From Android to the Mobile Web

From Android to
the Mobile Web
Copyright © 2013 CommonsWare, LLC

Who's the Target?
● Mass Market
– E.g., distribution on Play Store, App Store
– Pursue maximum fidelity strategy, as UI quirks
are more likely to be noticed
● Niche Market
– Enterprise, small business, government, etc.
– Pursue minimum maintenance strategy, as
budgets preclude otherwise

Objectives... Of Developers
● Maximum Fidelity Strategy
– Native apps for major platforms
– Mobile Web apps for secondary platforms
● Minimum Maintenance Strategy
– Mobile Web apps for all platforms
– Possibly augmented on some platforms


Objectives... Of This Workshop
● Demonstrate Developing for the Mobile Web
– Emphasis on installable apps (vs. HTML5 Web
apps)
● Approach from an Android Mindset
– E.g., widget library vs. low-level HTML
– Seek analogous solutions to help with climbing
the learning curve


Prerequisites
● Experience in Android development
● Basic understanding of JavaScript
● At least a vague concept of the role of CSS
● ~3 hours


Ingredients
● Widget Library: Enyo
– Offshoot of WebOS
– Pros
● Works on desktop (mouse-centric) and mobile
(touch-centric)
● Apache license
– Cons
● Relatively new


Ingredients
● Widget Library Alternative: Sencha Touch
– Pros
● Around longer, plus based on ExtJS (around longer
still)
– Cons
● Mobile-only (similar to, but not identical to, ExtJS)
● Licensing


Ingredients
● Container: Apache Cordova/Adobe PhoneGap
– Wrapper around Web assets for deployable app
(e.g., APK)
– JavaScript library for access to device-specific
capabilities
● For things that are beyond the scope of current
standards


Ingredients
● Cordova/PhoneGap Platform Support
– Android
– iOS
– Windows Phone
– Blackberry (5.x+)
– Symbian
– Bada
– More to come

Demo:
HelloWorld

Playing Around Here
● Option #1: Build Android PhoneGap App
– Set up for command-line build
– Or import into Eclipse or other IDE
● Option #2: Web browser
– Works for the first few samples
– Eventual Limitations
● PhoneGap integration
● AJAX

Local Android PhoneGap Build
● Copy desired Web content into
assets/www/ of PhoneGap template project
● Modify other aspects of project manifest
– Package name, label, icon, …
● Build and run
– Eclipse
– Command line


Enyo: Kinds and Components
● JavaScript: OO, Not Class-Based
– Prototype-based, a la Self
● Kinds: Enyo's Quasi-Class Structure
– Functions ~= Java methods
– Declared in object notation
● Components: Adds Property Management
– ~= Java data members with accessors

Demo:
EnyoHelloWorld

Enyo: Controls
● Android: Activities, Fragments, Widgets, and
Containers
– Loosely coupled constructs
● Enyo: Controls, All The Way Down
– Activity = a control
– Fragments = controls
– Containers = controls
– Widgets = controls

Enyo: Controls
● Key Properties
– name ~= Java class name
– content = the HTML to start with
● Alternative: tag
– classes = CSS classes to apply
● Alternative: style for inline CSS
– components = child controls
● ~= ViewGroup
● Children rendered inside the control itself

Demo:
EnyoHelloWorld,
Revisited

Activity → Top-Level Control
● Contains the rest of the controls
– Simply inline-defined in components array
– First-class custom controls, instantiated via
components array
● Contains top-level behaviors
– Directly or by delegation to some sort of
controller


Onyx
● Partly, a Widget Library
– Enyo has core controls
– Onyx extends, refines, elaborates
– Example: Button vs. ToggleButton
● Partly, a Theme
– Applies a stock style to all widgets
– You tailor via CSS


Common Enyo Controls
● onyx.Button
– ~= Button, ImageButton
● onyx.RadioButton
– ~= RadioButton, ToggleButton
● onyx.ToggleButton
– ~= Switch


Demo: Now


Common Enyo Controls
● onyx.Checkbox
– ~= CheckBox
● onyx.Input, onyx.TextArea
– ~= EditText
● onyx.RichText
– ~= RichTextEdit
● onyx.DatePicker, onyx.TimePicker
– ~= DatePicker, TimePicker

Enyo Containers
● enyo.FittableColumns, enyo.FittableRows
– ~= LinearLayout (horizontal, vertical)
– fit:true on component has it fill space unused
by rest (~= android:layout_weight=“1”)
● enyo.Scroller
– ~= ScrollView


Enyo Containers
● enyo.Panels
– Organizes components according to an arranger
– GridArranger: ~= GridLayout/FlowLayout
– CollapsingArranger: ~= ViewPager
● Can also use for master-detail pattern based upon
available space
– CarouselArranger: ~= ViewPager in “infinite” mode
– CardArranger: ~= ViewSwitcher


Lists in Enyo
● enyo.List
– ~= ListView
– Components are duplicated for each row
– onSetupItem property supplies function to be
called to configure and populate the row
● ~= bindView() in a ListAdapter


