java4iphone-jug-cologne-v0

8/7/2019 java4iphone-jug-cologne-v0

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H ow t o w r i t e iPh on e a pp l i c a t i on sus ing J ava

Arno Puder

San Francisco State University

1. Introduction to Objective-C2. Cross-Compiling Java applications3. Running the toolchain

Outline:


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J ava fo r t he iPhone

iPhone applications are based on Objective-C andCocao.

Sun Microsystems would like to ports its JVM to theiPhone.Apples iPhone SDK prohibits the development of certainapplications (e.g., VoIP).

There have been questions about whether Apple'siPhone SDK agreement would allow a JVM on theiPhone.


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His t o ry o f Objec t ive -C

Early 1980s: Objective-C language was designed by Brad J. Cox: Object-oriented extension of C. Inspired by Smalltalk. Strict superset of C.

1988: NeXT Software licensed the Objective-C language anddeveloped its libraries and a development environment calledNEXTSTEP.1992: FSF adds Objective-C support to GNU compiler suite.

1994: NeXT Computer and Sun Microsystems released astandardized specification of the NEXTSTEP system calledOPENSTEP.The Free Software Foundation's implementation of OPENSTEP iscalled GNUStep.1996: Apple acquires NeXT Software and theNEXTSTEP/OPENSTEP environment became the basis for thenext major release of Apple's operating system, OS X. Apple'sversion of this development environment is called Cocoa.


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@int e r f ac e

#import

@interface Fraction: NSObject {int numerator;int denominator;

}-(void) print;-(void) setNumerator: (int) d;-(void) setDenominator: (int) d;-(int) numerator;-(int) denominator;@end


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@im ple m ent a t ion

#import "Fraction.h#import

@implementation Fraction-(void) print

{ printf("%i/%i", numerator,denominator); }

-(void) setNumerator: (int) n{ numerator = n; }

-(void) setDenominator: (int) d{ denominator = d; }

-(int) denominator{ return denominator; }

-(int) numerator{ return numerator; }

@end


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Crea t ing and Us ing Ob jec t s

int main(int argc, const char *argv[]){

// create a new instance Fraction

Fraction *frac = [[Fraction alloc] init];// set the values[frac setNumerator: 1];

[frac setDenominator: 3];// print itprintf("The fraction is: ");[frac print];printf("\n");// free memory [frac release];return 0;

}


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Mul t ip l e Pa ram e t e r s

...-(void) setNumerator: (int) n andDenominator: (int) d;...

...-(void) setNumerator: (int) n andDenominator: (int) d

{numerator = n; denominator = d;

}...

Fraction *frac = [[Fraction alloc] init];[frac setNumerator: 1 andDenominator: 5];

Invocation

setNumber:andDenominator: is called a selector.

@interface

@implementation


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Referenc e Count ing

Class inheriting from NSObject have reference counting.

Fraction *frac = [[Fraction alloc] init];printf(Retain count: %i\n", [frac retainCount]);[frac retain]; // 2[frac retain]; // 3

printf(Retain count: %i\n", [frac retainCount]);[frac release]; // 2printf(Retain count: %i\n", [frac retainCount]);[frac release]; // 1

[frac release]; // 0. Object will be deleted


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Dy n am i c I n vo c a t i o ns

Method invocations are bound at runtime:id obj = ;[obj someMethod];

id is a generic object type (similar to java.lang.Object )obj may or may not implement someMethod . If not, aruntime error occurs.

Dynamic invocations are heavily used in the delegate pattern(e.g., UITable )


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Objec t ive-C Hel lo Wor ld

@interface helloWorld : UIApplication-(void) applicationDidFinishLaunching: (NSNotification) n;@end

@implementation helloWorld

-(void) applicationDidFinishLaunching: (NSNotification) n{

CGRect rect = [UIHardware fullScreenApplicationContentRect];UIWindow* window = [[UIWindow alloc] initWithContentRect: rect];[window orderFront: self];[window makeKey: self];[window _setHidden: false];rect.origin.x = rect.origin.y = 0;UIView* mainView = [[UIView alloc] initWithFrame: rect];[window setContentView: mainView];UITextLabel *_title = [[UITextLabel alloc] initWithFrame: rect];[_title setText: @"Hello World!"];[_title setCentersHorizontally: true];[mainView addSubview: _title];

