This document provides an overview of Android and Kotlin for mobile app development. It discusses Android versions and history starting from 2008. It also covers Kotlin as a modern programming language that is fully compatible with Java and highly integrated with Android. The document demonstrates basic Kotlin syntax and concepts. It provides examples of how to write Android apps using Java or Kotlin in Android Studio, including activities, layouts, intents, and the recycler view. It also briefly introduces architectural concepts like MVVM and libraries like Retrofit for network requests.

1. Tim

2. About Me
● NCTU AM96
● Android GDE
● Software Engineer in Amazon
● Android 十全大補
● Kotlin 全面啟動
● https://github.com/Jintin
● https://medium.com/@jintin
● https://www.facebook.com/jintinlin

3. Android

4. Android
● Start from 2008
● Android 13 this year
● App normally written in Java / Kotlin
● Mostly in Phone, but also TV, car & watch
● App can also run in Windows 11, Chromebook

5. Android Versions

6. Historical Versions

7. Recent Versions

9. Kotlin

10. Kotlin
● Build by JetBrain
● Modern programing language
● Multi-platform
○ JVM, JS, Native ...
● Statically typed OOP with lot’s FP feature
● Rank 23 in TIOBE DEC 2022

11. Kotlin
● 100% compatible with Java
● No NPE (Null Pointer Exception)
● Less code to write, high productivity

12. Kotlin vs Java

13. Kotlin & Android
● Kotlin first in Google I/O 2019
● Lot’s of KTX extension lib
● Highly integrate Kotlin feature like Coroutine, Flow

14. Basic syntax
var a: String = "test"

15. Type Omit
var a = "test"

16. Immutable
var a = "a"
val b = "b"
a = "new a"
b = "new b" //Error

17. Optional
var a: String?
var b: String
a = null
b = null //Error

18. Optional Chaining
var a: String? = null
val b: Int? = a?.substring(7)?.length
val c: Int = a?.substring(7)?.length ?: 0
val d: Int = a?.substring(7)?.length!!

19. Function
fun sum(a: Int, b: Int): Int {
a + b
}

20. Function
fun sum(a: Int, b: Int): Int =
a + b

21. Function
fun sum(a: Int, b: Int) = a + b

22. Lambda
val sum: (Int, Int) -> Int = {
a, b ->
a + b
}

23. Lambda
val sum = { a: Int, b: Int ->
a + b
}

24. interface Animal {
fun walk()
}
class Cat(val age: Int) : Animal {
override fun walk() {
println("cat walk")
}
}
Class

25. data class Cat(
val age: Int,
val color: String,
)
Data Class

26. Extension Function
fun Cat.fly() {
println("Now I can fly")
}

27. Collection
val list = listOf("a", "b", "c")
val set = mutableSetOf(1, 3, 4)
val map = mapOf<String, Any>(
"a" to 1,
"b" to "test",
"c" to false
)

28. Functional Operation
listOf(1, 2, 3, 4, 5)
.filter { it % 2 == 1 }
.map { it * 2 }
.forEach {
println(it)// 2, 6, 10
}

29. Playground
https://play.kotlinlang.org

30. How to write Android Apps
● Java / Kotlin
● Android Studio

31. Android Studio
● Android IDE base on IntelliJ IDEA
○ IntelliJ IDEA is built by JetBrain, who built Kotlin
● Include full functionality we need
○ Build / Debug / Profile / Logging
○ Android SDK / Emulator management
○ Layout Preview / Inspect
● https://developer.android.com/studio

33. New Project Template

34. New Project Template

35. Project Structure

36. Project Structure

37. Demo

38. Activity
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val textView = findViewById<TextView>(R.id.textView)
textView.text = "some text"
}
}

39. Layout XML
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"/>
</androidx.constraintlayout.widget.ConstraintLayout>

40. Activity
● Minimal Unit to display View/Page
● Need register in AndroidManifest.xml
● Launched by Intent

41. AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.jintin.myapplication">
<application
android:label="@string/app_name"
android:theme="@style/Theme.MyApplication">
<activity
android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

42. Intent
Android System
App 1
Activity A Activity B
App 2
Activity A’ Activity B’
Intent

43. Launch Intent
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val button = findViewById<TextView>(R.id.textView)
button.setOnClickListener {
startActivity(Intent(this, MainActivity::class.java))
}
}
}

