Climbing Mount Android (June 2011)

Climbing Mount Android

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Rajesh Vasa, 2011

Twitter: @rvasahttp://www.rvasa.com

http://www.rvasa.com

http://www.rvasa.com

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Mobile Eco-System

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Ad Networks

Platform

Content Providers(Music/Video/Books)

Handset OEMs

Telephone Networks

App. Distribution

Cloud Infrastructure

Billing

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Android Eco-System

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Ad Networks

Platform


Handset(OEMs)

Telephone Networks

App. Distribution


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Google, Double Click

Google, Amazon

Android

Google, Amazon

Samsung, HTC, Motorola, Sony ...

Billing

Google Checkout

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Focus of this talk...

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Ad Networks

Android Platform


Handset(OEMs)

Telephone Networks

App. Distribution


**

Google, Double Click

Google, Amazon

Google, Amazon

Samsung, HTC, Motorola, Sony ...

Billing

Google Checkout

This talk will present a development perspective

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Talk Overview

•Devices

•What is Android?

•Development Tools

•The Android Way

•Anatomy of a Simple Android Application

•An Interactive Android Application

•Dealing with Multiple Activities

•Activity Life Cycle (the odd thing)

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Roadmap - Where are we?

•Devices

•What is Android?

•The Android Way





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Android Device User Interaction

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Menu

HomeBack

Android devices have three key buttons

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Vendors can add additional buttons

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There are variations in physical form

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But all phones have Home, Menu, & Back Buttons

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Home Button...

•Typically, this will take you back to the Home Screen of the phone

•Default behaviour ~ iPhone / iPad button

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Home

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Back Button

•This will take you back to the previous screen

•If app. has only one screen, this will exit app.

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BackPersonal Opinion: iPhone / iPad should borrow this button

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Menu Button

•Shows a contextual menu (if one is available)

•Developers can write their own menus

•Quite handy (but, causes Usability issues)

• Low Discoverability

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Menu (as open)

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Android for tablets is slightly different...

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Back, Home

Where is the menu button?

Action Bar

(Buttons need not be physical in Android)

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Tablet Menu Icon Visibility is contextual

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Menu

Sadly, menu position is not mandated (yuk?)

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•Devices

•What is Android?


•The Android Way





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What is Android?

•Android is a platform

•Operating System (with primitive API)

• Frameworks (incl. components and libraries)

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Applications

Operating System(Customised Linux Kernel)

Android Frameworks

API

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Android

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Image Source: http://developer.android.com

Programming languages: Java, C/C++

http://developer.android.com


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Android is a bi-lingual platform

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Image Source: http://www.tbray.org

JavaC/C++

http://www.tbray.org

http://www.tbray.org

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Most Android Code is in Java (but...)

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Android Java is not 100% Sun Java

≠

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Android Java is different (in many ways)

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No RMI

No Bytecode

No AWT / Swing UI

Different 2D/3D libs

Different Class Load Mechanism

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•Devices

•What is Android?


•The Android Way





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Development Tools

•Android SDK (Compiler and Emulator)

•Eclipse IDE + Android Plug-in

•Powerful debugger

•Visual UI Builder

•Ant (Build System)

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Download from http://developer.android.com



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Eclipse IDE

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Eclipse IDE - Graphical UI Editor

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Android Emulator

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Permits checking Portrait and Landscape views

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Emulator is nice .. but phone is better

•The emulator runs the Android O/S (you can run any version: 1.6 to 3.0)

•Emulates the phone hardware (like VM Ware)

•Emulator does not have sensors (e.g. GPS, Gyro, Accelerometer, Cell phone etc.)

• It however offers ways to simulate these events

• So, I can send an SMS to the emulator or make a phone call to it

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Emulators Vs Simulator

•iOS offers a simulator

•Android has gone down the emulator path

•Trade-offs (pros and cons),

• Simulators start-up faster, good enough

•Emulators allow checking against rel. 1.6 of the O/S easily + closer to phone hardware

•Emulators and Simulators cannot mimic real CPU speed, disk speed, network speed etc. (yet!)

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If your Java is rusty

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Free e-Book: http://www.mindview.net/Books/TIJ/

http://www.mindview.net/Books/TIJ/

http://www.mindview.net/Books/TIJ/

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•Devices

•What is Android?


•The Android Way





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The Android Way

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Convention

Configuration

Development is organised around a few conventions

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Android Project Structure (convention)

•Source code (src)

•Generated code (gen)

•Resources (res)

•Images (drawable)

•Layout of app (layout)

•Constants/Strings (values)

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Needs Resources @Multiple Resolutions

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High

Low

Medium

Convention

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•Devices

•What is Android?


•The Android Way



•Dealing with Multiple Screens (Activities)

•Activity Life Cycle (interesting design choice)

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A Simple Android App.

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What is involved?

•Place UI controls (Text and Image)

•Layout the controls

•Centre text

•Make text large font

•Display Image to take up all space

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Each Screen is an Activity

•Android app. is made up of Activities

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Activity

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Views are Android’s Key UI Building Block

•We need two views on the Activity

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TextView

ImageView

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Views are Placed inside a View Group

•Different types of pre-defined layouts

• Linear, Relative, Table, Frame etc..

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View Group

a.k.a Layout

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Android App. - Building Blocks

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Activity Layout Views(View Group)

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Separation of Concerns in Android

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Presentation Functionality

Layout Definition (main.xml)

Activity Class

Event Handling, I/O ...

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UI (Layout) Definition

•Layout definition is generally in an XML file

•Hand coded or Visual Editor

•Can be also be done in Java Code (yuk!)

