android under the hood: how viewmodel, state, and restoration work

Series: android under the hood: how viewmodel, state, and restoration work

Android Under the Hood: How ViewModel, State, and Restoration Work · Part 1

ViewModel in Activity Under the Hood: How It Survives Recreation

What actually happens to ViewModel when Activity is destroyed and recreated? We break down the entire chain: ViewModelStore, NonConfigurationInstances, ActivityThread, and ActivityClientRecord. We show in detail where and how state is stored, and how Android magically restores everything during configuration changes.

Osman Suleimanov Feb 28, 2025 20 min read

Android Under the Hood: How ViewModel, State, and Restoration Work · Part 2

ViewModel in Fragment Under the Hood: From ViewModelStore to Retain Fragments

How fragments manage their ViewModelStore, what FragmentManagerViewModel is, why child fragments are needed, and why Retain fragments are considered deprecated. A complete breakdown of architectural connections and call chains that allow fragments to preserve state during recreation.

Osman Suleimanov Mar 10, 2025 22 min read

Android Under the Hood: How ViewModel, State, and Restoration Work · Part 3

ViewModel Under the Hood: How it Works in Compose and View

What happens under the hood when we call viewModel() in Compose or View? How does ViewModelStoreOwner lookup work, what does LocalViewModelStoreOwner do, how does Compose connect to the View hierarchy, and how are DI delegates like hiltViewModel() and koinViewModel() structured? A deep technical look at the scoping and state mechanism.

Osman Suleimanov Mar 20, 2025 18 min read

Android Under the Hood: How ViewModel, State, and Restoration Work · Part 4

SavedStateHandle and Bundle Under the Hood: How Android Saves State

A comprehensive article about how Android saves and restores state: from onSaveInstanceState and Bundle to modern architecture with SavedStateHandle and SavedStateRegistry. How everything is connected to the lifecycle of Activity, Fragment, and ViewModel, what roles ActivityThread, Instrumentation, and ActivityClientRecord play. A complete low-level data flow that demystifies all the magic moments.

Osman Suleimanov May 10, 2025 30 min read

Android Under the Hood: How ViewModel, State, and Restoration Work · Part 5

Decompose and Essenty: Under the Hood of State Saving without ViewModel

In this article, we dive deep inside Decompose and Essenty: how they save state without using ViewModel and onSaveInstanceState, what happens at the StateKeeper and InstanceKeeper level, how all this relates to Android SavedStateRegistry and serialization through kotlinx.serialization. A detailed, step-by-step analysis of the entire chain : from components to low-level details.

Osman Suleimanov Jun 21, 2025 15 min read