炎炎夏日學 Android 課程 - Part1: Kotlin 語法介紹

炎炎夏⽇日學 Android
Johnny Sung
Part1: Kotlin 語法介紹

Mobile device developer
Johnny Sung
https://fb.com/j796160836
https://blog.jks.coﬀee/
https://www.slideshare.net/j796160836
https://github.com/j796160836

⼤大綱
• Kotlin 語法介紹

• Android 元件介紹

• Hello Android

環境準備
• 電腦⼀一台 💻

• 安裝 Android Studio & Android SDK

• Android ⼿手機⼀一⽀支（極建議，非必要）

• 夠快的網路路 Wiﬁ

• 你最愛的飲料⼀一杯 🥤

純命令列列環境
• 電腦版 IntelliJ 新增 Kotlin JVM 專案

• IntelliJ IDEA CE 
https://www.jetbrains.com/idea/

• Kotlin 線上編譯器 
https://play.kotlinlang.org

• Java 線上編譯器 
https://www.tutorialspoint.com/compile_java_online.php

純命令列列環境
線上版電腦版
• 優點：跨平台，不需安裝， 
不佔硬碟空間，快速⽅方便便使⽤用。

• 缺點：編輯器語法⾃自動完成較陽春， 
無⾃自動格式化。
• 優點：編譯較快， 
編輯器語法⾃自動完成較完整，

• 缺點：需安裝，佔硬碟空間。

IntelliJ IDEA CE 
https://www.jetbrains.com/idea/

Kotlin 線上編譯器 
https://play.kotlinlang.org

Java 線上編譯器 
https://www.tutorialspoint.com/compile_java_online.php

炎炎夏日學 Android 課程 - Part1: Kotlin 語法介紹

https://www.citiesocial.com/products/picardie-500ml-6
glass

var glass: String = "檸檬紅茶茶"
變數名稱型態值
宣告（指定給...）
（初始化）

http://www.royalhost.com.tw/m/mealList.php?class_type=07&pid=132
glass

• 數字

• String 字串串（陸譯：字符串串）

• Boolean 布林林（陸譯：布爾）

• Array 陣列列（陸譯：數組）

• Char 字元（陸譯：字符）
• Double ⾼高精度浮點數 (64 bit)

• Float 浮點數 (32 bit)

• Long 長整數 (64 bit)
基礎資料型態
https://www.kotlincn.net/docs/reference/basic-types.html
• Int 整數 (32 bit)

• Short 整數 (16 bit)

• Byte 整數 (8 bit)

var val宣告⼀一個可修改的變數宣告⼀一個不可改的常數

var number: Int? = null
var number2: Int = 1
有問號
沒有問號

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Int? Int
有問號沒有問號
變數可以為空值變數不可為空值

var 
（變數可修改）
val 
（變數不可改）
型態有問號 
（可以為空值）
✅ ❌
型態沒有問號 
（不可為空值）
✅  
（需給初始值）
✅ 
（需給初始值）

var myString1: String = "abc"
var myString2: String? = null
val myString3: String = "abc"
宣告⼀一個 myString 的字串串，初始為 "abc" (不為 null，⼀一定要給值)
宣告⼀一個可為 null 的字串串叫 myString，初始為 null
宣告⼀一個不可改的字串串叫 myString，值為 "abc"

流程與判斷  
(Conditions & Flows)

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（⾃自動判斷為布林林值，省略略型態寫法）
var temperature = 15
if (temperature > 40) {
print("是熱⽔水")
} else {
print("是冷⽔水")
}

var isCreature = true
if (isCreature) {
print("是⽣生物")
} else {
print("不是⽣生物")
}
（⾃自動判斷為布林林值，省略略型態寫法）

常⽤用運算元
== 等於
> ⼤大於
>= ⼤大於等於
< ⼩小於
<= ⼩小於等於
&& AND
|| OR
! NOT
真值表
A B A && B A || B
false false false false
false true false true
true false false true
true true true true

