I am embarking on a new PhoneGap project that will have to run on many platforms… iOS, Android, BlackBerry, and Windows Phone. This will actually be my first foray into modern Window Phone development. (I did some experimental work with the Windows Mobile platform many years ago, but a lot has changed since then.)
One of the caveats with Windows Phone development is that it has to be done from Windows, just like iOS development has to be done from OS X (normally, although some cross platform technologies enable development via other OS/platforms).
Of course, I did not want to give up OS X, so here’s how I have my environment setup… I have a virtual machine running Windows 7, in which I can run the Visual Studio development tools. I am able to deploy to a physical Windows Phone device using the USB connection.
Windows Phone Development with PhoneGap, on OS X
However, with this configuration you will NOT be able to use the Window Phone emulator, which is a part of the Windows Phone development SDK. The Windows Phone emulator is not supported inside of a VMWare virtual machine because the emulated operating system environment does not meet the minimum requirements (specifically the graphics drivers are not WDDM 1.1 compliant). If you try to use the phone emulator inside the virtual machine, you will just get a blank screen. I spent a few hours trying to find a workaround, to no avail. You can use the Windows Phone emulator if you boot your Mac into Windows using Bootcamp, but I wanted to keep OS X as my primary operating system.
Being able to deploy directly to a device works for me, and is (in my opinion) better than being able to deploy to an emulator, thus I am happy with this workflow. I have heard that other people have had trouble deploying to Windows Phone devices through a VMWare emulator, so here are the details on how I have my environment setup and a few “getting started” links for PhoneGap development on Windows Phone:
Note: All of the project setup work will be done through the Windows virtual machine instance.
There is a detailed “Getting Started” guide for PhoneGap and Windows Phone available at http://phonegap.com/start#wp. This will provide you with all the information that you need to get started with PhoneGap applications for Windows Phone.
As a part of the setup process, you will need to download and install the Windows Phone SDK from http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=27570. This will include a copy of Visual Studio Express 2010 for Windows Phone, as well as additional tools for Windows Phone development.
To be able to deploy an application to a physical Windows Phone device, you will need to register as a Windows Phone developer on MSDN App Hub at http://create.msdn.com/en-US/home/membership. This is a very similar model to Apple’s iOS developer program. There is a $99 annual fee, and once you are registered, you will be able to debug on devices and distribute applications via the Windows Phone Marketplace. However, debug provisioning is much easier. Instead of signing each application with a debug certificate, you just have to register your device as a development device. Once the device is registered, you will be able to deploy to it without any other special steps; this is very similar to the provisioning model for Nook devices.
When linking my AppHub account to my Windows Live account (a required step), I ran into a vague error message “There’s a temporary problem with the service. Please try again. If you continue to get this error message, try again later.” After scouring the web for this error message, I found a few threads that mentioned this error is likely the result of an incomplete profile for your Windows Live account. Sure enough, I went into live.com and filled out my profile (including contact information), and this error went away.
My Setup
Below are the specifics for my setup; I did not have any issues connecting a Windows Phone device with this configuration.
To deploy an application to a Windows Phone device, you just have to use the Windows Phone Developer Registration Tool, and walk through a few simple steps to associate your phone with your developer account. This tool is installed when you install the Windows Phone SDK. You can read full details about debugging Windows Phone applications on MSDN.
As I mentioned above, I have heard that others have encountered problems when trying to deploy applications to Windows Phone devices via a virtual machine on OSX, but I have not had any problems with this configuration.
I was inspired to write this post by several recent conversations. I was in a debate about whether with the Flex/Flash platform you could easily repurpose content to the desktop using Adobe AIR (and vice-versa), but that you couldn’t easily do that with PhoneGap applications. (My stance was that yes, you could repurpose content.)
I wanted to make sure that people were aware that you can repurpose your content, and here’s an example of how.
A while back, I wrote a sample PhoneGap application that allows you to browse information from the 2010 US Census. You can read more about this application and download the source code here. This application supports lots of platforms… iOS, Android, BlackBerry, and web (everything except IE because I was targetting WebKit browsers).
While this application is a mobile app wrapped in the PhoneGap container, I actually didn’t use any PhoneGap-specific libraries, so it was very easy to repurpose as a desktop application. I created an AIR version of this application, which you can download at:
I had to use my Android 2.x branch of the US Census Browser code because the WebKit instance inside of AIR doesn’t support SVG. I also changed the container scrolling to use normal CSS “overflow: auto” instead of using iScroll for touch-based scrolling. There were a few other one-off CSS changes to tweak the layout in the AIR web container, but otherwise the code is identical.
You just need to create an AIR application XML file and point it to your HTML content, and then package it using ADT.
If you were using PhoneGap APIs, you would have to migrate your code to take advantage of AIR APIs, but all other HTML/CSS/JS could be reused with minimal changes.
Even though I used AIR for this example, AIR isn’t the only game in town for HTML-based desktop applications… There’s an open source project called MacGap, you can use HTA for Windows, and it’s not hard to write a HTML/Web View wrapper for any platform. It’s even been reported that you are going to be able to write apps for Windows 8 purely using HTML & JS, and you would be able to repurpose your code for this as well.
