1. App Development for Android
Prabhaker Mateti

2. CEG 436 Specifics
Because CEG 436 is a 10-week term course skipped for now refreshers on
Operating Systems
TCP/IP Networking
Cellular Telephony
“Definitions”
Mobile Devices/Smart Phone
What is Android?
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3. Development Tools (Android) Java Eclipse ADT Plugin for Eclipse
Java syntax is the same. But, not all libs are included.
Unused: Swing, AWT, SWT, lcdui
Eclipse
ADT Plugin for Eclipse
developer.android.com/sdk/eclipse-adt.html
Android SDK
developer.android.com/sdk/tools-notes.html
Android Device Emulator
Development Platforms: Linux, Mac OSX, or Windows
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4. The Emulator QEMU-based ARM emulator
Displays the same image as the device
Limitations:
No Camera support
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5. Debugging
adb acts as a middleman between a device and your development system. It provides various device management capabilities, including moving and syncing files to the emulator, running a UNIX shell on the device or emulator, and providing a general means to communicate with connected emulators and devices.
Dalvik Debug Monitor Server DDMS is a graphical program that communicates with your devices through adb. DDMS can capture screenshots, gather thread and stack information, spoof incoming calls and SMS messages, and has many other features.
Device or Android Virtual Device An adb device daemon runs on the device or emulator and provides a means for the adb host daemon to communicate with the device or emulator.
JDWP debugger The Dalvik VM supports the JDWP protocol to allow debuggers to attach to a VM. Java IDEs include a JDWP debugger, or you can use a command line debugger such as jdb.
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6. Android Application Package
res/layout: declaration layout files
res/drawable: intended for drawing
res/anim: bitmaps, animations for transitions
res/values: externalized values
strings, colors, styles, etc
res/xml: general XML files used at runtime
res/raw: binary files (e.g., sound)
An application consists of:
Java Code
Data Files
Resources
Files
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7. Android Application Package
Using Java/Eclipse/ADT develop several source code files.
An Android application is bundled by the “aapt” tool into an Android package (.apk)
An .apk file is a zip file. Invoke unzip if you wish.
“Installing” an Application is a built-in op of Android OS.
May need to enable the trustworthiness of developer
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8. A Launcher: zeam-2.9.0.apk ( … a highly incomplete list … )
res/anim/apps_fade_in.xml
res/color/bright_text_dark_focused.xml
res/drawable/box_launcher_top.xml
res/drawable/timepicker_up_selected.9.png
res/layout/application_list.xml
res/xml/preferences.xml
AndroidManifest.xml
resources.arsc
res/drawable-hdpi/action_notifications.png
res/layout-land/application.xml
classes.dex
META-INF/MANIFEST.MF
META-INF/CERT.SF
META-INF/CERT.RSA
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9. Android Architecture

10. Android Architecture
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11. Linux Kernel Works as a Hardware Abstraction Layer (HAL)
Device drivers
Keypad, Display, Power Mgmt, FlashMem, Binder, WiFi, Audio, Camera
Memory management
Process management
Networking
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12. Linux Kernel Enhancements
Alarm
Ashmem (Anonymous SHared MEMory)
ashmem uses virtual memory, whereas pmem (process memory allocator) uses physically contiguous memory
Binder
an Android-specific inter-process communication mechanism, and remote method invocation system.
Power Management
Low Memory Killer
echo "1536,2048,4096,15120,15360,23040" > /sys/module/lowmemorykiller/parameters/minfree
Kernel Debugger
Logger (system logging facility)
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13. Android Runtime Dalvik VM Core Libraries
a newly developed Java Virtual Machine
dx tool translates .class files to .dex files
Compact compared to .class files
Optimized for memory and battery power
Core Libraries
Java Std Edition
Collections, I/O etc…
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14. Libraries
Surface Manager: A compositing window manager similar to Compiz. Instead of drawing directly to the screen buffer, drawing commands go into off-screen bitmaps that are then combined with other bitmaps to form the display the user sees. Can create see-through windows, fancy transitions, …
2D and 3D graphics: Use 3D hardware or a software renderer. OpenGL.
Media codecs: AAC, AVC (H.264), H.263, MP3, MPEG-4, …
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15. Libraries SQLite database engine Browser engine:
Provides persistent storage.
Also used in Firefox and the iPhone.
Browser engine:
WebKit library for rendering web pages
the same engine is used in KDE, the Google Chrome browser, Apple’s Safari browser, the iPhone, and Symbian 60.
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16. Android NDK: Native C/C++ libraries
not the full glibc as in Linux distros
Supported CPUs: ARM, x86
libc (C library) headers
libm (math library) headers
JNI interface headers
libz (Zlib compression) headers
liblog (Android logging) header
OpenGL ES headers
libjnigraphics (Pixel buffer access) header
A Minimal set of headers for C++ support
OpenSL ES native audio libraries
Android native application APIS
Cross-toolchains (compilers, linkers, ...)
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17. OpenGL ES OpenGL ES is a subset of OpenGL graphics standard.
low-level interface for graphics acceleration.
floating-point and fixed-point systems.
OpenGL ES 1.X is for fixed function hardware and offers acceleration, image quality and performance.
OpenGL ES 2.X enables full programmable 3D graphics.
OpenGL SC is tuned for the safety critical market.
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18. Application Framework
Views  lists, grids, text boxes, buttons, and even an embeddable web browser
Content Providers to access data from other applications (such as Contacts), or to share their own data
A Resource Manager, providing access to non-code resources such as localized strings, graphics, and layout files
A Notification Manager that enables all applications to display custom alerts in the status bar
An Activity Manager that manages the lifecycle of applications and provides a common navigation backstack [sic]
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19. Standard Applications
Android provides a set of core applications:
Client
SMS Program
Calendar
Maps
Browser
Contacts
Etc
All applications are written using the Java language.
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20. Android Application Internals

