Android SL4A

Before called ASE (Android Scripting Environment)



Started in 2009 by Damon Kohler 
20% time project at Google.
Python, Perl, Ruby, Lua, BeanShell, Javascript, Tcl, Shell and more. 


IS SL4A Useful?

SIMPLE EXAMPLE

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 SimpleName extends Activity {
    private EditText m_text = 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?");
        m_text = new EditText(this);
        builder.setView(mEditText);        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {            @Override           public void onClick(DialogInterface dialog, int which) {               Toast.makeText(SimpleName.this, "Hello World!",        Toast.LENGTH_SHORT).show();} });...

SIMPLE EXAMPLE IN PYTHON




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

Python program: 4 SLOC


HOW does it work?


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

SL4a Architecture





  • Interoperation of scripting language engines, ported to the Android platform API via remote procedure calls (RPCs) to a server implemented as a standard Android Java application. 

  • API facade exposing subset or Android API , accesible using JSON-RPC
  • RPC API compiled in dex bytecode, no additional interpreting in Java

JSON-based RPC

Any program that implements a compatible JSON–based RPC interfacing module or set of routines can potentially invoke the SL4A RPC Server. 


https://github.com/damonkohler/sl4a/blob/master/python/ase/android.py

{
  "Image": {
   "Width": 800,
   "Height": 600,
   "Title": "View from 15th Floor", "Thumbnail": {
   "Url": "http://www.example.com/image/481989943", "Height": 125,
   "Width": "100"
  },
  "IDs": [116, 943, 234, 38793],... 

SL4a Functionality

  • ActivityResult
  • Android
  • ApplicationManager • BatteryManager
  • Camera
  • CommonIntents
  • Contacts
  • Event
  • EyesFree
  • Location
  • MediaPlayer
  • MediaRecorder
  • Phone
  • Preferences
  • SensorManager 
  • Settings
  • Sms
  • SpeechRecognition 
  • ToneGenerator
  • WakeLock
  • Wifi
  • UI 

FACADES


  • A facade represents a collection of functionality
  • @Rpc annotation exposes methods
  • @RpcParameter, @RpcDefault, @RpcOptional describe method arguments.



UI using WEB View

Communicating through events

example.html
 <script language= "javascript" type= "text/javascript">
  var droid = new Android();
  var date = new Date();
  droid.eventPost("EVENT_A", "Page Loaded On " + date);
</script>
example.py
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)


Examples

Speech Recognition



import android
droid = android.Android()
message = droid.recognizeSpeech("Say something?")
droid.makeToast("You said: %s" % message.result)


text-to-speech



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

Web view



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

SMS



import android
droid = android.Android()
droid.smsSend(someNumber,"SMS Sent!")

Dialogs




Python for android

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


UI with FULLSCREENWRAPPER2


You can make Screens like this


Demo code


import android, random
from fullscreenwrapper2 import *

class DemoLayout(Layout):
    def __init__(self):
        super(DemoLayout,self).__init__(xmldata,"FullScreenWrapper Demo")
        
    def on_show(self):
        self.add_event(key_EventHandler(handler_function=self.close_app))
        self.views.but_change.add_event(click_EventHandler(self.views.but_change, self.change_color))
        self.views.but_exit.add_event(click_EventHandler(self.views.but_exit, self.close_app))
        self.views.txt_colorbox.background="#ffffffff"
        
    def on_close(self):
        pass
    
    def close_app(self,view,event):
        FullScreenWrapper2App.exit_FullScreenWrapper2App()

    def change_color(self,view, event):
        colorvalue = "#ff"+self.get_rand_hex_byte()+self.get_rand_hex_byte()+self.get_rand_hex_byte()
        self.views.txt_colorbox.background=colorvalue
    
    def get_rand_hex_byte(self):
        j = random.randint(0,255)
        hexrep = hex(j)[2:]
        if(len(hexrep)==1):
            hexrep = '0'+hexrep   
        return hexrep 

if __name__ == '__main__':
    droid = android.Android()
    random.seed()
    FullScreenWrapper2App.initialize(droid)
    FullScreenWrapper2App.show_layout(DemoLayout())
    FullScreenWrapper2App.eventloop()

PACKAGING IN APK



Python project template 

that will embed a Python interpreter 

and your Python scripts into an APK.



and

YOUR OWN PYTHON DISTRIBUTION



APK compiling:

  • Python libraries
  • All selected libraries (kivy, pygame, pil...)
  • A java bootstrap
  • A build script

Cross-compiling python 

for android



Where is SL4A USED?


Not much more, really, but some cool examples.

Android SL4A

By Jorge Vila Forcén

Made with Slides.com

Android SL4A

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