Android Life Cycles

A concise Android sample app (Java) demonstrating core Activity lifecycle callbacks, navigation between activities, and basic state persistence with onSaveInstanceState().

Tech Stack

• Android (Java) • Gradle (Groovy DSL)
• compileSdk 34, minSdk 28, targetSdk 33

App Details

• applicationId: com.lifecycle
• Launcher Activity: com.lifecycle.MainActivity
• Other Activities: com.lifecycle.ChildActivity

What You'll Learn

• When and how Android calls lifecycle callbacks (onCreate, onStart, onResume, onPause, onStop, onDestroy, onRestart).
• How to save & restore UI state with onSaveInstanceState / onRestoreInstanceState.
• Navigating between activities and observing how transitions affect callbacks.

Project Structure

- .gitignore
  - .gitignore
- README.md
▸ app
  - .gitignore
  - build.gradle
  - proguard-rules.pro
  - readme.md
  ▸ src
    ▸ androidTest
      ▸ java
    ▸ main
      - AndroidManifest.xml
      ▸ java
      ▸ res
    ▸ test
      ▸ java
- build.gradle
▸ gradle
  ▸ wrapper
    - gradle-wrapper.jar
    - gradle-wrapper.properties
- gradle.properties
- gradlew
- gradlew.bat
- local.properties
- settings.gradle

Key Source Files

• ChildActivity — overrides: onCreate
• MainActivity — overrides: onCreate, onStart, onResume, onPause, onStop, onDestroy, onSaveInstanceState

Layouts

• app/src/main/res/layout/activity_child.xml
• app/src/main/res/layout/activity_main.xml

Dependencies

• implementation → androidx.appcompat:appcompat:1.6.1
• implementation → com.google.android.material:material:1.11.0
• implementation → androidx.constraintlayout:constraintlayout:2.1.4
• implementation → androidx.activity:activity:1.8.2
• testImplementation → junit:junit:4.13.2
• androidTestImplementation → androidx.test.ext:junit:1.1.5
• androidTestImplementation → androidx.test.espresso:espresso-core:3.5.1

Getting Started

1. Prerequisites

   • Android Studio (latest stable)
   • JDK 17+
   • Android SDK & Build-Tools for API 34

2. Open & Build

   • Open this folder in Android Studio: AndroidLifeCycles/.
   • Let Gradle sync and index the project.

3. Run

   • Select an emulator or device (API 28+).
   • Use the Run button to launch MainActivity (com.lifecycle.MainActivity).

4. Try It

   • Navigate to ChildActivity from the UI (if provided) or via an explicit Intent.
   • Rotate the device or send the app to background/foreground to watch lifecycle logs.
   • Observe onSaveInstanceState being called when rotating or process-kill occurs.

How It Works (Brief)

• MainActivity

  • Demonstrates the full lifecycle, overriding: onCreate, onStart, onResume, onPause, onStop, onDestroy, onSaveInstanceState.
  • Use logs or on-screen indicators to visualize callback order.

• ChildActivity

  • Simple secondary screen to trigger lifecycle transitions when navigating forward/back.

Tip: Open Logcat and filter by your tag to see callback order clearly.