You can check out the AIR version of the US Census Browser at:
While looking at the analytics for my blog, I’ve recently started to see a lot of search phrases similar to “what is phonegap?”, “how does a phonegap app look?”, “how to get started in phonegap?”, among many, many others. In this post, I hope to shed some light on some basic questions to help you understand and start working with PhoneGap.
In case you don’t feel like reading the whole thing, here are quicklinks to each question:
PhoneGap is an application framework that enables you to build natively installed applications using HTML and JavaScript. The easiest way to think of PhoneGap is a web view container that is 100% width and 100% height, with a JavaScript programming interface that allows you to access underlying operating system features. You build your user interface using traditional web development skills (HTML, CSS, & JavaScript), and use the PhoneGap container to deploy to different application ecosystems and devices. When packaged for deployment, the PhoneGap application is a binary distributable file that can be distributed by the “normal” application marketplaces (iTunes, Google App Market, Amazon Market, etc…).
PhoneGap can be used to build applications that target multiple platforms, including Apple iOS, Google Android, Windows Phone, BlackBerry, HP WebOS, Symbian, and Bada.
Since the UI rendering engine is the mobile device’s web browser, PhoneGap applications can literally look like anything. You can use standard HTML & CSS to make it look like a normal web page, you can use a UI framework like jQuery UI, Kendo UI, Sencha, Twitter Bootstrap, or Skeleton (or any other HTML/CSS/JS user interface framework). You can also use CSS styles/themes to make your web content look like native apps, such as iUI to mimic iOS or Android, or bbUI to mimic BlackBerry.
PhoneGap applications can have static UIs based on normal HTML, or can have dynamic & interactive experiences developed using JavaScript. It depends upon the specific application, user experience design, target audience, and use cases to dictate how a PhoneGap application will appear.
PhoneGap applications can use pinch/zoom gestures to zoom in & out, or you can lock the viewport scale using the viewport metadata tag. You can have the page scroll using normal browser behaviors, or you can use a library like iScroll to enable touch-based scrolling of specific container elements.
There really are lots of ways to create a user interface with HTML, CSS & JavaScript, so there really isn’t any “typical” look. If you do not apply any CSS styles at all, then all user interface elements will use the operating system/browser default for that specific platform. This includes buttons, links, and color/highlight states. This behaves in the exact same manner as the operating system’s default web browser.
How do I get started in PhoneGap?
Getting started in PhoneGap is easy. For 90% of a PhoneGap application, all you need is a text editor. PhoneGap also integrates with device-specific development environments very easily. You can view “getting started” guides for all application platforms at the links below:
When developing PhoneGap applications, just keep in mind that you are running code inside of a web browser instance. You develop your applications using HTML and JavaScript, not native code, so you don’t need anything special. In fact, I personally do most of my development on the desktop using an HTML editor and the Chrome browser. When I need device-specific functionality, or I need to test on a device, then I switch over the the device-specific environments.
How do you debug PhoneGap applications?
Debugging PhoneGap applications can sometimes be the trickiest part of development. If you are testing on a physical device, you can’t always get access to JavaScript exceptions when they happen. There are a few strategies for debugging PhoneGap applications.
Develop as much as possible on the desktop browser
Since PhoneGap applications are written with HTML, CSS, and JavaScript, you can develop most of them using any HTML editor and debug them within a desktop web browser. The latest versions of all major web browsers (including Chrome, IE, Firefox, Opera and Safari) provide rich debugging features. In the developer tools for the browsers, you can inspect HTML DOM elements, inspect CSS styles, set breakpoints in JavaScript, and introspect into memory & JavaScript variables. You can learn more about the desktop browser development tools at:
Once you build the main aspects of your application using desktop tools, you can switch over to a device-specific environment to add device-specific behavior and integrate with PhoneGap APIs.
It is imperative that you test your applications on actual devices! Actual devices will have different runtime performance than desktop browsers and simulators, and may unearth different bugs/issues including API differences and different UX scenarios.
Debug With debug.phonegap.com
PhoneGap provides a hosted service that allows you to perform remote, on-device debugging through debug.phonegap.com. This uses the Weinre (Web Inspector Remote) debugging tool to allow you to remotely inspect the DOM, resource loading, network usage, timeline, and console output. If you have used any of the developer tools listed above, this will look very familiar. You will not be able to set breakpoints on the mobile device, but it is certainly better than nothing at all.
Remote Web Inspector Through iOS 5
There is a little known undocumented API introduced in iOS5 that allows you to perform remote debugging through the iOS5 Simulator. You just need to enable remote debugging
Then launch the application in the desktop iOS Simulator. Once the app is running, open a local Safari instance to: http://localhost:9999/. This will launch the remote debugger, complete with breakpoints and script introspection.
You generally architect PhoneGap applications the same way that you create mobile web experiences. The difference is that the initial HTML assets are available locally, instead of on a remote server. The PhoneGap application loads the initial HTML, which can then request resources from a server, or from the local environment. Since PhoneGap is based in a browser, it behaves exactly as you would expect a web browser to behave. You can load multiple pages; however, keep in mind that once you load/unload a page you may lose any data that is stored in memory via JavaScript. PhoneGap also supports the single-page web experience model. I strongly suggest using the single-page architecture approach.
