Mobile Development. A primer

Mobile Development A primer

Giuseppe SollazzoNational Audit Office

25/7/2014

#0The obligatory intro

Goals

● Understanding mobile development● Exploring alternative technologies● Brainstorming apps● Get some first-hand experience

Outline

AM● A quick history of mobile development● Concepts of modern development● Simple code examples

PM● Practical exercises

Me

● Senior Systems Analyst at St George’s, University of London

● Freelance Developer● Open Data & Government Geek

#1The Mobile Scenario

#1.1A lifetime of mobile development

2006: my first app

2012: on the press

Sony Ericsson P990i

Symbian OS 9.1 - UIQ 3

ARM9 208MHz

RAM 64MB (OS: 48MB, User: 16MB)

Resolution 240x320

Java Micro Edition

iPhone 4

iOS

ARM Cortex ~1GHz

RAM 512MB

Resolution 960x640

Objective-C / Cocoa

29 June 2007 Image CC BY-NC-SA 2.0 by Stijn Vogels https://www.flickr.

com/photos/stijnvogels/351867946/

But it started much earlier!

● 1G phones have been out since the 80s○ lack of apps capabilities

● 2G phones (GSM) reach critical mass in early 90s○ dominated by Nokia○ limited features and memory○ small monochromatic screen○ pre-installed games

■ no easy way to install extra apps

Snake!(1998)

Image CC BY-NC-SA 2.0 by Utku Kalı https://www.flickr.com/photos/utku/6799941621

https://www.flickr.com/photos/utku/

WAP(1997)

Image CC BY-NC 2.0 by Esko Kurvinen https://www.flickr.com/photos/ekurvine/853687173

WAP

● Protocol suite for data transfer on wireless devices ● Wap PUSH● Wireless Markup Language

<?xml version="1.0"?><!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"

"http://www.wapforum.org/DTD/wml_1.1.xml" >

<wml> <card id="main" title="First Card"> <p mode="wrap">This is a sample WML page. </p> </card></wml>

WAP

● Deck = WML document ● Deck structured in cards (=pages)● Wap 2.0 (2002): cut-down version of XHTML/HTTP

But it didn’t work

● Hard to type URL with numeric keypad● Limited screen -> limited applications● Extremely slow connections● Users accustomed to full web pages● No authoring tools, no content providers

i-Mode (1999)

● Created by DoCoMo, paid-for service● Similar to WAP but

○ C-HTML on HTTP clone○ 12K official sites (supervised by DoCoMo)○ 100K unofficial sites○ 80M subscribers

● Licensed in the UK by O2, it never took off

BlackBerry

● BB 850: 2-way pager launched in Munich (1999)● Focus on e-mail● Evolution in 2003 with convergent services

○ push email, telephone, SMS, …● Inconsistent developer support

○ Java SDK for BlackBerry OS 7○ Today: BB 10, BB PlayBook, BB OS

Psion Revo (1999)Image CC BY-NC 2.0 by Modrak https://www.flickr.com/photos/modrak/239348772

Psion EPOC

● Graphical OS● PDAs with apps● EPOC16: Open Programming Language

PROC main:

PRINT "Hello World!"

PAUSE 40

ENDP

● EPOC32 (1997): C++ but mostly closed● EPOC32 becomes Symbian (1998)

Palm Zire(2002)

Image CC BY 3.0 by Soxred93 http://commons.wikimedia.org/wiki/File:Zirepalm.JPG

Palm OS

● Launched in 1996 and still alive!○ Now called WebOS

● C/C++/Pascal● Java was briefly available● No drivers for DBMS

○ developers need to use middleware● First system to provide emulators

Symbian

● A long and troubled story...● 1998: Psion becomes Symbian Ltd.

○ participation by Ericsson, Motorola, Nokia● 2008: Nokia acquires Symbian Ltd.

○ establishment of Symbian Foundation○ most Nokia devices run Symbian○ licensing issues

● 2011: Nokia partners with Microsoft. Symbian dies.

Symbian

● S60 = Native graphics toolkit (for Nokia, 2001)● QT framework (Symbian 3, 2010)● Development in

○ Java MIDP○ C++○ Python○ Flash

Symbian

● One (major) weakness: platform fragmentation

source: Wikipedia “S_60”

J2ME / Java ME

● Stripped down version of Java● Foundation standards

○ CLDC 1.0, 1.1, … (defines basic set of libraries)○ MIDP 1.0, 2.0, 3.0 (defines APIs)

■ apps are called “midlets”● Extensions, e.g.

