Intent.putExtras()←これ

Activityを呼び出す儀式をめぐる冒険

1. Intent.putExtras()←これ Yahoo! JAPAN　森洋之
2. in the Stone Age
3. val intent = Intent(this, MyActivity2::class.java) intent.putExtra("foo", "FOO") intent.putExtra("bar", 333) startActivity(intent)
4. val intent = Intent(this, MyActivity2::class.java) intent.putExtra("foo", "FOO") intent.putExtra("bar", 333) startActivity(intent) ・口伝でのみ伝えられる、必須パラメータ ・パラメータの型は、ムラハチレベルの掟
5. val intent = Intent(this, MyActivity2::class.java) intent.putExtra("foo", "FOO") intent.putExtra("bar", 333) startActivity(intent) ・キモい
6. val intent = Intent(this, MyActivity2::class.java) intent.putExtra("foo", "FOO") intent.putExtra("bar", 333) startActivity(intent) ・手続き的で、あまり読みたくないコード
7. 拡張関数
8. inline fun <reified T : Activity> Context.startActivity( noinline extras: (Intent.() -> Unit)? = null) { val intent = Intent(this, T::class.java) extras?.let { intent.extras() } startActivity(intent) }
9. startActivity<MyActivity2>{ putExtra("foo", "FOO") putExtra("bar", 333) } ・だいぶ読みやすくなった
10. startActivity<MyActivity2>{ putExtra("foo", "FOO") putExtra("bar", 333) } ・相変わらず、村の掟ベースのActivity起動
11. Companion Object
12. companion object { const val EXTRA_FOO = "foo" const val EXTRA_BAR = "bar" fun showFoo(context: Context, foo: String, bar: Int) { context.startActivity<MyActivity2> { putExtra(EXTRA_FOO, foo) putExtra(EXTRA_BAR, bar) } } }
13. MyActivity2.showFoo(this, "FOO", 333) ・型セーフ ・Null安全 ・村の掟からの解放
14. companion object { const val EXTRA_FOO = "foo" const val EXTRA_BAR = "bar" const val EXTRA_HOGE = "foo" const val EXTRA_FUGA = "bar" fun showFoo(context: Context, foo: String, bar: Int) { context.startActivity<MyActivity2> { putExtra(EXTRA_FOO, foo) putExtra(EXTRA_BAR, bar) } } fun showHoge(context: Context, hoge: String, fuga: String) { context.startActivity<MyActivity2> { putExtra(EXTRA_HOGE, hoge) putExtra(EXTRA_FUGA, fuga) } } } 受け付けるパターンが増えると
15. companion object { const val EXTRA_FOO = "foo" const val EXTRA_BAR = "bar" const val EXTRA_HOGE = "foo" const val EXTRA_FUGA = "bar" fun showFoo(context: Context, foo: String, bar: Int) { context.startActivity<MyActivity2> { putExtra(EXTRA_FOO, foo) putExtra(EXTRA_BAR, bar) } } fun showHoge(context: Context, hoge: String, fuga: String) { context.startActivity<MyActivity2> { putExtra(EXTRA_HOGE, hoge) putExtra(EXTRA_FUGA, fuga) } } }
16. override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main2) when { intent.extras.containsKey(EXTRA_FOO) && intent.extras.containsKey(EXTRA_BAR) -> { // foo pattern } intent.extras.containsKey(EXTRA_HOGE) && intent.extras.containsKey(EXTRA_FUGA) -> { // hoge pattern } else -> throw IllegalArgumentException("staticメソッドから起動してね ") } }
17. Sealed Class
18. private sealed class Extras { data class Foo(val foo : String, val bar : Int) : Extras(), Parcelable { companion object { @JvmField @Suppress("unused") val CREATOR: Parcelable.Creator<Foo> = object : Parcelable.Creator<Foo> { override fun createFromParcel(source: Parcel): Foo = Foo(source) override fun newArray(size: Int): Array<Foo?> = arrayOfNulls(size) } } protected constructor(parcelIn: Parcel) : this(parcelIn.readString(), parcelIn.readInt()) override fun writeToParcel(dest: Parcel?, flags: Int) { dest?.writeString(foo) dest?.writeInt(bar) } override fun describeContents(): Int = 0 } data class Hoge(val hoge : String, val fuga : String) : Extras(), Parcelable { companion object { @JvmField @Suppress("unused") val CREATOR: Parcelable.Creator<Hoge> = object : Parcelable.Creator<Hoge> { override fun createFromParcel(source: Parcel): Hoge = Hoge(source) override fun newArray(size: Int): Array<Hoge?> = arrayOfNulls(size) } } protected constructor(parcelIn: Parcel) : this(parcelIn.readString(), parcelIn.readString()) override fun writeToParcel(dest: Parcel?, flags: Int) { dest?.writeString(hoge) dest?.writeString(fuga) } override fun describeContents(): Int = 0 } }
