java 4 iphone google

Developing iPhone Applicationsusing Java

Arno PuderSan Francisco State University

[email protected]

1. Introduction to Objective-C2. Cross-Compiling Java applications3. Demo

Outline:

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History of Objective-C

Objective-C language was designed byBrad J. Cox:– Object-oriented extension of C. Inspired by Smalltalk.– Strict superset of C.

NeXT Software licensed the Objective-C language and develops NEXTSTEP.

FSF adds Objective-C to GNU compiler suite.

NeXT Computer and Sun Microsystems released a standardized OPENSTEP specification.

Apple acquires NeXT Software. Use for OS X. OPENSTEP now called Cocoa.

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@interface

#import <Foundation/NSObject.h>

@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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@implementation

#import "Fraction.h“#import <stdio.h>

@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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Creating and Using Objects

int main(int argc, const char *argv[]){// create a new instance FractionFraction *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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Multiple Parameters

...-(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

setNumerator:andDenominator: is called a selector.

@interface

@implementation

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Reference Counting

Classes inheriting from NSObject have reference counting.

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

Sending message autorelease will add object to autorelease pool.Releasing the pool will decrement reference counter of all managed object by 1.If reference count drops to 0, object will be deleted.Autorelease pools can be nested.Cocoa automatically adds objects to autorelease pool.

NSAutoreleasePool *pool =[[NSAutoreleasePool alloc] init];

Fraction *frac =[[[Fraction alloc] init] autorelease];

[pool release]; // ‘frac’ will be deleted

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Dynamic Invocations

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

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iPhone “Hello World” in Objective-C

@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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iPhone “Hello World” in Java

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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Toolchain Overview

“Hello World”Java app.

“Hello World”Objective-C

Objective-CWrapper Classes.

Native iPhone application

Cocoa JavaCompat Lib

Desktop application( iPhone emulator)

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Challenges

Design goal: if possible, Java API mimics 1:1 the Objective-C API.Objective-C challenges:– Namespaces, method overloading: use name-mangling.– Garbage collection: use Objective-C reference counting.– 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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Example: Creating XMLVM

// Javaclass Calc {

int x;void add(int y){

x += y;}

}

Calc.java Calc.class

Calc.xml

javacBCEL/JDOM

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Example: XMLVM of Class Calc

<?xml version="1.0" encoding="UTF-8"?><xmlvm xmlns:jvm="http://xmlvm.org/jvm"><class name="Calc">

<field name="x" type="int"/><method name="add" stack="3" locals="2">

<signature><return type="void"/><parameter type="int"/>

</signature><code><jvm:load type="Calc" index="0"/><jvm:dup/><jvm:getfield class-type="Calc" type="int" field="x"/><jvm:load type="int" index="1"/><jvm:iadd/><jvm:putfield class-type="Calc" type="int" field="x"/><jvm:return/>

</code></method>

</class></xmlvm>

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Example: Executing XMLVM

<code><jvm:load type="Calc" index="0"/><jvm:dup/><jvm:getfield class-type="Calc" type="int" field="x"/><jvm:load type="int" index="1"/><jvm:iadd/><jvm:putfield class-type="Calc" type="int" field="x"/><jvm:return/>

</code>

locals[0]: this

locals[1]: 31

Stack:

<code>

x: 11

(y)

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</code>


thisStack:

<jvm:load type="Calc" index="0"/>

locals[0]: this

locals[1]: 31

x: 11

(y)

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</code>


thisthis

Stack:

<jvm:dup/>

locals[0]: this

locals[1]: 31

x: 11

(y)

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</code>


this11

Stack:

<jvm:getfield class-type="Calc" type="int" field="x"/>

locals[0]: this

locals[1]: 31

x: 11

(y)

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</code>


this1131

Stack:

<jvm:load type="int" index="1"/>

locals[0]: this

locals[1]: 31

x: 11

(y)

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</code>


this42

Stack:

<jvm:iadd/>

locals[0]: this

locals[1]: 31

x: 11

(y)

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</code>


Stack:

<jvm:putfield class-type="Calc" type="int" field="x"/>

locals[0]: this

locals[1]: 31

x: 42

(y)

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Cross-Compiling XMLVM to Objective-CSince the Java VM is a simple, stack-based machine, XMLVM can easily be mapped to other languages.Simply mimic stack machine using target language!These translations are done using XSLT.Mappings exist for different languages.The XSLT excerpt below demonstrates the translation of <jvm:iadd/> (Integer add) to Objective-C.