}@end


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J ava He l lo Wor ld

import org.xmlvm.iphone.*;

public class HelloWorld extends UIApplication{

public void applicationDidFinishLaunching(NSNotification n){

CGRect rect = UIHardware.fullScreenApplicationContentRect();UIWindow window = new UIWindow(rect);window.orderFront( this );window.makeKey( this );window._setHidden( false );rect. origin . x = rect. origin . y = 0;UIView mainView = new UIView(rect);window.setContentView(mainView);UITextLabel _title = new UITextLabel(rect);_title.setText( "Hello World!" );_title.setCentersHorizontally( true );mainView.addSubview(_title);

}

}


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Chal lenges

Design goal: if possible, Java API mimics 1:1 theObjective-C API.Objective-C challenges: Namespaces, method overloading: use name-mangling. Garbage collection: use Objective-C reference counting. No multiple inheritance: use Objective-C dynamic

invocations. No static member variables: use global variables.

Cocoa challenges: Makes use of C-functions (e.g., CGColorCreate )

Uses value types (e.g., CGRect ) Uses pointers for output parameters (e.g.,

NSURLConnection ) Makes heavy use of delegation (e.g., data source for

UITable )


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Ex am ple : Crea t ing XMLVM

// Javaclass Calc {

int x;

void add(int y){x += y;

}}

Calc.java Calc.class

Calc.xml

javacBCEL/JDOM


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Ex am ple : XMLVM o f Class Calc


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Ex am ple : Ex ec u t ing XMLVM

locals[0]: this

locals[1]: 31

Stack:

x: 11

(y)


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thisStack:

locals[0]: this

locals[1]: 31

x: 11

(y)


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thisthis

Stack:

locals[0]: this

locals[1]: 31

x: 11

(y)


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this11

Stack:

locals[0]: this

locals[1]: 31

x: 11

(y)


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this1131

Stack:

locals[0]: this

locals[1]: 31

x: 11

(y)


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this42

Stack:

locals[0]: this

locals[1]: 31

x: 11

(y)


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Stack:

locals[0]: this

locals[1]: 31

x: 42

(y)


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XMLVM t o Ot he r Languages

Since the Java VM is a simple, stack-based machine,XMLVM can easily be mapped to other languages.These translations are done using XSLT.Mappings exist for JavaScript and Objective-C.The XSLT excerpt below demonstrates the translation of (Integer add) to JavaScript.


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He l lo Wor ld in XMLVM


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Hel lo Wor ld in Objec t ive -C

@interface org_xmlvm_test_iphone_HelloWorld :org_xmlvm_iphone_UIApplication

-(void) applicationDidFinishLaunching___org_xmlvm_iphone_NSNotification:(org_xmlvm_iphone_NSNotification*)n1;

@end

-(void) applicationDidFinishLaunching___org_xmlvm_iphone_NSNotification:(org_xmlvm_iphone_NSNotification*)n1

{XMLVMElem _stack[4];

XMLVMElem _locals[6];int _sp = 0;XMLVMElem _op1, _op2, _op3;_op1.o = [org_xmlvm_iphone_UIHardware

fullScreenApplicationContentRect];_stack[_sp++].o = _op1.o;_op1.o = _stack[--_sp].o;[_op1.o retain];[_locals[2].o release];_locals[2].o = _op1.o;...


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Out look

Still lots to do: Complete Java-to-Objective-C mapping. Support for all iPhone UI elements.

iPhone UI for other phones: iPhone simulator mimics the iPhone UI. The simulator is completely written in Java.

Idea: why not port these Java classes to other cell phonesthat support Java? Benefit: iPhone-like UI on different cell phones!


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I n s t a l l i ng t h e To ol c h a in

Prerequisites for running the iPhone simulator: Java 5 or 6 Eclipse

Prerequisites for cross-compiling to the iPhone: Jail-broken iPhone/iPod Touch:

http://www.ziphone.org/

iPhone development toolchain:http://code.google.com/p/iphone-dev/wiki/BuildingXMLVM Cross-Compiler and iPhone simulator availablefrom SourceForge:

http://sourceforge.net/cvs/?group_id=152977Use anonymous CVS to checkout module xmlvm .
http://www.ziphone.org/http://code.google.com/p/iphone-dev/wiki/Buildinghttp://sourceforge.net/cvs/?group_id=152977http://sourceforge.net/cvs/?group_id=152977http://code.google.com/p/iphone-dev/wiki/Buildinghttp://www.ziphone.org/


