Mc android

Google Android
Based on android-sdk_2.2

Mobile Computing

Bruce Scharlau, University of Aberdeen, 2010

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/


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

Android makes mobile Java easier

Well, sort of…

http://code.google.com/android/goodies/index.html

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

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


The Dalvik runtime is optimised
for mobile applications

Run multiple VMs efficiently

Each app has its own VM

Minimal memory footprint

Android has many components


Can assume that most have
android 2.1 or 2.2

http://developer.android.com/resources/dashboard/platform-versions.html

Android has a working emulator


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


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

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


There is a common file structure
for applications
code
Autogenerated
files resource list
images

UI layouts

constants


Standard components form
building blocks for Android apps
Notifications
Has life-cycle
Activity
screen
Views
App to handle content
Intents
Background app
Service Like music player

manifest

ContentProviders Other applications

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>

Activity is one thing you can do

From fundamentals page in sdk

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


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

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


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


UI layouts are in Java and XML

setContentView(R.layout.hello_activity); //will load the XML UI file

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>

There are lots of sources of
information
• The sdk comes with the API references,
sample applications and lots of docs
• Blog http://android-developers.blogspot.com/
which has lots of useful examples, details
• There is http://www.anddev.org


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