Android App

DevelopmentAhmad Tayeb

Ahmad Tayeb

Lecturer @ Department of Information Technology, Faculty of Computing and

Information Technology, KAU

Master degree from Information Sciences and Technologies , B. Thomas

Golisano College of Computing and Information Sciences, Rochester Institute

of Technology , Rochester, NY, USA

http://ahmadt.com

Twitter: @ahmad_tayeb

Android

Android is a software package and Linux based operating system for mobile

devices such as tablet computers and smartphones.

It is developed by Google and later the OHA (Open Handset Alliance). Java

language is mainly used to write the android code even though other

languages can be used.

What is Open Handset Alliance (OHA) ?

It's a consortium of 84 companies such as google, samsung, AKM, synaptics,

KDDI, Garmin, Teleca, Ebay, Intel etc.

Features of Android

It is open-source.

Anyone can customize the

Android Platform.

There are a lot of mobile

applications that can be chosen

by the consumer.

Android Architecture

Linux kernel

Native libraries (middleware)

Android Runtime

Application Framework

Applications

Android Architecture

1) Linux kernel

It is the heart of android architecture that exists at the root of android

architecture.

Linux kernel is responsible for device drivers, power management, memory

management, device management and resource access.

Android Architecture

2) Native Libraries

On the top of Linux kernel, their are Native libraries such as WebKit, OpenGL,

FreeType, SQLite, Media, C runtime library (libc) etc.

The WebKit library is responsible for browser support, SQLite is for database,

FreeType for font support, Media for playing and recording audio and video

formats.

Android Architecture

3) Android Runtime

In android runtime, there are core libraries and DVM (Dalvik Virtual Machine)

which is responsible to run android application.

DVM is like JVM but it is optimized for mobile devices. It consumes less

memory and provides fast performance.

Android Architecture

4) Android Framework

On the top of Native libraries and android runtime, there is android

framework.

Android framework includes Android API's such as UI (User Interface),

telephony, resources, locations, Content Providers (data) and package

managers.

It provides a lot of classes and interfaces for android application

development.

Android Architecture

5) Applications

On the top of android framework, there are applications.

All applications such as home, contact, settings, games, browsers are using

android framework that uses android runtime and libraries.

Android runtime and native libraries are using Linux kernel.

Android Core Building Blocks

An android component is simply a piece of code that has a well defined life

cycle e.g. Activity, Receiver, Service etc.

The core building blocks or fundamental components of android are activities,

views, intents, services, content providers, fragments and

AndroidManifest.xml.

Android Core Building Blocks

Activity

An activity is a class that represents a single screen. It is like a Frame in AWT.

Android Core Building Blocks

View

A view is the UI element such as button, label, text field etc. Anything that

you see is a view.

Android Core Building Blocks

Intent

Intent is used to invoke components. It is mainly used to:

Start the service

Launch an activity

Display a web page

Display a list of contacts

Broadcast a message

Dial a phone call etc.

Android Core Building Blocks

Service

Service is a background process that can

run for a long time.

There are two types of services local and

remote.

Local service is accessed from within the

application whereas remote service is

accessed remotely from other

applications running on the same device.

Android Core Building Blocks

Broadcast Receiver

Broadcast Receiver handles communication

between Android OS and applications.

Broadcast Receivers simply respond to

broadcast messages from other applications

or from the system.

For example, applications can also initiate

broadcasts to let other applications know

that some data has been downloaded to the

device and is available for them to use, so

this is broadcast receiver who will intercept

this communication and will initiate

appropriate action.

Android Core Building Blocks

Content Provider

Content Providers are used to share data between the applications.

Android Core Building Blocks

Fragment

Fragments are like parts of activity.

An activity can display one or more fragments on the screen at the same

time.

Android Core Building Blocks

AndroidManifest.xml

It contains informations about activities, content providers, permissions etc.

It is like the web.xml file in Java EE.

Android Core Building Blocks

Android Virtual Device (AVD)

It is used to test the android application without the need for mobile or tablet

etc.

It can be created in different configurations to emulate different types of real

devices.

Prerequisites

Android programming is based on Java programming language so if you have

basic understanding on Java programming then it will be a fun to learn

Android application development.

Android Studio

Android Studio is the official IDE for android application development.

It works based on IntelliJ IDEA.

https://developer.android.com/studio/

Your First Android App ☺

Directory & Resource Type

Directory & Resource Type

Directory & Resource Type

Directory & Resource Type

Alternative Resources

Your application should provide alternative resources to support specific

device configurations.

For example, you should include alternative drawable resources ( i.e.images )

for different screen resolution and alternative string resources for different

languages.

At runtime, Android detects the current device configuration and loads the

appropriate resources for your application.

Alternative Resources

Steps

To specify configuration-specific alternatives for a set of resources, follow the

following steps:

Create a new directory in res/ named in the form <resources_name>-

<config_qualifier>. Here resources_name will be any of the resources mentioned

in the above table, like layout, drawable etc. The qualifier will specify an

individual configuration for which these resources are to be used.

Save the respective alternative resources in this new directory. The resource files

must be named exactly the same as the default resource files, but these files will

have content specific to the alternative. For example though image file name will

be same but for high resolution screen, its resolution will be high.

Alternative Resources

Configuration Qualifier Names

Android supports several configuration qualifiers and you can add multiple

qualifiers to one directory name, by separating each qualifier with a dash.

https://developer.android.com/guide/topics/resources/providing-resources

Android Activity Lifecycle

Intents

An Intent is a messaging object you can use to request an action from

another app component.

Although intents facilitate communication between components in

several ways, there are three fundamental use cases:

Starting an activity

Starting a service

Delivering a broadcast

There are two types of intents:

Explicit intents

Implicit intents

Intents Types

Explicit Intents

Explicit intents specify which application will satisfy the intent, by supplying

either the target app's package name or a fully-qualified component class

name.

You'll typically use an explicit intent to start a component in your own app,

because you know the class name of the activity or service you want to start.

For example, you might start a new activity within your app in response to a

user action, or start a service to download a file in the background.

Intents Types

Implicit Intents

Implicit intents do not name a specific component, but instead declare a

general action to perform, which allows a component from another app to

handle it.

For example, if you want to show the user a location on a map, you can use

an implicit intent to request that another capable app show a specified

location on a map.

References

https://www.techotopia.com/index.php/Handling_Android_Activity_State_Changes

https://developer.android.com/guide/topics/resources/providing-resources

https://developer.android.com/guide/components/intents-filters

http://donkcowan.com/blog/2013/4/21/android-activity-lifecycle-method-typical-uses

https://www.javatpoint.com/android-tutorial

https://www.tutorialspoint.com/android

https://www.devglan.com/android/android-service-example

https://devcfgc.com/introduction-to-android-content-providers-685ed2468935

Head First Android Development: A Brain-Friendly Guide 1st Edition, By Dawn Griffiths.