Presentation at Jfokus about And

1. Jumpstart to Android
App development
Lars Vogel
http://www.vogella.de
Twitter: @vogella

2. What is Android?
Fundamentals
Constructs of Android
Live Coding
Q&A

3. About me – Lars Vogel
Independent Eclipse and Android consultant,
trainer and book author
Eclipse committer
Maintains http://www.vogella.de Java, Eclipse
and Android related Tutorials with more then a
million visitors per month.

4. More Android Sessions:
Wednesday, 11.10 -
12.00 - So whats so cool about Android 4.x
Thuersday – Friday – Full day Android training

5. Android Experience?

6. What is
Android?

7. Android from 10 000 feet
- Open Source
- Full stack based on Linux
- Java programming interface
- Project is lead by Google
- Tooling available for Eclipse (and other IDE's)

9. On Android you develop in Java
(There is also the NDK which allows development in C / C++...)

10. Overview of the API Capabilities
Rich UI components
Threads and Background Processing
Full network stack (Http, JSON)
Database available
Images
Access to the hardware (GPS, Camera,
Phone)
and much more............

11. Its like
programming for
hardware which is
10 years old

12. … with insame
performance
requirements

13. On Android you develop in Java
Really?

14. Android Programming
You use the Java
programming language
but Android does not run
Java Bytecode

15. Dalvik
Run Dalvik Executable Code (.dex)
Tool dx converts Java Bytecode into .dex
• Register based VM vrs. stack based as the JVM
• .dex Files contain more then one class
• Approx. 50 % of the size of a class file
• op codes are two bytes instead of one in the JVM
• As of Android 2.2 Dalvik JIT compiler
• Primary engineer: Dan Bornstein

16. Developer
Toolchain

17. Android Development Tools (ADT)
for Eclipse
Eclipse based tooling
• Provide the emulator
• Wizard for creating new project
• Additional Tooling, e.g views

18. Emulator
QEMU-based ARM emulator runs
same image as a device
Use same toolchain to work with
device or emulator
Inital startup is
slooooowwwwww.....

19. Demo

20. AndroidManifest.xml
• General configuration files for
your application
• Contains all component
definitions of your appication

21. Resources from /res are
automatically „indexed“

22. ADT maintains a
reference to all
resources in the R.java

23. Main Android programming
constructs
Activity
Views
Intents
Broadcast Receiver
Services
ContentProvider

24. Context

25. Context
Global information about an application environment.
Allows access to application-specific resources and classes
Support application-level operations such as launching
activities, broadcasting and receiving intents, etc.
Basically all Android classes need a context
Activity extends Context

26. Demo
Activities project
Your first

27. Activity
Extends Context
An activity is a single, focused
thing that the user can do.
Kind of a screen but not entirely...

28. View vrs ViewGroup
android.viewView: UI Widget
- Button
- TextView
- EditText

29. Layouts
android.view.ViewGroup
- Layout
- extends View
• Layouts are typically defined via XML
files (resources)
• You can assign properties to the
layout elements to influence their
behavior.

30. Demo – Hello JFokus

31. Andoid is
allowed to kill
your app to
save memory.

32. Life Cyle of an Activity
void onCreate(Bundle savedInstanceState)
void onStart()
void onRestart()
void onResume()
void onPause()
void onStop()
void onDestroy()

33. States of an Activity
• Active/ Running – Visible and interacts with user
• Paused – still visible but partically obscured (other
transparant activity, dialog or the phone screen),
instance is running but might be killed by the
system
• Stopped – completely obscured, e.g. User presses
the home screen button, instance is running but
might be killed by the system
• Killed – if stopped or paused, system might calling
finish or by killing it

35. To test flip your
device

36. Def
inin
gA
ctiv
itie
s

37. Calling Activities
Calling Activities
creates a stack ->
Back button goes
back to the
previous activity
-> Think of it as a
stack of cards

38. Defining Activities
• Create a class which extends
„Activitiy“
• Create an entry in
„AndroidManifest.xml“ for the activity.
• <activity
android:name=“MyNewActivity“></a
ctivity>

39. I had only the
best intents....

40. Intents
Message passing mechanism to start
Activities, Services or to trigger
(system) events.
Allow modular architecture
Can contain data (extra)

41. Intents
• Explicit: Asking someone to do something
• Implicit: Asking the system who can do something
Intent

42. Demo Intents

43. Implicit Intents
• new Intent(Intent.ACTION_VIEW,
Uri.parse("http://www.vogella.de"));
• new Intent(Intent.ACTION_CALL, Uri.parse("tel:
(+49)12345789"));
• new Intent(Intent.ACTION_VIEW,
Uri.parse("geo:50.123,7.1434?z=19"));
• new
Intent("android.media.action.IMAGE_CAPTURE");

44. Gettings results
Intent intent = new
Intent("android.media.action.IMAGE_CAPTURE");
startActivityForResult(intent, 0);
public void onActivityResult(int requestCode, int
resultCode, Intent data) {
if (resultCode == Activity.RESULT_OK && requestCode
== 0) {
String result = data.toURI();
Toast.makeText(this, result, Toast.LENGTH_LONG);
}
}

45. XML
Drawables

46. XML Drawables
• XML Resources
• Can be used to define transitions,
shapes or state
A drawable resource is something
that can be drawn to the screen

47. Services and receiver

48. Services
Allow real multitasking and background processing
De-coupled from the Activity life-cyle

49. Services
Service runs in the background without interacting with the user.
Android provides a multitude of system services
• NotificationService
• VibratorService
• LocationService
• AlarmService
• ....
Access via context.getSystemService(Context.CONST);
You can define your own service for things that should run in the
background

