The document discusses key aspects of the Android mobile platform. It notes that Android applications are written in Java and compiled to Dalvik bytecode, and that the Dalvik runtime is optimized for mobile applications. It also describes several important Android components like Activities, Services, Intents, and ContentProviders that applications use to perform tasks and share data.

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

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

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

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

5. Bruce Scharlau, University of Aberdeen, 2010
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);
}
}

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

7. Code for intent passing
messages
Bruce Scharlau, University of Aberdeen, 2010

8. First activity
• Button search = (Button) findViewById(R.id.btnSearch);
search.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent intent = new Intent(Search.this, SearchResults.class);
Bundle b = new Bundle();
EditText txt1 = (EditText) findViewById(R.id.edittext);
EditText txt2 = (EditText) findViewById(R.id.edittext2);
b.putString("name", txt1.getText().toString());
b.putInt("state", Integer.parseInt(txt2.getText().toString()));
//Add the set of extended data to the intent and start it
intent.putExtras(b);
startActivity(intent);
}
});
Bruce Scharlau, University of Aberdeen, 2010

9. Second activity
• @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.search_results);
• Bundle b = getIntent().getExtras();
int value = b.getInt("state", 0);
String name = b.getString("name");
TextView vw1 = (TextView) findViewById(R.id.txtName);
TextView vw2 = (TextView) findViewById(R.id.txtState);
vw1.setText("Name: " + name);
vw2.setText("State: " + String.valueOf(value));
}
Bruce Scharlau, University of Aberdeen, 2010

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

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

12. 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

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

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

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

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

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

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

19. Bruce Scharlau, University of Aberdeen, 2010
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>

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

21. Bruce Scharlau, University of Aberdeen, 2010
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
Written as action/data pairs such as:
VIEW_ACTION/ACTION content://contacts/1

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

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

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

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

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