App Components

App components are the essential building blocks of an Android app.

Each component is an entry point through which the user can enter your app.

There are four main components, Each type serves a distinct purpose and has a distinct lifecycle that defines how a component is created and destroyed.

Context

Context is an object that provides information about the current state of the application and facilitates access to application resources and system-level operations.

Using a Context, you can:
- Access resources (strings, layouts, drawables)
- Start activities and services
- Get system services (LayoutInflater, NotificationManager, etc.)
- Access application assets
- Show toasts, dialogs, notifications
- Access preferences, databases, file system

For example,

Accessing Resources

// Accessing a string resource
String appName = context.getString(R.string.app_name);

Accessing System Services

// Accessing the Alarm Service
AlarmManager alarmManager = getSystemService(AlarmManager.class);

Accessing App Components

// Starting an Activity
Intent intent = new Intent(context, MainActivity.class);
context.startActivity(intent);

Types of Context

1. Application Context

Lifetime: entire app process
Tied to: Application
Use when you need something that should live as long as the app
Examples:
- Starting a Service
- Accessing shared preferences
- Long-lived objects (singletons, repositories)

Context appContext = getApplicationContext();

2. Activity Context

Lifetime: as long as the Activity
Tied to: UI and theme
Required for anything that touches the screen
Examples:
- Inflating layouts
- Showing dialogs
- Starting another Activity

Context activityContext = this;

Use this for UI. Period.

3. Service Context

Lifetime: as long as the Service
Similar to Application Context, but scoped to the service
Used when:
- You’re inside a Service and need context-aware operations

Mistakes when using the Context

Using Application Context for UI stuff Enjoy your crashes and un-themed dialogs.
Holding Activity Context in static variables Congrats, you invented a memory leak.

Last modified: 05 February 2026