Google Cloud Messaging with Erlang

I have been working on Facebook matchmaking code for Android/Unity to mimic iOS Game Center like flow of match making where other player receives notification on phone. Server side is coded with Mochiweb in Erlang. Here is simple code to send GCM Notification.

 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

send_gcm_msg(ApiKey, Pnstoken, Message, Game) -> Baseurl = "http://android.googleapis.com/gcm/send", ApiKey1 = string:concat("key=",ApiKey), %% Create Json struct Body = lists:flatten(mochijson:encode({struct, [{registration_ids,{array, [Pnstoken]}}, {data,{struct, [{message,Message},{game,Game}]}}, {time_to_live,3600}, {collapse_key,game_invite}]})), try httpc:request(post, {Baseurl,[{"Authorization",ApiKey1}],"application/json",Body},[],[]) of {ok, {{_,200,_},_,RespBody}} -> {ok, mochijson:decode(RespBody)}; {error, Reason } -> {error, Reason}; {ok, {{StatusLine,_,_},_,RespBody}} -> {error, {StatusLine, RespBody}}; BigError -> {error, BigError} catch Throw -> {error, caught, Throw} end.

Android Development with Scala

I learned a few weeks back about Scala programming language. I never liked Java and thought to try Scala as I would learn functional language and be able to still use JVMs.
I also wanted to learn Android development as I have done previously Windows Mobile, Symbian and iPhone development. Using Scala with Android was my idea to hit 2 birds with one stone.

Android Decelopment using Eclipse and Scala language

All the information that I could find about using Scala with Android was for Android 1.6/1.7 but not with Android 2.0.1. Today finally I got Scala-Android development working for me. I am using Eclipse for development on OSX.

The steps involved are documented in detail here which can be followed till Step 4 as after that I will explain the trick to use Scala . If you are an advanced programmer then you should be able to follow my brief guide below.

Increasing memory of Eclipse

Edit eclipse.ini file which can be found in OSX at /Applications/Eclipse/Eclipse.app/Contents/MacOS/eclipse.ini
If you have not made changes to an app contents before in OSX then for your information right-click Show Package Contents displays all the internal directories in .app bundle.
Make sure that these parameters are there in config file as below

256m
-vmargs
-Xms256m
-Xmx1024m
-XX:PermSize=64m

Goto android sdk tools directory at <ANDORID_SDK>/platforms/android-2.0.1/tools/dx.sh and edit it and make sure this param is there

defaultMx="-Xmx512M"

It can be different on windows as windows uses batch file. You can find it as -Xmx<NNN>M where NNN is the memory size.

Note: mine was setup as 1024M so I kept it like that. 512M should work fine as well.

Install Android 2.x.x SDK

Download and install Android SDK and Tools from this link http://developer.android.com/sdk/eclipse-adt.html
I had to use HTTP instead of HTTPS for installing ADT plugin on Eclipse.

Install Scala

Download and install Scala plugin for Eclipse
You can put this URL directly in Install New Software feature of Eclipse
Scala – http://www.scala-lang.org/scala-eclipse-plugin
More details can be found at http://www.scala-lang.org/node/94

Download and install full Scala installer as well to get more control on Scala as well as get sbaz support.
http://www.scala-lang.org/downloads/distrib/files/scala-2.7.6.final-installer.jar or find whatever is the latest version at the time of reading.

Install scala-android library for development

Download and install scala-android.jar (library)

sbaz install scala-android

You can compile it yourself by visiting this link http://robey.lag.net/2009/01/19/scala-on-android.html

Create an Android project

Add Scala Nature by right clicking on project and then Scala->Add Scala Nature

Fix Project settings to use Scala

Scala Eclipse Settings

Goto Properties->Builders tab and make Scala Builder as 2nd last item in list.

Goto Java Build Path->Libraries and Remove Scala Library Version 2.x
In same Java Build Path->Libraries, Add External Jar and locate scala-android.jar in lib directory of Scala SDK.

