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Introduction to Android- A session by Sagar Das
- 1. BASICS OF ANDROIDAPP DEVELOPMENT By Sagar Das
- 2. SAGAR DAS • StaffAndroid Engineer at Vivint Smart Home. • 10 years of experience. • Lives in Boston, MA • Public speaker, GDE for Android • GDG Organizer About me
- 3. AGENDA 01 Why Android? 02Android Studio 03 Android SDK 04 Jetpack Compose 05 Hands on 06 Best practices Play Console 07
- 4. • Android isa mobile operating system based on Linux, primarily for touchscreens • Developed by Google and the Open Handset Alliance • World's most popular operating system, powering billions of devices globally • Open-source nature allows for customization and flexibility
- 5. ANDROID 01 Open Source 02Popularity 03 Versatility Why matters
- 6. Activity Service Android app components 01 02 03 Contentprovider 04 Broadcast receiver
- 7. • Activities arethe fundamental units of user interaction in an Android app. • Each activity represents a single, focused screen that the user can see and interact with. Examples: A login screen An email composition screen A settings page Activity
- 8. • Services arecomponents that run in the background without a direct user interface. • Handle long-running tasks or operations that need to continue even if the user switches away from the app. Examples: Playing music Downloading files in the background Periodically updating data from a server Service
- 9. • Content providersmanage access to a central repository of data. • Act as an intermediary between your app's data and other apps or components. • Enforce a standard way to read and write data, ensuring consistency and security. Common Use Cases: Storing and retrieving contacts Accessing media files (images, videos) Sharing data between multiple apps Content Provider
- 10. • Broadcast receiversallow apps to respond to system- wide or custom messages (broadcasts). • Act as passive listeners for specific events they are registered to receive. Examples of broadcasts: Battery level change Incoming SMS App installation/removal Broadcast receiver
- 11. Android Studio Available flavors: 1. Stable 2.Beta 3. Canary Android Studio is the official IDE created by Google for Android app development. It is based on Jetbrains IDE. https://developer.android.com/studio Download
- 12. Kotlin https://kotlinlang.org • Kotlin isa statically typed programming language designed for the JVM (Java Virtual Machine). • Official language for Android development, fully supported by Google. • Supports multiplatform. Kodee – Kotlin’s mascot
- 13. Kotlin – Data types •Supports all of the commonly used data types: Int, Double, String, Boolean, etc. • Properties can be written as val (can’t be modified) or var (which can be modified). Example val name: String = "Alice" var age: Int = 25
- 14. Kotlin – Functions • Kotlinfunctions can be declared at the top level in a file, meaning you do not need to create a class to hold a function. • You must explicitly declare if a variable can hold null values. Example fun greet(name: String) { println("Hello, $name!") } fun main() { greet("Bob") // Output: Hello, Bob! }
- 15. Kotlin – Operators • ?.(Safe call operator): Calls a method or accesses a property only if the object is not null. • !! (Not-null assertion operator): Asserts an expression is not null; throws an exception if it is. • Elvis Operator: ?: Provides a default value when an expression might be null. Example val length = maybeNullString?.length val nonNullValue = definitelyNotNullValue!! val result = value ?: defaultValue
- 16. Material Design https://m3.material.io Google’s design guidelines. Usuallyused for Android app development.
- 17. Imperative Programming Tell the code“How” to do it. Example val textView = view.findViewById(R.id.myTextView) textView.text = "Hello, world!" Developer’s role is to provide the sequence of operations.
- 18. Declarative Programming Tell the code“what” needs to be done. Example @Composable fun MyComposableView() { Text(text = "Hello, world!") } Developer’s role on the sequence is abstracted. The framework takes care of achieving the goal.
- 19. Jetpack Compose https://developer.android.co m/jetpack/compose A declarative programming frameworkfor building UI elements in an Android app.
- 20. Why use jetpackCompose? • Less Code: Declarative style reduces verbosity. • Faster Development: Real-time previews and intuitive code updates. • Improved Maintainability: Clear separation of UI and logic. • Modern Approach: Aligned with industry trends and Google's focus.
- 21. LIVE DEMO Android Project structureand navigating the IDE.
- 22. Android project structure •app/src/main: Contains the core components of your Android project. • java (or kotlin): Houses your source code in Java or Kotlin files. • res: Stores resources like layouts, images, and strings. • drawable: For image assets (PNG, JPEG, etc.). • layout: XML files defining your app's user interface. • mipmap: Launcher icons of different resolutions. • values: Houses XML files for various resources like strings, colors, dimensions. • app/manifests: • AndroidManifest.xml: Essential file describing your app's structure, activities, permissions, etc. • app/build.gradle: Build configuration file for your app module. • build.gradle (Project): Top-level build configuration for the entire project.
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- 24. Android Virtual Device •AVDs are software emulators that mimic real Android devices within your computer. • Essential for testing your apps on different: • Screen sizes and resolutions • Android API levels (versions) • Hardware configurations (camera, sensors, etc.)
