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Stephen Bourdeau

Mobile Tech Lead

TripAdvisor, LLC

Hybrid App DevelopmentMoMo Mobile Camp, February 19th, 2011

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Who is TripAdvisor? And what’s with the owl?

• TripAdvisor is the world’s most popular & largest travel community with..• 40 million unique monthly visitors• 20 million registered members• 40 million reviews and opinions• Present in 18 countries and 26 languages

• TripAdvisor Mobile Site and Apps• 5 million unique monthly visitors

• We hit 1 million unique monthly visitors the month after we launched• Same global coverage• Native apps on a variety of platforms

• iOS (iPad app reached #1 in more than 50 countries)• Android• Nokia Ovi• HP/Palm webOS

… and our mobile site only launched 14 months ago (12/7/2009)!How did we get there so fast?

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Types of Mobile Apps

• Mobile web app• Built using HTML, CSS, JavaScript (maybe some tool kits)• Pros

• Quick to launch and update• Easier to track metrics

• Cons• Does not have access to low level features such as camera,

accelerometer, etc.• Native app

• Built using a variety of languages such as Objective-C (iOS), Java (Android), J2ME (BB), etc.

• Pros• Has access to lower level features

• Cons• Higher development cost across multiple platforms• In some cases (iOS) slower launch/update times due to

approval process• Tougher to track metrics

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A dark corner…

• Then there is a dark corner where native apps are actually web apps in disguise

• HP/Palm webOS apps are built with HTML, CSS, and JS just like a web app but have access to native functionality

• Nokia Ovi does the same thing • Provides access to low level features via JS

Hmmm… that sounds like a good idea

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What is a Hybrid app?

• Hybrid Apps combine the best of both worlds• Develop the basic building blocks of the app in HTML, CSS, JS and

display through a web view• Build features leveraging those low level APIs natively• Quick(er) to launch & update most features• Easy(er) to track metrics• Wrap them up together and shake well before drinking

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Mobile Frameworks

• There are many frameworks out there to help ease the cross-platform pain of native development

• PhoneGap• RhoMobile• Appcelerator• Etc…

• So should you use them?• They serve a purpose, but with limitations (still maturing, not perfect)• Introduce another layer of abstraction (good and bad)

• Hybrid apps can be considered as an alternative cross-platform solution

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HTML5 vs Native apps

• There is a big debate over what the future holds for mobile• Some think that native apps are here to stay

• MG Siegler, TechCrunch - http://techcrunch.com/2011/02/09/html5-versus-native-apps/

“…the fact that very few [developers], if any, choose to go HTML5-only is telling…” - Siegler

• Some think that HTML5 is the way to go• John Ciancutti, VP of Personalization Technology, Netflix -

Why We Choose HTML5 for User Experiences on Devices

“Our customers don’t have to go through a manual process to install new software every time we make a change, it ‘just happens.’” - Ciancutti

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Hybrid App Strategy

• With a hybrid app you are free to implement whatever works best• Choose the right tool for the job!

• Use simple HTML, CSS, JS to build the simple stuff• Use HTML5 to build more complicated features and push them out

cross-platform• Use native code for the most complicated/low level features

Entire page built with HTML & CSS

Photo viewer built with DHTML/JS

Photo upload built natively

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Photo viewer & Photo upload

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In the end…

• You want to spend your time building cool stuff, not reinventing the wheel for each platform (hello “Owl Cam”)

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How do we know where we are?

• Is the web site page view from a mobile web browser or app?• Android – Allows you to change your user agent• iOS – Does not allow you to change your user agent

• But wait! In iOS the webView does have a different user agent than mobile safari.

• Doh… what if another hybrid app looks at your web page?

• Best solution we have found for iOS? A cookie (who doesn’t love a cookie?)

• Set the cookie on the web view every time the app opens

• Then there is Windows Phone 7 – doesn’t allow you to set a cookie natively on the web view

• But we can set it server side…

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Hybrid Technique #1: URL Modification

• If you know you are serving a web page inside your hybrid app you can send modified URLs to perform native actions

• Facebook does (did?) this in their iOS API with a return to their own fake protocol: fb://do-something-useful

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Hybrid Technique #2: URL Interception

• From within your native app most web views allow you to listen for a change to the URL

• iOS – UIWebView – shouldStartLoadWithRequest:• Android – WebViewClient - shouldOverrideUrlLoading()

• Example: location services on webOS• Not currently supported by the webOS browser• Instead we navigate the web view to a URL with dummy values

which gets intercepted by the native wrapper

http://www.tripadvisor.com?latitude=LAT&longitude=LNG

turns into

http://www.tripadvisor.com?latitude=42.313156&longitude=-71.21274

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Hybrid Technique #2: URL Interception (contd.)

• As an added benefit you can include a link on both the web page and native app that gets intercepted.

• Remember that link to launch a native photo upload? If viewed from a mobile browser it gives a promo to download the app… have your cake and drive app downloads too!

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Hybrid Technique #3: The JavaScript drop

• Some platforms allow you to execute JavaScript against the web view• Place data in the page you return from the server in JavaScript variables• On page load pull out the data with the native wrapper and put it to good

use

WebView loads and contains location pin data in a JS variable

Pin data gets pulled out and rendered natively

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Stephen Bourdeau

Mobile Tech Lead

TripAdvisor, LLC

Questions?

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Shameless “We are hiring!” plug

• Hiring like crazy!

• Lots of interesting mobile projects in the pipeline

• Lots of interesting social projects in the pipeline (what could you do with 1.2 billion geographic place pins from our Facebook users?)