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val viewType: Int = 1
when (viewType) {
1, 2 -> {
// Do something with value 1 or 2
}
3 -> {
// Do something with value 3
}
else -> {
// Do something with default
}
}

switch (viewType) {
case 1:
case 2:
break;
case 3:
break;
default:
}
val viewType: Int = 1
when (viewType) {
1, 2 -> {
}
3 -> {
}
else -> {
}
}
Java Kotlin
😮

Java Kotlin
if (item instanceof ModelA) {
// ...
} else if (item instanceof ModelB) {
// ...
} else if (item instanceof ModelC) {
// ...
} else {
// ...
}
when (item) {
is ModelA -> {
// ...
}
is ModelB -> {
// ...
}
is ModelC -> {
// ...
}
else -> {
// ...
}
}
😎
型態判斷
型態判斷

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( 0 到 1
0 )
for (i in 0..10) {
println(i)
}
開始值結束值
關鍵字的點點
賦予計數的變數名 
（計數器的變數）

開始值結束值
關鍵字 downTo
賦予計數的變數名 
（計數器的變數）
for (i in 10 downTo 0 step 1) {
println(i)
}
步進值
( 10 到 0 )

Java
Kotlin
for (i in 10 downTo 0 step 1) {
println(i)
}
for (int i = 10; i >= 0; i--) {
System.out.println(i);
}
for (i in 0..10) {
println(i)
}
for (int i = 0; i <= 10; i++) {
System.out.println(i);
}
( 0 到 10 )
( 10 到 0 )
( 0 到 10 )
( 10 到 0 )

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Java
Kotlin
String[] strings = new String[]{"a", "b"};
陣列列型態
陣列列型態
val strings: Array<String> = arrayOf("a", "b")
ArrayList<String> strings = new ArrayList<>();
strings.add("a");
strings.add("b");
strings.add("c");
val strings:ArrayList<String> = ArrayList<String>()
strings.add("a")
strings.add("b")
strings.add("c")
ArrayList 型態
ArrayList 型態

陣列列搭配 for 迴圈是好⿇麻吉
☺

Java
Kotlin
val strings = arrayOf("a", "b", "c")
for ((index, value) in strings.withIndex()) {
println("The element at $index is $value")
}
String[] strings = new String[]{"a", "b", "c"};
for (int index = 0; index < strings.length; index++) {
String value = strings[index];
System.out.println("The element at " + index + " is " + value);
}

Kotlin
型態省略略
val strings = arrayOf("a", "b")
val strings = ArrayList<String>()
strings.add("a")
strings.add("b")
strings.add("c")
型態省略略
val num = 1
val str = "hello"
型態省略略
型態省略略
val str:String = "hello"
val num:Int = 1

Java
Kotlin
for (int i = 0; i < strings.length; i++) {
String string = strings[i];
// ...
}
for (String string : strings) {
// ...
}
for (string in strings) {
// ...
}
String[] strings = new String[]{"a", "b"};
陣列列
陣列列
val strings: Array<String> = arrayOf("a", "b")
for (i in 0 until strings.size) {
// ...
}

a0
a1
a2
a3
a4
b0
b1
b2
b3
b4
c0
c1
c2
c3
c4
d0
d1
d2
d3
d4

val ice = arrayOf(
arrayOf("a0", "a1", "a2", "a3", "a4"),
arrayOf("b0", "b1", "b2", "b3", "b4"),
arrayOf("c0", "c1", "c2", "c3", "c4"),
arrayOf("d0", "d1", "d2", "d3", "d4")
)

ice[0][0]
ice[0][1]
ice[0][2]
ice[0][3]
ice[0][4]
ice[1][0]
ice[1][1]
ice[1][2]
ice[1][3]
ice[1][4]
ice[2][0]
ice[2][1]
ice[2][2]
ice[2][3]
ice[2][4]
ice[3][0]
ice[3][1]
ice[3][2]
ice[3][3]
ice[3][4]

fun plus(a: Int, b: Int): Int {
return a + b
}
參參數1 參參數1型態參參數2 參參數2型態函式名字回傳值型態(宣告)
(呼叫)
val c = plus(1,3)

