Custom layouts in Android Kotlin - UI Render Trace

Component - Custom layouts

This UI component demonstrates how to create a custom layout in Android using Kotlin. It arranges child views manually by overriding the onMeasure and onLayout methods, allowing precise control over their size and position.

Widget Tree

CustomLayout
├── TextView (Child 1)
└── Button (Child 2)

The root is a CustomLayout which contains two children: a TextView and a Button. The CustomLayout controls how these children are measured and positioned on the screen.

Render Trace - 3 Steps

Step 1: CustomLayout

Step 2: TextView (Child 1)

Step 3: Button (Child 2)

State Change - Re-render

Trigger:Button click triggers a state change to update TextView text

Before

TextView text is 'Hello Custom Layout'

→

After

TextView text changes to 'Button Clicked!'

Re-renders:CustomLayout subtree re-measures and re-layouts children to reflect new TextView size

UI Quiz - 3 Questions

What method does CustomLayout override to control child sizes?

A onDraw

B onMeasure

C onCreate

D onClick

Key Insight

Creating custom layouts in Android lets you control exactly how child views are sized and placed. Overriding onMeasure and onLayout is key. This approach is useful when standard layouts don't meet your design needs.