Single-Page Architecture
A single-page architecture refers to the practice of having a single HTML page that dynamically updates based upon data and/or user input. You can think of this as closer to a true client/server architecture where there is a client application (written with HTML & JS) and a separate server structure for serving data. All client-side application logic resides in JavaScript. The client application may request data and update its views without reloading the current web page.
Using a Single-Page architecture allows you to maintain data in-memory, in JavaScript, which allows you to have a stateful, yet dynamic user interface. You can read more about single-page architectures at: http://en.wikipedia.org/wiki/Single-page_application
How do you get PhoneGap apps on devices and into application ecosystems?
PhoneGap applications can be deployed using the same guidelines for native applications for each given platform. You must follow the rules of each hardware platform/vendor, and there is no way to get around that. You can compile the executables for each platform yourself using each platform’s specific build process, or you can use build.phonegap.com to compile them for you. build.phonegap.com is a hosted service that will compile platform-specific application distributable files for you. In either case, the output of the build process is a platform-specific binary file: IPA for iOS, APK for Android, etc… You can read more about distributing to various application ecosystems, and each system’s signing/certificate requirements at:
The most fundamental differences between PhoneGap and AIR is that you develop AIR applications using tools rooted in the Flash Platform (Flex, Flash, ActionScript, MXML), and you develop PhoneGap applications using HTML, CSS, & JavaScript. AIR applications use the AIR runtime, which allows you to have a single code base, with the exact same expected behavior across all supported platforms. PhoneGap applications run inside of the native web browser component for each supported platform. For this reason, a PhoneGap codebase may behave slightly different between separate platforms, and you will need to account for this during your development efforts.
Air applications can be built for iOS, Android, BlackBerry Playbook, and the desktop (mac and windows), with future support for Windows Metro (Windows 8 mobile interface). You can read more about AIR’s supported platforms at: http://www.adobe.com/products/air/tech-specs.html
PhoneGap applications can be built for iOS, Android, BlackBerry, Windows Phone 7, HP WebOS, Symbian, and Samsung Bada. You can read more about PhoneGap’s supported platforms at: http://phonegap.com/about/features
ActionScript has strongly-typed objects and supports classical inheritance programming models. AIR applications can also be built using the Flex framework, which allows you to rapidly build enterprise-class applications. Components in AIR applications are logical objects that have behaviors, properties, and a graphics context.
JavaScript-based applications support prototypal inheritance, and have numerous open-source frameworks/tools that can be used. HTML/JS applications are all visualized through HTML DOM elements. HTML interfaces can be created through basic string concatenation or JavaScript templating, but in the end you are really just creating DOM elements that have properties and styles.
There are some fundamental difference in the syntax of building these applications, however the basic concepts of interactive design and interactive development are identical. Both platforms have valid strengths, which I could write about ad nauseum… I’ll save that for another post.
Back in the summer, I was lucky enough to get my hands on some early builds of Stage3D for mobile. I built some simple examples, including basic geometric shapes and simple 3D bubble charts inside of mobile Flex/AIR applications. I have been asked numerous times for the source code, and I’ve finally given in, and am sharing some source code.
I am not posting the full mobile application source code, since Stage3D for mobile is not yet available. However, I have ported the 3D bubble chart example to run in a Flex application targeting the desktop (Flash Player 11). The bubble chart example extends the concepts explored in the basic geometric shapes example.
Before you say “shoot, he didn’t give us the mobile code”, let me explain… When I ported the code from the mobile project to the desktop Flex project, all I changed was code specific to the mobile Flex framework. I changed <s:ViewNavigatorapplication> to <s:Application> and the corresponding architecture changes that were required, and I changed the list item renderers to Spark item renderers based on <s:Group> instead of mobile item renderers. In the mobile item renderers, all my drawing logic was done using the ActionScript drawing API. For simplicity in the port, I just used <s:Rect> to add the colored regions in the desktop variant.
That is all I changed!
The stage3D code between the desktop and mobile implementations is identical. You can see the desktop port in action in the video below:
The source code was intended to be exploratory at best… I was simply experimenting with hardware accelerated content, and how it can be used within your applications. There is one big “gotcha” that you will have to watch out for if you want Stage3D content within a Flex application… Stage3D content shows up behind Flex content on the display list. By default, Flex apps have a background color, and they will hide the Stage3D content. If you want to display any Stage3D content within a Flex application (regardless of web, desktop AIR, or mobile), you must set the background alpha of the Flex application to zero (0). Otherwise you will pull out some hair trying to figure out why it doesn’t show up.
The source code for the web/Flex port of this example is available at:
If you have ever tried to develop any kind of application using HTML5 audio that is widely supported, then you have likely pulled all the hair from your head. In its current state, HTML5 Audio is wrought with issues… lack of consistent codec support across browsers & operating systems, no polyphony (a single audio clip can not be played on top of itself), and lack of concurrency (on some of the leading mobile browsers you can only play one audio file at a time, if at all). Even the leading HTML5 games for desktop browsers don’t even use HTML5 audio (they use Flash). Don’t believe me? Just take a look at Angry Birds, Cut the Rope, or Bejeweled in a proxy/resource monitor…
The Problem
You want fast & responsive audio for your mobile applications. This is especially the case for multimedia intensive and/or gaming applications.
