Android is an open source operating system developed by the Open Handset Alliance for use in mobile devices. Applications are written in Java and use common Android components like activities, services, notifications and content providers. The AndroidManifest file defines application details and required permissions. Activities provide screens, intents allow communication between components, and services run in the background.

1. Google Android
Based on android-sdk_2.2
Mobile Computing
Bruce Scharlau, University of Aberdeen, 2010

2. Android is part of the ‘build a
better phone’ process
Open Handset Alliance produces
Android
Comprises handset manufacturers,
software firms, mobile operators, and
other manufactures and funding
companies
http://www.openhandsetalliance.com/
Bruce Scharlau, University of Aberdeen, 2010

3. Android is growing
Uneven distribution of OS by regions
Does not include iTouch or iPad, as not smartphones
http://metrics.admob.com/wp-content/uploads/2010/06/May-2010-AdMob-Mobile-Metrics-Highlights.pdf
Bruce Scharlau, University of Aberdeen, 2010

4. Android makes mobile Java easier
Well, sort of…
Bruce Scharlau, University of Aberdeen, 2010
http://code.google.com/android/goodies/index.html

5. Android applications are written
in Java
package com.google.android.helloactivity;
import android.app.Activity;
import android.os.Bundle;
public class HelloActivity extends Activity {
public HelloActivity() {
}
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.hello_activity);
}
Bruce Scharlau, University of Aberdeen, 2010
}

6. Android applications are
compiled to Dalvik bytecode
Write app in Java
Write app in Java
Compiled in Java
Compiled in Java
Transformed to Dalvik bytecode
Transformed to Dalvik bytecode
Loaded into Dalvik VM
Loaded into Dalvik VM
Linux OS
Bruce Scharlau, University of Aberdeen, 2010

7. The Dalvik runtime is optimised
for mobile applications
Run multiple VMs efficiently
Each app has its own VM
Minimal memory footprint
Bruce Scharlau, University of Aberdeen, 2010

8. Android has many components
Bruce Scharlau, University of Aberdeen, 2010

9. Can assume that most have
android 2.1 or 2.2
Bruce Scharlau, University of Aberdeen, 2010
http://developer.android.com/resources/dashboard/platform-versions.html

10. Android has a working emulator
Bruce Scharlau, University of Aberdeen, 2010

11. All applications are written in
Java and available to each other
Android designed to enable reuse of
components in other applications
Each application can publish its
capabilities which other apps can use
Bruce Scharlau, University of Aberdeen, 2010

12. Android applications have
common structure
Views such as
Views such as
lists, grids, text
lists, grids, text
boxes, buttons,
boxes, buttons,
and even an
and even an
embeddable web
embeddable web
browser
browser
An Activity Manager that
An Activity Manager that
manages the life cycle of
manages the life cycle of
applications and provides
applications and provides
a common navigation
a common navigation
backstack
backstack
Content
Content
Providers that
Providers that
enable
enable
applications to
applications to
access data from
access data from
other applications
other applications
(such as
(such as
Contacts), or to
Contacts), or to
share their own
share their own
data
data
A Notification Manager
A Notification Manager
that enables all apps to
that enables all apps to
display custom alerts in the
display custom alerts in the
status bar
status bar
A Resource Manager,
A Resource Manager,
providing access to nonproviding access to noncode resources such as
code resources such as
localized strings,
localized strings,
graphics, and layout files
graphics, and layout files
Bruce Scharlau, University of Aberdeen, 2010

13. Android applications have
common structure
Broadcast
Broadcast
receivers can
receivers can
trigger intents that
trigger intents that
start an application
start an application
Data storage
Data storage
provide data for
provide data for
your apps, and
your apps, and
can be shared
can be shared
between apps –
between apps –
database, file,
database, file,
and shared
and shared
preferences
preferences
(hash map) used
(hash map) used
by group of
by group of
applications
applications
Activity is the presentation
Activity is the presentation
layer of your app: there will
layer of your app: there will
be one per screen, and the
be one per screen, and the
Views provide the UI to the
Views provide the UI to the
activity
activity
Intents specify what
Intents specify what
specific action should be
specific action should be
performed
performed
Services run in the
Services run in the
background and have
background and have
no UI for the user –
no UI for the user –
they will update data,
they will update data,
and trigger events
and trigger events
Bruce Scharlau, University of Aberdeen, 2010

14. There is a common file structure
for applications
code
Autogenerated
resource list
files
images
UI layouts
constants
Bruce Scharlau, University of Aberdeen, 2010

15. Standard components form
building blocks for Android apps
Notifications
Activity
screen
Views
Intents
Has life-cycle
App to handle content
Service
Background app
Like music player
manifest
ContentProviders
Bruce Scharlau, University of Aberdeen, 2010
Other applications

16. The AndroidManifest lists
application details
<?xml version="1.0" encoding="utf-8"?>
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
package="com.my_domain.app.helloactivity">
<application android:label="@string/app_name">
<activity android:name=".HelloActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category
android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
Bruce Scharlau, University of Aberdeen, 2010

17. Activity is one thing you can do
Bruce Scharlau, University of Aberdeen, 2010
From fundamentals page in sdk

18. Intent provides late running
binding to other apps
It can be thought of as the glue between
activities. It is basically a passive data
structure holding an abstract description of
an action to be performed.
Written as action/data pairs such as:
VIEW_ACTION/ACTION content://contacts/1
Bruce Scharlau, University of Aberdeen, 2010

19. Services declared in the manifest
and provide support
Services run in the background:
Music player providing the music playing in
an audio application
Intensive background apps, might need to
spawn their own thread so as to not block
the application
Bruce Scharlau, University of Aberdeen, 2010

20. Notifications let you know of
background events
This way you know that an SMS arrived,
or that your phone is ringing, and the
MP3 player should pause
Bruce Scharlau, University of Aberdeen, 2010

21. ContentProviders share data
You need one if your application shares data
with other applications
This way you can share the contact list with the
IM application
If you don’t need to share data, then you can
use SQLlite database
Bruce Scharlau, University of Aberdeen, 2010

22. UI layouts are in Java and XML
setContentView(R.layout.hello_activity); //will load the XML UI file
Bruce Scharlau, University of Aberdeen, 2010

23. Security in Android follows
standard Linux guidelines
Each application runs in its own process
Process permissions are enforced at user
and group IDs assigned to processes
Finer grained permissions are then
granted (revoked) per operations
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.google.android.app.myapp" >
package="com.google.android.app.myapp" >
<uses-permission id="android.permission.RECEIVE_SMS" />
<uses-permission id="android.permission.RECEIVE_SMS" />
</manifest>
</manifest>
Bruce Scharlau, University of Aberdeen, 2010