Extending Scala class from Java

I always had issue compiling Android app written in Scala with class not being found as per manifest file. The issue was somewhere between Java expecting .java file as starting point and not being able to find it. So, I found a solution to leave original .java file as entry point and make a new file for Scala. Now the Java startup/main class extends Scala class which allows me to write rest of application in Scala.
My project was called ScalaTest and the ScalaTest.java was boilerplate code generated by android new project wizard.
The file looks like this after changes made for Scala

package android.ScalaTest;

import android.app.Activity;
import android.os.Bundle;

public class ScalaTest extends MainScala {}

The MainScala.scala looks like this

class MainScala extends Activity {
    override def onCreate(savedInstanceState: Bundle) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main)
    }
}




First Scala Application

Thats it. Scala can be used to do rest of Android Development as well as Debugging. Now I am off to learn Scala with Android.

Android 1.5 on HTC

Installing Android on HTC was much easier than I had expected.
I only tried installing Android on HTC Diamond. Kaiser,Vogue and Touch Dual are also possible.

To get started with Android on HTC Diamond download the android build from
http://connect-utb.com/index.php?option=com_rokdownloads&view=file&Itemid=68&id=53:android-1

The steps to install are simple. Just extract the bundle package and copy it to root of your Internal Storage.
Note: Make sure you replace the STARTUP.TXT with diam100.txt from startup-configs directory. The original STARTUP.TXT is for RALPH100
Note: Disable PINCode for your SIM if you have any before using it with Android on HTC.
Disconnect phone from PC and simply run Haret.

Related links

http://glemsom.anapnea.net/android/htc-msm-android/
http://www.androidonhtc.com/

AirplaySDK for Cross Mobile OS Game Development

I am totally astonished as to how well AirplaySDK works. The guys at Ideaworks Labs have done it right.

They have made all the right choices when developing an SDK for cross mobile OS game development.

The issue with mobile game development is dealing with all the different Mobile OS plus dealing with different hardware using same OS. Game developers are somewhat lucky if there is OpenGLES implementation available as then they don’t have to worry too much about the rendering part. The sound and file IO and network features still mostly remain as an issue. OpenAL is not supported on most phones for sound. EdgeLib appeared a few years back to solve the problem of IO, Sound and Network features plus to allow software renderer in case OpenGLES is not available. More on EdgeLib in another post.

I tested the kartz sample from AirplaySDK on N82, N80, HTC Diamond, Samsung Omnia.

It is much easier to just list the feature pros and cons of AirplaySDK that I figured out so far by reading and trying out.

PROS

• Native binary without any VM.
• Good packaging tools for all OS.
• Fixed point computation as well as floating point available.
• Speedy Software rendering engine
• Auto fallback to software rendering when no hardware accelerator present.
• Sticking to opensource libraries.
• One Dynamic Engine (ODE) for rigid body physics.
• Support for multiple Mobile OS including Symbian, iPhone, Windows Mobile, Android,BREW and Linux). Edgelib doesn’t support Anrdoid and BREW.
• Highly optimised compression of assets for games. Not just simple zip compression but usage of Derbh which uses shared buffer across files. Claims on site say that Metal Gear Solid came down to 1.5MB.
• Arm debugger/emulator available that runs on Windows. Debugging is much easier this way.
• Windows emulator allows testing of software in various different scenerios (tilt/compass/keypad/touch/resolution)
• VS Studio programmers would love it as they can use VS with this SDK. Very tight integration.
• UI development possible for softwares other than games. This is interesting feature but as the Core System API is not extensive, it won’t be possible for creating full applications. Only simple apps can be built. There is possibilty of extensions that can do OS dependent API calls but this system is not exposed to developers to create their own extensions. There seems to be discussion of this opening up on AirplaySDK Forum.
• Extensions available (only for iPhone) for some of iPhone specific API
• Phone Orientation awareness and auto rotation of GUI.
• Human Interface limitations/possiblities awareness. Can detect touch screen and keypad and control based on that.
• Handling of phone events (incoming call/notifications) without extra code.
• UI code for input is intelligent enough to display touch keypad on touch UI systems without any extra work. MoSync can’t do that. EdgeLib has no support for UI controls/widgets.

