Demian Neidetcher's presentation to the Denver Open Source Users Group on the Android mobile phone platform. Full details and source code available at http://neidetcher.com/android.html

1. Android Mobile Phone Development
Context
Android
Dalvik
Development

2. Me First
http://stuff
Computer
Stuff data
Stuff
x 10
neidetcher.com/android.html

3. Context | Timeline
● 2001: Google starts filing mobile patents
● 2005 July: Google Acquires Android Inc
● 2005 Oct: Dan Bornstein joins Google to work on Dalvik
● 2007 Nov: Open Handset Alliance is formed and
Android SDK is released
● 2008 Oct: T-Mobile G1 is released
● 2009 Jan: Palm Pre announced
● 2009 Feb: Pay apps available on market
● 2009 Jun: Samsung Android phones in EU
● 2009 Nov: Motorola releasing Android phone
● 2009: Possible Acer, Dell and HP net-books
http://www.flickr.com/photos/ram_/1637873367/sizes/l/

4. Context | Open Handset Alliance
47 Companies
Sprint, T-Mobile,
Telecom Italia,
Vodafone, Intel, Texas
Instruments, NVIDIA,
Asus, Garmin, HTC,
LG, Motorola,
Samsung, Sony,
Toshiba...

5. Context | Market
T-Mobile recently shared some statistics from the Android
Market. Right now, there are about 2,300 applications
available, which is under one-tenth the size of the iPhone
Apps Store's whopping 25,000+.
--InformationWeek March 25, 2009
Job Listing Comparison
May 9, 2009
how does
Android’s growth simplyhired.com
compare to
iPhone’s growth dice.com
at launch? Our android java
best answer: both iPhone
indeed.com
grew more quickly j2me
than the market,
but iPhone growth monster.com
was much faster
than Android. careerbuilder.com
--admob.com
0 200 400 600 800 1000 1200 1400 1600

6. Context | Criticism
● Google helps T-Mobile block tethering
● Not standard C library (Bionic)
● Portions of SDK not open (yet)
● Too many free apps
● Android is Not POSIX
● Dalvik is Not Java
http://www.flickr.com/photos/scjohnson/3475073977/

7. Android | Open Source
Runtime Stack Development Stack
Apache Harmony: Apache2 QEMU: LGPL
JFree Chart: LGPL
SQLite: Public Domain WebKit: LGPLv2
JCommon: BSD
Android: Apache2 Bionic: BSD
Eclipse: EPL
Linux: GPLv2

8. Android | Market

9. Android | Architecture
Home Contacts
Map Phone Browser Email
Telephony Activity Location Notification Package
Core Libraries
SQLite WebKit OpenGL bionic
Dalvik VM
WiFi Driver
WiFi Camera Power Display Keypad

10. Dalvik | Background
● Dan Bornstein
● Made for low end machines
● low ram (no disk swap space)
● battery
● Register based (not stack based)
● Not a JVM
● No JIT (it's on the road map)
● most heavy lifting is in native code
● Does no memory management or threading
http://www.flickr.com/photos/fremat/447395038/sizes/l/

11. Dalvik | Pro/ Con of Approach
● All those Java coders ● James Gosling
● All that tooling hates you
● Don't have to deal ● Sun hates you
with Sun and JCP ● Java fragmentation
● Optimize byte-code
● No more write
for hardware
once run
everywhere
http://www.flickr.com/photos/catwommn/3374184512/

12. Dalvik | .dex vs .class
● Single constant pool
for all classes 120
Compression
100
● Uncompressed
libs
browser app
alarm app
80
● More pointing 60
40
● More sharing
20
0
uncompressed jar compressed jar uncompressed dex
http://retrodev.com/android/dexformat.html
http://sites.google.com/site/io/dalvik-vm-internals (handouts)

13. Dalvik | Other Languages?
anything that dynamically
reads .class files or
dynamically manipulates Java
binaries won't work without
Android specific tweaks
scala works :)
http://chneukirchen.org/blog/archive/2009/04/programming-for-android-with-scala.html

