Android Overview


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Theme day presentation @Futurice

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Android Overview

  1. 1. Date, time, etc.
  2. 2. What is Android? • Android is an open-source mobile platform • Source code available under the Apache license • • Roadmap available: • Google apps not open source (Market, Gmail, Maps) • Built on Linux • Offers full stack: OS, middleware, applications, developer APIs and tools, QEMU-based emulator • Developed by the Open Handset Alliance (OHA) • Includes companies such as Broadcom, Google, HTC, Intel, LG, Marvell, Motorola, Nvidia, Quallcom, Samsung, Sprint, T-Mobile, TI • Strongly driven by Google Date, time, etc.
  3. 3. So why is Android interesting • Modern mobile OS that could rival iPhone OS • Many OEMs • Still very young but lots of potential • Platform is developing • Just starting to get momentum • Easy to get started with development • Ready and working store solution Date, time, etc.
  4. 4. Date, time, etc.
  5. 5. Android timeline • 2005/07 Google acquires Android, Inc. • 2007/11 Android is announced by OHA • Early look SDK made available strait away • 2008/08 Android market announced • 2008/09 First Android device announced: T-Mobile G1 (HTC Dream) • Android SDK 1.0 announced the same day • 2008/10 Source code released to Android Open Source Project • Android Market opened. Free apps only • 2009/02 Android 1.1 released • Paid apps to UK and US Markets • 2009/04 Android 1.5 ”Cupcake” released • 2009/06 Android NDK released. • 2009/09 Android 1.6 ”Donut” released Date, time, etc.
  6. 6. Android devices • HTC has multiple models: • HTC Dream, 1st ever Android device • HTC Magic • HTC Hero • HTC Tattoo • ~15 devices on market, and more coming all the time • HTC, Motorola, LG, Samsung, Philips, Huawei, Lenovo and even Dell • Some manufacturers create their own UI layer, e.g. Motorola MOTOBLUR and HTC SenseUI Date, time, etc.
  7. 7. Developing for Android • Easy to get started • SDK + Eclipse plugin (ADT). • On-device debugging • Plenty of documentation: • OpenIntents-project: • Applications written in Java • Not JME or proper JSE. Java language syntax • Core Android libraries provide most of the functionality in the core Java libraries as well as additional Android-specific libraries • NDK enables compiling native code to be used via Java Native Interface (JNI) • All application are equal • You can even replace the dialer app if you want to Date, time, etc.
  8. 8. Android Software Stack Date, time, etc.
  9. 9. Dalvik VM • Register based virtual machine • As opposed to normal stack based VMs • Optimized to ensure that a device can run multiple instances efficiently. More info at and • Uses own bytecode not Java bytecode • No JIT • Android programs are compiled into Dalvik executable files (.dex) which are then zipped into Android packages (.apk). • Dex-files are used to ensure minimal memory footprint. • Uncompressed dex-file is usually still smaller than the same Java code as compressed jar-file. Date, time, etc.
  10. 10. Android application framework • Framework services • Activity manager • Views • Notification manager • Content providers • Resource manager • Lots of APIs: telephony, media, sensors, location, WebKit- based browser, Google Maps, P2P & Google Talk,home screen widgets,OpenGL, FreeType,SQLite to name a few Date, time, etc.
  11. 11. Main building blocks • Activities • Visible screen of the application • Services • Background services • Content providers • Share data between activities and applications • Intents • Activate services and components • Broadcast receivers • Received and react to broadcasted events • Resources • Support different localizations and form factors easily Date, time, etc.
  12. 12. Activity • Foreground activity is a visible screen in the application • Handles user interaction and feedback • Android applications have no exit. Platform handles the lifecycle. • Developer takes care of • onCreate • onStart • onResume • Running • onPause • onStop • onRestart • onDestroy Date, time, etc.
  13. 13. Date, time, etc.
  14. 14. Service • Used for background processing for other activities • Runs still on the main Activity’s thread • Need to separate to own thread if needed • Communication using e.g. Handlers if in separate threads • Lifecycle differs from Activity • Entire lifecycle vs active lifecycle • onCreate, onStart, onDestroy or • onCreate, onBind, onUnbind, (onRebind), onDestroy • According to starting mechanism. Date, time, etc.
  15. 15. Service lifecycle Date, time, etc.
  16. 16. Content providers • Store and share data between activities and services • Most content providers use SQLite as the data store • Usage via ContentResolvers and Content URIs: • Single row: content://com.futurice.fututwit/tweets/3815526750 • All rows: content://com.futurice.fututwit/tweets/ Date, time, etc.
  17. 17. Intents • Intents are used to activate other activities or services • You specify your intent: ”I want to make a phone call to number 555 2368” • Intent call = new Intent(Intent.ACTION_DIAL, Uri.parse(tel:555- 2368)); • startActivity(call) • Activities mapped to intent with Intent filters in the manifext xml-file • You can provide your own replacements even to platform’s own intent handlers, e.g. Dialer • Promotes loose coupling Date, time, etc.
  18. 18. Broadcast receivers • Used to listen to events sent by activities or services • Declared in the manifest as Intent Filter • Extend BroadcastReceiver Date, time, etc.
  19. 19. User interface • Is composed of Views and ViewGroups • Uses layouts • Layouts are ViewGroups • Lots of ready-made Views • ListView, TextView, EditText, Buttons, all the usual suspects • Also ready made components to include maps or a browser control in to your application. OpenGL ES can be used as well. • Easy to create custom Views Date, time, etc.
  20. 20. User interface continued • Declarative approach using XML preferred over in-code • I18N and L10N is simple using XML resources • ResourceManager matches with dir structure according to precedence • Drawable-fr • Drawable-en-notouch • Drawable-en-port-92dpi • 9-Patch bitmaps • No SVG support! • Animations: • Tweened, declared in XML • Frame-by-frame Date, time, etc.
  21. 21. Application data and security • Underlying Linux user account created for each app • Security based on app permissions • Declarative permissions • Signed by developer’s certificate • User approves permissions when installing • Applications are sandboxed • Use Content providers to share data • Store light weight preferences in app dir • For more data SQLite Date, time, etc.
  22. 22. Android Market • Since October 2008 • Started with free apps only • In February 2009 paid apps were introduced in UK and US Markets. • Payment via Google Checkout • Paid apps available in 10 countries (not Finland) • $25 registration fee for developers • 70% to developer • Price range: free - $200 (No I Am Rich apps) • 24h money back guarantee! • Ratings, upgrades, stats Date, time, etc.
  23. 23. Thank you Date, time, etc.
  24. 24. References • Images courtesy of • • Date, time, etc.