21. Application Fundamentals
Each application is a different “user”.
Each application gets a unique Linux user ID. The system sets permissions for all the files in an application so that only the user ID assigned to that application can access them.
Each process has its own Dalvik VM.
Every application runs in its own Linux process. A process can have multiple threads.
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22. Application Components
Activity 
represents a single screen with a user interface.
Service 
runs in the background; Long-running; for remote processes
no user interface.
Content provider 
manages a shared set of application data.
Broadcast receiver 
responds to broadcast announcements.
An application can have multiple instances of the above four types.
Each component is a different point through which the system can enter an application.
Every component has a managed lifecycle.
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23. .apk Internals
AndroidManifest.xml — deployment descriptor for applications.
IntentReceiver as advertised by the IntentFilter tag.
*.java files implement Android activity
Main.xml — visual elements, or resources, for use by activities.
R.java —automatically generated by Android Developer Tools and "connects" the visual resources to the Java source code.
Components share a Linux process: by default, one process per .apk file.
.apk files are isolated and communicate with each other via Intents or AIDL.
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24. Application Resources
anything relating to the visual presentation of the application
images, animations, menus, styles, colors, audio files, …
resource ID
alternate resources for different device configurations
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25. AndroidManifest.xml Declares all application components:
<activity>
<service>
<provider> for content providers
<receiver> for broadcast receivers
The manifest can also:
Identify any user permissions the application requires, such as Internet access or read-access to the user's contacts.
Declare hardware and software features used or required by the application
API libraries the application needs
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26. Life cycle of an Android activity
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27. Activity
Typically, one of the activities is marked as the first one that should be presented to the user when the application is launched.
Created “Activity” must be defined into the application’s manifest.
An activity is usually a single screen:
Implemented as a single class extending Activity.
Displays user interface controls (views).
Reacts on user input/events.
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28. Activity An application typically consists of several screens:
Each screen is implemented by one activity.
Moving to the next screen means starting a new activity.
An activity may return a result to the previous activity.
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29. Service
A service does not have a visual user interface, but rather runs in the background for an indefinite period time.
Examples: music player, network download, etc
Each service extends the Service base class.
It is possible to bind to a running service and start the service if it's not already running.
While connected, it is possible communicate with the service through an interface defined in AIDL (Android Interface Definition Language).
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30. Services Similar to daemons in Linux/Unix or Windows services.
Interprocess communication (IPC).
A service is "started" when a component does a startService(). Stops with  stopSelf() or stopService()
A service is "bound" when a component does a  bindService(). Multiple components can bind to the service at once. When all of them unbind, the service is destroyed.
Can work both ways. (i) onStartCommand() allows components to start it and (ii) onBind() allows binding.
(iii) onCreate() (iv) onDestroy()
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31. Broadcast Receivers
A broadcast receiver is a component that receives and reacts to broadcast announcements (Intents).
All receivers extend the BroadcastReceiver base class.
Many broadcasts originate in system code.
the time zone has changed
the battery is low
Applications can also initiate broadcasts.
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32. Content Providers Enables sharing of data across applications
E.g. address book, photo gallery
the only way to share data between applications.
Provides uniform APIs for query, delete, update and insert.
Applications do not call these methods directly.
They use a ContentResolver object and call its methods instead.
A ContentResolver can talk to any content provider.
Content is represented by URI and MIME type.
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33. Content Providers Activity Application Content Provider Service Data
SQLite
XML
Remote
Store
Content Resolver
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34. Intent
Intents are system messages that notify applications of various events:
Activity events ( launch app, press button)
Hardware state changes (acceleration change, screen off, etc)
Incoming data (Receiving call, SMS arrived)
An intent object is an action to be performed on some data Uri. It provides runtime binding between the code in different applications.
Examples:
ACTION_DIAL content://contacts/people/13
Display the phone dialer with the person #13 filled in.
ACTION_VIEW content://contacts/people/
Display a list of people, which the user can browse through.
startActivity(new Intent(Intent.VIEW_ACTION, Uri.parse( "
startActivity(new Intent(Intent.VIEW_ACTION, Uri.parse("geo: , "));
startActivity(new Intent(Intent.EDIT_ACTION, Uri.parse("content://contacts/people/1"));
secondary attributes: category, type, component, extras 
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35. public class Intent startActivity to launch an activity.
broadcastIntent to send it to a BroadcastReceiver
Communicate with a Service
startService(Intent) or 
bindService(Intent, ServiceConnection, int)
Explicit Intents specify a component to be run.
setComponent(ComponentName) or
setClass(Context, Class))
Implicit Intents match an intent against all of the <intent-filter>s in the installed applications.
Will return to this topic later.
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36. Intent Filters
A component can have any number of intent filters, each one declaring a different set of capabilities.
The first filter in the example indicates that the activity is the entry point for the application.
The second filter declares an action that the activity can perform on a particular type of data.
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37. IntentReceivers Components that respond to broadcast ‘Intents’
Way to respond to external notification or alarms
Apps can invent and broadcast their own Intent
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38. Example App: Hello World!
developer.android.com/resources/tutorials/hello-world.html

