Mobile Application Development Framework

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Mobile Application Development Framework
4/16/2009 Richard Yang
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Recap

• What are the major considerations in developing a
  software environment and application framework
  for mobile wireless applications?
• Handle heterogeneous devices/configurations
• Efficient (memory, battery, )
• Easy programming for event-driven programming

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Recap TinyOS
ADC.nc interface ADC async command result_t
getdata()  async command result_t
getContinuousData()  event result_t
dataReady(uint 16_t data)

• Software componentsprovide commands andrequire
  callback hooks
• A configuration linkscomponents and uses only
  necessary components
• Two threads
• one for event
• one for task

configuration SenseTask // this module does
not provide any interfaces implementation
components Main, SenseTaskM, LedsC, TimerC,
DemoSensorC as Sensor Main.StdControl -gt
TimerC Main.StdControl -gt Sensor
Main.StdControl -gt SenseTaskM
SenseTaskM.Timer -gt TimerC.Timerunique("Timer")
SenseTaskM.ADC -gt Sensor SenseTaskM.Leds -gt
LedsC
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Recap J2ME/.NetCF

• Scale down a popular programming environment to
  ease learning
• Use virtual machines to mask device heterogeneity
• Use versioning to handle configuration
  heterogeneity and avoid using lowest common
  denominator
• Provide classes to support user-interface driven
  applications

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Application Framework (Android) Key Concepts

• Activity
• Visible screen for user interaction
• Service
• Background services
• Content provider
• Shared data
• Service/Event discovery
• Broadcast receivers Receive and react to
  broadcast events
• Intent and Intent Filter

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Andriod Features

• Linux kernel as foundation
• Java based framework (J2SE not J2ME)
• Dalvik Virtual machine

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Andriod
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Activity (Visual User Interaction)
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Discussion Key Issues in Designing Activity
Support in Mobile Env.

• Constrained display screen
• Solution specially simple display components
• Need smart layout management
• Event handling of UI
• Lifecycle support
• May need frequent resource (memory)
  release/acquisition
• Fast switch between activities/screens
• Frozen app. Management
• Persistent state management

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MIDP GUI

• Implementations control the look and layout of
  screen components

Title
High-level Components
Ticker tape (Optional device manufacturer can
place it at the top or bottom of the screen)
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MIDP Visual Display Management

• Display
• the manager of the display and input devices
• Each MIDP has one instance of Display
• Display.getDisplay(this) to get the manager
• At any instance of time at most one Displayable
  object can be shown on the display device and
  interact with user
• display.setCurrent(ltDisplayable objectgt)

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MIDP GUI

• Lists
• Text Boxes
• Alerts
• Forms
• Form Items
• Labels
• Image Items
• String Items
• Text Fields
• Date Fields
• Gauges
• Choice Groups

• Similar to J2SE GUI but reduced

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MIDP Visual Display

• Displayable
• Canvas
• GameCanvas
• Screen
• Alert, List, TextBox, Form
• Form can contain multiple form items for
  organization
• Labels, Image Items, String Items, Text Fields,
  Date Fields, Gauges, Choice Groups

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MIDP User Interaction

• Displayable objects can declare commands and
  declare a command listener
• addCommand(Command cmd)
• addCommandListener()
• Command(ltlabelgt, lttypegt, ltprioritygt)
• Type BACK, CANCEL, EXIT, HELP, ITEM, OK, SCREEN,
  and STOP

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MIDP Lifecycle

• MIDlets move from state to state in the
  lifecycle, as indicated
• start acquire resources and start executing
• pause release resources and become quiescent
  (wait)
• destroy release all resources, destroy threads,
  and end all activity

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Example

• See HelloMIDlet.java

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Check on MIDP

• Constrained display screen
• Display components
• Layout management
• Event handling of UI
• Lifecycle support
• May need frequent resource (memory)
  release/acquisition
• Fast switch between activities/screens
• Frozen app. Management
• Persistent state management

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MIDP Persistent State

• Record store defined in javax.microedition.rms
• Record store identified by name
• recordStore RecordStore.openRecordStore("scores"
  , true)
• recordId addRecord(byte data, int offset,
  int numBytes)
• getRecord(int recordId)

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• Android Activity Life cycle

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Android Service Life Cycle

• void onCreate()
• void onStart(Intent intent)
• void onDestroy()

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Android Visual Display

• Similar to J2SE
• Interesting feature using xml resources for GUI
  management

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Example
see tablelayout.xml
http//developer.android.com/guide/tutorials/views
/hello-tablelayout.html
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Example Calculator
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Check on Android

• Constrained display screen
• Display components
• Layout management
• Event handling of UI
• Lifecycle support
• May need frequent resource (memory)
  release/acquisition
• Fast switch between activities/screens
• Frozen app. Management
• Persistent state management

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Persistent Data Storage

• Preference
• store and retrieve key-value pairs of primitive
  data types, e.g., font, greeting
• See preference.java
• File
• SQL

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Inter-Activity Data Exchange
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MIDP

• Uses Record Store
• static String listRecordStores()

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Android Content Provider

• Each provider can expose its data as a simple
  table on a database model
• Each content provider exposes a public URI that
  uniquely identifies its data set
• android.provider.Contacts.Phones.CONTENT_URI
  android.provider.Contacts.Photos.CONTENT_URI
  android.provider.CallLog.Calls.CONTENT_URI
  android.provider.Calendar.CONTENT_URI

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Android Content Provider

• See ContentProvider for query example

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Inter-Activity Service/Event Discovery
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Intent

• ltComponent namegt optional
• Action
• Data, e.g., mpeg
• Category, e.g., browserable

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Intent

• An Intent object is passed to Context.startActivit
  y() or Activity.startActivityForResult() to
  launch an activity or get an existing activity to
  do something new.
• An Intent object is passed to Context.startService
  () to initiate a service or deliver new
  instructions to an ongoing service. Similarly, an
  intent can be passed 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.
• Intent objects passed to any of the broadcast
  methods (such as Context.sendBroadcast(),
  Context.sendOrderedBroadcast(), or
  Context.sendStickyBroadcast()) are delivered to
  all interested broadcast receivers. Many kinds of
  broadcasts originate in system code.

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Intent Resolution

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

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Intent filter
action
category
data
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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)