An introduction to the Android platform and how to develop for it with Java and the provided tools. Also covers best practices and some resources to aid in the development process.

1. INTRODUCTIONTO
ANDROID DEVELOPMENT
Jim McKeeth
@JimMcKeeth
jim@mckeeth.org
1
Tuesday, August 20, 13

2. AGENDA
• Hello Android
• Overview of Platform
• PlatformTools
• UI - XML
• Views & Widgets
• Architecture
• Manifest & Permission
• Activities & Intents
• Debugging
• Resources
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3. ABOUT ME
• Live here in Boise - jim@mckeeth.org
• Lead Developer Evangelist for EmbarcaderoTechnologies
• www.embarcadero.com - Delphi for Android coming soon
• Google Developer Group - www.gdgb.org
• Boise Software Developers Group - www.bsdg.org
• Boise Code Camp - www.BoiseCodeCamp.com
Tuesday, August 20, 13

4. DEMO: HELLO ANDROID
Tuesday, August 20, 13

5. GOOD PLACESTO KNOW
• developer.android.com - Official developer site
• developers.google.com/android/ - Google on Android
• developers.google.com/events/io/ - Google I/O Replays
• stackoverflow.com - Great Q&A community
• android.stackexchange.com - End user Q&A
• vogella.com/android.html - Detailed tutorials
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6. ANDROID
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7. ANDROID STACK
• Tweaked Linux 2.6
• Tweaked Java (Dalvik)
• Android OS
• Android Apps
• (Mostly open source)
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8. VERSION HISTORY
• November 5th, 2007 is Android’s Birthday
• Each version has a version number, name and API level
• Version number is most specific
• Name is group of versions and API levels
• Latest:Android 4.3 Jelly Bean (API 18)
http://en.wikipedia.org/wiki/Android_version_history#Version_history_by_API_level
Tuesday, August 20, 13

9. VERSION POPULARITY
As of August 2013
http://sn.im/platform-versions9
40% = Jelly Bean
63% >= ICS
96% >= Gingerbread
40%
23%
33%
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10. Tuesday, August 20, 13

11. ARCHITECTURE
http://sn.im/what-is-android
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12. FRAMEWORK
• DalvikVM
• WebKit Browser
• 2d Graphics Library, 3D w/OpenGL
• SQLite
• MPEG4, MP3, PNG, JPEG, etc
• GSMTelephony, Bluetooth,WiFi
• Camera, GPS, Compass,Accelerometer
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13. CORE APPLICATIONS
• Phone
• eMail and SMS clients
• Calendar
• Contacts
• Web Browser
• Geographic Support via Google Maps
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14. ANDROID DEVELOPMENT
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15. ANDROID SDK
• http://developer.android.com/sdk
• 3 Options
• ADT Bundle (in Eclipse)
• “Existing IDE” download
• Android Studio preview (in IntelliJ)
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16. RELATEDTOOLS
• Managers
• Android SDK Manager
• AVD Manager (AndroidVirtual Device)
• Command-LineTools
• adb (Android Debug Bridge -Your best friend!)
• Others
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17. ANDROID DEVELOPMENT
JDK$
Android'
SDK'
Dalvik'
Virtual'
Machine'
Linux&
kernel&
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18. BUILD PROCESS
Android'App'Package'
APK'
DEX'Compiler'
Dalvik'byte'code'
Java'Compiler'
Java'JAR'
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19. THE APK FILE
• Zip file containing
• Manifest, etc.
• Compiled code
• Resources & Assets
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20. ACTIVITY ARCHITECTURE
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21. Applica'on*Context*
PARTS OF AN ANDROID APP
Intent%
Ac#vity(
Class% Layout' String'
Resources'
Android'
Manifest'
Other&
Classes&
Drawables)
Services(
Broadcast)
Receiver)
Content&
Providers&
Ac#vity( Intent%
Tuesday, August 20, 13

22. PROJECT LAYOUT
• AndroidManifest.xml
• bin (APK file, compiled DEX files)
• gen (generated resources)
• res (resources you create)
• src (Java source files)
Tuesday, August 20, 13

23. MANIFEST
• Mandatory XML file “AndroidManifest.xml”
• Describe application components
• Default Activity
• Permissions,Attributes
• Non-SDK libraries
http://sn.im/android-manifest
Tuesday, August 20, 13

24. MULTIPLE ACTIVITIES
• Each Activity must be defined in manifest by class name and
“action”
• Activities reside on a “task stack” - visible activity is “top of
stack”
• Transition to an Activity using Intent
• Return from Activity using Activity.finish() which pops off task
stack
Tuesday, August 20, 13

