Android Kotlin Development Overview

Android Kotlin Development

• Android is a mobile operating system based on a modified version of Linux, primarily designed for touchscreen devices like smartphones and tablets.
• Android is open-source, allowing manufacturers, developers, and enthusiasts to customize it freely.
• Android holds a significant share of the global mobile OS market due to its flexibility, vast app ecosystem, and hardware compatibility.
• The Android ecosystem includes Google Play, Google Mobile Services, and various app distribution channels supporting a wide range of apps and features.

Platform Architecture

• Android's architecture is organized into layers with specific roles:
• Linux Kernel: The core interacting directly with hardware. Manages drivers, memory, process management, and low-level functions.
• Hardware Abstraction Layer (HAL): Acts as an intermediary providing standard interfaces for hardware components (camera, Bluetooth, sensors).
• Android Runtime (ART): Manages Android app execution via Ahead-of-Time (AOT) compilation. It replaced the older Dalvik Runtime, improving performance.
• Native C/C++ Libraries: Support core Android functionality (graphics, databases like SQLite, web rendering like WebKit).
• Java API Framework: Provides components allowing app development (system services and APIs).
• System Apps: Preinstalled apps like Phone, Messages, often acting as templates for third-party app developments.

API Levels

• API level is an integer value representing an Android OS version's framework API.
• API levels ensure apps interact with specific system features on compatible devices.
• Developers specify a minimum API level to ensure apps run on devices with required features, avoiding installation on incompatible devices.
• New Android versions introduce new API levels with improved functionalities, security enhancements, and fixes for existing issues.
• Android has reached API level 34 (Android 14) currently.

App Components

• Android apps comprise four main components defining their structure:
• Activities: Represent a single screen and handle user interface interactions within an app (e.g., logging in, viewing a list).
• Services: Perform long-running tasks in the background without a user interface (e.g., playing music, fetching data from a server).
• Content Providers: Manage and share data between applications (e.g., contacts, media files), facilitating database interactions.
• Broadcast Receivers: Respond to system-wide events without continuously running (e.g., battery level change), allowing apps to react to events.

Android Fundamentals

• Crucial steps for Android development include installing Android Studio and Kotlin.

Creating a Project in Android Studio

• A fundamental step involves selecting a layout for your Kotlin application using Android Studio.
• Choosing the appropriate project name and selecting Kotlin as the project language in Android Studio are key.
• Launching the project involves clicking the "Finish" button after specifying the app name and selecting Kotlin.

Run Apps on the Android Emulator

• The emulator simulates Android devices enabling testing on various devices (including Android phones, tablets, Wear OS, etc.) and various Android API testing levels.
• The emulator allows for testing app fidelity—simulates incoming calls, text messages and simulates various network speeds and hardware sensors.
• Testing on the emulator provides faster and easier testing compared to physical devices due to direct transfer of data.

Emulator System Requirements

• 16GB RAM as a minimum spec for optimal emulator performance.
• 64-bit operating systems (Windows 10 or higher, macOS 12 or later, Linux, or ChromeOS) are recommended.
• A minimum of 16GB disk space is crucial for the Android Emulator.

Develop a UI with Views

• Android UI layouts are typically set up in XML files.
• XML Layouts: Defining the UI elements in XML files (buttons, text fields, layouts in XML structure) is a method to create layouts (using Android Studio layout editor). This approach keeps layout organization separate from the code.
• Programmatic Layouts: Creating or modifying UI elements directly in code, dynamically responding to app states or user interactions; this approach is adaptable.

Types of Android Layouts

(LinearLayout, RelativeLayout, ConstraintLayout, FrameLayout, TableLayout, WebView, ListView, GridView)

• LinearLayout: Arranging elements in a single row or column.
• RelativeLayout: Positioning elements relatively to each other or the parent layout.
• ConstraintLayout: Provides flexible positioning and sizing using constraints for creating complex layouts.
• FrameLayout: Layering elements one upon another.
• TableLayout: Organising elements in rows and columns (similar to an HTML table).
• WebView: Browsing web pages within the app.
• ListView: Arranging elements in a scrollable list (single column).
• GridView: Arranging elements in a scrollable grid (rows and columns).

Using XML

• Android XML layouts structure similarly to HTML.
• Root element: The starting point in every XML layout file (View or ViewGroup).
• Hierarchy: Nested inside the root, adding child elements (layouts or widgets) for structure.

Load the XML resource

• Android XML is compiled into View resource when compiling the app.
• In the onCreate() method of the Activity, load the layout resource.

Attributes

• Various attributes in Android XML layouts control positioning, appearance, and behavior of elements.
• Views and ViewGroups have attributes; some are specific to the view (e.g., textSize for TextView).
• Attributes can be inherited by views, thus attributes are also common to root view classes.
• Attributes describe the view's layout parameters and the parent ViewGroup's layout.

Common Attributes for All Layouts

• android:layout_width and android:layout_height: Specify the size of the view.
• android:layout_margin/padding: Add space around (margin) or inside (padding).
• android:background: Set a background color or drawable.

Layout-Specific Attributes

• Different layout types (LinearLayout, RelativeLayout, ConstraintLayout, FrameLayout and TableLayout) have their own layout-specific attributes.
• Attributes like android:orientation, android:gravity, and android:layout_weight control how elements are arranged and their spacing.

Common View Attributes

• android:id: Unique identifier for the view; essential for referencing it in code.
• android:visibility: Control the view's visibility (visible, invisible, gone).
• android:text: Set the text content of various views (e.g., TextView, Button).
• android:textSize and android:textColor: For example control the text size or color.

XML Attributes (Further Detail)

• Tables providing additional details on specific XML attributes used in Android layouts.

UI Layouts

• Android Studio's Layout Editor enables visual UI design, building and previewing layouts for different devices and versions.
• The Layout Editor is particularly useful when working with ConstraintLayout.

This quiz covers the fundamentals of Android development using Kotlin. It explores the architecture of the Android operating system, including the Linux kernel and hardware abstraction layer. Test your knowledge of the Android ecosystem and its diverse app capabilities.