○ JSR #82 Bluetooth○ JSR #179 Location API

J2ME / Java ME

● Modern framework○ Provides configurable simulators○ Coding of application lifecycle

● Relatively successful○ 2.1B Java ME enabled mobile phones

● Problems○ memory footprint○ device fragmentation

J2ME / Java ME

import javax.microedition.midlet.*;import javax.microedition.lcdui.*;

public class HelloWorld extends MIDlet implements CommandListener { private Command exitCommand; private TextBox tbox;

public HelloWorld() { exitCommand = new Command("Exit", Command.EXIT, 1); tbox = new TextBox("Hello world MIDlet", "Hello World!", 25, 0); tbox.addCommand(exitCommand); tbox.setCommandListener(this); }

protected void startApp() { Display.getDisplay(this).setCurrent(tbox); }

protected void pauseApp() {

}

protected void destroyApp(boolean bool) {

}

public void commandAction(Command cmd, Displayable disp) { if (cmd == exitCommand) { destroyApp(false); notifyDestroyed(); } }

}

J2ME / Java ME

import javax.microedition.midlet.*;import javax.microedition.lcdui.*;

public class HelloWorld extends MIDlet implements CommandListener { private Command exitCommand; private TextBox tbox;

public HelloWorld() { exitCommand = new Command("Exit", Command.EXIT, 1); tbox = new TextBox("Hello world MIDlet", "Hello World!", 25, 0); tbox.addCommand(exitCommand); tbox.setCommandListener(this); }

protected void startApp() { Display.getDisplay(this).setCurrent(tbox); }

protected void pauseApp() {

}

protected void destroyApp(boolean bool) {

}

public void commandAction(Command cmd, Displayable disp) { if (cmd == exitCommand) { destroyApp(false); notifyDestroyed(); } }

}

Opera Mini(2007)

Image CC BY 2.0 by Johan Larsson https://www.flickr.com/photos/johanl/4424185115

Opera Mini

● Mobile-oriented web browser● Reformats web pages to a “compressed” version

○ all content goes through proxy server● Pilot project started in 2004, launched 2007● Growing interest in mobile web standards

HTC Dream(2008)

Image GPL by Akela NDE http://en.wikipedia.org/wiki/File:HTC_Dream_Orange_FR.jpeg

Android

● Founded in 2003, acquired by Google in 2005● Based on Linux● Open Handset Alliance (2007)

○ HTC, Sony, Samsung, T-Mobile, Texas Instruments, etc…

● Nexus devices○ Nexus One (2010)

iOS

● iPhone launched in 2007 with iOS 1.x○ iPod Touch and iPad follow

● Developers not welcome until March 2008○ iPhone SDK released (iPhone OS)○ iOS was “a version of OS X” before then

● Apple did not want an “app economy”○ issues with control, market submission, etc…

iOS

● Controversies with developers and suppliers● Java and Flash originally not allowed● Competition wars

○ Sun agrees with Apple and Java gets in○ Adobe discontinues Flash mobile (2011)

HP Jornada 680(1998)

Image CC BY 2.0 by Noah (ax0n) https://www.flickr.com/photos/kc-bike/2532722221

Windows Mobile

● Microsoft joined the market early○ Windows CE (1996)○ Pocket PC (2000)○ Windows Mobile 2003○ Windows Mobile 5, 6 (2005)○ Windows Phone 7, 8 (2010)

● Windows 8 unifies desktop & mobile platforms

Windows Mobile

● Development with Microsoft tools● From Windows Phone 7, also web technologies● Windows Mobile lost momentum

#1.2In the public sector...

We are not ‘appy...

● (Tom Loosemore, GDS, 2013)

Stand-alone mobile apps will only be considered once the core web service works well on mobile devices, and if specifically agreed with the Cabinet Office.

(GDS Strategy, Action 6)

● Gov.Uk doesn’t have apps○ website adapts to mobile screens○ use of CSS3 technologies, media queries

...but we are!