25. “RES” - RESOURCES
• XML Files
• drawable
• layout
• values
• etc.
• Graphics
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26. RES/LAYOUT
• Each Activity should have dedicated layout XML file
• Layout file specifies Activity appearance
• Several layout types
• Default LinearLayout provides sequential placement of widgets
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27. RES/VALUES
• strings.xml contains String constants
• Prefer strings.xml to hardcoded values (warnings)
• L10N/I18N (Localization/Internationalization)
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28. • Application/Task is a stack of Activities
• Visible activity = top of stack
• Activities maintain state, even when notTOS
• “Back” button pops stack.
• “Home” key would move stack to background
• Selecting application brings to foreground or launches
new instance
APPLICATION AKATASK
Tuesday, August 20, 13

29. ANDROID.APP.ACTIVITY
• Activity extends Context
• Context contains application environment
• “a single focused thing a user can do”
• An application consists of 1 or more Activities
• Provides a default window to draw in, might be smaller than
screen or float on top of others
• UI elements are “View(s)” or widgets
Tuesday, August 20, 13

30. ANDROID.VIEW.VIEW
• Extends java.lang.Object
• Basic building block for UI components
• Rectangular area on display
• Responsible for drawing and event handling
• View is the base class for widgets
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31. Callback Methods
(delegates)
Major States
Activity
Lifecycle
http://sn.im/android-activity
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32. SAVING STATE
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33. FRAGMENTS
http://sn.im/android-fragments
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34. ANDROID.CONTENT.INTENT
• Interprocess Communication messaging
• Can launch an Activity or start a Service
• new Intent(String action, Uri uri);
• new Intent(Context packageCtx, Class class);
• Intent.putExtra()
• Intent.setAction()
http://sn.im/android-intent
Tuesday, August 20, 13

35. INTENT (CONTINUED)
• android.intent.action.MAIN (receiver on main activity)
• many options:ACTION_VIEW, etc
• category = extra information
• MIME type
• extras (i.e. getAction(), getExtra(), etc)
Tuesday, August 20, 13

36. INTENT USAGE
• Activity Switch:
• new Intent(this, NextActivity.class);
• Web Browser:
• Uri uri = Uri.parse(“http://foobar.com”);
• new Intent(Intent.ACTION_VIEW, uri);
• Phone Dialer:
• Uri uri = Uri.parse(“tel:4085551212”);
• new Intent(Intent.ACTION_VIEW, uri);
http://sn.im/android-intent
Tuesday, August 20, 13

37. VIEWS
Tuesday, August 20, 13

38. VIEW LISTENERS
• GUI is event driven
• Event source: button press, mouse click, etc.
• Listener catches event and performs action
• Events are delivered to view w/current focus
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39. EVENT LISTENER
• onClick()/View.OnClickListener()
• (boolean) onLongClick()/View.OnLongClickListener()
• onFocusChange()/View.OnFocusChangeListener()
• (boolean) onKey()/View.OnKeyListener()
• (boolean) onTouch()/View.OnTouchListener()
• onCreateContextMenu()/
View.OnCreateContextMenuListener()
• return true to stop event propagation
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40. VIEW SIZE
• FILL_PARENT = parent sized (minus pad)
• Now “MATCH_PARENT” w/API Level 8
• WRAP_CONTENT = just big enough (plus pad)
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41. LAYING OUTVIEWS
• Gravity = position (i.e. left, right, center)
• Weight = extra/empty space allocation
• priority for expansion
• default weight is zero
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42. DIMENSIONVALUES
• Dimension values:
• dp/dip = density independent pixels
• sp = Scale independent pixels
• px = pixels
• in/mm = inches/millimeters
• pt = point (1/72 inch)
RecommendedNotRecommended
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43. DENSITY INDEPENDENT
PIXELS
• An abstract unit that is based on the physical density of the screen.These units
are relative to a 160 dpi (dots per inch) screen, so 160dp is always one inch
regardless of the screen density.
• The ratio of dp-to-pixel will change with the screen density, but not necessarily
in direct proportion.
• You should use these units when specifying view dimensions in your layout, so
the UI properly scales to render at the same actual size on different screens.
• The compiler accepts both "dip" and "dp", though "dp" is more consistent with
"sp".
Tuesday, August 20, 13

