Mobile Software Development Framework: Android

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Mobile Software Development Framework Android
2/23/2011 Y. Richard Yang
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Admin.

• Homework 2 due today
• Please schedule time to meet with the TA to demo
  your program
• Midterm Wednesday after spring break

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Recap Mobile Programming Requirements

• Handle heterogeneous devices/configurations
• Be extremely efficiency on using resources
  (memory, battery, )
• Easy programming for event-driven programming

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Recap tinyOS

• Customized OS for each app.
• Reusability achieved through
• Components and interfaces structure
• Execution model two threads
• One for tasks
• One for event handling

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HelloWorldMIDlet.java
import javax.microedition.midlet. import
javax.microedition.lcdui. public class
HelloWorldMIDlet extends MIDlet implemen
ts CommandListener private Command
exitCommand private Display display private
TextBox t public HelloWorldMIDlet()
display Display.getDisplay(this) exitCom
mand new Command("Exit", Command.EXIT, 2) t
new TextBox(CS434", "Hello World!", 256,
0) t.addCommand(exitCommand) t.setCommandL
istener(this) public void startApp()
display.setCurrent(t) public void pauseApp()
public void destroyApp(boolean
unconditional) public void
commandAction(Command c, Displayable s) if
(c exitCommand) destroyApp(false) no
tifyDestroyed()
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Recap J2ME

• Scale down a popular programming environment to
  ease learning
• Use virtual machines to mask device heterogeneity
• Use configuration/profile to handle device
  heterogeneity to avoid using lowest common
  denominator
• MIDLet and Displayable to support user-interface
  driven applications
• MIDLet manages app life cycle
• Displayable has commands and provides command
  listener
• Introduce persistent record store

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Recap Android

• Scale down a popular programming environment to
  ease learning
• Use virtual machines to mask device heterogeneity
• Activity and View

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Activity

• A screen with which users can interact
• Activity haslife cycle to yield resources

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View

• A view component is a building block for user
  interface components.
• Widget Toolbox
• TextView, EditText, Button, Form, TimePicker
• ListView
• Layout
• Positions of controls
• LinearLayout, Relativelayout

http//developer.android.com/guide/tutorials/views
/index.htm
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View by XML
main.xml

• Layout of visual interface
• Java Code
• Initialize
• Access
• TextView myTextView
  (TextView)findViewById(R.id.myTextView)

lt?xml version1.0 encodingutf-8?gt ltLinearLayo
ut xmlnsandroidhttp//schemas.android.com/a
pk/res/android androidorientationvertical
androidlayout_widthfill_parent
androidlayout_heightfill_parentgt ltTextView
androidid_at_id/myTextView androidlayout_widt
hfill_parent androidlayout_heightwrap_cont
ent androidtextHello World,
HelloWorld /gt lt/LinearLayoutgt
_at_Override public void onCreate(Bundle icicle)
super.onCreate(icicle) setContentView(R.layout.
main)
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User Interaction Event

• onKeyDown. onKeyUp
• onTrackBallEvent
• onTouchEvent

registerButton.setOnClickListener(new
View.OnClickListener() public void
onClick(View arg0) .
myEditText.setOnKeyListener(new OnKeyListener()
public boolean onKey(View v, int keyCode,
KeyEvent event) if (event.getAction()
KeyEvent.ACTION_DOWN) if (keyCode
KeyEvent.KEYCODE_DPAD_CENTER)
return true return false )
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Example TipCal
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Application Framework (Android) Key Concepts

• Activity and view
• Visible screen for user interaction
• External resources

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External Resources
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Application Framework (Android) Key Concepts

• Activity and view
• Visible screen for user interaction
• External resources
• Service

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Service Working in Background

• A basic function of Android Service
• A facility for an application to tell the
  system about something it wants to be doing in
  the background (even when the user is not
  directly interacting with the application).
• The system to schedule work for the service, to
  be run until the service or someone else
  explicitly stop it.
• NO GUI, higher priority than inactive Activities
• Note
• A Service is not a separate process. The Service
  object itself does not imply it is running in its
  own process unless otherwise specified, it runs
  in the same process as the application it is part
  of.
• A Service is not a thread. It is not a means
  itself to do work off of the main thread (to
  avoid Application Not Responding errors).

