Introductory lecture to Android development. Faculty of Mathematics and Physics in Prague, 2014.

1. Android Development
- the basics
Tomáš Kypta

2. Agenda
• Android platform and ecosystem"
• Android SDK and development tools"
• Hello World"
• building blocks of Android apps & the
manifest file"
• activities, widgets, intents"
• toasts

3. Android platform
• Linux-based operating system"
• open-source (http://source.android.com/)"
• originally phone OS"
• tablet support (since Honeycomb, Android
3.0)

4. Android platform
• Google TV"
• Google Glass"
• Google Wear

5. History
• 2003, Android inc."
• 2005, acquired by Google"
• Sep 2008, the first Android phone"
– T-Mobile G1"
• May 2010, Froyo (Android 2.2)"
• Feb 2011, Honeycomb (Android 3.0)

6. History
• Oct 2011, Ice Cream Sandwich (Android
4.0)"
• July 2012, Jelly Bean (Android 4.1)"
• July 2013, Jelly Bean (Android 4.3)"
• Oct 2013, KitKat (Android 4.4)"
• June 2014, Android L (developer preview)

7. Platform Versions

8. Android ecosystem
• thousands of devices"
• the most popular mobile platform"
• 1.5 million new devices activated every day"
– Q2 2013"
• September 3, 2013, 1 billion Android
devices have been activated"
• most devices made by Samsung "
– 65%, Feb 2014

9. Google Play
• apps are distributed by app stores"
– Google Play, http://play.google.com"
– other stores (Amazon, Samsung, …)"
• > 50 billion apps have been installed from
Google Play"
• > 1.3 million apps

10. Google Play
• customers can purchase"
• developers can sell"
• Play Music "
• Play Books "
• Play Movies

11. Monetization
• selling apps"
– 15 min return period"
• in-app billing"
– freemium model"
• ads"
– AdMob, ...

12. Android “problems”
• fragmentation"
• manufacturer/carrier enhancements"
• updates & support"
• openness - low quality apps in Google Play"
• malware"
– users

13. Android security
• app can be installed directly"
– .apk file"
• user accepts app permissions when
installing or updating the app

14. Android security
• Verify Apps (Android 2.3+)"
– checks every app install"
• Google Play can remotely uninstall harmful
apps

17. Development
• programming in “Java”"
– Java SE 7 (KitKat)"
• native apps possible (C++)"
• development tools platform friendly"
– Windows, Linux, Mac OS X

18. Development
• IDE support"
– Android Studio, IntelliJ IDEA"
– ADT plugin for Eclipse"
– Netbeans"
• you can freely develop on any device

19. Android SDK
• android - Android SDK and AVD Manager"
• adb - Android Debug Bridge"
• monitor - (ddms & hierarchyviewer)"
• emulator"
• lint, Traceview, ProGuard"
• docs, samples

20. Support Libraries
• compatibility libraries"
– v4 - backports lots of newer functionality
to Android 1.6+"
– Fragments, NotificationCompat, ViewPager"
– v7"
– AppCompat"
– v8"
– v13

21. Google Play Services
• Google Maps"
• In-app Billing"
• Games"
• Google+"
• Authorization

22. Libraries
• AdMob"
• Google Analytics, Flurry, Crittercism

24. Android building blocks
• Activity"
• Service"
• Content provider"
• Broadcast receiver"
• AndroidManifest.xml

25. Activity
• screen with user interface"
• the only visual component"
• example - an email app"
– list of emails"
– details of an email"
– email composition

26. Service
• has no UI"
• long-running tasks"
• examples"
– music playback service"
– download service"
– sync service

27. Content Provider
• managers and shares application data"
• data storage doesn’t matter (db, web,
filesystem)"
• apps can query and modify data through
content provider"
• r/w permissions can be defined"
• examples - all system dbs (SMS,
contacts, ...)

28. Broadcast Receiver
• responds to broadcasts"
• broadcasts are system wide"
• can be registered statically or dynamically"
• system or custom messages"
• examples - incoming SMS, incoming call,
screen turned off, low baterry, removed SD
card, BT device available, ...