// Objective-Ctypedef union {

id o;int i;float f;double d;

} XMLVMElem;

<!– XSL template --><xsl:template match="jvm:iadd">

<xsl:text>_op2.i = _stack[--_sp].i; // Pop operand 1_op1.i = _stack[--_sp].i; // Pop operand 2_stack[_sp++].i = _op1.i + _op2.i; // Push sum

</xsl:text></xsl:template>

_op1, _op2, and_stack are based on

XMLVMElem

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Example: Class Calc in Objective-C

// Objective-C generated via stylesheet @implementation Calc;

-(void) add___int :(int)n1 {

XMLVMElem _stack[3];XMLVMElem _locals[2];int _sp = 0;XMLVMElem _op1, _op2; NSAutoreleasePool* _pool = [[NSAutoreleasePool alloc] init]; _locals[0].o = self; _locals[1].i = n1; _stack[_sp++].o = _locals[0].o; _op1 = _stack[_sp - 1]; _stack[_sp++] = _op1; _op1.o = _stack[--_sp].o; _op2.i = ((Calc*) _op1.o)->x; _stack[_sp++].i = _op2.i; _op1.i = _locals[1].i; _stack[_sp++].i = _op1.i; _op2.i = _stack[--_sp].i; _op1.i = _stack[--_sp].i; _stack[_sp++].i = _op1.i + _op2.i;_op1.i = _stack[--_sp].i; _op2.o = _stack[--_sp].o; ((Calc*) _op2.o)->x = _op1.i; [_pool release]; return;

} @end

<load>

<dup>

<getfield>

<load>

<iadd>

<putfield>

<return>

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Abstract Virtual Machine

Currently several flavors of XMLVM:– XMLVMJVM: Java byte code– XMLVMCLR: .NET byte code– XMLVMYARV: Ruby YARV byte code

Idea: XMLVMAVM: heterogeneous mix of instructions from different virtual machines.Application: Aspect Oriented Programming (AOP).Challenge: define operational semantics of XMLVMAVM.

C# Application

XMLVMAVM

Java Aspect

Byte Code Weaver

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Outlook

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

.NET Cocoa compatibility classes.Android -> iPhone cross-compilation.

http://xmlvm.org

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Installing the Toolchain

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 available from 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/Building

http://sourceforge.net/cvs/?group_id=152977

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Running the Simulator

Simulator automatically launched when a Java-based iPhone 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.Main

All these applications are in source folder src/test/iphone

The implementation of the iPhone simulator is in source folder src/xmlvm2objc/compat-lib/javaThe remote control application is in org.xmlvm.iphone.remote.Main

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Cross-Compiling “Hello World” to Objective-C

The cross-compiler is in source folder src/xmlvm class org.xmlvm.MainTo generate the XMLVM for “Hello World” use the following command line options (under Eclipse):--console ${workspace_loc:xmlvm}/bin/org/xmlvm/test/iphone/HelloWorld.classTo cross-compile the XMLVM to Objective-C use:--console --objc${workspace_loc:xmlvm}/bin/org/xmlvm/test/iphone/HelloWorld.classTo write the Objective-C source code to a file, use:--out=tmp --objc${workspace_loc:xmlvm}/bin/org/xmlvm/test/iphone/HelloWorld.classThe previous command will generate two files:– ${workspace_loc:xmlvm}/tmp/HelloWorld.h– ${workspace_loc:xmlvm}/tmp/HelloWorld.m

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Info.plist

<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN“"http://www.apple.com/DTDs/PropertyList-1.0.dtd">

<plist version="1.0"><dict>

<key>CFBundleDevelopmentRegion</key><string>English</string><key>CFBundleExecutable</key><string>HelloWorld</string><key>CFBundleIdentifier</key><string>org.puder.HelloWorld</string><key>CFBundleInfoDictionaryVersion</key><string>6.0</string><key>CFBundlePackageType</key><string>APPL</string><key>CFBundleSignature</key><string>????</string><key>CFBundleVersion</key><string>1.0</string>

</dict></plist>

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Makefile 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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Makefile 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)

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Makefile 3/3

$(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)/%.mmkdir -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 *~

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Compile and run “Hello World”

Type “make” in ${workspace_loc:xmlvm}/tmpType “make deploy”On the iPhone, type “killall SpringBoard”The previous command can be accomplished by either ssh-ing into the iPhone, or by using a terminal application on the iPhone.Restarting the SpringBoard is necessary only once so that it picks up the new “Hello World” application.

java 4 iphone google

Documents

int numerator int denominator

frac retaincount frac

frac setdenominator

int d void setdenominator

puder slide

int n anddenominator

objectivec reference

void print void setnumerator