How apps work

Jetpack

Most of the "Android API" you use today isn't in the OS.

4 pages47 min4 interactive6500 words

01Support Library to AndroidXFor ten years, one library existed to backport new APIs to old Android versions. In 2018 it was renamed, reset and split into sixty independently versioned artifacts — and that reset is what made the modern ecosystem possible.intermediate11 mininteractive
02The Jetpack mapSeventy-two artifacts, sixteen families, and one rule: each one earns its place by removing a specific piece of boilerplate you would otherwise write badly.beginner14 mininteractive
03Platform or library?Two phones on the same Android version can run your app differently, because half the API you call is compiled into your APK and half is provided by the device.intermediate11 mininteractive
04Google Play servicesThe most-used API on Android is not in Android. Play services is an app, and a large fraction of what developers think of as 'the platform' only exists on devices that ship it.intermediate11 mininteractive

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Test yourself: Jetpack

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Modern Google guidance has started moving some capabilities out of Play services and into AndroidX — Credential Manager is an example.