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Runn ing t he Sim ula t o r

Simulator automatically launched when a Java-basediPhone application is executed.Currently there are four demos:

org.xmlvm.test.iphone.HelloWorld

org.xmlvm.test.iphone.Android

org.xmlvm.test.iphone.ifireworks.Main

org.xmlvm.test.iphone.todo.MainAll these applications are in source foldersrc/test/iphone

The implementation of the iPhone simulator is in sourcefolder src/xmlvm2objc/compat-lib/java


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Cross-Com pi l ing Hel lo Wor ld t o Objec t ive-C

The cross-compiler is in source folder src/xmlvm classorg.xmlvm.Main

To generate the XMLVM for Hello World use the followingcommand line options (under Eclipse):--console${workspace_loc:xmlvm}/bin/org/xmlvm/test/iphone/HelloWorld.class

To cross-compile the XMLVM to Objective-C use:--console --objc${workspace_loc:xmlvm}/bin/org/xmlvm/test/iphone/HelloWorld.class

To write the Objective-C source code to a file, use:--out=tmp --objc

${workspace_loc:xmlvm}/bin/org/xmlvm/test/iphone/HelloWorld.class

The previous command will generate two files: ${workspace_loc:xmlvm}/tmp/HelloWorld.h ${workspace_loc:xmlvm}/tmp/HelloWorld.m


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Info .p l i s t


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Mak ef i le 1 /3

PRODUCT_NAME=HelloWorldSOURCES=\

HelloWorld.m \../bin/XMLVMCompatLib.m

SRCROOT=.BUILT_PRODUCTS_DIR=buildCONFIGURATION_TEMP_DIR=objINFOPLIST_FILE=Info.plist

CC=arm-apple-darwin-gccCFLAGS=-g -O2 -Wall -I. -I../binLD=$(CC)LDFLAGS=-lobjc -ObjC -framework CoreFoundation \

-framework Foundation -framework CoreGraphics \-framework GraphicsServices \-framework UIKit -framework LayerKit


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Mak ef i le 2 /3

WRAPPER_NAME=$(PRODUCT_NAME).appEXECUTABLE_NAME=$(PRODUCT_NAME)SOURCES_ABS=$(addprefix $(SRCROOT)/,$(SOURCES))INFOPLIST_ABS=$(addprefix $(SRCROOT)/,$(INFOPLIST_FILE))

OBJECTS=\$(patsubst %.c,%.o,$(filter %.c,$(SOURCES))) \$(patsubst %.cc,%.o,$(filter %.cc,$(SOURCES))) \$(patsubst %.cpp,%.o,$(filter %.cpp,$(SOURCES))) \$(patsubst %.m,%.o,$(filter %.m,$(SOURCES))) \

$(patsubst %.mm,%.o,$(filter %.mm,$(SOURCES)))OBJECTS_ABS=$(addprefix $(CONFIGURATION_TEMP_DIR)/,$(OBJECTS))APP_ABS=$(BUILT_PRODUCTS_DIR)/$(WRAPPER_NAME)PRODUCT_ABS=$(APP_ABS)/$(EXECUTABLE_NAME)

all: $(PRODUCT_ABS)

f


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$(PRODUCT_ABS): $(APP_ABS) $(OBJECTS_ABS)$(LD) $(LDFLAGS) -o $(PRODUCT_ABS) $(OBJECTS_ABS)

$(APP_ABS): $(INFOPLIST_ABS)

mkdir -p $(APP_ABS)cp $(INFOPLIST_ABS) $(APP_ABS)/cp $(SRCROOT)/$(RESOURCES)/*.png $(APP_ABS)/

$(CONFIGURATION_TEMP_DIR)/%.o: $(SRCROOT)/%.m

mkdir -p $(dir $@)$(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $@

deploy:cd build; scp -r $(WRAPPER_NAME) \

[email protected]:/Applications

clean:rm -rf $(CONFIGURATION_TEMP_DIR)rm -rf $(BUILT_PRODUCTS_DIR)

rm -f *~

C i l d H l l W ld


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Com pi le and run Hel lo Wor ld

Type make in ${workspace_loc:xmlvm}/tmpType make deployOn the iPhone, type killall SpringBoardThe previous command can be accomplished by eitherssh-ing into the iPhone, or by using a terminal applicationon the iPhone.

Restarting the SpringBoard is necessary only once sothat it picks up the new Hello World application.

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