HTML5 audio is not *yet* ready for prime-time. There are some great libraries like SoundManager, which can help you try to use HTML5 audio with a failover to Flash, but you are still limited without polyphony or concurrency. In desktop browsers, Flash fixes these issues, and Flash is still vastly superior to HTML5 for audio programming.
If you are building mobile applications, you can have great audio capabilities by developing apps with AIR. However, what if you aren’t using AIR? In native applications, you can access the underlying audio APIs and have complete control.
If you are developing mobile applications with PhoneGap, you can use the Media class, which works great. If you want polyphony, then you will have to do some work managing audio files for yourself, which can get tricky. You can also write native plugins that integrate with the audio APIs for the native operating systems, which is what i will be covering in this post.
Before continuing further, let’s take a minute to understand what I am talking about when I refer to concurrency, polyphony, and low-latency…
Concurrency
Concurrency in audio programming refers to the ability to play multiple audio resources simultaneously. HTML5 in most mobile devices does not support this – not in iOS, not in Android. In fact, HTML5 Audio does not work *at all* in Android 2.x and earlier. Native APIs do support this, and so does PhoneGap’s Media class, which is based on Android MediaPlayer and iOS AVAudioPlayer.
In this case, polyphony is the production of multiple sounds simultaneously (I’m not referring to the concept of polyphany in music theory). In describing concurrency, I refered to the ability to play 2 separate sounds at the same time, where with polyphony I refer to the ability to play the same sound “on top” of itself. There can be multiple “voices” of the same sound. In the most literal of definitions concurrency could be considered a part of polyphony, and polyphony a part of concurrency… Hopefully you get what I’m trying to say. In its current state, HTML5 audio supports neither concurrency or polyphony. The PhoneGap Media class does not support polyphony, however you can probably manage multiple media instances via javascript to achieve polyphonic behavior – this requires additional work in the JavaScript side of things to juggle resources.
Low Latency
Low latency refers to “human-unnoticeable delays between an input being processed and the corresponding output providing real time characteristics” according to wikipedia. In this case, I refer to low latency audio, meaning that there is an imperceptible delay between when a sound is triggered, and when it actually plays. This means that sounds will play when expected, not after a wait. This means a bouncing ball sound should be heard as you see the ball bouncing on the screen. Not after it has already bounced.
In HTML5, you can auto-load a sound so that it is ready when you need it, but don’t expect to play more than one at a time. With the PhoneGap Media class, the audio file isn’t actually requested until you invoke “play”. This occurs inside “startPlaying” on Android, and “play” on iOS. What I wanted was a way to preload the audio so that it is immediately ready for use at the time it is needed.
The Solution
PhoneGap makes it really easy to build natively installed applications using a familiar paradim: HTML & JavaScript. Luckily, PhoneGap also allows you to tie into native code using the native plugin model. This enables you to write your own native code and expose that code to your PhoneGap application via a JavaScript interface… and that is exactly what I did to enable low-latency, concurrent, and polyphonic audio in a PhoneGap experience.
I created PhoneGap native plugins for Android and iOS that allow you to preload audio, and playback that audio quickly, with a very simple to use API. I’ll get into details how this works further in the post, but you can get a pretty good idea of what I mean by viewing the following two videos.
The first is a basic “Drum Machine”. You just tap the pads to play an audio sample.
The second is a simple user interface that allows you to layer lots of complex audio, mimicking scenarios that may occur within a video gaming context.
Assets used in this example from freesound.org. See README for specific links & attribution.
You may have noticed a slight delay in this second video between the tap and the actual sounds. This is because I am using “touchStart” events in the first example, and just using a normal <a href=”javascript:foo()”> link in the second. There is always a delay for “normal” links in all multi-touch devices/environments because there has to be time for the device to detect a gesture event. You can bypass this delay in mobile web browsers by using touch events for all input.
Side Note: I have also noticed that touch events are slightly slower to be recognized on Android devices than iOS. My assumption is that this is related to specific device capabilities – this is more noticeable on the Amazon Kindle Fire than the Motorola Atrix. The delay does not appear to be a delay in the actual audio playback.
How it works
The native plugins expose a very simple API for hooking into native Audio capabilities. The basic usage is:
Preload the audio asset
Play the audio asset
When done, unload the audio asset to conserve resources
The basic components of a PhoneGap native plugin are:
A JavaScript interface
Corresponding Native Code classes
You can learn more about getting started with native plugins on the PhoneGap wiki.
Let’s start by examining the native plugin’s JavaScript API. You can see that it just hands off the JavaScript calls to the native layer via PhoneGap:
Next, let’s examine some intricacies of the plugin… One thing to keep in mind is that I do not have callbacks to the phonegap app once a media asset is loaded. If you need “loaded” callbacks, you will need to add those yourself.
preloadFX: function ( id, assetPath, success, fail)
params:
id – string unique ID for the audio file assetPath – the relative path to the audio asset within the www directory success – success callback function fail – error/fail callback function
detail:
The preloadFX function loads an audio file into memory. These are lower-level audio methods and have minimal overhead. These assets should be short (less than 5 seconds). These assets are fully concurrent and polyphonic.
On Android, assets that are loaded using preloadFX are managed/played using the Android SoundPool class. Sound files longer than 5 seconds may have errors including (not playing, clipped content, not looping) – all will fail silently on the device (debug output will be visible if connected to debugger).