44. SCALE-INDEPENDENT PIXELS
• This is like the dp unit, but it is also scaled by the user's font
size preference.
• Recommend you use this unit when specifying font sizes, so
they will be adjusted for both the screen density and the
user's preference.
Recom
m
ended
for
Fonts
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45. COLORS
• #RGB
• #ARGB ( Alpha / Red / Green / Blue )
• #RRGGBB (i.e. #3d1ec4)
• #AARRGGBB
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46. VIEW /VIEWGROUP
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47. LAYOUTS (VIEWGROUPS)
• AbsoluteLayout -Absolute X,Y (depreciated)
• FrameLayout - Pinned to top left (simplest)
• LinearLayout - Horizontal orVertical - one per row
• RelativeLayout - Child specify relative widgets
• SlidingDrawer - Hides until dragged out by handle
• TableLayout - Rows & Columns
• ScrollView - Child can be larger than window
• TabWidget - Manages collection of “Tab Hosts”
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48. ORIENTATION
• landscape or portrait
• dedicated layout file
• /res/layout = default layout directory
• /res/layout-land = landscape layout directory
• /res/layout-port = portrait layout directory
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49. DEMO - LAYOUTS &VIEWS
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50. TRACE LOGGING
• android.util.Log
• Log.d(“tag”,“debug”);
• Log.e(“tag”,“error”);
• Log.i(“tag”,“informational”);
• Log.v(“tag”,“verbose”);
• Log.w(“tag”,“warning”);
• View output using “adb logcat”
http://sn.im/android-log
Tuesday, August 20, 13

51. ADB - ANDROID DEBUG
BRIDGE
• Manages devices & emulators
• Issue debug commands
• Log output (adb logcat)
• Shell (adb shell)
• Copy files to/from emulator (adb push/pull)
http://sn.im/android_debug_bridge
Tuesday, August 20, 13

52. DEMO - ADB & LOGCAT
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53. BEST PRACTICES
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54. BEST PRACTICES
• Support multiple screen sizes and densities
• Use the Action Bar pattern - Good-bye menu button
• Build Dynamic UI with Fragments
• Know when to persist and restore state
• Don’t block main thread - use AsyncTask -Test with
StrictMode
http://sn.im/android-practices
http://sn.im/android-performance
Tuesday, August 20, 13

55. SUPPORT MULTIPLE SCREENS
SIZES & DENSITIES
• Use wrap_content, fill_parent, or dp units when
specifying dimensions in an XML layout file
• Do not use hard coded pixel values in your
application code
• Do not use AbsoluteLayout (it's deprecated)
• Supply alternative bitmap drawables for
different screen densities
• ldpi, mdpi, hdpi, xhdpi
http://sn.im/android-screens
Tuesday, August 20, 13

56. SCREEN SIZES & DENSITIES
Tuesday, August 20, 13

57. ACTION BAR
1. App Icon - optional “up” affordance
2. View control - Navigation
3. Dynamic number of “important” action buttons
4. Action overflow
http://sn.im/android-actionbar
http://actionbarsherlock.com/
Tuesday, August 20, 13

58. ASYNCTASK
private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
protected Long doInBackground(URL... urls) {
int count = urls.length;
long totalSize = 0;
for (int i = 0; i < count; i++) {
totalSize += Downloader.downloadFile(urls[i]);
publishProgress((int) ((i / (float) count) * 100));
// Escape early if cancel() is called
if (isCancelled()) break;
}
return totalSize;
}
protected void onProgressUpdate(Integer... progress) {
setProgressPercent(progress[0]);
}
protected void onPostExecute(Long result) {
showDialog("Downloaded " + result + " bytes");
}
}
http://sn.im/android-asynctask
Tuesday, August 20, 13

59. STRICT MODE
• Place a policy on a thread - provides feedback when blocked
public void onCreate() {
if (DEVELOPER_MODE) {
StrictMode.enableDefaults(); // Or configure
}
super.onCreate();
}
• http://sn.im/android-strictmode
• http://sn.im/android-strictmode-blog
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60. FIN.
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61. GOOD PLACESTO KNOW
• developer.android.com - Official developer site
• developers.google.com/android/ - Google on Android
• developers.google.com/events/io/ - Google I/O Replays
• stackoverflow.com - Great Q&A community
• android.stackexchange.com - End user Q&A
• vogella.com/android.html - Detailed tutorials
61
Tuesday, August 20, 13

62. ABOUT ME
• Live here in Boise - jim@mckeeth.org
• Lead Developer Evangelist for EmbarcaderoTechnologies
• www.embarcadero.com - Delphi for Android coming soon
• Google Developer Group - www.gdgb.org
• Boise Software Developers Group - www.bsdg.org
• Boise Code Camp - www.BoiseCodeCamp.com
Tuesday, August 20, 13