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- 26. This work islicensed under the Apache 2.0 License goo.gle/compose-samples
- 27. This work islicensed under the Apache 2.0 License @Composable fun SurveyAnswer(answer: Answer) { Row { Image(answer.image) Text(answer.text) RadioButton(false, onClick = { /* … */ }) } } // SurveyAnswer.kt
- 28. This work islicensed under the Apache 2.0 License Construct UI by describing what, not how.
- 29. This work islicensed under the Apache 2.0 License
- 30. This work islicensed under the Apache 2.0 License
- 31. This work islicensed under the Apache 2.0 License
- 32. This work islicensed under the Apache 2.0 License Architecture patterns solves large scale problems, Where as Design patterns solve small scale problems.
- 33. This work islicensed under the Apache 2.0 License Design Patterns
- 34. This work islicensed under the Apache 2.0 License Design patterns solves problems in one layer of the app.
- 35. This work islicensed under the Apache 2.0 License Design Patterns Singleton Repository Observer
- 36. This work islicensed under the Apache 2.0 License Architecture Patterns
- 37. This work islicensed under the Apache 2.0 License Architecture patterns solves problems in multiple layers of the app.
- 38. This work islicensed under the Apache 2.0 License Separation of concerns principle, states that different parts of a software system should be responsible for different things.
- 39. This work islicensed under the Apache 2.0 License MVP Model View Presenter
- 40. This work islicensed under the Apache 2.0 License Model - Stores the data. View - Displays the data. Presenter - Manages the data. Drawback: No place to handle user inputs.
- 41. This work islicensed under the Apache 2.0 License MVVM Model View ViewModel
- 42. This work islicensed under the Apache 2.0 License Model - Stores the data. View - Displays the data. ViewModel - Handles user input and manages the data.
- 43. This work islicensed under the Apache 2.0 License Event handler UI element onClick()
- 44. This work islicensed under the Apache 2.0 License UI State
- 45. This work islicensed under the Apache 2.0 License UI 2 State 2
- 46. Play Console • GooglePlay Console: Developer platform to publish and manage your apps. • One-Time Fee: $25 registration fee to create a developer account. • App Preparation: Follow Google's guidelines for content, quality, and security. • Release Process: Create store listings, upload your app, and submit for review.
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- 50. Best Practices forPerformance • Efficient background tasks: Use threads, coroutines, or WorkManager judiciously to prevent blocking the main UI thread. • Focus on accessibility: Design your app to be usable by people with disabilities (screen readers, large text sizes, etc.) • Thorough testing: Test on a range of devices and network conditions to ensure a consistent experience.
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- 52. https://www.linkedin.com/in/ sagar-das-077a4a7b/ THANKS Feel free toconnect on LinkedIN https://medium.com/@sagar.das Performance Engineering Blogs GDG BOSTON ANDROID @bostonandroid
Editor's Notes
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- #27 Let’s see how we can build the single choice question screen of Jetsurvey.
- #28 Instead of writing this in XML, we would define our elements directly in code—in Kotlin. Doing it this way, we no longer have to jump between XML and code, as the UI would already be declared in code.
- #29 This is what we mean by ‘what not how’. We are declaring what our UI should look like by providing the necessary state to our UI functions, but we’re not telling Compose how it should render that state. So if State controls the UI, how do we go about updating State to update the UI?
- #30 To understand how to think about building this in Compose, let’s first look at how we might build this using Views. To simplify things, let’s look at a single component in this screen—a single answer in the survey.
- #31 To understand how to think about building this in Compose, let’s first look at how we might build this using Views. To simplify things, let’s look at a single component in this screen—a single answer in the survey.
- #32 To understand how to think about building this in Compose, let’s first look at how we might build this using Views. To simplify things, let’s look at a single component in this screen—a single answer in the survey.
- #33 Constructing UI by describing what, not how, is a key difference between Compose and Views—it is what makes Compose much more intuitive to work with.
- #35 Data Layer, UI Layer
- #36 This component is composed of an image, some text, and a radio button, all arranged horizontally.
- #38 Data Layer, UI Layer
- #39 Data Layer, UI Layer
- #40 This component is composed of an image, some text, and a radio button, all arranged horizontally.
- #41 Data Layer, UI Layer
- #42 This component is composed of an image, some text, and a radio button, all arranged horizontally.
- #43 Data Layer, UI Layer
- #44 In Compose, we do that through events. When a user interacts with a UI element, the UI emits an event, such as onClick(), and the event handler can then decide if the UI’s state should be changed.
- #45 If UI state changes, the functions, or UI elements, that depend on that state will be re-executed. This process of regenerating the UI when state changes is called recomposition.
- #46 The process of converting state into UI and state changes causing UI to regenerate, is at the core of how Compose works as a UI framework. Let’s revisit our example and update our implementation so that the RadioButton gets toggled when it is clicked.
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