Presentation at OSDC.tw 2010.

1. Programming Android
Application in Scala
BrianHsu / OSDC.2010

2. 關於我

3. 墳墓 (BrianHsu)

4. 表面上
軟體工程師

5. 實際上
萌系阿宅

6. 入用
侵萌
藍化
星的
是手
也機

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

8. 用 Java 寫程式卻燃不起來

9. 高手大師兄

10. 聽說高手都要精通 Multiple Language……

11. ASE+Ruby/Python/Perl

12. 寫作
Dynamic Scripting
Language

13. 唸作
快、狠、準

14. 等等

15. 還要先裝 Runtime 啊？

16. 等等

17. 動態型別？

18. def boom
puts "Hello World"
end
puts " 一個小小的 typo"
booom
執行期爆炸

19. 結論

20. 我是懦夫
不敢用 ASE

22. What is Scala?

23. 樓
梯

24. A Postfunctional
Programming Language
on Java Virtual Machine

25. Compile to
JVM .class Byte Code

26. 理論上
Full Java
Interoperability

27. 可以直接拿來寫
Android Application

28. What is Scala?

29. A Scalable Language

30. 會隨 User 變形的程式語言

31. A Scalable Language

32. A Scalable Language

33. Why Scala?

35. 三個願望一次滿足

36. REPL
Scripting
Compiling

37. REPL

38. Scripting

39. Compiling

40. 三個願望一次滿足

41. Procedure
Object Oriented
Functional

42. Procedure Programming

43. Object Oriented Programming

44. Functional Programming

45. 三個願望一次滿足

46. Concise
Static Typing
Duck Typing

47. Concise (Ruby)

48. Concise (Scala)

49. Static Typing (Ruby)

50. Static Typing (Scala)

51. 真、 Duck Typing (Ruby)

52. 偽‧ Duck Typing (Scala)

53. 結論

54. 有 Scala 、無懦夫

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

56. Scala vs Java

57. Scala compared to Java
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

62. 當機器人爬上樓梯

63. Android Application
開發流程

64. Java / ANT

65. $ android create project -p …
$ vim .....
$ ant install

66. http://asantoso.wordpress.com/2009/09/15/how-to-build-android-application-package-
apk-from-the-command-line-using-the-sdk-tools-continuously-integrated-using-
cruisecontrol/

67. http://asantoso.wordpress.com/2009/09/15/how-to-build-android-application-package-
apk-from-the-command-line-using-the-sdk-tools-continuously-integrated-using-
cruisecontrol/

68. How?

69. XML 地獄
ANT

70. Perfect
SBT

71. Simple Build Tool

72. 以 Scala 為
Host Language

73. Rake=>Ruby
SBT =>Scala

74. 不用任何設定
支援連續編譯

75. Android-Plugin

76. android-plugin
http://github.com/jberkel/android-plugin
project/build/MyProject.scala

77. android-plugin

78. 我不會用
功能完整

79. 阿宅的通病
自己寫一個

80. sbt-android
project/build/MyProject.scala

81. sbt-android
project/plugins/Plugins.scala

82. Live Demo

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

85. Android/Scala Project Struture

86. Build Scala/Android Project
●
$ sbt action
●
$ sbt install
●
$ sbt android-compile
●
$ sbt proguard
● $ sbt zipalign
● $ ...

87. Scala in Android

88. Trait 是好幫手

89. SQL 再見！
Collection 最高！

90. 善用偽 Duck Typing

91. 結論
可以把 Java 丟了……應該唄？

92. 等等，這是孔明的陷阱！

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

94. Thanks!