On iOS, assets that are loaded using preloadFX are managed/played using System Sound Services from the AudioToolbox framework. Audio loaded using this function is played using AudioServicesPlaySystemSound. These assets should be short, and are not intended to be looped or stopped.
preloadAudio: function ( id, assetPath, voices, success, fail)
params:
id – string unique ID for the audio file assetPath – the relative path to the audio asset within the www directory voices – the number of polyphonic voices available success – success callback function fail – error/fail callback function
detail:
The preloadAudio function loads an audio file into memory. These have more overhead than assets laoded via preloadFX, and can be looped/stopped. By default, there is a single “voice” – only one instance that will be stopped & restarted when you hit play. If there are multiple voices (number greater than 0), it will cycle through voices to play overlapping audio. You must specify multiple voices to have polyphonic audio – keep in mind, this takes up more device resources.
On Android, assets that are loaded using preloadAudio are managed/played using the Android MediaPlayer.
On iOS, assets that are loaded using preloadAudio are managed/played using AVAudioPlayer.
play: function (id, success, fail)
params:
id – string unique ID for the audio file success – success callback function fail – error/fail callback function
detail:
Plays an audio asset. You only need to pass the audio ID, and the native plugin will determine the type of asset and play it.
loop: function (id, success, fail)
params:
id – string unique ID for the audio file success – success callback function fail – error/fail callback function
detail:
Loops an audio asset infinitely. On iOS, this only works for assets loaded via preloadAudio. This works for all asset types for Android, however it is recommended to keep usage consistent between platforms.
stop: function (id, success, fail)
params:
id – string unique ID for the audio file success – success callback function fail – error/fail callback function
detail:
Stops an audio file. On iOS, this only works for assets loaded via preloadAudio. This works for all asset types for Android, however it is recommended to keep usage consistent between platforms.
unload: function (id, success, fail)
params:
id – string unique ID for the audio file success – success callback function fail – error/fail callback function
detail:
Unloads an audio file from memory. DO NOT FORGET THIS! Otherwise, you will cause memory leaks.
I’m not just doing this for myself, the audio is completely open source for you to take advantage of as well. You can download the full code, as well as all examples from github at github:
Recently I’ve been spending a fair amount of time working on HTML-based applications – both mobile web and mobile applications using PhoneGap. Regardless of whether you are targeting a mobile web browser or a mobile app using the PhoneGap container, you are still targeting a mobile web browser instance. If you haven’t noticed, mobile web browsers can often have peculiarities with how content is rendered, or how you interact with that content. This happens regardless of platform – iOS, Android, BlackBerry, etc… All have quirks. Here are a few tips that I have found useful for improving overall interaction and mobile HTML experiences.
Disclaimer: I’ve been targeting iOS and Android primarily, with BlackBerry support on some applications. I don’t have a Windows Phone device to test with, so I can’t comment on support for the Windows platform.
AutoCorrect and AutoCapitalize
First things first: autocorrect and autocapitalize on Apple’s iOS can sometimes drive you to the brink of insanity. This is especially the case if you have a text input where you are typing in a username, and it keeps “correcting” it for you (next thing you know, you are locked out of the app). You can disable these features in web experiences by setting the “autocorrect” and “autocapitalize” attributes of an <input> instance.
Have you ever experienced an an app or web site on a mobile device where you have to enter numeric data, and the default keyboard pops up. Before entering any text, you have you switch to the numeric input. Repeat that for 100 form inputs, and try to tell me that you aren’t frustrated… Luckily, you can manage the keyboard in mobile HTML experiences very easily using HTML5 Form elements.
One way to easily determine that an application is really HTML is that everything on the UI is selectable and can be copied/pasted – Every single piece of text, every image, every link, etc… Not only is this annoying in some scenarios (and very useful in others), but there may be instances where you explicitly don’t want the user to be able to easily copy/paste content. You can disable user selection by applying the following CSS styles. Note: This works on iOS, and partially works on BlackBerry/QNX for the PlayBook. It did not work on Android in my testing.
The -webkit-touch-callout css rule disables the callout, and the -webkit-user-select rule disables the ability to select content within an element. More details on webkit css rules from the Mobile Safari CSS Reference. More detail about disabling copy/paste on iOS is available at StackOverflow.com.
Disable Zoom
If you want your content to feel like an app instead of a web page, then I strongly suggest that you disable gestures for pinch/zoom and panning for all use cases where pinch/zoom is not required. The easiest way to do this is to set the viewport size to device-width and and disable user scaling through the HTML metadata tag.
This technique works on both Android and iOS devices, and I assume other platforms. However, I don’t have the devices to test all of them.
Touch Based Scrolling
Touch-based scrolling is critical to having an application that feels native. I dont mean that the whole page should be able to scroll… Your browser will be able to take care of that alone. Instead I mean that you should be able to scroll individual elements so that they mimic clipped views, lists, or large blocks of content. You should be able to scroll content where it is, and not have to scroll an entire page to reveal something in only one area of the screen. You should minimize scrolling when it may cause poor UX scenarios. This is especially the case in tablet-based applications which have a larger UI than phone-based applications.
