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৽ݴޠ
KotlinͰ
Androidϓϩάϥϛϯά
%SPJE,BJHJ
!
ຊ,PUMJOϢʔβάϧʔϓ
ᖒଠ!OHTX@UBSP
͜ͱΓΜ
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ࣗݾհ
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͡Ί·ͯ͠ʂ
w ᖒଠ!OHTX@UBSP
w ࣄͰ+BWB
"OESPJEɺͱ͖Ͳ͖4DBMB
w ࡀɺֈ࠲ɺͱ͕େ͖
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Θͨ͠ͱAndroid
w ग़ձ͍ɻ)5"Ͱ༡ΜͰΈͨͷ͕࠷ॳ
w ݸਓͰʮເͱຐ๏ͷͪ࣌ؒʯͱ͍͏ΞϓϦΛ։
ൃɾެ։͍ͯ͠·͢ ສ%-
w ॻ੶ٕज़ܥಉਓࢽͳͲʹܞΘΒ͍͍ͤͯͨͩͨ
ܦݧ͕͋Γ·͢
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Θͨ͠ͱKotlin
w ເதʹͳΓ࢝Ίͨͷ
w ҎདྷɺϒϩάษڧձͰใൃ৴
w 4PGUXBSF%FTJHO ٕධ
Ͱ,PUMJOهࣄΛ࿈ࡌத
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͘͡
,PUMJOͱ
+BWBͱൺΔ
,PUMJOͰ"OESPJEϓϩάϥϛϯά
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1. Kotlinͱ
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࣭
Kotlinͱ͍͏ϓϩάϥϛϯάݴޠ
Λฉ͍ͨ͜ͱ͕͋Γ·͔͢ʁ
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w !+BLF8IBSUPO͞Μ
w ʮ6TJOH1SPKFDU,PUMJOGPS"OESPJEʯ
w !LJSJNJO͞Μ
w ʮͷ"OESPJE։ൃ,PUMJOͰܾ·Γ͔
͠Εͳ͍ʯ
Androidք۾Ͱόζͬͨʁ
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Kotlinͱ
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Kotlinͱ
Better Java
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w Նʹ+FU#SBJOTʹΑΓൃද
w Φʔϓϯιʔε "QBDIF-JDFOTF
w +7.ݴޠɺBMU+4ɺ"OESPJEαϙʔτ
w ੩తܕ͚ΦϒδΣΫτࢦݴޠ
Kotlinͱ (ৄ͘͠)
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ଞͷJVMݴޠͱͷҧ͍
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ଞͷJVMݴޠͱͷҧ͍
ϚΠϧυ
ݱ࣮ݟͯΔײ
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Kotlinͷಛ
؆୯
҆શ
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2. JavaͱൺΔ
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Hello World (Java)
class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, world!");
}
}
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Hello World (Kotlin)
fun main(args: Array) {
println("Hello, world!")
}
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Hello World (Kotlin)
fun main(args: Array) {
println("Hello, world!")
}
τοϓϨϕϧʹ
ؔΛஔ͚Δ
ྻʹ
δΣωϦΫε
ηϛίϩϯ
ෆཁ
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ม (Java)
final int a = 0;
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ม (Kotlin)
val a = 0
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ม (Kotlin)
val a = 0
ܕਪ
Մมͳมʹ
WBSΩʔϫʔυΛ
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Ϋϥε (Java)
class User {
private final long id;
private final String name;
public User(long id, String name) {
this.id = id;
this.name = Objects.requireNonNull(name);
}
public long getId() { return id; }
public String getName() { return name; }
/
/ toString, equals, hashCodeͱ͔
}
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Ϋϥε (Kotlin)
class User(val id: Long, val name: String) {
/
/ toString, equals, hashCodeͱ͔
}
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Ϋϥε (Kotlin)
class User(val id: Long, val name: String) {
/
/ toString, equals, hashCodeͱ͔
}
ίϯετϥΫλҾ͕
ͦͷ··ϓϩύςΟʹ
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dataΞϊςʔγϣϯ
data class User(val id: Long, val name: String)
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σʔλΫϥε
val taro = User(123, "Taro")
println(taro.id) /
/ => 123
println(taro.name) /
/ => Taro
println(taro) /
/ => User(id=123, name=Taro)
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ؔܕΠϯλϑΣʔε (Java)
/
/ anonymous class
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
toast("Clicked!");
}
});
!
/
/ lambda
button.setOnClickListener(v -> toast("Clicked!"));
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ؔܕΠϯλϑΣʔε (Kotlin)
var count = 0
button.setOnClickListener { toast("${count++}") }
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ؔܕΠϯλϑΣʔε (Kotlin)
var count = 0
button.setOnClickListener { toast("${count++}") }
Ϋϩʔδϟ
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ߴ֊ؔͰίϨΫγϣϯૢ࡞
(1..999)
.filter { it % 3 == 0 || it % 5 == 0 }
.reduce { a, b -> a + b }
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ߴ֊ؔͰίϨΫγϣϯૢ࡞
(1..999)
.filter { it % 3 == 0 || it % 5 == 0 }
.reduce { a, b -> a + b }
ʮΠϯϥΠϯؔʯ
ؔϦςϥϧ͕ల։͞Ε
ΦϒδΣΫτΛੜ͠ͳ͍
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ಠࣗศརϝιου (Java)
/
/ ఆٛ
static void toast(Context c, String s) {...}
!