39. Goal Create a very simple application Run it on the emulator
Examine its structure
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40. Package Content All source code here Java code for our activity
Generated Java code
Helps link resources to
Java code
All non-code
resources
Layout of the activity
Images
Strings used in the
program
Android Manifest
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41. Android Manifest <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="
package="com.example.helloandroid"
android:versionCode="1"
android:versionName="1.0">
<application
<activity android:name=".HelloAndroid"
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
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42. HelloAndroid.java Inherit from the Activity Class
package com.example.helloandroid; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class HelloAndroid extends Activity {    /** Called when the activity is first created. */      public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        TextView tv = new TextView(this);        tv.setText("Hello, Android – by hand");        setContentView(tv);    } }
Set the view “by hand” – from the program
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43. Run it!
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44. HelloAndroid.java
package com.example.helloandroid; import android.app.Activity; import android.os.Bundle; public class HelloAndroid extends Activity { /** Called when the activity is first created. public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); }
Set the layout of the view as described in the main.xml layout
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45. /res/layout/main.xml Further redirection to /res/values/strings.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_height="wrap_content"
/>
</LinearLayout>
Further redirection to /res/values/strings.xml
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46. /res/values/strings.xml <?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="hello">Hello World, HelloAndroid – by resources!</string>
<string name="app_name">Hello, Android</string>
</resources>
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47. /gen/R.java
package com.example.helloandroid; public final class R {     public static final class attr {     }     public static final class drawable {         public static final int icon=0x7f020000;     }     public static final class id {         public static final int textview=0x7f050000;     }     public static final class layout {         public static final int main=0x7f030000;     }     public static final class string {         public static final int app_name=0x7f040001;         public static final int hello=0x7f040000;     } }
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48. Run it!
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49. Introduce A Bug
package com.example.helloandroid; import android.app.Activity; import android.os.Bundle; public class HelloAndroid extends Activity {     /** Called when the activity is first created. */       public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         Object o = null;         o.toString();         setContentView(R.layout.main);     } }
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50. Run it!
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51. Case Studies of Applications

52. ADW.Launcher
ADW.Launcher is an open source Home Replacement app. it is included as the main Launcher in Cyanogen's custom ROMs.
I will be (??) using the source code of this app as a running example.
Download the source from
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53. Project Suggestions Augmented Campus Reality Games
camera + maps + compass = heads up info
Games
multi-player (bluetooth, wifi, cell)
location-based (scavenger hunt)
Custom overlays for maps
weather, traffic, friends
Web scraping
news filters
sport scores
dook news eliminators
more on next slide …
Distributed computing?
10,000 phones all donating their idle time
tiny terminal (phone) + fast cpu/network (server)
Shared whiteboard
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54. Project Suggestions
Web Scrapers [movies, weather, sports, <topic> news]
Find multiple web sources
Scrape them for the relevant information
Present in a custom UI on the phone
Asynchronous games [chess, poker, risk]
Develop an API for all games to communicate through
Establish connections by phone number
Send and receive game data
Ability to reopen connections 
Planner/To-do list with location data
Decide route to next class, meeting, etc
Find a order/route for non time-critical tasks
Connect to campus directory to find teachers/classmates
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55. Source Code for Android Examples
Sources for many Android applications that can be enhanced:
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