明日からちょっと KotlinでAndroidが書きたくなる(かもしれない?)SAM変換と拡張関数

2014/07/04 かわいいKotlin勉強会で行った発表の資料です

※ 元々はSlideShareで公開していた資料です。

1. ໌೔͔Βͪΐͬͱ KotlinͰAndroid͕ॻ͖ͨ͘ͳΔ(͔΋͠Εͳ͍ʁ) SAMม׵ͱ֦ுؔ਺ ɹ ࣨ੕྄ଠ 2014/7/4(ۚ))ୈ2ճ)͔Θ͍͍Kotlinษڧձ)#jkug
2. ಥવͰ͕࣭͢໰Ͱ͢ʂ
3. Kotlinॻ͍ͨ͜ͱ͋Δํʁ
4. ʮKotlin'ॻ͍ͨ͜ͱͳ͍ʯ ͬͯΠϕϯτϖʔδʹॻ͍͚ͨΕͲ ຊ౰͸ॻ͍ͨ͜ͱ͋Δํʁ
5. AndroidΞϓϦ ։ൃͨ͜͠ͱ͋Δํʁ
6. ͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ
7. ͓લͩΕΑ • ໊લ":"ࣨ੕྄ଠ • ࢓ࣄ":"AndroidΞϓϦ։ൃ(Java)ɺUnityήʔϜ։ൃ(C#) • Twi6er":"@RyotaMurohoshi • ౤ߘઌ":"h6p:/ /qiita.com/RyotaMurohoshi • ڵຯ":"Kotlin,"Groovy,"C#,"Unity,"SonyͷWearable"Device
8. AndroidΞϓϦΛJavaͰ։ൃ͍ͯͯ͠ɺ ʮͳΜͰ͜Μͳʹ৑௕ͳίʔυ͕ඞཁͳΜͩʂʯ ͬͯΠϥͬͱ͢Δ͜ͱ͸͋Γ·ͤΜ͔ʁ
9. ࢲ͸͋Γ·͢ʂ C#Λۀ຿Ͱ࢖͍࢝ΊͨΓͨ͠Γɺ GroovyΛ΄Μͷͪΐͬͱษڧͨ͠Βɺ ʮͳΜͰJavaɺʓʓͰ͖ͳ͍ͷʔʂʯ ͬͯɺΠϥοͱͳΓ·ͨ͠
10. ͦ͜ͰKotlinͰ͢Ͷʂ
11. ໌೔͔Βͪΐͬͱ KotlinͰAndroid͕ॻ͖ͨ͘ͳΔ(͔΋͠Εͳ͍ʁ) SAMม׵ͱ֦ுؔ਺ ͱ୊ͯ͠ࠓ೔͸LT͠·͢ʂ
12. ͍Βͬͱ͢Δ৑௕ͳίʔυ̍ button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Log.v(TAG, "clicked"); } }); ͲΜͳAndroidೖ໳ॻʹ΋ࡌ͍ͬͯΔɺΞΫςΟϏςΟͰΑ͘ΈΔίʔυ KotlinͰॻ͍ͨ΍ͭͱൺ΂Δͱɺ৑௕ͳͷ͕Ұ໨ྎવʂ
13. Kotlinͩͱ͖ͬ͢Γ button.setOnClickListener { Log.v(TAG, "clicked") }
14. JavaɺKotlinͦΕͧΕͷΫϦοΫϦεφʔ Kotlin button.setOnClickListener { Log.v(TAG, "clicked") } Java button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Log.v(TAG, "clicked!"); } });
15. ߦ਺͕୹͘ͳͬͨ͜ͱͰ͸ͳ͘ɺ ʮ৑௕ͳ෦෼͸ॻ͘ඞཁ͕ͳ͘ ຊ࣭తͳ͜ͱ͚ͩॻ͚͹Α͘ͳͬͨʯ ͱ͍͏ͷ͕ϛι
16. JavaͷίʔυΛ΋͏Ұ౓ݟͯΈ·͠ΐ͏ button.setOnClickListener(new View.OnClickListener() { // newҎ߱ຊ࣭͡Όͳ͍ @Override // <- ຊ࣭͡Όͳ͍ public void onClick(View v) { // <- ຊ࣭͡Όͳ͍ Log.v(TAG, "clicked!"); } // <- ຊ࣭͡Όͳ͍ }); // <- ຊ࣭͡Όͳ͍ Java͸ຊ࣭͡Όͳ͍෦෼͕ଟ͍ɻKotlin͸ຊ࣭ͷΈΛهड़͢Ε͹͍͍ Kotlin͸ͳͥ͋Μͳهड़͕Ͱ͖Δͷ͔ʁ
17. Single'Abstract'Method'Conversions SAMม׵ h"p:/ /blog.jetbrains.com/kotlin/2013/08/kotlin;m6;is;here/
