEnd_toEndOf="parent"
android:layout_alignTop="@id/view"	app:layout_constraintTop_toTopOf="@id/view"
android:layout_alignBottom="@id/view"	app:layout_constraintBottom_toBottomOf="@id/view"
android:layout_alignStart="@id/view"	app:layout_constraintStart_toStartOf="@id/view"
android:layout_alignEnd="@id/view"	app:layout_constraintEnd_toEndOf="@id/view"
android:layout_alignBaseline="@id/view"	app:layout_constraintBaseline_toBaselineOf="@id/view"
android:layout_above="@id/view"	app:layout_constraintBottom_toTopOf="@id/view"
android:layout_below="@id/view"	app:layout_constraintTop_toBottomOf="@id/view"
android:layout_toStartOf="@id/view"	app:layout_constraintEnd_toStartOf="@id/view"
android:layout_toEndOf="@id/view"	app:layout_constraintStart_toEndOf="@id/view"