Differences between ConstraintLayout and RelativeLayout
The intention of ConstraintLayout is to optimize and flatten the view hierarchy of your layouts by applying some rules to each view to avoid nesting.
The Rules are similar to RelativeLayout, for example setting the bottom edge to the bottom of some other view.
app:layout_constraintBottom_toBottomOf="@+id/view1"
Unlike RelativeLayout, ConstraintLayout offers a bias value that is used to position a view in terms of 0% and 100% horizontal and vertical offset relative to the handles (marked with a red circle). These percentages (and fractions) offer seamless positioning of the view across different screen densities and sizes.
app:layout_constraintHorizontal_bias="0.33" <!-- from 0.0 to 1.0 -->
app:layout_constraintVertical_bias="0.53" <!-- from 0.0 to 1.0 -->
The Baseline handle (a long pipe with rounded corners, below the circle handle) is used to align the content of the view with another view reference.
Square handles (on each corner of the view) are used to resize the view in dps.
This is totally opinion based and my impression of ConstraintLayout
Relative Layout and Constraint Layout equivalent properties
(1) Relative Layout:
android:layout_centerInParent="true"
(1) Constraint Layout equivalent :
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"
(2) Relative Layout:
android:layout_centerHorizontal="true"
(2) Constraint Layout equivalent:
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintEnd_toEndOf="parent"
(3) Relative Layout:
android:layout_centerVertical="true"
(3) Constraint Layout equivalent:
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toTopOf="parent"
(4) Relative Layout:
android:layout_alignParentLeft="true"
(4) Constraint Layout equivalent:
app:layout_constraintLeft_toLeftOf="parent"
(5) Relative Layout:
android:layout_alignParentStart="true"
(5) Constraint Layout equivalent:
app:layout_constraintStart_toStartOf="parent"
(6) Relative Layout:
android:layout_alignParentRight="true"
(6) Constraint Layout equivalent:
app:layout_constraintRight_toRightOf="parent"
(7) Relative Layout:
android:layout_alignParentEnd="true"
(7) Constraint Layout equivalent:
app:layout_constraintEnd_toEndOf="parent"
(8) Relative Layout:
android:layout_alignParentTop="true"
(8) Constraint Layout equivalent:
app:layout_constraintTop_toTopOf="parent"
(9) Relative Layout:
android:layout_alignParentBottom="true"
(9) Constraint Layout equivalent:
app:layout_constraintBottom_toBottomOf="parent"
(10) Relative Layout:
android:layout_alignStart="@id/view"
(10) Constraint Layout equivalent:
app:layout_constraintStart_toStartOf="@id/view"
(11) Relative Layout:
android:layout_alignLeft="@id/view"
(11) Constraint Layout equivalent:
app:layout_constraintLeft_toLeftOf="@id/view"
(12) Relative Layout:
android:layout_alignEnd="@id/view"
(12) Constraint Layout equivalent:
app:layout_constraintEnd_toEndOf="@id/view"
(13) Relative Layout:
android:layout_alignRight="@id/view"
(13) Constraint Layout equivalent:
app:layout_constraintRight_toRightOf="@id/view"
(14) Relative Layout:
android:layout_alignTop="@id/view"
(14) Constraint Layout equivalent:
app:layout_constraintTop_toTopOf="@id/view"
(15) Relative Layout:
android:layout_alignBaseline="@id/view"
(15) Constraint Layout equivalent:
app:layout_constraintBaseline_toBaselineOf="@id/view"
(16) Relative Layout:
android:layout_alignBottom="@id/view"
(16) Constraint Layout equivalent:
app:layout_constraintBottom_toBottomOf="@id/view"
(17) Relative Layout:
android:layout_toStartOf="@id/view"
(17) Constraint Layout equivalent:
app:layout_constraintEnd_toStartOf="@id/view"
(18) Relative Layout:
android:layout_toLeftOf="@id/view"
(18) Constraint Layout equivalent:
app:layout_constraintRight_toLeftOf="@id/view"
(19) Relative Layout:
android:layout_toEndOf="@id/view"
(19) Constraint Layout equivalent:
app:layout_constraintStart_toEndOf="@id/view"
(20) Relative Layout:
android:layout_toRightOf="@id/view"
(20) Constraint Layout equivalent:
app:layout_constraintLeft_toRightOf="@id/view"
(21) Relative Layout:
android:layout_above="@id/view"
(21) Constraint Layout equivalent:
app:layout_constraintBottom_toTopOf="@id/view"
(22) Relative Layout:
android:layout_below="@id/view"
(22) Constraint Layout equivalent:
app:layout_constraintTop_toBottomOf="@id/view"