programming android application in scala

Programming Android Application in Scala

BrianHsu / OSDC.2010

關於我

墳墓 (BrianHsu)

表面上

軟體工程師

實際上

萌系阿宅

用萌化的手機

入侵藍星是也

寫Andro

id

萌程式

　　　　　

是燃的

我最喜歡女

僕了！

我要讓手上機

全都是女僕！

用 Java 寫程式卻燃不起來

高手大師兄

聽說高手都要精通 Multiple Language……

ASE+Ruby/Python/Perl

寫作Dynamic Scripting

Language

唸作快、狠、準

等等

還要先裝 Runtime 啊？

等等

動態型別？

執行期爆炸

def boom puts "Hello World"end

puts " 一個小小的 typo"booom

結論

我是懦夫不敢用 ASE

What is Scala?

樓梯

A Postfunctional Programming Language on Java Virtual Machine

Compile toJVM .class Byte Code

理論上

Full Java Interoperability

可以直接拿來寫Android Application

What is Scala?

A Scalable Language

會隨 User 變形的程式語言

A Scalable Language

Why Scala?

三個願望一次滿足

REPLScriptingCompiling

Scripting

Compiling

Procedure

Object Oriented

Functional

Procedure Programming

Object Oriented Programming

Functional Programming

Concise

Static Typing

Duck Typing

Concise (Ruby)

Concise (Scala)

Static Typing (Ruby)

Static Typing (Scala)

真、 Duck Typing (Ruby)

偽‧ Duck Typing (Scala)

結論

有 Scala 、無懦夫

用Scala

寫萌程式

　　　　　

是燃的

我最喜歡女

僕了！

我要讓手上機

全都是女僕！

Scala vs Java

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, …

Scala cheat sheet (1): Definitions

Scala method definitions:

def fun(x: Int): Int = { result}

def fun = result

Scala variable definitions:

var x: Int = expressionval x: String = expression

Java method definition:

int fun(int x) { return result}

(no parameterless methods)

Java variable definitions:

int x = expressionfinal String x = expression

Scala cheat sheet (2): Expressions

Scala method calls:

obj.meth(arg)obj meth arg

Scala choice expressions:

if (cond) expr1 else expr2

expr match { case pat1 => expr1 .... case patn => exprn

}

Java method call:

obj.meth(arg)(no operator overloading)

Java choice expressions, stmts:

cond ? expr1 : expr2 if (cond) return expr1; else return expr2;

switch (expr) { case pat1 : return expr1; ... case patn : return exprn ;} // statement only

Scala cheat sheet (3): Objects and Classes

Scala Class and Object

class Sample(x: Int, val p: Int) { def instMeth(y: Int) = x + y}

object Sample { def staticMeth(x: Int, y: Int) = x * y}

Java Class with statics

class Sample { private final int x; public final int p; Sample(int x, int p) { this.x = x; this.p = p; } int instMeth(int y) { return x + y; } static int staticMeth(int x, int y) { return x * y; }}

Scala cheat sheet (4): Traits

Scala Trait

trait T { def abstractMth(x: String): Int def concreteMth(x: String) = x + field var field = “!”}

Scala mixin composition:

class C extends Super with T

Java Interface

interface T { int abstractMth(String x)}

(no concrete methods)(no fields) Java extension + implementation:

class C extends Super implements T

當機器人爬上樓梯

Android Application開發流程

Java / ANT

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

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/

XML 地獄

ANT

Perfect

SBT

Simple Build Tool

以 Scala 為Host Language

Rake=>RubySBT =>Scala

不用任何設定

支援連續編譯

Android-Plugin

android-pluginhttp://github.com/jberkel/android-plugin

project/build/MyProject.scala

android-plugin

我不會用

功能完整

阿宅的通病

自己寫一個

sbt-android

project/build/MyProject.scala

sbt-android

project/plugins/Plugins.scala

Live Demo

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

Create Android/Scala Project

● Create SBT project● $ mkdir AndroidTest● $ cd AndroidTest● $ sbt● Edit project/build/MyProject.scala● Edit project/plugins/Plugins.scala● $ sbt update

Android/Scala Project Struture

Build Scala/Android Project

● $ sbt action● $ sbt install

● $ sbt android-compile● $ sbt proguard● $ sbt zipalign● $ ...

Scala in Android

Trait 是好幫手

SQL 再見！Collection 最高！

善用偽 Duck Typing

結論

可以把 Java 丟了……應該唄？

等等，這是孔明的陷阱！

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 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

Missing dependency

Thanks!

programming android application in scala

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