Activities, Fragments, Navigation, Intents, and Lifecycle
Understand how Android screens and navigation work and why lifecycle management is central to mobile app stability.
Inside this chapter
- Activities and Screens
- Fragments
- Intents and Navigation
- Lifecycle Awareness
- Common Lifecycle Mistakes
- Real-World Usage Snapshot
Series navigation
Study the chapters in order for the clearest path from Android setup and Kotlin basics to architecture, background work, release engineering, and advanced mobile development practice. Use the navigation at the bottom to move smoothly through the full tutorial series.
Activities and Screens
An activity represents a major user interaction screen or container in Android. Historically, apps were heavily activity-driven. Modern apps may use fewer activities and more fragment or navigation-based structure, but activity lifecycle still matters greatly.
Fragments
Fragments help organize UI into reusable or modular pieces. They are common in multi-pane interfaces, navigation architectures, and legacy or hybrid Android projects.
Intents and Navigation
val intent = Intent(this, DetailActivity::class.java)
startActivity(intent)Intents are used to start activities, pass data, and interact with system features or other apps. Navigation components provide more structured routing for modern apps.
Lifecycle Awareness
Android components can be paused, stopped, destroyed, and recreated by the system. This means developers must think carefully about state, memory, background work, and configuration changes.
Common Lifecycle Mistakes
- Doing heavy work in the wrong lifecycle phase
- Losing UI state on rotation or recreation
- Holding references too long and causing leaks
- Ignoring lifecycle in async tasks
Real-World Usage Snapshot
Lifecycle management is one of the biggest differences between Android and ordinary desktop or backend programming. Developers who understand it build much more stable mobile apps.