Anonymous function
匿名函式

my_button.setOnClickListener {
// ...
}

my_button.setOnClickListener(object : View.OnClickListener {
override fun onClick(v: View?) {
// ...
}
})
my_button.setOnClickListener {
// ...
}

val doneCallback: () -> Unit = {
// I'm done!
}
doneCallback()
doneCallback.invoke()
(宣告)
(呼叫)
變數型態
呼叫

val doneCallback: (String) -> Unit = { str ->
println(str)
}
(宣告)
(呼叫)
變數型態
呼叫
doneCallback.invoke("The result")

var doneCallback: ((String) -> Unit)? = null
doneCallback = { str ->
println(str)
}
doneCallback?.invoke("The result")
(宣告)
(呼叫)
可能為 null 的型態
如果是 null 就不呼叫
if (doneCallback != null) {
doneCallback.invoke("The result")
}

錯誤處理理
try {
// ...
throw IllegalArgumentException("Invalid argument.")
// ...
} catch (e: Exception) {
e.printStackTrace()
}
拋出錯誤
接住錯誤

class MyClass {
private val str = "hello"
public fun printHello() {
println(str)
}
}
類別名
類別變數
類別⽅方法

public class MyClass {
private String str = "hello";
public void printHello() {
System.out.println(str);
}
}
class MyClass {
private val str = "hello"
public fun printHello() {
println(str)
}
}
Java Kotlin

class 類別 object 物件
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class MyDataModel {
var name: String? = ""
var num: Int = 0
}
val model = MyDataModel()
model.name = "John"
model.num = 123
建立 MyDataModel 物件

Java Kotlin
class Student {
private String name;
public Student(String name) {
this.name = name;
}
public void printName() {
System.out.println(name);
}
}
class Student {
var name: String
constructor(name: String) {
this.name = name
}
fun printName(){
println(name)
}
}
建構⼦子

建構⼦子的變形
class Student {
var name: String
constructor(name: String) {
this.name = name
}
fun printName(){
println(name)
}
}
class Student(var name: String) {
fun printName(){
println(name)
}
}

class MyClass {
companion object {
fun staticMethod() {
}
}
}
public class MyClass {
public static void staticMethod() {
}
}
Java
Kotlin

Kotlin
class MyClass {
companion object {
}
}
}
object MyClass {
}
}

物件導向程式設計 
（Object-oriented programming)
• 抽象（Abstraction）

• 封裝（Encapsulation）

• 繼承（Inheritance）

• 多型（Polymorphism）
陸譯：⾯面向对象程序设计

interface Animal {
fun sound()
}
class Cat : Animal {
override fun sound() {
println("喵喵喵～")
}
}
class Dog : Animal {
override fun sound() {
println("汪汪汪～")
}
}
繼承（或實作）
val pet: Animal = Cat()
pet.sound()
// 喵喵喵～

class HairClipperForDog {
fun haircut(dog: Dog) {
println("(理理髮器聲...)")
dog.sound()
println("頭⽑毛理理好了了！")
}
}
class HairClipperForCat {
fun haircut(cat: Cat) {
cat.sound()
}
}
val myCat = Cat()
val catClipper = HairClipperForCat()
catClipper.haircut(myCat)
val myDog = Dog()
val dogClipper = HairClipperForDog()
dogClipper.haircut(myDog)

class HairClipper {
fun haircut(animal: Animal) {
animal.sound()
}
}
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val hairClipper = HairClipper()
val myDog = Dog()
hairClipper.haircut(myDog)
val myCat = Cat()
hairClipper.haircut(myCat)

Java Kotlin
interface Animal {
public void eat();
}
class Cat implements Animal {
@Override
public void eat() {
// ...
}
}
class Dog implements Animal {
@Override
public void eat() {
// ...
}
}
interface Animal {
fun eat()
}
class Cat : Animal {
override fun eat() {
// ...
}
}
class Dog : Animal {
override fun eat() {
// ...
}
}

變數轉型
• 基本型別的轉型

• 有對應函式能使⽤用

變數轉型
• 物件的轉型

• 要是繼承樹裡的才能轉型
open class Father {
// ...
}
class Brother: Father() {
// ...
}
var a: Father = Brother()
var b = a as? Brother
如果轉型失敗就回傳 null
變數型態為：Brother?