“Click” events on HTML elements on mobile devices generally have a delay that is caused by the operating system logic used to capture gestural input based on touch events. Depending on the device, this could be 300-500 MS. While this doesn’t sound like much, it is very noticeable. The workaround is to use touch events instead of mouse events: touchStart, touchMove, touchEnd. You can learn more about touch events from html5rocks.com. There’s also a great script from cubiq that adds touch events for you to optimize the experience for onClick event handlers on iOS devices.
Add To Home Screen
If you want your web app to fee like a real app and take up the full screen without using PhoneGap as an application container, then you can always add it to the device’s home screen. Although this can only be done manually through the mobile browser, there are a few open source scripts to guide the user through this processs: cubiq.org or mobile-bookmark-bubble should get you started.
Use Hardware Acceleration
Animations will generally be smoother and faster if your content is hardware accelerated (and the device supports hardware acceleration). You can make html elements hardware accelerated just by adding the translate3d(x,y,z) css style to the element (be sure to set all three x, y, and z attributes otherwise hardware acceleration may not be applied. If you don’t want any translation changes, you can use the translate3d CSS rule with all zero values: translate3d(0,0,0).
In your development/testing, you can even visualize which content is hardware accelerated in both desktop and mobile Safari using the technique shown at http://mir.aculo.us/.
Make You Apps Fast
Last, but certainly not least, make your apps fast. Follow best practices, and be efficient in code execution and the loading of assets (both local and remote). Here are a few links to get you going in the right direction:
I hope these get you moving in the right direction! If you have read this, and aren’t sure what it all means, check out the Adobe Developer Connection to ramp up on HTML5, or theexpressiveweb.com to see what HTML5 & CSS3 can do.
Did you know that apps built on top of iOS can have a multi-screen workflow? For example in Keynote, you can have an external screen show a presentation while you control it on your iOS device. In the Jimi Hendrix app, you can view the audio player on an external screen, and in Real Racing HD, you can view the game on an external screen while the iOS device becomes your controller. (among others)
Real Racing HD
This is all made possible by the UIWindow and UIScreen APIs in iOS. Even better, on the iPad 2 and iPhone 4Gs, this can be done wirelessly using Airplay with an Apple TV device. On other iOS devices, you can have a second screen using a VGA output.
One of the benefits of using a cross platform solution like PhoneGap or Flex/Air is that you can build apps with an easier to use/more familiar paradigm. However, cross platform runtimes don’t always offer access to every API feature that native development enables.
Out of the box, PhoneGap apps are confined to a single screen. You can use screen mirroring to mirror content on an external screen, but you can’t have a second screen experience. It’s a good thing you can write native plugins/extensions to enable native functionality within your applications.
ExternalScreen Native Plugin For PhoneGap
I recently did exactly that… I created a PhoneGap native plugin that enables second screen capability for PhoneGap applications. The plugin listens for external screen connection notifications, and if an additional screen is available, it creates a new UIWebView for HTML-based content in the external screen – complete with functions for injecting HTML, JavaScript, or URL locations.
Why?
You might be wondering “Why?” you would want this plugin within PhoneGap… this plugin enables the multi-screen experiences described in the apps mentioned above. They extend the interactions and capabilities of the mobile hardware. With this PhoneGap native plugin, you can create rich multi-screen experiences with the ease of HTML and JavaScript. Here are a few ideas of the types of apps that you can build with this approach (scroll down for source code):
Fleet Manager
Let’s first consider a simple Fleet Manager application which allows you monitor vehicles in a mobile app. This is a similar concept which I’ve used in previous examples. The basic functionality allows you to see information on the tablet regarding your fleet. What if this app connected to a larger screen and was able to display information about your vehicles for everyone to see? Watch the video below to see this in real life.
This application example is powered by Google Maps, and all of the data is randomly generated on the client.
Law Enforcement
Let’s next consider a mobile law enforcement application application which gives you details to aid in investigations and apprehension of criminals. Let’s pretend that you are a detective who is searching for a fugitive, and you walk into a crowded bar near the last known location of that fugitive. You connect to the bar’s Apple TV on their big screen TV, pull up images and videos of the suspect, then say “Have you seen this person?”. This could be incredibly powerful. Check out the video below to see a prototype in real life.
This law enforcement demo scenario is a basic application powered by the FBI’s most wanted RSS data feeds.
Tip Of The Iceberg
There are lots of use cases where a second screen experience could be beneficial and create a superior product or application. Using PhoneGap allows you to build those apps faster & with the ease of HTML and JavaScript, using traditional web development paradigms.
The PhoneGap native plugin is written in Objective C, with a JavaScript interface to integrate with the client application. PhoneGap plugins are actually very easy to develop. Basically, you have to write the native code class, write a corresponding JS interface, and add a mapping in your PhoneGap.plist file to expose the new functionality through PhoneGap. There is a great reference on the PhoneGap wiki for native plugins which includes architecture & structure, as well as platform specific authoring and installation of those plugins. Here are quick links to the iOS-specific native plugin content authoring and installation.
The ExternalScreen plugin creates a UIWebView for the the external screen, and exposes methods for interacting with the UIWebView. Note: This is just a normal UIWebView, it does not have support for all PhoneGap libraries… just a standard HTML container.
