Pycon2011 android programming-using_python

Android Development using Python

George Goh10 June 2011PyCon APAC

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+Friday, June 10, 2011

HP Labs Singapore

2

http://www.hpl.hp.com/singapore/

Friday, June 10, 2011

http://www.hpl.hp.com

http://www.hpl.hp.com

Agenda

• Android Programming (Java vs. Python)

• Python Examples / UI Examples

• A More Complex Example

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Android Rocks!!!

4


Why Python?

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Programming Android

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Plus Python

7 http://www.blangy.com/Photos.htmlFriday, June 10, 2011

http://www.blangy.com/Photos.html

http://www.blangy.com/Photos.html

A simple program

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Simple Program in Javapackage com.spodon.pycon;

import android.app.Activity;import android.app.AlertDialog;import android.content.DialogInterface;import android.os.Bundle;import android.widget.EditText;import android.widget.Toast;

public class Demo extends Activity { private EditText mEditText = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setTitle("Hello!"); builder.setMessage("What is your name?"); mEditText = new EditText(this); builder.setView(mEditText);

builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { Toast.makeText(Demo.this, "Cancelled", Toast.LENGTH_SHORT).show(); } });

...9


Simple Program in Python

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• Java program: 35 SLOC

• Equivalent Python program: 4 SLOC

import android

droid = android.Android()name = droid.getInput("Hello!", "What is your name?")droid.makeToast("Hello, %s" % name.result)


Android module

• Exposes android functionality via an Android() object.

• Talks to a service called SL4A (Scripting Layer for Android).

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import android



AndroidPython Interpreter

android.py

Invoking functionality

SL4A

functionality exposedvia RPC methods

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import android



Scripting Layer for Android (SL4A)

Search keyword: android-scripting13


Scripting Layer for Android (SL4A)

• Started in 2009 by Damon Kohler

• 20% time project at Google.

• Supports Python, Ruby, Perl, Lua, JavaScript, BeanShell and more.

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Users of SL4A

• Rockets

• SmallSat

15 http://www.flickr.com/photos/jurvetson/


http://www.flickr.com/photos/jurvetson/

http://www.flickr.com/photos/jurvetson/

Users of SL4ACellbots - http://www.cellbots.com

16 http://www.flickr.com/photos/motorbikematt/


http://www.cellbots.com


http://www.flickr.com/photos/motorbikematt/


SL4A Functionality

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• ActivityResult

• Android

• ApplicationManager

• BatteryManager

• Camera

• CommonIntents

• Contacts

• Event

• EyesFree

• Location

• MediaPlayer

• MediaRecorder

• Phone

• Preferences

• SensorManager

• Settings

• Sms

• SpeechRecognition

• ToneGenerator

• WakeLock

• Wifi

• UI


Examples

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import android

droid = android.Android()message = droid.recognizeSpeech("What is your command?")droid.makeToast("You said: %s" % message.result)

Speech Recognition


Examples

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Text-to-Speech

import android

droid = android.Android()droid.vibrate()droid.ttsSpeak("Hello, this is android speaking!")


Examples

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Web View

import android

droid = android.Android()message = droid.webViewShow("http://xkcd.com/353/")


http://xkcd.com/353/


Examples

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SMS

import android

droid = android.Android()droid.smsSend(someNumber,"Let’s meet for drinks!")


Dealing with UI

22


UI

• WebView Frontend (HTML + Javascript)

• Python Backend

• Frontend talks to Backend using Events

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Events

• eventPost(name, data)

• eventWaitFor(eventName, timeout)

• eventClearBuffer()

• eventPoll(number_of_events)

• eventWait()

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Example

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import android

droid = android.Android()droid.webViewShow("/sdcard/sl4a/scripts/html/example.html")

result = droid.eventWaitFor("EVENT_A").result[“data”]self.droid.log("Received data from EVENT_A: " + result)

...<script language= "javascript" type= "text/javascript"> var droid = new Android(); var date = new Date();

droid.eventPost("EVENT_A", "Page Loaded On " + date);</script>...

example.html

example.py


Before we move on...

• What was discussed so far

• Using the android.py module in Python programs.

• android.py talks to SL4A, which exposes Android functionality to clients.

• UI can be built using HTML+Javascript, and it can talk to Python backend using SL4A events.

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A more complete example?

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Control robots!