18. SAM$ΠϯλʔϑΣʔε Ұͭͷ(Single))ந৅(Abstract))ϝιου(Method) Λ΋ͭΠϯλʔϑΣʔε • Runnable):)void)run() • View.OnClickListener):)void)onClick(View)v) • Response.Listener<T>):)void)onResponse(T)response)) ͳͲɺଞʹ΋ͨ͘͞Μ
19. SAMม׵ ؔ਺Ϧςϥϧ!">!SAMΠϯλʔϑΣʔε!ͳม׵ KotlinͰ͸ɺSAMΠϯλʔϑΣʔεΛҾ਺ʹͱΔϝιουͰɺ Ҿ਺ͷܕͱॱংͦͯ͠ฦ஋ܕ͕Ұக͢Δؔ਺ϦςϥϧΛ౉͢ͱ ΠϯλʔϑΣʔεʹม׵ͯ͘͠ΕΔ SAMΠϯλʔϑΣʔε͕ඞཁͳॴ΋ɺؔ਺ϦςϥϧͰεοΩϦʂ
20. SAMม׵Ͱ͖Δྫ button.setOnClickListener( { (v : View): Unit -> Log.v(TAG, "clicked") }) button.setOnClickListener( { v -> Log.v(TAG, "clicked")}) button.setOnClickListener{ v -> Log.v(TAG, "clicked") } button.setOnClickListener{ Log.v(TAG, "clicked") } val listener : (View) -> Unit = {v -> Log.v(TAG, "clicked") } //or val listener : (View) -> Unit = { Log.v(TAG, "click") } //or val listener = { (v : View) : Unit -> Log.v(TAG, "clicked") } button.setOnClickListener(listener)
21. SAMม׵Ͱ͖ͳ͍ྫ // Լه͸ίϯύΠϧΤϥʔ // Type mismatch val listener : View.OnClickListener = { (v : View) : Unit -> Log.v(TAG, "clicked") } // Լه͸࣮ߦ࣌Τϥʔ // java.lang.ClassCastException val listener = { (v : View) : Unit -> Log.v(TAG, "clicked") } as View.OnClickListener Ҿ਺ʹؔ਺ϦςϥϧΛ౉͞ͳ͍ͱ͍͚ͳ͍
22. SAMม׵ͰແବίʔυΛແͤ͘·͢Ͷʂ ΋͏Ұྫ VolleyͷStringRequest
23. VolleyͷStringRequest0Java൛ StringRequest request = new StringRequest( "https://www.google.co.jp/", new Response.Listener<String>() { @Override public void onResponse(String response) { Toast.makeText(getApplicationContext(), response, Toast.LENGTH_LONG).show(); } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError volleyError) { Toast.makeText(getApplicationContext(), "onErrorResponse", Toast.LENGTH_LONG).show(); } } ); ແବͳ෦෼͕ଟ͘ɺॎʹ௕͍ɽɽɽ