/
/ ݺͼग़͠
MyUtils.toast(context, "Hello");
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ಠࣗศརϝιου (Kotlin)
/
/ ఆٛ
fun Context.toast(s: String) {...}
!
/
/ ݺͼग़͠
context.toast("Hello")
!
/
/ ݺͼग़͠(ActivityͳͲͷத)
toast("Hello")
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ಠࣗศརϝιου (Kotlin)
/
/ ఆٛ
fun Context.toast(s: String) {...}
!
/
/ ݺͼग़͠
context.toast("Hello")
!
/
/ ݺͼग़͠(ActivityͳͲͷத)
toast("Hello")
ϝιουΛੜͤΔ
ʮ֦ுؔʯ
੩తʹղܾ͞ΕΔʂ
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Optional (Java)
String a = "hoge";
Optional b = Optional.of("fuga");
Optional c = null;
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Optional (Java)
String a = "hoge";
Optional b = Optional.of("fuga");
Optional c = null;
ΦϒδΣΫτੜ
୭ʹOVMMࢭΊΒΕͳ͍ʂ
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Optional (Kotlin)
val a: String = "hoge"
val b: String = null /
/ NG
!
val c: String? = "hoge"
val d: String? = null /
/ OK
!
d.toUpperCase() /
/ NG
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NULL҆શ
val a: String? = "hoge"
val b: String? = null
!
if (a != null) a.toUpperCase() else null /
/ => HOGE
if (b != null) b.toUpperCase() else null /
/ => null
!
a?.toUpperCase() /
/ => HOGE
b?.toUpperCase() /
/ => null
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NULL҆શ
val a: String? = "hoge"
val b: String? = null
!
if (a != null) a.toUpperCase() else null /
/ => HOGE
if (b != null) b.toUpperCase() else null /
/ => null
!
a?.toUpperCase() /
/ => HOGE
b?.toUpperCase() /
/ => null
OVMMͰͳ͍͜ͱ͕อূ͞Ε͍ͯΔ
ॴͰ/PU/VMMܕͱͯ͠ѻ͑Δ
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3. KotlinͰ
Androidϓϩάϥϛϯά
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Android StudioͰ͏
ී௨ʹϓϩδΣΫτΛ࡞
+BWB,PUMJOม Φϓγϣϯ
CVJMEHSBEMFͷઃఆ
ָ͍͠,PUMJOϥΠϑͷ࢝·Γʂ
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KotterKnife
w,PUMJO൛#VUUFS,OJGF
w࡞ऀ+BLF8IBSUPO͞Μ
wಋೖΈղઆͪ͜ΒΛࢀর
IUUQRJJUBDPNOHTX@UBSPJUFNTDEDEE
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KotterKnife ༻લ
var button: Button? = null
!
button = findViewById(R.id.button) as Button
!
button?.setOnClickListener {...}
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KotterKnife ༻લ
var button: Button? = null
!
button = findViewById(R.id.button) as Button
!
button?.setOnClickListener {...}
"DUJWJUZͱ͔ͷϓϩύςΟ
ຖͷpOE7JFX#Z*E
ͦͯ͠Ωϟετʜ
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KotterKnife ༻ޙ
var button: Button by bindView(R.id.button)
!
button.setOnClickListener {...}
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KotterKnife ༻ޙ
var button: Button by bindView(R.id.button)
!
button.setOnClickListener {...}
ϓϩύςΟ ಉ͡
CZΩʔϫʔυʹଓ͚ͯ
3JECVUUPOΛόΠϯυ
pOE7JFX#Z*EෆཁͰ
ී௨ʹ͑ΔΑ͏ʹͳͬͯΔ
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Kotlin Android Extensions
w"4 ͱ*OUFMMJ+*%&"
ͷϓϥάΠϯ
wpOE7JFX#Z*EΛۦஞ͢Δͭ
wνϡʔτϦΞϧͪ͜ΒΛࢀর
IUUQLPUMJOMBOHPSHEPDTUVUPSJBMTBOESPJEQMVHJOIUNM
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༻ྫ
import kotlinx.android.synthetic.activity_main.button
!
public class MainActivity: Activity() {
override fun onCreate(savedInstaceState: Bundle?) {
super.onCreate(savedInstaceState)
setContentView(R.layout.activity_main)
button.setOnClickListener {...}
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Anko
w͍ΖΜͳ%4-
wओʹϨΠΞτΛΉ%4-
wܕ҆શɺ؆ܿɾϦʔμϒϧɺ෦Խɾ
࠶ར༻ੑ
wৄࡉͪ͜Β
IUUQTHJUIVCDPN+FU#SBJOTBOLP
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No content
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·ͱΊ
w ,PUMJOϓϩάϥϚʹ༏͍͠ʮݱ࣮ࢦʯݴޠ
w "OESPJEͰ͏ͱͤʹͳΕΔ͔
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͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠
Let’s enjoy Kotlin!