● Tracy Green, UK Parliament (2013)○ 11% traffic to site from mobile○ of which 90% from iPad

● 400+ MPs have iPads○ demand for native apps “because they work

better”

Image CC BY-NC 2.0 by IDEO https://www.flickr.com/photos/ideopostcards/6334836459/

The PM wanted an app

Number 10 Dashboard

● (No one has ever seen it)● iPad app (maybe)● Purpose-built for the PM● By Adzuna (according to the FT)● Intranet front-end (according to The Register)

○ presumably a custom front-end to data.gov.uk● Dashboard of stats and data visualisation

HMRC Tax Calculator

● Native iOS/Android app

ParliQuiz

● Developed with “PugPig”○ publishing system○ £4K per year per single app

MyConstituency

● Hybrid app○ iPad only vs any Android○ not the same version

Some suggestions...

● ONS developed a case study about “MyConstituency”○ It meets the needs of MPs and their staff○ It engages with the general public○ Mini-tender: no big procurement drive!○ Tips

■ internal resources to handover app after project■ be specific about API / web service■ allow for flexibility

#1.3Some stats

<Stats slides omitted from SlideShare due to licensing. Contact me for details>

#2Modern mobile development

concepts

In this module...

● iOS, Windows 8 Phone, Android, and more● For each platform:

○ system architecture○ development model○ languages○ data storage○ UI building

● Markets

#2.1iOS

Assumptions

Focus on iOS 7● released in September 2013● it runs on iPhone 4 and later, iPad 2 and later● 87% of iOS devices (6/4/2014)● iOS 8 / Swift are currently beta

Basics

● Layered system architecture● MVC model● Objective-C● Interface Builder

● Apps are object (of type UIApplication)● Mac OS X required● XCode: iOS SDK + iOS Simulator

Tools: Xcode + iOS SDK

Tools: iOS Simulator

System Architecture: Abstraction Layers

Core OS

Core Services

Media

Cocoa Touch

These layers provide “Frameworks” to be added to any iOS project to provide certain functionalities


Core OS

Core Services

Media

Cocoa Touch

Low-level features: security, communications, I/O, maths, networking, etc...


Core OS

Core Services

Media

Cocoa Touch

System Services: Core Foundation, Foundation, iCloud, Automatic Reference Counting (ARC), Grand Central Dispatch (GCD), in-App Purchase, SQLite, Core Data, Core Location, etc...


Core OS

Core Services

Media

Cocoa Touch

UIKit, Core Graphics, Core Animation, Core Audio, Core Media, AV Foundation, etc...


Core OS

Core Services

Media

Cocoa Touch Storyboards, Push & Local Notifications, Gesture Recognisers, iAd, etc...

Model View Controller (MVC)

● Software Design Pattern● Separation of Data, UI, Logic

○ Model encapsulates data ○ View displays user interface○ Controller ties model to the view

● We will see this at work in the next session


ModelThe Model is about Data● data functions● data objects● data classes● i.e. data store + procedures that can access it


Model

View

The View is about User Interface● UI elements: buttons, sliders, text fields● object / classes / functions ● (or Storyboards / Interface Builder)


Model

View

The Model knows nothing about the UI


Model

View

Controller

The Controller is about bi-directional Orchestration● it intercepts user actions on the UI (View)● modifies the data accordingly (Model)

or● it detects data changes (Model)● modifies the UI accordingly (View)


Model

View

Controller


Model

View

Controller

user action

data change


Model

View

Controller

UI update

data changenotification


To accomplish communications we use links ● Outlets

○ from the controller to the view ○ to access info of an UI element

■ e.g. access the text typed in a text field● Actions

○ from the view to the controller ○ they announce an action on the UI

■ e.g. detect a button click, perform an action

Objective-C

● Object-oriented○ strict superset of C○ object syntax from Smalltalk

● Message passing to object instances○ i.e. not method calling

● Used on Mac OS X (Cocoa) and iOS (Cocoa Touch)

Objective-C: Message Passing

C++

Object* obj;

obj->method(argument);

Java

Object obj;

obj.method(argument);

Objective-C

Object* obj;

[obj method:argument];

Objective-C: Hello, world!

