This document provides an overview of Android development basics. It discusses the Android platform, ecosystem, and SDK tools. It describes key Android concepts like activities, services, content providers, and broadcasts. It also covers user interface components, resources, handling different device configurations, fragments, threads, menus, dialogs, notifications and more. The document is intended as an introduction to the fundamentals of Android development.

1. Android Development
- the basics
Tomáš Kypta
@TomasKypta

4. Outline
● Android platform
● Android ecosystem
● Android SDK and development tools
● Hello World
● building blocks & the manifest file
● activities, widgets, intents
● dialog, toasts, notifications
● fragments

5. Android platform
● Linux-based operating system
● open-source
● originally phone OS
● tablet (since Honeycomb, Android 3.0)
● Google TV
● hundreds of devices

6. History
● 2003, Android inc.
● 2005 acquired by Google
● Sep 2008 first Android phone – T-Mobile G1
● since then rapid development of the platform
● May 2010 Froyo
● Feb 2011 Honeycomb
● Oct 2011 Ice Cream Sandwich
● Jul 2012 Jelly Bean

8. Android ecosystem
● the world's most popular mobile platform
● 1.3M new devices activated every day
● of that 70k tablets
● total number of devices ~ 500 million
● play.google.com (market.android.com)
● other store – Amazon Appstore for Android, ...

9. Google Play
● ~ 675 000 apps in the market
● total downloads > 25 billion
● ~ 70% free apps
● ads, in-app billing
● selling – 15 min return period
● buy – ČR, SR
● sell – ČR
● Google Play contains also music, books
– not available in ČR, SR

10. Android problems
● fragmentation
● manufacturer/carrier enhancements
● updates & support
● openness – low quality apps in Google Play
● malware - users

11. Permissions
● users accept when installing or updating the
app
● apps can be installed directly from .apk file

12. Sources
● developer.android.com
● android-developers.blogspot.com
● source.android.com
● stackoverflow.com
● youtube.com/androiddevelopers
● svetandroida.cz

13. Development
● programming in “Java”
● native apps possible (C++)
● development tools platform friendly
● Windows, Linux, Mac OS X
● IDE support – ADT plugin for Eclipse,
Netbeans, IntelliJ IDEA, ...
● you can freely develop on your device

14. Android SDK
● android – Android SDK and AVD Manager
● adb – Android Debug Bridge
● ddms – Dalvik Debug Monitor
● emulator
● lint, hierarchyviewer, Traceview
● ProGuard
● docs, samples

15. Libraries
● compatibility libraries
– v4 – backports lots of newer
functionality to android 1.6+
● licensing, billing libraries
● AdMob
● Google Analytics, Flurry, Crittercism, ...
● C2DM

16. Android internals

17. Hello World

18. Build

20. Android Building Blocks
● Activity
● Service
● Content provider
● Broadcast receiver
● AndroidManifest.xml

21. Activity
● screen with user interface
● the only visual component
● example – an email app can contain:
– list of emails
– email detail
– email composition
– preference screen
– ...

22. Service
● has no UI
● long-running tasks
● examples:
– music playback service
– download service
– sync service

23. Content Provider
● manages and shares application data
● data storage doesn't matter – database, web,
filesystem
● apps can query and modify data through
content provider
● read/write permissions can be defined
● examples:
– all system databases
– contacts
– SMS

24. 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

25. AndroidManifest.xml
● defines what parts the app have
● defines which endpoints are exposed
● minimum/maximum API level
● permissions
● declare hardware and software features
● required configuration

26. Intent
● asynchronous message
● binds components together (all of them
except ContentProvider)
● starting activities
● starting services and binding to services
● sending broadcasts

27. Activity
● a subclass of android.app.Activity
● app usually has many activities
● activities managed in activity stack
– newly started activity is place on the top of
the stack

28. Activity Lifecycle
● activity can be in different states during it's
lifecycle:
– foreground
– visible
– stopped
– killed
● when activity state changes a system
callback is called

29. Activity callbacks
● onCreate() - activity created
● onStart() - becoming visible to the user
● onResume() - gains user focus
● onPause() - system resuming previous
activity
● onStop() - becoming invisible to the user
● onDestroy() - before activity destroyed
● onRestart() - if it was previously stopped,
prior to onStart()

31. Intent & Activity
● starting activity explicitly
● starting activity implicitly
● starting activity for result

32. Configuration changes
● when configuration changes activities are
destroyed and recreated by default
– place for lots of bugs
● behaviour can be changes
● it is preferred to properly handle config
changes
– onSaveInstanceState(Bundle)

33. User Interface
● defined by hierarchy of views
● layouts = containers
– LinearLayout
– RelativeLayout
– FrameLayout
– AdapterView – ListView, GridView, Spinner
● widgets = UI objects
– Button, TextView, EditText
– WebView

34. List Widgets
● displays a list of items (some view)
– ListView, Spinner, GridView, Gallery
● use adapter to bind list to data

35. Resources
● drawables – bitmaps, 9-patch png, state-list,
layer list, shape drawable, ...
● layouts
● strings
● colors
● menus
● animations
● arrays, ids, dimensions, raw, ...

36. Screen sizes and densities
● How to handle so many different devices?

37. Resource units
● dp/dip – density-independent pixel
● sp – scale-independent pixel

38. Resources
● generated file R.java
● resource ids
● makes resources accessible in the code
●
● resources can be created in several versions
– proper resource is selected according to
current device configuration in runtime

39. 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, ...
● since Android 3.2
– w<N>dp – available screen width, w600dp
– h<N>dp – available screen height, h720dp
– sw<N>dp – smallest width (does not change with
orientation change)
● combinations

40. Android version fragmentation
● How to handle different API levels avialable
on devices?
● build target
– project.properties
– target=android-16
● AndroidManifest.xml
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="16" />

41. Android version fragmentation
if (Build.VERSION.SDK_INT <
Build.VERSION_CODES.GINGERBREAD) {
// only for android older than gingerbread
}

42. 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;
}

43. Fragments
● a piece of application UI
● fragment != activity
● fragments used within activities
● since Android 3.0
● support library v4 backports it to Android 1.6+
● introduced to support more flexible UI –
phones and tablets together in one app

44. Threads
● main thread = UI thread
● do not block the UI thread
● use worker threads for time consuming
operations
● UI toolkit not thread safe – never manipulate
UI from a worker thread

45. Menu
● Android pre 3.0 – menu hidden under menu
button
● Android 3.0+ has ActionBar:
– items can be displayed in the action bar
– if not enough space the bahaviour depends:
● hidden under menu button, if the device has
menu button
● otherwise an overflow icon created in the
action bar
● menu resource

46. Dialogs and Toasts
● Dialog – floating window screen
– standard dialogs
– custom dialogs
– since fragments used via DialogFragment
● Toast – simple non-modal information
displayed for a short period of time
– doesn't have user focus

47. Notifications
● a message that can be displayed to the user
outside your normal UI
● displayed in notification area
● user can open notification drawer to see the
details
● app can define UI and click action on the
notification
● NotificationCompat.Builder

48. THE END