Introductory lecture to Android development. Faculty of Mathematics and Physics in Prague, 2013.

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

3. Agenda
• dialogs, toasts, notifications
• fragments

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

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)

7. Platform Versions

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

9. Google Play
• app can be acquired by app stores
• Google Play, http://play.google.com
• other stores
• > 50 billion apps have been installed from
Google Play
• July 2013, 1 million apps

10. Google Play
• purchasing
• selling
• Play Music, Play Books, ...

11. Google Play
• selling apps
• 15 min return period
• ads
• AdMob, ...
• in-app billing

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
app

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

18. Development
• IDE support
• Android Studio, IntelliJ IDEA, ADT plugin
for Eclispse, 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. Libraries
• compatibility libraries
• v4 - backports lots of newer functionality
to Android 1.6+
• Google Play In-app Billing

21. Libraries
• Google Play Services
• Google Maps
• Games
• Google+
• Authorization

22. Libraries
• AdMob
• Google Analytics, Flurry, Crittercism
• Google Cloud Messaging

24. Hello World

25. Build

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

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

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

31. 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, ...)

32. 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, ...

33. 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

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

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
• onPause() - system resuming another
activity
• onStop() - activity becoming invisible to
the user

38. Activity callbacks
• onDestroy() - before activity is
destroyed
• onRestart() - called if activity was
previously stopped, called prior to onStart()

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

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

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

44. User Interface
• widgets
• UI objects
• Button, TextView, EditText,
RadioButton, ...
• WebView

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

46. Resources
• drawables
• bitmaps
• 9-patch png
• state lists
• layer lists
• shape drawables

47. Resources
• layout
• strings
• colors
• menus
• dimensions
• animations

48. Resources
• arrays
• ids
• raw
• xml
• ...

49. Screen sizes and
densities

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

51. Resources
• resources can be created in several
versions
• the best version is selected according to
current device configuration in runtime
• resource units
• dp - density-independent pixel
• sp - scale-independent pixel (for fonts)

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

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

54. 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)

55. 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)

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

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

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

59. 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;!
}!

60. Fragments
• a piece of application UI
• introduced to support more flexible UI
• phones and tablets together in one app
• fragment != activity
• fragments are used within activities

61. Fragments
• since Android 3.0
• support library v4 backports them to
Android 1.6+

62. 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

63. Menu
• menu resource
• Android < 3.0 the whole menu hidden
under menu button
• ActionBar since Android 3.0
• items can be displayed in the action bar

64. Menu
• behaviour for items that don’t fit in the
action bar
• hidden under menu button (if the device
has one)
• system overflow icon in the action bar

65. Dialogs
• floating window screen

66. Dialogs
• standard dialogs
• custom dialogs
• activity with dialog style
• since fragments used via DialogFragment

67. Dialogs
• might be tedious to create
• difficult to style
• StyledDialogs
•
https://github.com/inmite/android-styled-dialogs
• the library makes styling and using dialogs
a piece of cake

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

69. Notifications
• a message that can be displayed to the user
outside your normal UI
• displayed in notification area

70. Notifications
• user can open notification drawer to see
the details
• app can define UI and click action
•
NotificationCompat.Builder

71. 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();

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

73. THE END