Demo:
CommonsBlog,
Native

Demo:
CommonsBlog,
Mobile Web
Part One

Displaying Web Content
● Option #1: Control
– Set allowHtml=true
– Assign HTML to content
– Pros: inline with the rest of your material
– Cons: inline with the rest of your material
● Only use with stuff you reasonably trust


● Option #2: InAppBrowser
– Feature supplied by PhoneGap
– Options
● _self = replaces your app with content
● _blank = starts up separate Web container within
your app for the content
● _system = launches the device default browser


● Option #2: InAppBrowser
– Pros: isolates the external material from your
app
– Cons
● Only works on URLs, not HTML you might get from
elsewhere (e.g., Web service call, Atom feed)
● Takes over the screen, not inline with your app


Demo:
CommonsBlog,
Mobile Web
Part Two

Multiple Screen Sizes
● At It's Core, No Different Than Desktop
– Web developers have had to deal with varying
browser window sizes since the dawn of the Web
– Techniques
● CSS media queries
● Detect size in JavaScript and run alternative
branches (e.g., enyo.dom.getWindowWidth())
● User agent/device model sniffing


● Master-Detail in Enyo
– Use enyo.CollapsingArranger with two panels
● Specify size for left-hand panel, right fills space... for
larger sizes
● Automatically switches into one-panel-at-a-time
mode at 800px (where px in CSS ~= dp in Android)
● Swiping to move between panels, plus can change
active panel via JavaScript code


● Want Behavior Change At Other Than 800px?
– narrowFit=false on your Panels
– Use CSS class with media query to determine
actual cutoff
– Optional: override isScreenNarrow() function
● Not used by framework, convenience for developers


Multiple Screen Densities
● CSS Media Queries
– min-device-pixel-ratio to determine
density
● 1.5, 2.0, etc.
– Apply changes
● Different icons
● Different font sizes (should automatically adjust, but
your mileage may vary)


Navigation
● Get Back to Where You Once Belonged
– Android: BACK button
– iOS: Back on-screen button in UI
– Other platforms will have their own conventions
– Challenge: supporting them all


Hooking the BACK Button
● Step #1: Do Not Render Until PhoneGap
Ready
– PhoneGap sends deviceready event
– We get control and render then
● Step #2: Tell Enyo to Route backbutton
– PhoneGap sends backbutton event
– Enyo can route through its standard event
dispatching mechanism

Hooking the BACK Button
● Step #3: Listen for Event in UI
– Add an enyo.Signals component to activity or
something
– Define function for onbackbutton
– Do something useful for navigation
● Back up a panel if first panel is not active
● Exit app via navigator.app.exitApp()


Demo:
CommonsBlog,
Mobile Web
Part Three

AJAX and Internet Access
● What Enyo Provides
– enyo.Async as base kind for asynchronous
operations
– enyo.Ajax for classic JS AJAX requests
– enyo.JsonpRequest for JSONP
● Means in a Web app of getting past cross-origin
restrictions inherent to AJAX


● What PhoneGap Provides
– Whitelist for what domains can be bypassed for
cross-origin restrictions
● For these domains, enyo.Ajax works directly
● Single domain, wildcards, etc.


● AJAX/JSONP Functions
– Constructor: supply URL
– go() to schedule the request
– response() to attach a function to be invoked
upon success, with results
– error() to attach a function to be invoked when
there is some HTTP error


Demo:
CommonsBlog,
Mobile Web
The End

PhoneGap Build
● Hosted Build Service
– Create config.xml describing the app and
requirements (based on W3C widget spec)
– Supply Web assets + config.xml to Build
● ZIP archive
● GitHub repo
– Build automatically creates builds for each
supported platform
● Minor complication with signing keys

Demo:
CommonsBlog,
Mobile Web
Beyond The End

PhoneGap API
● Accelerometer
● Camera
● Capture
● Compass
● Connection
– Determine if on WiFi or mobile data


PhoneGap API
● Device
– Make, model, OS version, etc.
● Events
● File
● Geolocation
● Globalization
● Media

PhoneGap API
● Notification
– Dialogs, beeps, vibrations
● Splashscreen
● Storage
– Web SQL implementation, to fill in for platforms
that lack it


PhoneGap Plugins
● Extends PhoneGap Environment with New
Native Capabilities
– All aforementioned PhoneGap APIs moving to
be plugins
– You can define your own, for whatever platforms
you are supporting
– Many third-party plugins already available
● May not support all your platforms, though

PhoneGap Plugins
● Step #1: Create JS objects/functions
– Call cordova.exec() to pass control to native layer
– Will need to arrange to load this JS
● Step #2: Implement Native Layer
– E.g., Android create CordovaPlugin class
● Step #3: Augment config.xml For Plugin
– Tells PhoneGap, PhoneGap Build to add your
native layer

HTML5 Storage Options
● Local Storage
– Simple associative array, strings to strings
● IndexedDB
– JSON database with developer-defined key
property
● Deprecated: Web SQL
– Still supported by PhoneGap


Summary
● Mobile Web Development: New and Growing
– Reminiscent of Android, circa 2009
● Not Suitable for All Scenarios
– Use where audience will accept it and provides
development, maintenance savings
● Widget Frameworks, PhoneGap Ease
Transition for Android Developers


Speaker Contact
Information

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From Android to the Mobile Web

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