Android XML Layouts & Theming

Instructions

The XML view system remains the canonical Android UI toolkit for Java projects. Keep layouts flat, use ConstraintLayout for complex screens, and push repeated attributes into styles and themes.

1. ConstraintLayout First

Prefer a single ConstraintLayout root over nested LinearLayouts. Chains, barriers, guidelines, and groups replace most nesting.

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">