CONS

• No support for OSX/XCode for development yet. It is planned though.
• Integrates best with visual studio which can be costly. Although express edition is free and should be enough
• Not very extensive API for core OS like System API.

My Test Results

Omnia Kartz Running in Portrait at 20 fps. Left/Right sides of screen can be used to steer.

OMNIA Kartz Running in Landscape at 18.65 fps. Left/Right sides of screen can be used to steer.

N82 running Kartz sample at 20 fps and steering with keypads. N82 has vfp

HTC Diamond running Kartz sample with 11.4 fps. HTC Diamond has no vfp/hardware acceleration

N80 running Kartz sample at 9.7 fps and steering is with keypad. N80 has no hardware accelration/vfp.

OS Independent Mobile Software Development with MoSync

Introduction

MoSync is truely amazing platform for cross platform development for Mobile Phone Softwares. It comes as a full IDE based on Eclipse. It supports currently Windows Mobile, Symbian, Blackberry (Java),Moblin and J2ME. Support for iPhone,Maemo and Android is planned. MoSync was made opensource a while ago and seems to have very active developers. The best thing is that it creates a binary instead of creating some sort of virtual machine code and thus slowing down the whole application.

In my experience as much as 80% of code needs be ported between platforms. Symbian’s disregard of providing standard C API initially and later requirement to install OpenC on phones with your software, overall confusing the install process for user, made it sub-optimum to use OpenC. The userinterface coding takes a long time on most phones even if there is standard API for core system like IO/Network.

Now MoSync promises that you can make one UI code and use it on other phones, as well as MoSync API translates to Core OS API which means no need to spend time in porting at all.

Test Results on a few phones

This sounded too good to be true so I had to try and spend a night playing with it. The IDE is based on Eclipse. I tried their UI samples on HTC Diamond, Samsung Omnia and N82.

Here are my findings

• There was no need to install each SDK for Symbian, Windows Mobile or Black berry.
• The binaries are made per Mobile phone and not per OS.This is a little inconvenience as they are not always compatible on different phones running same OS as I found out with Samsung Omnia.
  

  HTC Diamond with MAUIEx sample displaying a grid of images

  

  HTC Diamond MoSync Main interface (Diamond has higher resolution than Omnia)

• HTC Diamond binary was a native exe and when installed ran fine. Although the selection of items had to be done with keypad.
• The same HTC Diamond Windows Mobile binary when installed on Samsung didn’t run and crashed. The cab was created by MoSync. This is strange as it is same OS.
• The simple example which outputs keycodes when keys are pressed was not able to recognise back button on HTC Diamond.
  

  Omnia MoSync landscape didn't show properly

  

  Omnia MoSync Main Screen MAUIEx sample (jar file)

• When I compiled same code for Samsung Omnia, to my surprise, I got Java (jad/jar) files instead of native binaries. The UI ran fine but as it was not touch UI, I had to reboot phone.
• The HTC Diamond exe took over whole of screen on Samsung Omnia before crashing and had the taskbar on top hidden. Icouldn’t get that taskbar back and had to reboot phone. This is very scaryif all UI apps built with MoSync do it. This would mean that Windows Mobile Certification test will fail as they require ability to go to “Today Screen”(main screen of phone) using Start menu. More on that later.
  

  N82 Symbian Native BInary MoSync MAUIEx Clock sample

  

  N82 Symbian Native binary running MAUIEx created using MoSync

• The N82 was also a native binary that functioned pretty well as it is not a touch screen and soft-keys (keypad) was mapped perfectly fine.
• The UI development with MoSync has same limitation where support for both touch UI and keypad UI has to be coded by developer making it less automatic porting.

Final Thoughts

All in all MoSync would reduce development time by reducing the code portability needed but the need to test on each phone is highly increased due to uncertain behavior of same app on different phones. Again stressing here on HTC Diamond Windows Mobile app not able to run on Omnia which almost never happens with traditional development. I will play more with MoSync and create more entries on blog if I find something interesting or contradicting to my these initial findings.