ambienttalk, a scripting language for android devices - dries harnie, vub - droidcon.be 2011

AmbientTalk:A scripting languagefor Android devicesDries Harnie

Tuesday 25 January 2011

Hello everyone, my name is Dries Harnie and I’m here to present AmbientTalk: a scripting language for android devices.

The AmbientTalk Team

Stijn Mostinckx Elisa Gonzalez Boix

Andoni Lombide Christophe Scholliers

Tom Van CutsemWolfgang De Meuter

Kevin Pinte

Dries Harnie

Eline Phillips Lode Hoste


We are AmbientTalk. Resistance is futile.Look for us with the ambientTalk tshirts

Motivation


As discussed by the panel.

“Put everything in the cloud”What is wrong with this picture?


cloud printing.Who here has ever printed when he was not in walking range of a printer?You want to walk up to a printer and say “print this”, not find it in a cloud and then print to it over a slow connection.

A very cool cloud app.


This is a service I joined recently.They allow you to store files in the cloud.However, they do things differently.If you have two devices on the same network, they will communicate directly, saving bandwidth.This is something we should embrace in ALL applications: why go via the cloud if you can do it directly?

Goal


We want to write an app that allows people to collaborate on some task (ie. painting).

AmbientTalk- Asynchronous

- Peer to peer


AmbientTalk!Language designed to be robust against disconnections

Async. communicationBuffer when other side is down


Discovery“Sniffing around”

for other devices


Deployment on real devices


Because we wrote the AT interpreter in Java it runs unmodified on all desktop platforms.We managed to squeeze it onto HTC Touch Cruise phones running the IBM J9 VM, but we ran into all sorts of issues.iPhone .. no real java supportFinally android, but not without issues.

Portabilityissues:Multicast- Works in 1.0

- Broken in 1.5

- Fixed in 1.6

✓

✓

✗

✉


Portability issues:memory

AmbientTalk parser uses a lot of stack space

Many threads ... ++ungood.


Portability issues: serialization

ClassCastException: serialVersionUid doesn’t match

Three different classloaders

A) ClassLoader.getSystemClassLoader()

B) Thread.setContextClassLoader()

C) Foo.class.getClassLoader() # This is the only one that knows about your classes.


When transferring objects from/to android, make sure the serialVersionUid fields match.These are usually computed, but dalvik and sun jvms do it differently.

The proof of the pudding...

http://youtu.be/k0HYqRCxtHc


this is a demo we made yesterday.I wrote the app in four hours.~ 90 lines of ambienttalk, of which only 20 networking.400 lines of java. mostly stolen from api demo.



import /.demo.weScribbledeftype Painter;

def otherPainters := [];

whenever: Painter discovered: { |ref| Android.Log.v("Fingerpaint",

"Discovered other painter:" + ref); otherPainters := otherPainters + [ref];};

network.online;

def remoteInterface := object: { def touchStart(other, x, y, color) { ... drawing stuff ... }; def touchEnd(other, x, y) { ... drawing stuff ... }; def erase() { ... drawing stuff ... };};

export: remoteInterface as: Painter;


I’ll even show you the code!Look, an import statement ;)

Conclusion

http://ambienttalk.googlecode.com

@ambienttalk




ambienttalk, a scripting language for android devices - dries harnie, vub - droidcon.be 2011

Technology