14. Dalvik | Zygote
Home
Every new app isn't a VM cold start
Minimize memory requirements by
Application
Code
sharing what we can
Map
Zygote
Application
System Code
System
Libraries Browser
Libraries
Application
Code
Email ●Android creates Zygote at startup
●Zygote loads up system libraries
Application
Code ●Zygote finds out new app is starting
●Zygote forks process, giving all Dalvik VMs
(and apps) access to system libraries

15. Dalvik | Sandbox
● Every app is a process
● process gets its own
user id
● files is sandboxed
● SQLite DB is
sandboxed
http://www.flickr.com/photos/bauchidgw/2820627227/

16. Dalvik | Application Stack
Activity
Back button
Manager does a pop
on the stack
Map
Browser
Email
Low memory killer
Home will look at LRU apps
to destroy

17. Dev | Get Started
● Android SDK
● http://developer.android.com/sdk
● local documentation
● tools
● Eclipse plugin
● http://dl-ssl.google.com/android/eclipse/

18. android.*
Dev | APIs dalvik.* junit.framework
junit.runner
org.apache.http
org.json
org.w3c.dom
java.awt.font java.util.logging
java.beans java.util.prefs
org.xml.sax
java.io java.util.regex org.xmlpull.v1
java.lang java.util.zip org.xmlpull.v1.sax2
java.lang.annotation javax.crypto
java.lang.ref javax.microedition.khronos.egl
java.lang.reflect javax.microedition.khronos.opengles
java.math javax.net
java.net javax.security.auth
java.nio javax.security.auth.callback
java.security javax.security.auth.login
java.sql javax.security.auth.x500
java.text javax.security.cert
java.util javax.sql
java.util.concurrent javax.xml
java.util.jar
http://developer.android.com/reference/packages.html

19. Dev | Manifest.xml
manifest
application
activity
intent-filter
<action android:name=quot;android.intent.action.MAINquot; />
<category android:name=quot;android.intent.category.LAUNCHERquot; />
activity

20. Dev | Eclipse Plugin

21. Log.d(TAG, quot;position : quot; + position);
Log.d(TAG, quot;selection: quot; + POINTS[position]);
Dev | Logging

22. Dev | Emulator
●Select AVD to run
●Set up virtual SD card
●Simulate network and
CPU conditions
./emulator -skin QVGA-L

23. Dev | adb
shiv:~/opt/android-sdk-linux_x86-1.0_r2/tools>./adb devices
List of devices attached
emulator-5554 device
shiv:~/opt/android-sdk-linux_x86-1.0_r2/tools>./adb shell
# ls
sqlite_stmt_journals # cat /proc/cpuinfo
cache Processor : ARM926EJ-S rev 5 (v5l)
sdcard
etc BogoMIPS : 348.16
init Features : swp half thumb fastmult vfp edsp java
init.goldfish.rc CPU implementer : 0x41
init.rc CPU architecture: 5TEJ
data
system
CPU variant : 0x0
proc CPU part : 0x926
sys CPU revision : 5
sbin Cache type : write-through
default.prop Cache clean : not required
root
dev Cache lockdown : not supported
Cache format : Harvard

24. Dev | Hierarchy Viewer
shiv:~/opt/android-sdk-linux_x86-1.0_r2/tools>./hierarchyviewer
Click on device > Load View Hierarchy