/* hello.h */

# import <Foundation/Foundation.h>

@interface Hello : NSObject

-(void)sayHello:(char*)name;

@end


/* hello.m */

# import "hello.h"

@implementation Hello

-(void)sayHello:(char*)name {

printf("Hello, %s!\n", name);

}

@end


/* app.m */

# import "hello.h"

int main() {

Hello* myhello = [Hello new];

char* name = "Joe";

[myhello sayHello:name];

}

To compile: $ clang -lobjc -o app app.m hello.m

Objective-C: Protocols

● Add set of expected behaviours to an object○ or, in official speak, define messaging contracts

● An object can conform to a protocol● In practice: methods to be implemented

○ some required, some optional


/* politehello.h */

#import <Foundation/Foundation.h>

@protocol PoliteHello <NSObject>

-(void)helloFriend;

-(void)helloColleague ;

-(void)helloPrimeMinister ;

@end


/* hello.h */

#import <Foundation/Foundation.h>

#import "politehello.h"

@interface Hello : NSObject <PoliteHello>

-(void)sayHello:(char*)name;

@end


/* hello.m */

# import "hello.h"

@implementation Hello

-(void)sayHello:(char*)name {

printf("Hello, %s!\n", name);

}

-(void)helloFriend {

printf("Hey!\n");

}

-(void)helloColleague {

printf("How was your weekend? \n");

}

-(void)helloPrimeMinister {

printf("Good morning, sir \n");

}

@end

Delegation

● Software pattern, Obj-C protocol● Let an object control another object● Use a central object to customize the behaviour of

several others● Delegating object A keeps reference to delegate

object B● A sends a message to B● B reacts by updating UI/state

Data Source

● Similar to a Delegate● Delegated control of data● Outlet held by View objects● Implemented via Obj-C protocol

Table Data Source

Table Data Source

Table Delegate

Table Delegate

Application Delegate

● Most important delegate in an iOS project● Delegate for the UIApplication object● Starting point for coding● Startup/shutdown tasks

○ e.g. initialise database, verify license, etc...● App-wide tasks

○ e.g. handle push notifications, support window orientation, etc...

Application Delegate

Interface Builder

“UI Drawing” tool included in XCode● Add Window object● Add Content View*● Add UI Controls (buttons, text fields, etc…)● Add basic navigation between views (Storyboards)

(*) Views are hierarchical ○ i.e. they are containers for other subviews

Interface Builder

Storyboards

● Interface Builder on steroids● Define navigation relationships among Scenes● Each Scene has an associated view hierarchy● Scenes are connected by segues or relationships

○ segue = transition between two view controllers■ push, modal, custom, unwind

○ relationship = hierarchy

Storyboards

Auto Layout

● Define relationships between UI elements● Mathematical constraints● UI reacts dynamically to changes

○ screen size, orientation, localization, etc...

Auto Layout

Navigation Controllers

● To manage a stack of view controllers● To provide a drill-down interface for hierarchical

content● Several types, according to context & device type

○ Tab Bar○ Page View○ Split View○ etc…

Data Storage

● Preferences (key/value)● File system (for large files)● SQLite

○ a lightweight relational database○ de facto industry standard for embedded apps

● CoreData Framework○ object oriented wrapper○ infrastructure for search, save, restore, etc…

● iCloud (and other cloud storage providers)

#2.2Windows 8 Phone

Assumptions

Focus on Windows 8.1 Phone● released in October 2013● it runs on several architectures

○ IA-32, x64, ARMv7● marketed as “update” for Windows ● development overlaps with Windows 8 desktop

○ Windows Store and Windows Phone Store apps are converging into Windows Runtime apps

Windows 8 (desktop)Used with Permission from Microsoft

Windows 8 (phone)Used with Permission from Microsoft

● One architecture, several development options○ flow control languages○ UI definition language

● Windows 8.1 + Visual Studio Express 2013

Basics

Languages

Used with Permission from Microsoft

Differences

● Each language has a corresponding app model○ i.e. a set of files, design patterns, app entry point

● Certain languages more suitable to certain apps○ e.g. C++ / DirectX are good for 3D games

● Otherwise, philosophy is: use what you know● For this course, our choice is JavaScript / HTML5

Windows Runtime

● Often referred to as WinRT● Successor of Win32 API

○ Based on COM/.NET● Platform-homogenous app architecture for Win 8

○ unifies Windows 8 and Windows 8 Phone● Supports several languages

Tools: Visual Studio 2013 ExpressUsed with Permission from Microsoft


Tools: Emulator

UI definition

● In standard HTML5...● ...plus “Microsoft Phone WinJS” libraries

<script src=”//Microsoft.Phone.WinJS.2.1/js/base.js”></script>

<script src=”//Microsoft.Phone.WinJS.2.1/js/ui.js”></script>

● these libraries cover UI controls and behaviours

Application Entry Point

● method called by the system to start the app● onactivated() in js/default.js● main UI defined in default.html● allows to detect how the app was started

○ i.e. from launch, suspension, etc...


var app = WinJS.Application;

var activation = Windows.ApplicationModel.Activation;

app.onactivated = function (args) {

if (args.detail.kind === activation.ActivationKind.launch) {

if (args.detail.previousExecutionState !== activation.ApplicationExecutionState.terminated) {

// TODO: This application has been newly launched. Initialize

// your application here.