29. AndroidManifest.xml
• defines what parts the app have"
• defines which endpoints are exposed"
• minimum/maximum API level"
• permissions"
• declare hardware and software features"
• require configuration

30. Intent
• asynchronous message"
• binds components together (all except
Content Provider)"
• starting activities"
• starting services and binding to services"
• sending broadcasts

31. Hello World

32. Build

35. Activity
• a subclass of android.app.Activity"
• app usually has many activities"
• activities managed in activity stack"
– newly started activity is placed on the
top of the stack

36. Activity Lifecycle
• activity can be in different states during its
lifecycle"
– foreground, visible, stopped, killed"
• when activity state changes a system
callback is called

37. Activity callbacks
• onCreate() - activity created"
• onStart() - activity visible for the user"
• onResume() - activity gains user focus

38. Activity callbacks
• onPause() - system resuming another
activity"
• onStop() - activity becoming invisible to the
user"
• onDestroy() - before activity is destroyed

39. Activity callbacks
• onRestart() - called if activity was
previously stopped, called prior to onStart()

42. Configuration changes
• when configuration changes, activities are
destroyed and recreated"
– default behaviour, can be changed"
• properly handle config changes"
– onSaveInstanceState(Bundle)

43. Intent & Activity
• starting activity explicitly"
– new Intent(context, MyActivity.class)!
• starting activity implicitly"
– new Intent(Intent.ACTION_VIEW,
Uri.parse(“http://developer.android.com”))!
• starting activity for result

44. User Interface
• defined by a hierarchy of views"
• layouts = containers"
– LinearLayout, RelativeLayout, FrameLayout, ...

45. User Interface
• widgets"
– UI objects"
– Button, TextView, EditText,
RadioButton, ..."
– WebView

46. User Interface
• list widgets"
– subclasses of AdapterView"
– display a list of items"
– use adapter to bind list do data"
– ListView, GridView, Spinner, ...

47. Adapters
• provide data for Adapter views"
• are responsible for the creation of items

48. Resources
• drawables"
– bitmaps"
– 9-patch png"
– state lists"
– layer lists"
– shape drawables

49. • layout"
• strings"
• colors"
• menus"
• dimensions"
• animations
Resources

50. • arrays"
• ids"
• raw"
• xml"
• ...
Resources

51. Screen sizes and densities

52. Screen sizes and densities
• How to handle different screen sizes and
densities?

53. Resources
• resources can be created in several
versions"
– the best version is selected according to
current device configuration in runtime

54. Resources
• resource units"
– dp - density-independent pixel"
– sp - scale-independent pixel (for fonts)"
– never use px!!!

55. Resource qualifiers
• suffixes for resource folders"
– drawables, drawable-mdpi, ..."
– values, values-cs"
– layout, layout-sw640dp"
– drawable-hdpi-v11

56. Resource qualifiers
• screen density - ldpi, mdpi, hdpi, xhdpi, ..."
• screen size - small, normal, large, xlarge"
• screen orientation - port, land"
• language - en, cs, sk, en-rGB…"
• version - v11, v14, ...

57. Resource qualifiers
• since Android 3.2"
• w<N>dp - available screen width, w600dp"
• h<N>dp - available screen heights, h720dp"
• sw<N>dp - smallest width (does not
change with orientation)

58. Resources
• accessed from code via generated R.java
file and resource ids"
– view.findViewById(R.id.txt_name)!
– txtName.setText(R.string.txt_name_label)

59. Localization?

60. Android version fragmentation
• How to handle different API levels available
on different devices?

61. Android version fragmentation
• build target"
– API level the app is compiled against"
• AndroidManifest.xml"
– <uses-sdk android:minSdkVersion="8"
android:targetSdkVersion="16" />

62. Android version fragmentation
• handling versions in code"
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.GINGERBREAD) {!
! // code for Android < 2.3!
}

63. Android version fragmentation
private boolean functionalitySupported = false;!
static {!
try {!
checkFunctionalitySupported();!
} catch (NoClassDefFoundError e) {!
!functionalitySupported = false;!
}!
}!
private static void checkFunctionalitySupported() throws
! NoClassDefFoundError {!
! functionalitySupported = android.app.Fragment.class !=
null;!
}!

64. Threads
• main thread = UI thread"
• do not ever block the UI thread!!!"
• use worker threads for time consuming
operations"
• UI toolkit not thread safe - never
manipulate UI from a worker thread

65. Logging
• java.util.logging.Logger
• android.util.Log

66. Toast
• simple non-modal information"
• displayed for a short period of time"
• doesn’t have user focus

67. Preferences
SharedPreferences prefs = PreferenceManager!
! .getDefaultSharedPreferences(context);!
SharedPreferences prefs = !
! config.getSharedPreferences(PREFS_FILE_NAME,!
! Activity.MODE_PRIVATE);!
"
int storedValue = prefs.getInt(SOME_KEY, defaultValue);!
"
SharedPreferences.Editor editor = prefs.edit();!
editor.putInt(SOME_KEY, storedValue);!
editor.commit();

68. Sources
• developer.android.com"
• android-developers.blogspot.com"
• source.android.com"
• stackoverflow.com"
• youtube.com/androiddevelopers"
• svetandroida.cz

69. THE END