25. Dev | Activity Life Cycle
starting
running
stopped paused
destroyed

26. <?xml version=quot;1.0quot; encoding=quot;utf-8quot;?>
<LinearLayout
xmlns:android=quot;http://schemas.android.com/apk/res/androidquot;
Dev | View android:orientation=quot;verticalquot;
android:layout_width=quot;fill_parentquot;
android:layout_height=quot;fill_parentquot;
>
<TextView
android:id=quot;@+id/displayPointsTextViewquot;
android:layout_width=quot;fill_parentquot;
android:layout_height=quot;wrap_contentquot;
android:height=quot;400spquot;
android:width=quot;300spquot;
android:textColor=quot;#FFFquot;
android:gravity=quot;center_horizontal|center_verticalquot;
android:textSize=quot;210spquot;
/>
</LinearLayout>
public class DisplayActivity extends Activity
{
TextView myTextView = null;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.display);
// set value for the text
myTextView = (TextView) findViewById(
R.id.displayPointsTextView);
String points = getIntent().getExtras().getString(
ScrumPokerActivity.SELECTED_POINTS);
if (points.equals(quot;100quot;))
{
myTextView.setTextSize(180);
}
myTextView.setText(points);
}
}

27. Dev | Intents
Activity1 Intent Activity2
create(Activity2)
putExtra(key, value)
startActivity(intent)
onCreate
getIntent()
getExtras.get(key):value

28. Dev | Intents & Mashability
InterTubes
wheels down in PST
YourApp
K, thx, bai
classes.dex
NarcissisticProxy
TzChangeReceiverActivity
Location
AndroidManifext.xml
Manager
receiver
intent:ACTION_TIMEZONE_CHANGED

29. Dev | Packaging
.java .class
.java javac .class dx
.java .class
.xml
aapt classes
.xml
.dex
.png
.xml classes
.xml .dex
.png
.apk

30. Dev | apk
shiv:~/play>jar -xvf quot;Scrum Poker.apkquot;
shiv:~/play>tree
.
|-- AndroidManifest.xml
|-- Scrum Poker.apk
|-- classes.dex
|-- res
| |-- drawable
| | `-- refresh.png
| `-- layout
| |-- display.xml
| `-- main.xml
`-- resources.arsc
3 directories, 7 files

31. /** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
Dev | dexdump
setContentView(R.layout.main);
displayPointsListView = (ListView) findViewById(R.id.pointsListView);
int layoutId = android.R.layout.simple_list_item_1;
// populate the list view with an array
ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this,
layoutId, POINTS);
displayPointsListView.setAdapter(arrayAdapter);
displayPointsListView.setOnItemClickListener(mMessageClickedHandler);
Virtual methods - }
#0 : (in Lcom/neidetcher/scrumpoker/ScrumPoker;)
name : 'onCreate'
type : '(Landroid/os/Bundle;)V'
access : 0x0001 (PUBLIC)
code -
shiv:~/play>~/opt/android-sdk-linux_x86-1.0_r2/tools/dexdump -d classes.dex
registers : 5
ins : 2
outs : 4
insns size : 47 16-bit code units
000ad8: |[000ad8] com.neidetcher.scrumpoker.ScrumPoker.onCreate:(Landroid/os/Bundle;)V
000ae8: 6f20 0100 4300 |0000: invoke-super {v3, v4}, Landroid/app/Activity;.onCreate:(Landroid/os/Bundle;)V // method@00
000aee: 1401 0100 037f |0003: const v1, #float 174128887730233583002069148843976425472.000000 // #7f030001
000af4: 6e20 1e00 1300 |0006: invoke-virtual {v3, v1}, Lcom/neidetcher/scrumpoker/ScrumPoker;.setContentView:(I)V // met
000afa: 1401 0100 057f |0009: const v1, #float 176787343721803414747876762964537114624.000000 // #7f050001
000b00: 6e20 1c00 1300 |000c: invoke-virtual {v3, v1}, Lcom/neidetcher/scrumpoker/ScrumPoker;.findViewById:(I)Landroid/v
000b06: 0c01 |000f: move-result-object v1
000b08: 1f01 0d00 |0010: check-cast v1, Landroid/widget/ListView; // class@000d
000b0c: 5b31 0d00 |0012: iput-object v1, v3, Lcom/neidetcher/scrumpoker/ScrumPoker;.myListView:Landroid/widget/List
000b10: 1400 0300 0901 |0014: const v0, #float 0.000000 // #01090003
000b16: 2201 0b00 |0017: new-instance v1, Landroid/widget/ArrayAdapter; // class@000b
000b1a: 5432 0800 |0019: iget-object v2, v3, Lcom/neidetcher/scrumpoker/ScrumPoker;.POINTS:[Ljava/lang/String; // f
000b1e: 7040 0700 3120 |001b: invoke-direct {v1, v3, v0, v2}, Landroid/widget/ArrayAdapter;.<init>:(Landroid/content/Con
000b24: 5b31 0c00 |001e: iput-object v1, v3, Lcom/neidetcher/scrumpoker/ScrumPoker;.myArrayAdapter:Landroid/widget/
000b28: 5431 0d00 |0020: iget-object v1, v3, Lcom/neidetcher/scrumpoker/ScrumPoker;.myListView:Landroid/widget/List
000b2c: 5432 0c00 |0022: iget-object v2, v3, Lcom/neidetcher/scrumpoker/ScrumPoker;.myArrayAdapter:Landroid/widget/
000b30: 6e20 0800 2100 |0024: invoke-virtual {v1, v2}, Landroid/widget/ListView;.setAdapter:(Landroid/widget/ListAdapter
000b36: 5431 0d00 |0027: iget-object v1, v3, Lcom/neidetcher/scrumpoker/ScrumPoker;.myListView:Landroid/widget/List
000b3a: 5432 0b00 |0029: iget-object v2, v3, Lcom/neidetcher/scrumpoker/ScrumPoker;.mMessageClickedHandler:Landroid
field@000b
000b3e: 6e20 0900 2100 |002b: invoke-virtual {v1, v2}, Landroid/widget/ListView;.setOnItemClickListener:(Landroid/widget
000b44: 0e00 |002e: return-void
catches : (none)
positions :