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Layout Definition XML File

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Android Offers a number of UI Controls

•Offers all standard controls and lot more...

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Progress

These are a small

subset of available controls

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View Groups and Layouts

•Android offers the following View Groups,

• Linear Layout (Horizontal or Vertical)

•Absolute Layout (You set X, Y for each View)

•Table Layout (Rows and Columns)

•Relative Layout (Position relative to other Views)

• Frame Layout (Show only one view at a time)

• Scroll View (Permits scrolling of the screen)

•View Groups can be nested

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Generated Code, Layout & Resources

•How did Australia image get into the App.?

•How did we set the text to “Australia”?

•Conventions

• Layout Defined in /layout/main.xml

•Resources Placed in /res/drawable-*

• String values defined in /values/strings.xml

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Resources

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Resources in “res”

Convention

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Resources are given a unique ID

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A unique reference id to resources is

generated by the Android SDK tools

Convention

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Resources and Generated IDs

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Generated Code

static final int australia=0x7f020000;

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A Reference to Layout also Generated

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All References are Integers

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Identifiers are used to access resources

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Reference to the layout

This is the Activity Class

(Android Runtime will Render this Layout)

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Layout is Referred to from Java Code

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Activity

View Group(Layout)

Activity Class (Java)

Layout Definition (main.xml)

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Who writes the Activity code?

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This block of code is created by IDE/SDK when we create new Android project

You can also write you own

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Activity Creation

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Method called (by Application Launcher) when App is first launched

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Activity Creation - Layout Rendering

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Method call will pass the reference to the layout that needs to be rendered on the screen

(“Rendering” is a two-pass process: measure and draw)

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What is the “root” Activity?

•How does Android know which Activity to create first?

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Answer: Application Manifest File

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Application Manifest File

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Activity Name

Application Icon Reference

Category

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Category indicates that it can be launched

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Main action indicates that it is the starting point

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Layouts and String Information

•How did we set the text to “Australia”

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String constant

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Using Graphical Resources

•How did the Australia image get into layout?

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Layout can refer to resources

@drawable is a special tag

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What is it with the @ tag?

•Constant Resources in Android can be referred using the “@” tag in XML layout

•Example: @drawable, @string ...

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@drawable/australia

@drawable/bots

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@ Tag and Multiple Screen Resolutions

•Dealing with multiple screen resolutions

@drawable/icon

Android Runtime decides best resource to use based on hardware capabilities

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Significance of hdpi/ldpi/mdpi

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High-Res, 240 dpi screen

Low-Res, 120 dpi screen

Med-Res, 160 dpi screen

Different resolution images

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•Devices

•What is Android?


•The Android Way




•Life Cycle & interesting design choices

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Building an App with Simple Interaction

•Temperature Conversion (C -> F)

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Views

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TextView

EditText

Button

TextView

4 Views (UI components) using a Linear Layout

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Linear Layout (View Group)

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main.xml(Layout)

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View Identifiers

•We need a way to identify components that we created in the layout

•E.g. To read input data from the field

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@+id TAG creates new identifiers

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UI Interaction Handling Pattern

•Component.setOn......Listener ( handler )

•E.g. button.setOnClickListener

•Handler is an anonymous inner class

•On...Listener handler = new On....Listener() {}

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UI Interaction Handling Pattern

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The View identifiers are defined in XML

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•Devices

•What is Android?


•The Android Way




•Life Cycle & interesting design choices

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Wiring up Multiple Activities

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Select

Back

Contact List Activity Contact Details

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Activities are Stacked in Android

•All current activities are placed on a Stack

•Newly started activities come into foreground

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Contact List

Contact Details

Foreground/Active

starts Background/Paused

Back button will pop top most

activity from stack

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Activities are like mini-processes

•Android activities have their own life cycle

•Communication between Activities is done by Asynchronous Messaging

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Contact List Contact Detailsmessage

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Async. messaging called “Intents”

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Contact List Contact Detailsintent

Activities communicate with each other via Intents

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Async. messaging called “Intents”

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Activity-X Photo Viewerview photo

intent

You can send a general purpose message (intent), all applications capable of handling that Intent will respond

Framework prescribes conventions for common intents

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•Devices

•What is Android?


•The Android Way




•Life Cycle (& interesting design choices)

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Android Activities are Managed by O/S

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Activity-A

Activity-C

Activity-B

ApplicationActivities have a

parent application

Activity has Life Cycle Application is NOT managed

directly by the O/S

Life Cycle is Managed by Android Framework

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Android Activity Life Cycle

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Activity is re-started when orientation changes

Developers have to save and retrieve state if orientation changes

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Security -- Android Devices

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AndroidApplication

User UID (User ID)has

also has

The UID is generated at install time based on the signature and package name

File System Access Permissions

determines

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A Short Plug!!!

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Mobile Development @ Swinburne

•HIT8328 - Software Development for Mobile Devices

• Android focused

•HIT8329 - Creating Data Driven Mobile Applications

• iOS focused

• Portfolio Based Assessments

• We do not just cover API -- there is a strong conceptual foundation (prepare you to learn)

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We Offer Options to Study Just One Subject

Teaching material will be available openly shortly

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Mobile Development @ Swinburne

•HIT8328 - Software Development for Mobile Devices

•HIT8329 - Creating Data Driven Mobile Applications

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Teaching material will be available under an open license shortly

Follow @rvasa or @swinfict for update

Climbing Mount Android (June 2011)

Technology

Transcript of Climbing Mount Android (June 2011)