AndroidScripting_KCDC2012

This session will provide an introduction to Android and will illustrate how SL4A (Scripting Layer for Android) allows us to create Android apps using a variety of programming languages including: Python, Javascript, Perl, JRuby and Lua. We’ll demonstrate how to perform simple tasks like accessing the GPS location, taking a picture or sending a text message without writing a single line of Java code.
Then we’ll delve deeper into Android’s APIs and learn how to create a full blown Android App using a combination of Javascript and Python, complete with packaging the app for distribution on the Android Market.

Transcript

1. ANDROID SCRIPTING
   A Java-less approach to building apps
   Juan Gomez
   Android Dev @ Handmark, Inc
   Co-founder PythonKC
   Friday, April 27, 12
   

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2. AGENDA
   • Android 101
   • Scripting Layer for Android (SL4A)
   • Basic tasks (WiFi, GPS, camera, SMS) and basic UI
   • Using WebViews and Javascript for better UIs
   • Advanced Scripts (Twisted, PyBluez)
   • Packaging your scripts on an APK
   • Q & A
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3. ANDROID 101
   An Android application is actually a collection of several
   components, each defined in a file called AndroidManifest.xml
   The 4 main types of components are:
   • Activities
   • Services
   • Content Providers
   • Broadcast Receivers
   Apps are packaged on an APK file (myApp.apk)
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4. INTENTS
   • Apps can communicate with each other by providing and consuming each
   other’s Intents
   • Intents “link” activities, services, and
   receivers together
   • Intents consists of
   • An action (i.e. ACTION_VIEW)
   • Categories (i.e. CATEGORY_DEFAULT)
   • A URI (i.e. content://contacts/people/123)
   • “Extras” metadata
   • Intents can also be sent to hard-coded class names (com.foo.FooActivity)
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5. HOW DO I GET STARTED?
   • Download the Android SDK: http://developer.android.com/sdk
   • Add Android platforms and other packages to your SDK
   • Install the ADT plug-in for Eclipse (optional)
   • Enable app side-loading on your phone:
   • Settings > Application > Unknown Sources
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6. WHERE CAN I LEARN MORE?
   • Android’s Dev Guide
   http://developer.android.com/guide
   • Lots of Android Books
   • StackOverflow
   • Recommended resource:
   • http://commonsware.com/
   • The Busy Coder’s Guide to Android
   Development
   • Yearly subscription
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7. SCRIPTING LAYER FOR
   ANDROID (SL4A)
   • Brings scripting languages to Android
   • Allows you to edit and execute scripts and interactive
   interpreters directly on the Android device.
   • Scripts have access to many of the APIs available to full-
   fledged Android apps.
   • Supported languages include: Python, Perl, JRuby, Lua, BeanShell,
   JavaScript and Tcl
   • There’s limited support for PHP and Shell scripts
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8. SL4A ARCHITECTURE
   • As it name implies, SL4A sits
   between the actual Android JVM
   (Dalvik) and the executable
   Scripts.
   • The Facade API exposes a subset
   of Android system API's via JSON
   RPC calls
   • Only the parts of Android's APIs
   which has been wrapped by
   facades are available to
   interpreter
   • This is a fundamental feature of
   SL4A added by Google to avoid
   security concerns.
   AUTHENTICATION

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9. WHAT CAN SL4A DO?
   • Handle intents
   • Start activities
   • Make phone calls
   • Send text messages
   • Scan bar codes
   • Poll location and sensor data
   • Use text-to-speech
   &IGURE

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10. HOW TO DOWNLOAD?
    • Go to: http://code.google.com/p/android-scripting/
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11. HOW TO USE
    IT?
    SL4A installs as an App on
    your phone, you need to
    install separate interpreters
    for each language you want to
    use
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12. INTERPRETERS
    Open up the App, click on
    Menu > View > Interpreters to
    get a list of the available
    interpreters
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13. DOWNLOAD
    Click on Menu > Add to get a
    list of new interpreters you
    can install on your phone
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14. INSTALL
    Click on an Interpreter from
    the list and this will download
    an .APK with the installer.
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15. SCRIPTS
    When you open the SL4A
    app you get a list of your
    available scripts. You can use a
    quick action menu to run,
    edit, save or delete
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16. EDIT/RUN
    SL4A offers an environment
    to edit and run scripts on the
    phone but really limited
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17. USING ADB PUSH/PULL
    • It’s easier to edit scripts on your computer using your favorite
    text editor and leverage the Android Debug Bridge (ADB) to
    load them on the phone.
    • ADB is installed on //platform-tool/
    • adb pull /mnt/sdcard/sl4a/scripts/Camera.js ~/Documents/
    sl4a_scripts/
    • adb push ~/Documents/sl4a_scripts/Camera.js /mnt/sdcard/sl4a/
    scripts
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18. Friday, April 27, 12
    