19. private sealed class Extras { data class Foo(val foo : String, val bar : Int) : Extras(), Parcelable { companion object { @JvmField @Suppress("unused") val CREATOR: Parcelable.Creator<Foo> = object : Parcelable.Creator<Foo> { override fun createFromParcel(source: Parcel): Foo = Foo(source) override fun newArray(size: Int): Array<Foo?> = arrayOfNulls(size) } } protected constructor(parcelIn: Parcel) : this(parcelIn.readString(), parcelIn.readInt()) override fun writeToParcel(dest: Parcel?, flags: Int) { dest?.writeString(foo) dest?.writeInt(bar) } override fun describeContents(): Int = 0 } data class Hoge(val hoge : String, val fuga : String) : Extras(), Parcelable { companion object { @JvmField @Suppress("unused") val CREATOR: Parcelable.Creator<Hoge> = object : Parcelable.Creator<Hoge> { override fun createFromParcel(source: Parcel): Hoge = Hoge(source) override fun newArray(size: Int): Array<Hoge?> = arrayOfNulls(size) } } protected constructor(parcelIn: Parcel) : this(parcelIn.readString(), parcelIn.readString()) override fun writeToParcel(dest: Parcel?, flags: Int) { dest?.writeString(hoge) dest?.writeString(fuga) } override fun describeContents(): Int = 0 } } 論外
20. Parcelize
21. private sealed class Extras { @Parcelize data class Foo(val foo : String, val bar : Int) : Extras(), Parcelable @Parcelize data class Hoge(val hoge : String, val fuga : String) : Extras(), Parcelable } ・Kotlin Android Extensionsで、Parcelableは簡単に作れる ・experimental注意
22. companion object { fun showFoo(context: Context, foo : String, bar : Int) { context.startActivity<MyActivity2> { putExtra(EXTRAS_KEY, Extras.Foo(foo, bar)) } } fun showHoge(context: Context, hoge : String, fuga : String) { context.startActivity<MyActivity2> { putExtra(EXTRAS_KEY, Extras.Hoge(hoge, fuga)) } } }
23. override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main2) val extras = intent.getParcelableExtra<Parcelable>(EXTRAS_KEY) ?: throw IllegalArgumentException("staticメソッドから起動してね ") when(extras) { is Extras.Foo -> { // foo pattern } is Extras.Hoge -> { // hoge pattern } } }
24. override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main2) val extras = intent.getParcelableExtra<Parcelable>(EXTRAS_KEY) ?: throw IllegalArgumentException("staticメソッドから起動してね ") when(extras) { is Extras.Foo -> { // foo pattern } is Extras.Hoge -> { // hoge pattern } } }
25. 委譲Property
26. class ExtraParcelable : ReadOnlyProperty<Activity, Parcelable> { override fun getValue(thisRef: Activity, property: KProperty<*>) : Parcelable { return thisRef.intent.getParcelableExtra(EXTRAS_KEY) ?: throw IllegalArgumentException("extra parameter ${property.name} is null") } }
27. private val extras by ExtraParcelable() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main2) when(extras) { is Extras.Foo -> { // foo pattern } is Extras.Hoge -> { // hoge pattern } } }
28. おまけ
29. 改訂版が出ます ・2ヶ月半で500ページ書き直します