} else {

// TODO: This application has been reactivated from suspension.

// Restore application state here.

}

args.setPromise(WinJS.UI.processAll());

}

};

Application Lifecycle

Not Running Suspended

Running

Activated

Resuming

Suspending


var app = WinJS.Application;

var activation = Windows.ApplicationModel.Activation;

app.onactivated = function (args) {

if (args.detail.kind === activation.ActivationKind.launch) {

if (args.detail.previousExecutionState !== activation.ApplicationExecutionState.terminated) {

// TODO: This application has been newly launched. Initialize

// your application here.

} else {

// TODO: This application has been reactivated from suspension.

// Restore application state here.

}

args.setPromise(WinJS.UI.processAll());

}

};

UI.processAll()

● scans default.html for WinJS Controls○ if it finds any, it initialises them

● enclosed in setPromise to display splash screen until UI loading is complete

JavaScript

● Standard JavaScript ● Win JS = Open Source JavaScript library

○ helpers that expose the Windows Runtime○ provides page control, promises, data-binding○ allows Windows UI controls in HTML

■ using data binding and templating

Asynchronous Programming

● CommonJS Promises “A”● Promise = eventual result from an async operation● Object with “future value” is returned● then() function● In lay terms

○ when you finish task X, perform Y○ promise is Y’s result handler


● Promise object offers methods to deal with result● then()and done() functions

WinJS.Promise.timeout(1500, WinJS.xhr({ url: "http://www.microsoft.com" })

.then(function complete(result) {

WinJS.log && WinJS.log( "Downloaded the page" );

},

function error(error){

// ...

WinJS.log && WinJS.log( "Got error: " + error.statusText);

}

));

UI

● Standard HTML controls<button id="helloButton">Say "Hello"</button>

● WinJS controls<div

id="toggleControlDiv"

data-win-control="WinJS.UI.ToggleSwitch"

data-win-options="{title: 'Greeting Color'}">

</div>

UI actions

● by event handling○ register an event listener○ in app.onactivated(), after args.setPromise()

var helloButton = document.getElementById("helloButton");

helloButton.addEventListener("click", buttonHandler, false);

UI actions

● buttonHandler() is a standard JavaScript function

function buttonHandler(eventInfo) {

var inputString = document.getElementById("input").value;

document.getElementById("output").innerText = inputString;

}

● done in CSS3

● defaults for dark and light UI themes are provided

● add in /css/default.css

● e.g..toggle-on {

color:blue;

}

UI styling

● Effective way to add data into HTML/WinJS control

● Define UI control, define data, bind data to control

○ if data change, UI control is updated

○ e.g. useful with lists

Data Binding

Define binding for UI element:<span id="namespan" data-win-bind="innerText: name"></span>

Then, in the Javascript:var person = { name: "Fran" };

…

var personSpan = document.querySelector('#nameSpan');

WinJS.Binding.processAll(personSpan, person);

Data Binding

● It’s HTML, so we can use linking

● Single-page Navigation

○ Microsoft-recommended

○ There are still multiple files

○ Better for transferring app context

○ One “central” PageControl object loads other files

Navigation

● Several navigation patterns can be combined

○ due to HTML, developer has maximum freedom

● Typical examples

○ List with drill-down

○ Central app hub (panoramic view)

○ App tabs

○ Page shuffle

Navigation Patterns

Navigation Example: List with drill-down


Navigation Example: Page Shuffle


Navigation Example: Central app hub


Navigation Example: Central app hub


● User Data: document, files, etc…

○ File system

○ One Drive

○ HTML5 File API

Data Storage

● App Data: state, configuration, preferences, etc…

○ App Data API for WinRT

○ IndexdDB (ISAM)

○ Extensible Storage Engine (ISAM)

○ HTML5 Web Storage

○ WinJS.Application.sessionState, local, roaming

Data Storage

#2.3Android

Assumptions

● Android 4.4 “KitKat”○ released in October 2013

● 13.6% of android installs○ Android 2.3 “Gingerbread” is at 14.9%○ Android 4.0 “Ice Cream Sandwich” 12.3%

● Android versions have had a complicated history...