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Application Framework (Android) Key Concepts

• Activity and view
• Visible screen for user interaction
• External resources
• Service
• Intercommunications

• Communication among apps
• Intent
• broadcast
• data provider

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Application and Component Glues

• Intent
• An intent is an abstract description of an
  operation to be performed.
• To invoke operations from your own or others
• Can pass data back and forth between app.
• Intent Filter
• Register Activities, Services, and Broadcast
  Receivers as being capable of performing an
  action on a particular kind of data.

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Intent Description

• ltComponent namegt
• Action
• Data
• Category, e.g., LAUNCHER

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Intent Usage

• Pass to Context.startActivity() or
  Activity.startActivityForResult() to launch an
  activity or get an existing activity to do
  something new.
• Pass to Context.startService() to initiate a
  service or deliver new instructions to an ongoing
  service.
• Pass to Context.bindService() to establish a
  connection between the calling component and a
  target service. It can optionally initiate the
  service if it's not already running.
• Pass to any of the broadcast methods (such as
  Context.sendBroadcast(), Context.sendOrderedBroadc
  ast(), or Context.sendStickyBroadcast()) are
  delivered to all interested broadcast receivers.
  Many kinds of broadcasts originate in system
  code.

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Android Broadcast Receiver

• Sending a broadcast
• Context.sendBroadcast(Intent intent, String
  receiverPermission)
• Context.sendOrderedBroadcast()
• Receiving broadcast
• Intent registerReceiver (BroadcastReceiver
  receiver, IntentFilter filter)

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Intent Resolution Explicit

• Explicit intents component identified

Intent myIntent new Intent(IntentController.this
,
TipCal.class) startActivity(myIntent)

• Make sure AndroidManifest.xml announces
  activities to be started

ltapplication androidicon"_at_drawable/icon"
androidlabel"_at_string/app_name"gt
ltactivity androidname".IntentController"
androidlabel"Intent1"gt
ltintent-filtergt ltaction
androidname"android.intent.action.MAIN" /gt
ltcategory androidname"android.intent.
category.LAUNCHER" /gt
lt/intent-filtergt lt/activitygt
ltactivity androidname".TipCal"gtlt/activitygt
lt/applicationgt
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Intent Resolution Implicit

• Implicit intents
• System matches an intent object to the intent
  filters of others

http//developer.android.com/guide/topics/intents/
intents-filters.html
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Intent filter
action
category
data
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Intent Example II Implicit
String action "android.intent.action.VIEW" Uri
data Uri.parse("http//www.google.com") Intent
myIntent new Intent(action, data) startActivity
(myIntent)

• AndroidManifest.xml file for com.android.browser

ltintent-filtergt    ltaction androidname"android.
intent.action.VIEW" /gt    ltcategory
androidname"android.intent.category.DEFAULT"
/gt    ltscheme androidname"http" /gt    ltscheme
androidname"https" /gt    ltscheme
androidname"file" /gtlt/intent-filtergt
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Intent Example II Implicit
String action "android.intent.action.DIAL" Stri
ng phno "tel[phone]" Uri data
Uri.parse(phno) Intent dialIntent new
Intent(action, data) startActivity(dialIntent)
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A Design Template Invoker
String action com.hotelapp.ACTION_BOOK" String
hotel hotel//name/ selectedHotel Uri
data Uri.parse(hotel) Intent bookingIntent
new Intent(action, data) startActivityForResults(
bookingIntent, requestCode)
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A Design Template Provider
ltactivity androidname".Booking"
androidlabelBooking"gt ltintent-filtergt
ltaction androidnamecom.hotelapp.ACTION_BOOK"
/gt ltdata androidschemehotel"
androidhostname/gt lt/intent-filtergt lt/activi
tygt

• For more complex data passing, please read the
  tutorial

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A Design Template Provider
_at_Override public void onCreate(Bundle
savedInstanceState) super.onCreate(savedInst
anceState) setContentView(R.layout.main)
Intent intent getIntent() // why am I
called String action intent.getAction()
Uri data intent.getdata() String
hotelName data.getPath() // do the
booking setResult(RESULT_OK) finish()