32. Dev | Install Time
● What happens when you install the
.dex software...
● there is no JIT
● security
● verification of dex files
dexopt
● Optimization
● specific to hardware
● inlining
● pruning
.odex ● static linking
http://www.netmite.com/android/mydroid/dalvik/docs/dexopt.html

33. Dev | Good Android Code
● sleep, react quickly, sleep
● avoid allocation
Address[] addressArray = mgr.findAddresses()
for(int ii = 0; ii < addressArray.length; ii++)
Address[] addressArray = mgr.findAddresses()
for(Address currAddress : addressArray)
List<Address> addresses = mgr.findAddresses();
for(Address currAddress : addresses)
http://kohlerm.blogspot.com/2009/04/analyzing-memory-usage-off-your-android.html

34. Dev | Gotchas
● I accidentally imported the quot;super Rquot; instead of
my locally generated R. (2 hours)
● View layouts can't be camel cased. (30 minutes)
● The tools directory in the Android SDK needs be
set to executable to run and for the Eclipse plug-
in to work. (10 minutes)
● If your install didn't work on the phone you see a
deceptive green check-mark. (10 minutes)
● Don't put heavy object graphs in putExtra()
● Development upgrade to Cupcake was kludgy for me

35. Dev | Other Cool Stuff
● SQLite
● LocationManager
● Sensors
● Accelerometer
● Compass
● Telephony
● Blue Tooth
● OpenGL
● Camera
● Media

36. Wrap Up | Google IO
● 3 types of agreements
● 3 Ways to code
● 20 handsets in 2009
● Oprah moment
● Donut
● Universal search where universe is phone
● Text to speech
● Gestures/ handwriting recognition
http://www.flickr.com/photos/francois/3959737/

37. Wrap Up | Future ● The user experience
will be inconsistent
● Desktop phones ● Hardware might be
● Net-books flaky and clunky
● Televisions? ● IBM PC clone of the
● GPS? mobile market
Good for 1 well* drink if
Android does not have
greater than 50% of the
iPhone
mobile phone OS Android
market by June 1, 2014 All
Others
~Demian Neidetcher
*where well is water

38. Wrap Up | Questions?
http://neidetcher.com/android.html