How does ConstraintLayout help improve UI performance compared with nested LinearLayouts?

Short answer

It lets you build complex UIs with a flat hierarchy without nesting containers, which reduces the cost of double measure and layout.

Explanation

When several LinearLayouts that use layout_weight are nested, the system has to run multiple measure passes for each nesting level (double taxation), which negatively affects UI rendering. ConstraintLayout resolves all the relative relationships between elements (such as alignment, percentages, chains, and guidelines) in a single flat mathematical measurement step.

Code example

<!-- Flat UI with clear constraints -->
<androidx.constraintlayout.widget.ConstraintLayout ...>
    <ImageView
        android:id="@+id/avatar"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" ... />

    <TextView
        android:id="@+id/title"
        app:layout_constraintStart_toEndOf="@id/avatar"
        app:layout_constraintTop_toTopOf="@id/avatar" ... />
</androidx.constraintlayout.widget.ConstraintLayout>

Common mistakes

• Using ConstraintLayout everywhere, even for very simple UIs made of two elements, where a regular LinearLayout is faster and lighter.

Follow-up questions

• What are the three basic stages of drawing any View on the screen in Android?

Sources

• Android Developers — Build a Responsive UI with ConstraintLayout