You can read up on multi-screen programming at iOS from these useful tutorials:
The header file shows the method signatures for the native functionality. The corresponding PGExternalScreen.m contains all of the actual code to make it all work. Note: If you are using ARC (Automatic Reference Counting), you will need to remove the retain/release calls in PGExternalScreen.m.
The PGExternalScreen.js file defines the native methods that are exposed through PhoneGap. You invoke the function, and can add success/fail callback function references.
You can call any of these functions from within your PhoneGap application’s JavaScript just by referencing the exposed method on the PGExternalScreen instance.
// check if an external screen is available
PGExternalScreen.checkExternalScreenAvailable( resultHandler, errorHandler );
//load a local HTML resource
PGExternalScreen.loadHTMLResource( 'secondary.html', resultHandler, errorHandler );
//load a remote HTML resource (requires the URL to be white-listed in PhoneGap)
PGExternalScreen.loadHTMLResource( 'http://www.tricedesigns.com', resultHandler, errorHandler );
//load a HTML string
PGExternalScreen.loadHTML('</pre>
<h1>HTML</h1>
<pre>this is html content', resultHandler, errorHandler );
//invoke a JavaScript (passed as a string)
PGExternalScreen.invokeJavaScript('document.write(\'hello world\')', resultHandler, errorHandler );
The full code for the ExternalScreen PhoneGap native plugin, as well as both client applications and a basic usage example is available on github at:
In a previous post on capturing user signatures in mobile applications, I explored how you capture user input from mouse or touch events and visualize that in a HTML5 Canvas. Inspired by activities with my daughter, I decided to take this signature capture component and make it a bit more fun & exciting. My daughter and I often draw and sketch together… whether its a magnetic sketching toy, doodling on the iPad, or using a crayon and a placemat at a local pizza joint, there is always something to draw. (Note: I never said I was actually good at drawing.)
Olivia & the iPad
You can take that exact same signature capture example, make the canvas bigger, and then combine it with a tablet and a stylus, and you’ve got a decent sketching application. However, after doodling a bit you will quickly notice that your sketches leave something to be desired. When you are drawing on a canvas using moveTo(x,y) and lineTo(x,y), you are somewhat limited in what you can do. You have lines which can have consisten thickness, color, and opacity. You can adjust these, however in the end, they are only lines.
If you switch your approach away from moveTo and lineTo, then things can get interesting with a minimal amount of changes. You can use images to create “brushes” for drawing strokes in a HTML5 canvas element and add a lot of style and depth to your sketched content. This is an approach that I’ve adapted to JavaScript from some OpenGL drawing applications that I’ve worked on in the past. Take a look at the video below to get an idea what I mean.
Examining the sketches side by side, it is easy to see the difference that this makes. The variances in stroke thickness, opacity & angle add depth and style, and provide the appearance of drawing with a magic marker.
Sketches Side By Side
It’s hard to see the subtleties in this image, so feel free to try out the apps on your own using an iPad or in a HTML5 Canvas-capable browser:
Just click/touch and drag in the gray rectangle area to start drawing.
Now, let’s examine how it all works. Both approaches use basic drawing techniques within the HTML5 Canvas element. If you aren’t familiar with the HTML5 Canvas, you can quickly get up to speed from the tutorials from Mozilla.
moveTo, lineTo
The first technique uses the canvas’s drawing context moveTo(x,y) and lineTo(x,y) to draw line segments that correspond to the mouse/touch coordinates. Think of this as playing “connect the dots” and drawing a solid line between two points.
The code for this approach will look something like the following:
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
context.beginPath();
context.moveTo(a.x, a.y);
context.lineTo(b.x, b.y);
context.lineTo(c.x, c.y);
context.closePath();
context.stroke();
The sample output will be a line from point A, to point B, to point C:
lineTo(x,y) Stroke Sample
Brush Images
The technique for using brush images is identical in concept to the previous example – you are drawing a line from point A to point B. However, rather than using the built-in drawing APIs, you are programmatically repeating an image (the brush) from point A to point B.
First, take a look at the brush image shown below at 400% of the actual scale. It is a simple image that is a diagonal shape that is thicker and more opaque on the left side. By itself, this will just be a mark on the canvas.
Brush Image (400% scale)
When you repeat this image from point A to point B, you will get a “solid” line. However the opacity and thickness will vary depending upon the angle of the stroke. Take a look at the sample below (approximated, and zoomed).
Brush Stroke Sample (simulated)
The question is… how do you actually do this in JavaScript code?
First, create an Image instance to be used as the brush source.
brush = new Image();
brush.src = 'assets/brush2.png';
Once the image is loaded, the image can be drawn into the canvas’ context using the drawImage() function. The trick here is that you will need to use some trigonometry to determine how to repeat the image. In this case, you can calculate the angle and distance from the start point to the end point. Then, repeat the image based on that distance and angle.