Collections
• Map

• HashMap

• TreeMap
• List

• ArrayList

• LinkedList

• Stack

• Queue
• Set

• SortedSet

• HashSet

• TreeSet
[ 清單類 ] [ 不重複類 ] [ key-value 類 ]

ArrayList
strings.add("a")
strings.add("b")
strings.add("b")
strings.add("a")
ArrayList 型態
( 有順序的清單 )
a b b a

Array 陣列列 ArrayList
可修改數量量數量量不可修改
（數量量在宣告時即固定，不可修改）

為何宣告不可改的東⻄西⼜又可以改？
strings.add("a")
strings.add("b")
strings.add("c")
宣告不可改
為什什麼⼜又可以改？

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倉庫
倉庫倉庫
倉庫
倉庫

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主臥室
⼩小孩房客廳
⼯工作室
倉庫

空間本⾝身不能變， 
內裝配置沒限制 😊

HashSet
val hashSet = HashSet<String>()
hashSet.add("a")
hashSet.add("a")
hashSet.add("b")
hashSet.add("b")
a
b
( 不允許重複的資料集 )

HashMap
val students = HashMap<String, String>()
students.put("A001", "王⼤大明")
students.put("A002", "黎黎曉彤")
students.put("A003", "桃⼤大姐")
students.put("A001", "王⼤大明")
王⼤大明
黎黎曉彤
桃⼤大姐A001 A002
A003
(⽤用 key-value 存放的不重複資料集 )

猛虎出柙雙劍合璧版--最新 OCA / OCP Java SE 7 Programmer 專業認證
https://books.google.com.tw/books?id=EElBCgAAQBAJ&pg=PA407&lpg=PA407&source=bl&ots=bPzrpKU4n4&sig=ACfU3U31_OKnAJo5ELdqMfu2E4TNIW218A&hl=zh-TW&sa=X&ved=2ahUKEwi-u5uYzPTiAhWKF6YKHVAXB-sQ6AEwAHoECAkQAQ#v=onepage&

程式設計原則 - SOLIDby Robert C. Martin

SOLID
• 單⼀一職責原則 Single responsibility

• 開放封閉原則 Open-Close

• ⾥里里⽒氏替換原則 Liskov substitution

• 接⼝口隔離原則 Interface segregation

• 依賴反轉原則 Dependency inversion
by Robert C. Martin
https://ithelp.ithome.com.tw/articles/10191553
http://teddy-chen-tw.blogspot.com/2014/04/solid.html

單⼀一職責原則 
(Single responsibility principle, SRP)
每個類別 (class)、函數 (method) 負責的功能，都應該只做⼀一件事。

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<物品名稱>
<物品>
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ArrayList
strings.add("a")
strings.add("b")
strings.add("c")
ArrayList 型態
泛型帶入的型別

class HairClipper<T : Animal> {
fun haircut(animal: T) {
animal.sound()
}
}
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⾃自⼰己取的型態 T
只限於 Animal 繼承樹上的

val myDog = Dog()
val hairClipperForDog = HairClipper<Dog>()
hairClipperForDog.haircut(myDog)
val myCat = Cat()
val hairClipperForCat = HairClipper<Cat>()
hairClipperForCat.haircut(myCat)

延伸閱讀
https://classroom.udacity.com/courses/ud9011/
https://classroom.udacity.com/courses/ud9012/
Kotlin Bootcamp for Programmers
Developing Android Apps with Kotlin

延伸閱讀
https://kotlinlang.org/docs/tutorials/
https://kotlinlang.org/docs/reference/
Kotlin Tutorials
Learn Kotlin
https://www.kotlincn.net/docs/reference/
https://www.kotlincn.net/docs/reference/
https://www.kotlincn.net/docs/tutorials/

炎炎夏日學 Android 課程 - Part1: Kotlin 語法介紹

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