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19. HELLO WORLD (PYTHON)
    import android
    droid = android.Android()
    droid.makeToast('Hello,
    Android!')
    print 'Hello world!'
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20. TAKING A PICTURE (JS)
    load("/sdcard/
    com.googlecode.rhinoforandroid/extras/rhino/
    android.js");
    var droid = new Android();
    result = droid.cameraCapturePicture("/mnt/
    sdcard/sl4a/pic.jpg", true);
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21. WIFI
    List all surrounding WiFi
    networks and their
    connection information
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22. LISTING WIFI NETWORKS (JS)
    load("/sdcard/com.googlecode.rhinoforandroid/extras/rhino/
    android.js");
    var droid = new Android();
    wifi_on = droid.checkWifiState();
    if (wifi_on) {
    success = droid.wifiStartScan();
    if (success) {
    list_of_networks = droid.wifiGetScanResults();
    for (var i = 0; i < list_of_networks.length; i++) {
    for (attr in list_of_networks[i]) {
    print(attr + ": " + list_of_networks[i][attr]);
    }
    print("\n");
    }
    }
    droid.makeToast("Done obtaining list of WiFi networks!");
    } else {
    droid.makeToast("WiFi radio is off");
    }
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23. USING GPS AND SMS (RUBY)
    require "android";
    def get_location(droid)
    droid.startLocating()
    droid.eventWaitFor("location")
    raw_location = droid.readLocation()
    droid.stopLocating()
    return raw_location["result"]["network"]
    end
    def format_address(loc_info)
    return loc_info["feature_name"] + " " + loc_info["thoroughfare"] + " " +
    loc_info["locality"] + ", " + loc_info["admin_area"] + " " +
    loc_info["postal_code"]
    end
    def get_address(droid, location)
    loc_info= droid.geocode(location["latitude"], location["longitude"])
    return format_address(loc_info["result"][0])
    end
    droid = Android.new
    location = get_location droid
    address = get_address droid, location
    phone = droid.pickPhone
    droid.smsSend phone["result"], "Greetings from SL4A, I'm at " + address
    puts "done sending SMS with location"
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24. BASIC UI
    SL4A provides basic Android
    UI elements to be used in
    scripts. But these UI elements
    are generally very limited
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25. USING NATIVE TYPES AND
    LIBRARIES
    import android
    from datetime import date
    droid = android.Android()
    today = date.today()
    droid.dialogCreateDatePicker(today.year, today.month, today.day)
    droid.dialogShow()
    selectedDate = droid.dialogGetResponse().result
    first_date = date(selectedDate['year'], selectedDate['month'], selectedDate['day'])
    droid.dialogCreateDatePicker(today.year, today.month, today.day)
    droid.dialogShow()
    selectedDate = droid.dialogGetResponse().result
    second_date = date(selectedDate['year'], selectedDate['month'], selectedDate['day'])
    timediff = abs(first_date - second_date)
    droid.dialogCreateAlert("Difference", "Days: " + str(timediff.days))
    droid.dialogSetPositiveButtonText('OK')
    droid.dialogShow()
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26. SIMPLE TWITTER CLIENT
    (RUBY)
    require 'android'
    require 'net/http'
    droid = Android.new
    url = URI.parse("http://twitter.com/statuses/update.xml")
    req = Net::HTTP::Post.new(url.path)
    req.basic_auth('user', 'password')
    status = droid.getInput 'Twitter Update', "What's going on?"
    req.set_form_data({'status' => status["result"],
    'source' => 'Android'})
    response = Net::HTTP.new(url.host, url.port).start do |http|
    http.request(req)
    end
    if response.code == "200"
    droid.makeToast "Your toot was successfully sent."
    end
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27. WEBVIEWS AS ADVANCED UI
    
    
    Text to Speech
    <br/>var droid = new Android();<br/>var speak = function() {<br/>droid.eventPost("say",<br/>document.getElementById("say").value);<br/>}<br/>
    
    
    
    What would you like to say?
    label>
    
    
    
    
    
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28. BACKGROUND SERVICE
    import android
    droid = android.Android()
    droid.webViewShow('file:///sdcard/sl4a/scripts/
    text_to_speech.html')
    while True:
    result = droid.eventWaitFor('say').result
    if result is not None:
    droid.ttsSpeak(result['data'])
    You can create a background service that acts as a controller in
    you favorite language to support your Web UI
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29. ADVANCED SCRIPTS
    • Python is by far the most
    complete language on SL4A
    • You can import more advanced
    libraries that are not part of the
    Python Standard Library.
    • Like PyBluez for Bluetooth
    • Or Twisted
    • Twisted is an extremely powerful event-
    driven networking engine written in
    Python.
    • Projects like BitTorrent and Launchpad
    use twisted as their networking engine.
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30. PACKAGING YOU APP FOR
    THE GOOGLE PLAY STORE
    • For this step you will need Eclipse :(
    • Download the skeleton Android project from here:
    http://android-scripting.googlecode.com/hg/android/
    script_for_android_template.zip
    • Follow these instructions to configure the project:
    http://code.google.com/p/android-scripting/wiki/SharingScripts
    • Make sure you can generate an APK and do a test install.
    • Follow these instructions to sign your APK:
    http://developer.android.com/guide/publishing/app-signing.html
    • Viola! you can upload your APK to the Play Store
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31. THAT’S IT FOR ME!
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32. Thanks
    To Our Sponsors
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33. BEGINNERS PYTHON
    WORKSHOP
    • The Beginners Python Workshop is a 2-day free event focused on
    teaching the basics of programming in the Python language.
    • Everybody is encouraged to attend, regardless of your previous
    experience with programming
    • The only requirements to attend are a laptop and a willingness to learn.
    • When:
    Friday, June 22nd 6pm - 10pm
    Saturday, June 23rd 10am - 4pm
    • Where:
    UMKC Campus 302 Flarsheim Hall
    5110 Rockhill Road, Kansas City, MO
    RSVP at: http://www.meetup.com/pythonkc/events/62339552
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34. @_JUANDG
    http://speakerdeck.com/u/juandg/p/androidscripting_kcdc2012#
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