24. VolleyͷStringRequest0Kotlin൛ val request = StringRequest( url = "https://www.google.co.jp/", listener = { response -> Toast.makeText(this, response, Toast.LENGTH_LONG).show() }, errorListener = { volleyError -> Toast.makeText(this, "onErrorResponse", Toast.LENGTH_LONG).show() } ); ܕύϥʔϝʔλ͕͋ΔΠϯλʔϑΣʔε΋SAMม׵Մೳ ໊લ෇͖Ҿ਺ͰՄಡੑΞοϓ
25. ͪΐͬͱGroovy΋ΈͯΈ·͠ΐ͏ Groovy΋SAMม׵͕࢖͑ΔΑ͏Ͱ͢ɻ button.setOnClickListener { v -> Toas.makeText(this, "click", Toast.LENGTH_LONG).show() } Groovy&2.2͔Βasԋࢉࢠ͕͍Βͳ͘ͳͬͨͦ͏Ͱ͢ɻ h"p:/ /groovy.codehaus.org/Groovy+2.2+release+notes
26. ͪΐͬͱGroovy΋ΈͯΈ·͠ΐ͏ SAMΠϯλʔϑΣʔε͚ͩͰͳ͘ɺෳ਺ϝιουΛ࣋ͭΠϯλʔϑΣʔε΋ Map+Ϋϩʔδϟʔ+asԋࢉࢠͰ͜Μͳײ͡ʹʂ viewPager.setOnPageChangeListener ([ onPageScrollStateChanged: { state -> Log.v(TAG, state) }, onPageScrolled : { position, positionOffset, positionOffsetPixels -> /*ུ*/ }, onPageSelected : { position -> Log.v(TAG, position) } ] as ViewPager.OnPageChangeListener) h"p:/ /groovy.codehaus.org/Groovy+way+to+implement+interfaces
27. ࣮͸AndroidStudioͱIntelliJͩͱ Ұ͚ͭͩϝιουΛ࣮૷ͨ͠ಗ໊Ϋϥε͕͍͍ײ͡ʹʂ(SAMܕ΋) button.setOnClickListener((v) -> {Log.v(TAG, "clicked");}); IDE্Ͱ͸͍͍ײ͡ͰંΓ৞·Εͯ·͕͢ɺ githubͱ͔ͰίʔυϦϏϡʔ͢Δͱ͖͸ɺ ΄Β৞·Εͳ͍͠ɽɽɽ h"p:/ /qiita.com/RyotaMurohoshi/items/0ce799c747d91756131a
28. Ҏ্ SAMม׵Ͱͨ͠ɻ
29. ͍Βͬͱ͢Δ৑௕ͳίʔυ̎ ImageView imageView = (ImageView)findViewById(R.id.image_view); ͲΜͳAndroidೖ໳ॻʹ΋ࡌ͍ͬͯΔɺΞΫςΟϏςΟͰΑ͘ΈΔίʔυ ͚ΕͲʮImageViewʯͬͯͳΜͰ2ճॻ͘ඞཁ͋ΔΜʁܕਪ࿦ͯ͘͠Εͯ΋͍͍͡ΌΜʂ
30. ͱΓ͋͑ͣܧঝ͠·͢ʁ Ac#vityΛܧঝͨ͠ΫϥεBaseAc#vityʹͯɺ͜Μͳϝιουఆٛ͢Ε͹ɺ public <T extends View> T findById(int viewId) { return (T)findViewById(viewId); } BaseAc'vityΛߋʹܧঝͨ͠ΫϥεͰ͸ɺ͜Μͳײ͡ͰΩϟετෆཁʹͳΓ·͢Ͷ ImageView imageView = findById(R.id.image_view);
31. ͚Ͳܧঝͬͯ • ܧঝΉ͍ͣ • ʮܧঝ͕ڐ͞ΕΔͷ͸খֶੜ·ͰͩΑͶʯɺͩͱɽɽɽ • Ac$vityͷαϒΫϥε͍͔ͭ͋͘Δ͚Ͳɺશ෦ʹߋʹαϒΫϥε ࡞ͬͯϝιουఆٛ͢Δʁ ͪΐͬͱͳ͍͔ͳɽɽɽ
32. ͯ͞Ͳ͏͠·͠ΐ͏ʁ • ৑௕ͳهड़͕සൃͨ͠ΓɺΑ͘࢖͏ॲཧ͕͋Δ • Ac$vityͱ͔ʹɺϝιουΛ௥Ճ͍ͨ͠ʂ • ͚Ͳܧঝͨ͘͠ͳ͍)or)Ͱ͖ͳ͍
33. Extension)Funcitons ֦ுؔ਺ h"p:/ /confluence.jetbrains.com/display/Kotlin/Extension+func=ons