50. Notification
Manager
Demo

51. Services
Service runs in the background without interacting with the user.
Android provides a multitude of system services
• NotificationService
• VibratorService
• LocationService
• AlarmService
• ....
Access via context.getSystemService(Context.CONST);
You can define your own service for things that should run in the
background

52. Broadcast Receiver – Listen to events
Example:
BATTERY_LOW,
ACTION_BOOT_COMPLETED
android.intent.action.PHONE_STATE
Defined statically in manifest or temporary
via code
Broadcast Receiver only works within the
onReceive() method
C2DM

53. Own Service
• Extend Service or IntentService
• start with startService(Intent) or
bindService(Intent).
• onStartCommand is called in the service
• bindService gets a ServiceConnection as
parameter which receives a Binder object
which can be used to communicate with the
service

54. How to start a service
Broadcast Receiver –
Event: BOOT_COMPLETED
Or
ACTION_EXTERNAL_APPLICATIONS_A
VAILABLE
startService in the onReceiveMethod()
Timer Service
Start BroadcastReceiver which starts the
service

55. Demo
alarm
receiver.phone

56. Security

57. Each apps gets into own Linux user
and runs in its own process

58. Android Application requires
explicit permissions, e.g. for
• DB access
• Phone access
• Contacts
• Internet
• System messages

59. Background Processing

60. Be fast!
Avoid ApplicationNotResponding
Error

61. Use Threads (not the UI one)
• Long running stuff should run in the
background
• Thread cannot modify the UI
• Synch with the UI thread
runOnUiThread(new Runnable)

62. Handler and AsyncTask
• Handler runs in the UI thread
• Allows to send Message object and or
to send Runnable to it
handler.sendMessage(msg)
handler.post(runnable)
• AsyncTask for more complex work

63. AsyncTask
• To use it subclass it
AsyncTask <TypeOfVarArgParams , ProgressValue ,
ResultValue>
doInBackground() – Do the work
onPostExecute() – Update the UI

64. Saving the thread
• If a thread runs in your Activity you
want to save it.

65. Lifecycle - Thread
• If Activity is destroyed the Threads should be
preserved.
• Close down Dialogs in the onDestroy() method
• One object can be saved via
onRetainConConfigurationInstance()
• Access via getLastNonConfigurationInstance()
• Only use static inner classes in your Threads
otherwise you create a memory leakage.

66. Option Menus and
Action Bar

67. Option Menu & Action Bar
• Option Menu displays if „Menu“
button is pressed
• You can decided if the entries are
displayed in the Action Bar or in a
menu
• Use „ifRoom“ flag if possible.

68. Option Menu & Action Bar
• Option Menu displays if „Menu“
button is pressed
• You can decided if the entries are
displayed in the Action Bar or in a
menu
• Use „ifRoom“ flag if possible.

69. Preferences

70. Read and Write Preferences
• Key – Value pairs
• PreferenceManager.getDefaultShared
Preferences(this);
– To read: getString(key), get...
– To change use edit(), putType(key, value),
commit()
• To maintain use PreferenceActivity

71. PreferenceActivity
• Create resource file (preference)
• New Activity which extends
PreferenceActivity
• To add preferences:
– addPreferencesFromResource(R.xml.prefer
ences);
• Saving and edits will be handled
automatically by the
PreferenceActivity

72. ListView

73. ListView
Can be used to display a list of items
Gets his data from an adapter

74. Adapter
Data for ListView
defined by Adapter
View per row defined
by Adapter

75. ListActivity
ListActivity has already a predefined ListView with the id @android:id/list
which will be used automatically.
Provides nice method hooks for typical operations on lists
If you define your own layout this layout must contain a ListView with the
ID:
@+android:id/list

76. What if the layout should
not be static?

77. Define your own Adapter

78. Reuse existing rows
If convertView is not null -> reuse it
Saves memory and CPU power (approx. 150 % faster according to
Google IO)
Holder Pattern saves 25%

79. Views and Touch

80. There is more....

81. I have
feelings
Camera API
Motion Detection
Location API (GIS)
Heat Sensor
Accelerator

82. Example Camera API

83. I can talk and
hear
Internet (java.net, Apache HttpClient, JSON...)
Bluetooth
Email
SMS
VoIP (SIP (Session Initiation Protocol))

84. Other Capabilities
Push to device
Interactive Widgets on the homescreen
Live Wallpapers (as background)
Animations and Styling
Simple List handling
(Multi-) Touch
NFC
Canvas / OpenGL ES (Game programming....)
Native Rendering

85. Android 4.0

86. Whats so cool about Android 4.0?
• Come to my talk on Wednesday... ;-)

87. Summary
Android powerful and well-
designed development
platform
Easy to get started
Power to the developer

89. Android: Where to go
from here:
Android Introduction Tutorial
http://www.vogella.de/articles/Android/article.html
Or Google for „Android Development Tutorial“
Android SQLite and ContentProvider Book
http://www.amazon.com/dp/B006YUWEFE
More on Android
http://www.vogella.de/android.html

90. Thank you
For further questions:
Lars.Vogel@gmail.com
http://www.vogella.de
Twitter http://www.twitter.com/vogella
Google+ http://gplus.to/vogella

91. License &
Acknowledgements
• This work is licensed under the Creative Commons
Attribution-Noncommercial-No Derivative Works 3.0
Germany License
– See http://creativecommons.org/licenses/by-nc-nd/3.0/de/deed.en_US