Transcript Android Application Development

Google Android
Introduction to Mobile Computing
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
Small, 1% of online
web requests
Bruce Scharlau, University of Aberdeen, 2009
Bigger, 10% of
online web requests
Android makes mobile Java easier
Well, sort of…
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);
}
}
Android applications are
compiled to Dalvik bytecode
Write app in Java
Compiled in Java
Transformed to Dalvik bytecode
Loaded into Dalvik VM
Linux OS
The Dalvik runtime is optimized
for mobile applications
Run multiple VMs efficiently
Each app has its own VM
Minimal memory footprint
Android has many components
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
common structure
Views such as
lists, grids, text
boxes, buttons,
and even an
embeddable web
browser
An Activity Manager that
manages the life cycle of
applications and provides
a common navigation
backstack
Content
Providers that
enable
applications to
access data from
other applications
(such as
Contacts), or to
share their own
data
A Notification Manager
that enables all apps to
display custom alerts in the
status bar
A Resource Manager,
providing access to noncode resources such as
localized strings,
graphics, and layout files
Android applications have
common structure
Broadcast
receivers can
trigger intents
that start an
application
Activity is the presentation
layer of your app: there will
be one per screen, and the
Views provide the UI to the
activity
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
Intents specify what
specific action should be
performed
Services run in the
background and have
no UI for the user –
they will update data,
and trigger events
There is a common file structure
for applications
code
files
images
Auto
generated
resource list
UI layouts
constants
Standard components form
building blocks for Android apps
Notifications
Has life-cycle
Activity
screen
Views
Intents
App to handle content
Service
Background app
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
Bruce Scharlau, University of Aberdeen, 2009
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"
package="com.google.android.app.myapp" >
<uses-permission id="android.permission.RECEIVE_SMS" />
</manifest>
There are lots of sources of
information
• The sdk comes with the API references,
sample applications and
docs/resources/bootcamp.pdf
• There are Google news groups
• There is http://www.anddev.org
• There is Google search
End of Overview
Next, start to build your first app!