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var halfBrushW = brush.width/2;
var halfBrushH = brush.height/2;
var start = { x:0, y:0 };
var end = { x:200, y:200 };
var distance = parseInt( Trig.distanceBetween2Points( start, end ) );
var angle = Trig.angleBetween2Points( start, end );
var x,y;
for ( var z=0; (z<=distance || z==0); z++ ) {
x = start.x + (Math.sin(angle) * z) - halfBrushW;
y = start.y + (Math.cos(angle) * z) - halfBrushH;
context.drawImage(this.brush, x, y);
}
For the trigonometry functions, I have a simple utility class to calculate the distance between two points, and the angle between two points. This is all based upon the good old Pythagorean theorem.
var Trig = {
distanceBetween2Points: function ( point1, point2 ) {
var dx = point2.x - point1.x;
var dy = point2.y - point1.y;
return Math.sqrt( Math.pow( dx, 2 ) + Math.pow( dy, 2 ) );
},
angleBetween2Points: function ( point1, point2 ) {
var dx = point2.x - point1.x;
var dy = point2.y - point1.y;
return Math.atan2( dx, dy );
}
}
The full source for both of these examples is available on github at:
This example uses the twitter bootstrap UI framework, jQuery, and Modernizr. Both the lineTo.html and brush.html apps use the exact same code, which just uses a separate rendering function based upon the use case. Feel free to try out the apps on your own using an iPad or in a HTML5 Canvas-capable browser:
Here are some interesting and quite surprising statistics for the US Census Browser HTML/PhoneGap showcase application that I released in December, which I wanted to share. The app is a browser for US Census data, full detail available here: http://www.tricedesigns.com/2010-census/. The Census Browser application was intended as a showcase app for enterprise-class data visualization in HTML-based applications, and all source code is freely available to the public.
What is really surprising is the “health” of my app within the given ecosystems. I offered the app as a free download in each market. The app is focused on Census data, so there is obviously not a ton of consumer demand, however the data is still interesting to play around with. I would not expect the same results for all types of apps in all markets.
Here are a few observations from the data:
Barnes & Noble Nook downloads far exceeded all other markets combined (69% of all downloads)
BlackBerry Playbook downloads were in 3rd, just behind iOS (BB is 11% of all downloads)
Android traffic was minimal (2% of all downloads)
The general public perception/assumption that I encounter is that the iOS market is strongest, followed by Android, and that BB is dead. These numbers show a conflicting reality. Barnes & Noble was the strongest, with iOS in second place, and BlackBerry just behind iOS.
iOS traffic peaked just after the inital release with an increase after the winter holidays, but has been more-or-less consistent with no “spike”:
Amazon Market only had 8 downloads on Christmas day – this is likely the result of the fact that the Kindle Fire is branded as a consumer media device, not an analytics/computing device:
Know what else is interesting? The charting/analytics for Amazon, Google, and Nook markets are all built with Adobe Flash, with both Amazon and Nook built using Adobe Flex.
I’d like to take this opportunity to introduce you to a new project I’ve been working on to showcase enterprise-class data visualization in HTML-based applications. The US Census Browser is an open source application for browsing data from the 2010 US Census.
The app is completely written using HTML and JavaScript, even for the charting/data visualization components. You can check it out in several application ecosystems today:
Support for additional platforms is planned for future development. Future targets include BlackBerry Playbook as well as Android 2.x devices, including the Amazon Kindle Fire and Barnes & Noble Nook Color – Android 2.x does not support SVG graphics in-browser, so I am working on some alternative features.
Update: Kindle Fire and Playbook have been approved, and are now supported. See links above.
Please keep in mind that this application was designed for mobile devices. Internet Explorer in particular does not work well with the Census Browser – use at your own risk. The browser-based application has been tested and works properly in the latest versions of Chrome, Safari, Firefox, and Opera. The US Census Browser application also does not work in Android 2.x and below, due to the fact that these versions of Android do not support SVG graphics in the mobile browser.
APPLICATION OVERVIEW
The application is essentially a single-page web site, which asynchronously loads data from the backend upon request, and displays that data to the user. The main application file is index.html, which loads the UI and appropriate client-side scripts. The main presentation logic is applied via CSS stylesheets, and the application control is handled by the ApplicationController class, inside of application.js. The ApplicationController class handles state changes within the application and updates the UI accordingly. The main data visualization and data formatting logic is all contained within the censusVisualizer class, which the ApplicationController class uses to render content. All DOM manipulation, event handling, and AJAX requests are performed using jQuery.
The data visualization is implemented 100% client-side, using the Highcharts JavaScript library. Highcharts renders vector graphics client-side, based upon the data that is passed into it. Check out the examples at: http://www.highcharts.com/demo/ for a sample of what it is capable of.
The fluid scrolling and swiping between views is implemented using the iScroll JavaScript library. Note: I’m using iScroll-lite.js. This is a great resource for any HTML-mobile, or mobile-web applications.
PHONEGAP USAGE
The client-side runtime does not have any dependencies for access to device-specific functionality. However, PhoneGap is being used as an application container so that the application can be distributed through various mobile “app stores”.
SERVER-SIDE
The back-end of this application is written using ColdFusion. Yep, that’s right. I used CF. In fact, the server side is ridiculously simple. It is only a single ColdFusion Component (CFC), with three remotely exposed methods for accessing data, and relies upon CF’s built in functionality to serialize JSON. CF is incredibly powerful, and made this project very simple and quick to develop.
Tomorrow (Thurs) I'm presenting an "Introduction to Mobile Development with PhoneGap" at Towson University http://t.co/Qch6pD93 Come on out! 3 hours ago
Recent Comments