34. Extension)Funcitons(֦ுؔ਺)ͱ͸ • ܧঝͤͣʹϝιουΛ௥ՃͰ͖Δ" • ܧঝېࢭͳΫϥεʹ΋ϝιουΛ௥ՃͰ͖Δ • privateͳϝϯόʹΞΫηε͸Ͱ͖ͳ͍ • ϝιουΛΦʔόʔϥΠυ͸Ͱ͖ͳ͍
35. Extension)Func-onsͷྫ)ఆٛଆ extensions.kt಺ʹͯ package com.mrstar.extensions import android.app.Activity import android.view.View fun <T : View> Activity.findById (id : Int) : T = findViewById(id) as T
36. Extension)Func-onsͷྫ)ར༻ଆ package com.mrstar.android_with_kotlin // ུ import com.mrstar.extensions.findById // <- ஫໨ public class MainActivity() : FragmentActivity() { // <- ஫໨ protected override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) val textView: ImageView = findById (R.id.image_view) // <- ஫໨ } }
37. • fun$ClassName.methodName(hoge$:$Hoge)$:$Fuga"Έ͍ͨͳײ͡Ͱ ϝιουΛఆٛ͠·͢ • ఆ֦ٛͨ͠ுϝιουΛimport͠·͢ • ͦ͏͢Δͱී௨ͷϝιουͷΑ͏ʹ࢖͑·͢ • ͜ͷྫͩͱAc+vityͷαϒΫϥε͚ͩͰͳ͘ɺ FragmentAc+vityɺAc+onBarAc+vityɺଞͷαϒΫϥεͰ΋࢖͑ ·͢(ܧঝͰఆٛ͢ΔͳΒɺ֤Ϋϥεʹϝιουఆ͕ٛඞཁ)
38. Extension)Func-onsΛ࢖͑͹ɽɽɽ • ܧঝ͠ͳͯ͘΋ϝιουΛ௥ՃͰ͖·͢Ͷ • ͨ͘͞ΜͷΫϥεʹϝιουΛ௥Ճ͠ͳͯ͘΋͍͍Ͱ͢Ͷ • ࣗ࡞ͷϝιουͰ৑௕ͳهड़ΛεοΩϦͰ͖·͢Ͷʂ
39. ͪΐͬͱC#΋ΈͯΈ·͠ΐ͏ C#ʹ΋֦ுؔ਺ͱಉ͡Α͏ͳ֦ுϝιου͕͋Γ·͢ɻ // ఆٛଆ public static class StringExtensions { public static string Decorate(this string str, string symbol) { return string.Format("{0}{1}{2}", symbol, str, symbol); } } //ར༻ଆ string decoratedMessage = "Hello!".Decorate("===") ͜Μͳײ͡Ͱɺsta$cͳΫϥεʹsta$cͳϝιουͱ֦ͯ͠ுϝιουΛఆٛ͠·͢ɻ
40. ͪΐͬͱC#΋ΈͯΈ·͠ΐ͏ C#͸ • JavaͷpackageΞΫηεͷΑ͏ͳɺϝϯόΛಉ໊͡લۭ͚ؒͩʹ ެ։͢Δͱ͍͏੍ݶ͕ͳ͍ • privateͰsta.cͳೖΕࢠͷΫϥε͸࡞ΕΔ • ͕↑ͳΫϥεͰ͸֦ுϝιουΛఆٛͰ͖ͳ͍ ͜ͷΫϥεʹ͚ͩɺ͜ͷ໊લۭؒͰ͚ͩ࢖͑Δͱ͍͏֦ுϝιουΛఆٛͰ͖ͳ͍ʂ
41. ҰํKotlinͰ͸ • packageʹͦͷ໊લۭؒͱͦͷαϒ໊લۭؒݶఆͰ • Ϋϥε಺ʹprivateΞΫηεϨϕϧͰ • ؔ਺಺ʹϩʔΧϧؔ਺಺ͱͯ͠ɺϩʔΧϧείʔϓͰ Kotlinͩͱ֦ுؔ਺ΛఆٛͰ͖Δʂ
42. Ҏ্ ֦ுؔ਺Ͱͨ͠ɻ
43. ࣭໰͋Γ·͔͢ʁ
44. ͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ ɹ SAMม׵ʹ͍ͭͯ(Qiita) h"p:/ /qiita.com/RyotaMurohoshi