Basics

● App lifecycle + MVC model● Java (Dalvik VM) + Native C Code (Bionic)● XML-based UI design● Android = software stack

○ OS based on Linux kernel ○ Middleware, Core Applications, SDK

● Eclipse, Android SDK, ADT, Simulator○ on PC, Mac, Windows, …

Architecture

CC-BY-SA 3.0 by Smieh

Manifest

● Synoptic view of an application○ Lists activities○ Adds permissions○ Register intents○ and more...

Activities

● Apps are collections of Activities○ Activities are Java objects○ Activities provide a screen

● Each Activity is the base for UI○ They can use Views and Fragments

■ Views = widgets (buttons, fields, etc…)■ Fragments = components with encapsulated

code

Activity Lifecycle

Image: Apache License from developer.google.com

Activity Code

Code: Apache License from developer.google.com

public class ExampleActivity extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

}

@Override

protected void onStart() {

super.onStart();

}

@Override

protected void onResume() {

super.onResume();

}

@Override

protected void onPause() {

super.onPause();

}

@Override

protected void onStop() {

super.onStop();

}

@Override

protected void onDestroy() {

super.onDestroy();

}

}

http://developer.android.com/reference/android/app/Activity.html#onCreate(android.os.Bundle)

http://developer.android.com/reference/android/app/Activity.html#onStart()

http://developer.android.com/reference/android/app/Activity.html#onStart()

http://developer.android.com/reference/android/app/Activity.html#onResume()

http://developer.android.com/reference/android/app/Activity.html#onResume()

http://developer.android.com/reference/android/app/Activity.html#onPause()

http://developer.android.com/reference/android/app/Activity.html#onPause()

http://developer.android.com/reference/android/app/Activity.html#onStop()

http://developer.android.com/reference/android/app/Activity.html#onStop()

http://developer.android.com/reference/android/app/Activity.html#onDestroy()

http://developer.android.com/reference/android/app/Activity.html#onDestroy()

Intents


Intents

● Runtime binding between code in different apps● Mostly used to launch activities● Explicit

○ specify exact class to be run● Implicit

○ include information to help the system “decide”○ concept of Intent Resolution

Intents

● Activities can register Intent Filters in the Manifest● Intents are used intra-app and between apps<activity class=".NotesList">

<intent-filter>

<action android:name="android.intent.action.MAIN" />

</intent-filter>

<intent-filter>

<action android:name="android.intent.action.VIEW" />

<action android:name="android.intent.action.PICK" />

<data android:mimeType="vnd.android.cursor.dir/vnd.google.note" />

</intent-filter>

</activity>


Intents

● Programmatically, switch to a different activity

Intent intent = new Intent(this, DisplayMessageActivity.

class);

String message = “Hello”;

intent.putExtra(EXTRA_MESSAGE, message);

startActivity(intent);


Intents

● Programmatically, switch to a different activity

Intent intent = new Intent(this, DisplayMessageActivity.

class);

String message = “Hello”;

intent.putExtra(EXTRA_MESSAGE, message);

startActivity(intent);


Data sharing

UI

● “Roughly” MVC ● Views are defined programmatically or in XML

○ Layout Inflater● Activity: setContentView()

○ views are nested● Hierarchy of Views grouped in View Groups

○ views are single UI widgets○ groups define how the views are laid out

XML Layout

main_layout.xml<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView android:id="@+id/text"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Hello, I am a TextView" />

<Button android:id="@+id/button"



android:text="Hello, I am a Button" />

</LinearLayout>Code: Apache License from developer.google.com

XML Layout



setContentView(R.layout.main_layout);

}


XML Layout



setContentView(R.layout.main_layout);

}


Resources & R

● All resources are under a folder called “res”○ drawables○ layouts○ localised strings

● Android exposes them through the R class○ R.layout.main_layout○ Smart system for localisation

■ values -> R.values.string■ values-en -> R.values.string

Resources & R

● All resources are under a folder called “res”○ drawables○ layouts○ localised strings

● Android exposes them through the R class○ R.layout.main_layout○ Smart system for localisation

■ values -> R.values.string■ values-en -> R.values.string

Images

● R.drawable.<image> makes access easy but…● ...there is massive diversity in device capabilities

○ drawable-hdpi○ drawable-ldpi○ drawable-mdpi○ etc…

● Screen support is a major pain

Images

Image & Text: Apache License from developer.google.com

Data Storage

● Shared Preferences○ key-value pairs of primitive types

● Internal and External File Storage● SQLite Database

UI Actions

● 2 options: define onClick function...