28 http://www.flickr.com/photos/motorbikematt/




The Design

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ArduinoCellbotsfirmware

analogmotorcontrol

Bluetoothmodule

directioncontrol

FWD

LEFT RIGHT

BACK

STOP


The DesignArduino

• Cellbots project for firmware

• PDE files on Cellbots site

Android

• HTML + Javascript for frontend UI

• Python for backend, Cellbot control

• Bluetooth module required (Py4A project)

30

FWD

LEFT RIGHT

BACK

STOP

ArduinoCellbotsfirmware

Bluetoothmodule


Cellbot Controller

• Looks for Cellbot devices via Bluetooth.

• Connects to a selected device and controls its movement.

• Invokes WebView to display UI.

• Interacts with UI using SL4A events.

31

Code available at https://github.com/georgegoh/cellbot-controller


https://github.com/georgegoh/cellbot-controller


Connecting to the Device

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cellbot.py

Start

Scan for list of nearby devices

and post

Connect to selected device

scan.html

User clicks “Scan”

UI shows devices list

User selects device

1. Display scan view

2. event(scanBluetooth)

3. event(bluetoothDevicesFound)

4. event(connectBluetoothDevice)


Bluetooth scanning

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def scan_bluetooth(self, arg): """ Discover nearby Bluetooth devices and trigger an SL4A event "bluetoothDevicesFound" with the list of devices found. """ self.droid.log("Scanning bluetooth devices") self.discovered_devices = \ bluetooth.discover_devices(lookup_names=True) self.droid.log("Devices found: " + \ str(self.discovered_devices)) self.droid.eventPost("bluetoothDevicesFound", json.dumps(self.discovered_devices))





Bluetooth connection

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def connect_bluetooth_device(self, bd_addr): """ Connect to a Bluetooth device specified by the bd_addr address and display the control view for the device. """ service = bluetooth.find_service(uuid=CELLBOT_UUID, address=bd_addr)[0] self.socket = bluetooth.BluetoothSocket(bluetooth.RFCOMM) self.socket.connect((service["host"], service["port"])) self.droid.webViewShow(CONTROL_VIEW)





Controlling the Device

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cellbot.py

Start

Send directionto connected

cellbot

control.html

User clicks a direction

1. Display control view

2. event(move)


Motion Control

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def move(self, direction): """ Move a connected Cellbot in one of the following directions: f - Forward b - Back l - Left r - Right s - Stop """ if self.socket: self.socket.send(direction + "\n")





Frontend HTML/JS Control 1

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<head> <title>Robot demo</title> <script type="text/javascript" src="./js/mootools.js"></script> <script language="javascript" type="text/javascript"> var droid=new Android();

function postToPython(data) { droid.eventPost("PYTHON", JSON.stringify(data)); }

function move(direction) { postToPython({action: "move", data: direction}); }

window.addEvent("domready", function() { $('bFwd').addEvent('click', function() { move("f"); }); $('bLeft').addEvent('click', function() { move("l"); }); $('bStop').addEvent('click', function() { move("s"); }); $('bRight').addEvent('click', function() { move("r"); }); $('bBack').addEvent('click', function() { move("b"); }); $('bExit').addEvent('click', function() { postToPython({action:"EXIT", data:""}); }); }); </script></head>


Frontend HTML/JS Control 2

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<body> <table align=center> <tr> <td /> <td align=center><button id="bFwd">FWD</button></td> <td /> </tr> <tr> <td align=center><button id="bLeft">LEFT</button></td> <td align=center><button id="bStop">STOP</button></td> <td align=center><button id="bRight">RIGHT</button></td> </tr> <tr> <td /> <td align=center><button id="bBack">BACK</button></td> <td /> </tr> </table> <button id="bExit">EXIT</button></body>


Python for Android (Py4A)

• Additional python modules added:- Bluez, Twisted, Zope, pyEphem

• Current maintainers:- Naranjo Manuel Francisco- Robbie Matthews

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References

• Scripting Layer for Androidhttp://code.google.com/p/android-scripting

• Python for Androidhttp://code.google.com/p/python-for-android

• In Love with a Droidhttp://android-scripting.blogspot.com/

• Cellbotshttp://www.cellbots.com

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http://code.google.com/p/android-scripting

http://code.google.com/p/android-scripting

http://code.google.com/p/python-for-android

http://code.google.com/p/python-for-android

http://android-scripting.blogspot.com/

http://android-scripting.blogspot.com/



Acknowledgements

• Damon Kohler

• Robbie Matthews

• Colleagues @ HP Labs Singapore

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?