44. Back Stack
Stack
Activity A
Stack
Activity A
Activity B
Stack Stack
Activity A
Activity A
Activity A

45. Demo

46. Lifecycle
onCreate
onStart
onResume
onDestroy
onStop
onPause
Running
Visible

47. RecyclerView
● List / Grid View that display huge data set
● Reuse when View is out of screen

48. RecyclerView.Adapter
● Adapt Data to View in RecyclerView
● Place to create ViewHolder

49. Add Dependency
dependencies {
implementation "androidx.recyclerview:recyclerview:1.2.1"
}

50. Structure
RecyclerView
Adapter
ViewHolder 1
View
ViewHolder 2
View
ViewHolder 3
View

51. Adapter
class MyAdapter : RecyclerView.Adapter<MyViewHolder>() {
override fun onCreateViewHolder(
parent: ViewGroup,
viewType: Int
): MyViewHolder
override fun getItemCount(): Int
override fun onBindViewHolder(
holder: MyViewHolder,
position: Int)
}

52. ViewHolder
class MyViewHolder(itemView: View) :
RecyclerView.ViewHolder(itemView) {
fun bind(data: Int) {
//TODO
}
}

53. LayoutManager
● Handle how to layout each View inside RecyclerView
● Can be Linear, Grid, or Custom

54. LayoutManager
recyclerView.layoutManager =
LinearLayoutManager(
this,
LinearLayoutManager.VERTICAL,
false
)

55. Demo

56. Retrofit
● Handle Api request
● Use dynamic proxy to generate implementation in runtime
● https://github.com/square/retrofit

57. Add Dependency
dependencies {
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
}

58. Model
data class Repo(
val id: Int,
val name: String,
val owner: User
)
data class User(
val id: Int,
@SerializedName("avatar_url")
val avatarUrl: String
)

59. Api Class
interface GitHubService {
@GET("users/{user}/repos")
fun listRepos(
@Path("user") user: String,
@Query("type") type: String? = null,
@Query("sort") sort: String? = null
): Call<List<Repo>>
}

60. Generate Instance
val retrofit = Retrofit.Builder()
.baseUrl("https://api.github.com")
.addConverterFactory(GsonConverterFactory.create())
.build()
val service = retrofit.create(GitHubService::class.java)

61. Usage
service.listRepos("Jintin")
.enqueue(object : Callback<List<Repo>> {
override fun onFailure(call: Call<List<Repo>>, t:
Throwable) {
// network fail
}
override fun onResponse(call: Call<List<Repo>>,
response: Response<List<Repo>>) {
if (response.isSuccessful) {
// success
} else {
// application level fail
}
}
})

62. Demo

63. Things not cover yet
● UI: ViewBinding, DataBinding, Compose
● Storage: File, DataBase, Room
● Architecture: MVVM, ViewMoel, LiveData
● RxJava, Coroutine, Flow
● DI: Dagger, Hilt, Koin
● Test: Mockito, MockK, Espresso
● Automation: CI, CD, Jenkins

64. Resources - Official Site
● Android Developer
● https://developer.android.com/
● Kotlin
● https://kotlinlang.org/
● Basic Android in Kotlin
● https://developer.android.com/courses/android-basics-
kotlin/course

65. Resources - FB Group
● Android Taipei 開發者社群
● https://www.facebook.com/groups/382275241893545
● Android Developer開發讀書會
● https://www.facebook.com/groups/523386591081376
● Taiwan Kotlin User Group 討論區
● https://www.facebook.com/groups/725458374837125
● Kotlin Taipei
● https://www.facebook.com/groups/117755722221972

66. Resources - Blog
● Android Weekly
● https://androidweekly.net/
● Kotlin Weekly
● http://www.kotlinweekly.net/
● Android Developer Medium
● https://medium.com/androiddevelopers
● ProAndroidDev
● https://proandroiddev.com/

67. Resources - Conference
● DroidCon
● https://www.droidcon.com/
● Coscup
● https://coscup.org/
● Mopcon
● https://mopcon.org/
● JCConf
● https://jcconf.tw/

68. Q&A