<?xml version="1.0" encoding="utf-8"?>

<Button xmlns:android="http://schemas.android.com/apk/res/android"

android:id="@+id/button_send"



android:text="@string/button_send"

android:onClick="sendMessage" />

public void sendMessage(View view) {

// Do something in response to

button click

}


UI Actions

● ...or create event listener

Button button = (Button) findViewById(R.id.button_send);

button.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {

// Do something in response to button click

}

});



● Unresponsive apps trigger the “ANR” dialog● Implement AsyncTask to run in background



● Define Task...private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {

protected Long doInBackground (URL... urls) {

int count = urls.length;

long totalSize = 0;

for (int i = 0; i < count; i++) {

totalSize += Downloader .downloadFile (urls[i]);

publishProgress ((int) ((i / (float) count) * 100));

// Escape early if cancel() is called

if (isCancelled ()) break;

}

return totalSize ;

}

// This is called each time you call publishProgress()

protected void onProgressUpdate (Integer... progress) {

setProgressPercent (progress[0]);

}

protected void onPostExecute (Long result) {

showNotification ("Downloaded " + result + " bytes");

}

}


● launch and continue with other activities● at the end, onPostExecute() will update with results

new DownloadFilesTask().execute(url1, url2, url3);

#2.4Alternatives

What else?

● Cross-platform native development● 100% Mobile Web● UI Frameworks

○ CSS libraries○ MVC-based

Apache Cordoba/PhoneGap

● Set of APIs to access native functions from JavaScript○ camera, geolocation, etc...

● Develop mobile apps in HTML, CSS, Javascript○ combine with UI framework

■ jQuery Mobile, Dojo Mobile, Sencha Touch, ...● “Package” it in a native app using the platform SDK● Supports: iOS, Android, Blackberry, Windows Phone,

Palm WebOS, Bada, Symbian (in future: Firefox OS)

Mobile Web

● “Apps are overrated”● Make web sites mobile-ready● HTML5, jQuery, JavaScript● Use Open Standards● Easier for accessibility

Sencha Touch

● HTML5 framework● Provides themes for most mobile platforms● Based on MVC pattern

jQuery Mobile

● HTML5-based UI system● Responsive web sites● Based on jQuery ● Provides

○ Ajax navigation○ Touch events○ Widgets

<Stats on cross-platform framework omitted due to licensing. Contact me for details.>

What lies ahead?

● Firefox OS● IndiePhone● FairPhone● ...and many others

#2.5App Distribution & conclusions

Markets

● Publicly available app-stores○ “Private apps” with authentication

● Android & Windows allow direct sideloading○ Recommended in Windows, not in Android

● Enterprise app distribution○ in iOS (£299/year)○ in Android (no extra cost)

The screen size war

Android iOSImages source: OpenSignal

The screen size war

● Fragmentation is predominant in the Android market○ Good for users○ Bad for developers

● Tablets are less affected○ Once you get past 7”, difference not that important

#3Hello, World!

#3.1iOS

#3.2Windows 8 Phone

Press the “play” button

Keep an eye on the console

#4Let’s get some practice

Exercise 0: Hello, World!

● Display a static “hello” string● iOS

○ view controllers, storyboards, outlets● Windows

○ simple html

Exercise 1: Basic interaction

● Display a dynamic “hello” string○ text and push a button

● iOS○ outlets & actions

● Windows○ event handlers

Exercise 2: Populate a table

● Display a table with some data from an array● iOS

○ table view, data source● Windows

○ list view, data-binding

Exercise 3: Pie Chart

● Display a simple pie chart● iOS

○ core plot● Windows

○ Raphael.js

Exercise 4: Line Chart

● Display a simple pie chart● iOS

○ core plot● Windows

○ Raphael.js

Exercise 5 (optional): Navigation

● Play with building a navigation framework● iOS

○ storyboards● Windows

○ page control tutorial

And more...

● Let’s put this all together● Display data from the Guardian?

Fin.