Introduction to Andriod
Android is an open-source mobile operating system developed by Google. It is based on the Linux kernel and is designed for touchscreen devices, smartphones, tablets, smart TVs, and wearables. Android apps are developed using Java, Kotlin, or Flutter (Dart).
Basic Structure of Andriod
An Android app consists of multiple components stored in a project directory.
.Key Files & Directories
.AndroidManifest.xml → Stores app permissions, activities, and services.
.MainActivity.java / MainActivity.kt → Main logic of the app.
.res/layout/activity_main.xml → Defines the UI layout.
.Gradle Scripts → Manages dependencies and app configuration.
Andriod Architecture
Android is built on multiple layers:
1.Linux Kernel → Handles device drivers, memory, and process management.
2.Native Libraries → Includes OpenGL, SQLite, WebKit, and Media Framework.
3.Android Runtime (ART) → Runs Android apps efficiently.
4.Application Framework → Provides APIs for UI, location, and notifications.
5.Applications → User-installed apps like WhatsApp, Instagram, and Gmail.
Activities and Lifecycle
An Activity represents a screen in an Android app. It follows a lifecycle managed by Android.
Life cycle states
onCreate() Activity is created.
onStart() Activity becomes visible.
onResume() Activity is in the foreground.
onPause() Activity is partially visible.
onStop() Activity is no longer visible.
onDestroy() Activity is destroyed.
Intents in Android
Intents help navigate between activities and pass data.
1.Explict Intents
2.Implict Intent
UI Components in Android
Android apps use XML for UI design. Common UI elements:
✅ TextView → Displays text
✅ EditText → User input field
✅ Button → Clickable button
✅ ImageView → Displays images
✅ RecyclerView → Lists items efficiently.
Android Permissions
Android apps require permissions to access device features (Camera, Location, Storage).
✅ Declaring Permissions in AndroidManifest.xml
✅ Requesting Permission in Code (Kotlin)
Databases in Android (SQLite & Room)
Android provides SQLite and Room Database for data storage.
✅ Creating SQLite Database (Kotlin)
✅ Using Room Database (Recommended)
Firebase in Android
Firebase provides real-time database, authentication, and cloud messaging.
✅ Adding Firebase to Android App
✅Go to Firebase Console and create a project.
✅Add the google-services.json file to your project.
✅Update build.gradle with Firebase dependencies.
Conclusion
Android is the most widely used mobile OS globally, offering flexibility, open-source tools, and a vast developer community. By learning Android development, you can build apps for business, entertainment, social media, and automation.