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Programming Android Application in Scala.
The document discusses using Scala to develop Android applications. Scala allows satisfying three desires at once: REPL, scripting, and compiling. It supports traits for mixin composition, functional programming, static typing with duck typing. SBT is introduced as a build tool for Scala/Android projects that does not require configuration and supports continuous compilation with an Android plugin. Live demos show installing SBT/SBT-Android and creating a sample Scala/Android project. Some limitations of Scala with Android like accessing static protected Java fields are also mentioned.
Programming Android Application in Scala.
- 1. Programming Android Applicationin Scala BrianHsu / OSDC.2010
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- 7. 僕我 了最 寫 ！喜 Android 歡 女 全我 都要 是讓 是萌 女手 僕上 燃程 ！機 的式
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- 12. 寫作 Dynamic Scripting Language
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- 18. def boom puts "Hello World" end puts " 一個小小的 typo" booom 執行期爆炸
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- 26. 理論上 Full Java Interoperability
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- 51. 真、 Duck Typing(Ruby)
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- 55. 僕我 用 了最 Scala ！喜 歡 女 寫 全我 都要 是萌 是讓 女手 燃程 僕上 ！機 的式
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- 57. Scala compared toJava Scala adds Scala removes + a pure object system - static members + operator overloading - primitive types + closures - break, continue + mixin composition with traits - special treatment of interfaces + existential types - wildcards + abstract types - raw types + pattern matching - enums Modeled in libraries: assert, enums, properties, events, actors, using, queries, …
- 58. Scala cheat sheet(1): Definitions Scala method definitions: Java method definition: def fun(x: Int): Int = { int fun(int x) { result return result } } def fun = result (no parameterless methods) Scala variable definitions: Java variable definitions: var x: Int = expression int x = expression val x: String = expression final String x = expression
- 59. Scala cheat sheet(2): Expressions Scala method calls: Java method call: obj.meth(arg) obj.meth(arg) obj meth arg (no operator overloading) Scala choice expressions: Java choice expressions, stmts: if (cond) expr1 else expr2 cond ? expr1 : expr2 if (cond) return expr1; else return expr2; expr match { case pat1 => expr1 switch (expr) { .... case pat1 : return expr1; case patn => exprn ... } case patn : return exprn ; } // statement only
- 60. Scala cheat sheet(3): Objects and Classes Scala Class and Object Java Class with statics class Sample { class Sample(x: Int, val p: Int) { private final int x; def instMeth(y: Int) = x + y public final int p; } Sample(int x, int p) { this.x = x; object Sample { this.p = p; def staticMeth(x: Int, y: Int) = } x*y int instMeth(int y) { } return x + y; } static int staticMeth(int x, int y) { return x * y; } }
- 61. Scala cheat sheet(4): Traits Java Interface Scala Trait trait T { interface T { int abstractMth(String x) def abstractMth(x: String): Int } def concreteMth(x: String) = x + field (no concrete methods) var field = “!” (no fields) } Java extension + implementation: Scala mixin composition: class C extends Super implements T class C extends Super with T
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- 63. Android Application 開發流程
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- 65. $ android createproject -p … $ vim ..... $ ant install
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- 72. 以 Scala 為 HostLanguage
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- 83. Install SBT/SBT-Android ● Install SBT ● http://code.google.com/p/simple-build-tool/ ● Download SBT-Android ● $ git clone http://github.com/brianhsu/sbt-android.git ● Install SBT-Android ● $ cd sbt-android ● $ sbt publish-local
- 84. Create Android/Scala Project ● Create SBT project ● $ mkdir AndroidTest ● $ cd AndroidTest ● $ sbt ● Edit project/build/MyProject.scala ● Edit project/plugins/Plugins.scala ● $ sbt update
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- 86. Build Scala/Android Project ● $ sbt action ● $ sbt install ● $ sbt android-compile ● $ sbt proguard ● $ sbt zipalign ● $ ...
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- 93. Scala 的限制與臭蟲 ● 限制 ● Cannot acess static protected Java field. – 對不起， Google Maps API 用到了。 ● 臭蟲 ● Static Java Inner class 造成 classfile borken / Missing dependency missing dependcy – Google Maps API 踩到地雷了 ● Cyclic dependcy – Google Data API 中計了 – 以於 Scala 2.8 main trunk 中修正 ● 解決方式 ● 用 Java 寫個 Wrapper 唄
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