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@georgegoh

https://github.com/georgegoh/

http://www.linkedin.com/in/georgegoh

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Thank you






fin

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Bonus/Misc Slides

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Event loop

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while action != "EXIT": self.droid.log("Python: Waiting for event.") event_data = self.droid.eventWaitFor("PYTHON").result["data"] self.droid.log("Python: Event received. Processing...") # unpack the event data and perform action(if available). properties = json.loads(event_data) self.droid.log("Result: " + str(properties)) action = properties["action"] if action in self.handlers: self.handlers[action](properties["data"])





Packaging your app• Download the template project archive

• http://android-scripting.googlecode.com/hg/android/script_for_android_template.zip

• Modify the following according to your project

• Import into Eclipse

• Refactor package name from com.dummy.fooforandroid to your package name.

• Modify or put your script into the res/raw directory.

• http://code.google.com/p/android-scripting/wiki/SharingScripts

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http://code.google.com/p/android-scripting/wiki/SharingScripts

http://code.google.com/p/android-scripting/wiki/SharingScripts

How SL4A works

• Android functionality is abstracted into methods.

• These methods are grouped in subsystems called ‘Facades’.

• A JSON-RPC server exposes the methods contained in these Facades.

48


SL4A Architecture

Facade 0

JsonRpcServerFacade N

.

.

.FacadeManagerfunctionality exposed

via RPC methodsClient

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Facades

• A facade represents a collection of functionality

• @Rpc annotation exposes methods

• @RpcParameter, @RpcDefault, @RpcOptional describe method arguments.

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RPCReceiver

XYZFacade

<<Rpc>> + doIt()

<<implements>>


Facades

Common/src/com/googlecode/android_scripting/facade/ui/UIFacade.javapublic class UiFacade extends RpcReceiver {

[...]

@Rpc(description = "Create a text input dialog.") public void dialogCreateInput( @RpcParameter(name = "title", description = "title of the input box") @RpcDefault("Value") final String title, @RpcParameter(name = "message", description = "message to display above the input box") @RpcDefault("Please enter value:") final String message, @RpcParameter(name = "defaultText", description = "text to insert into the input box") @RpcOptional final String text) throws InterruptedException { dialogDismiss(); mDialogTask = new AlertDialogTask(title, message); ((AlertDialogTask) mDialogTask).setTextInput(text); }

[...]}

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public void dialogCreateInput(final String title, final String message, final String text) throws InterruptedException { dialogDismiss(); mDialogTask = new AlertDialogTask(title, message); ((AlertDialogTask) mDialogTask).setTextInput(text);}

@Rpc annotation to indicate method is exposed via RPC

@RpcParameter used in generating user-readable

descriptionsDefault values can be

specified using the @RpcDefault annotation

RpcReceiver is the abstract parent of all Facade classes


Code details

For details, see:

• AndroidProxy

• FacadeManagerFactory

• FacadeManager

• FacadeConfiguration

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Facades

http://code.google.com/p/android-scripting/wiki/ApiReference

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Remote Control

• Write programs using your computer keyboard and monitor and control an Android device remotely.

• Start a SL4A server on your Android, export some environment variables and import the “android.py” module.

• http://bit.ly/startpy4a

54 http://xkcd.com/722/


https://github.com/georgegoh/Android-Scripting/blob/master/py4a_start.sh

https://github.com/georgegoh/Android-Scripting/blob/master/py4a_start.sh



Language specific library

SL4A Architecture

Facade 0

JsonRpcServerFacade N

.

.

.FacadeManagerfunctionality exposed

via RPC methods

Language Interpreter

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What you need• On your dev machine

• Android SDK

• Python 2.6

• On your Android

• Barcode Scanner

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If you don’t have a barcode scanner1. Start the Android Market App.

2. Search for pub: “ZXing Team”

3. Install “Barcode Scanner”

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So I’ve installedSL4A and Py4A.

What’s next?

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Install more...

• Py4A is not the Python environment.

• It is the manager for the Python interpreter, extras, and scripts.

• Extras => libraries

• Scripts => sample python scripts to get you started.

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Install the env

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• Start “Python for Android”

• Click “Install”


Technology

Pycon2011 android programming-using_python