- (void)webViewDidFinishLoad:(UIWebView *)webView is slow. “You’re running an interpreter (JavaScript runtime) on top of a device with a small CPU and small memory. Go figure.”
The JavaScript bridge does not appear to block the main thread. This is a good/bad thing. You can invoke JavaScript code within the WebKit via your native Objective-C code.
The JavaScript bridge is one directional. From Objective-C/UIKit you can invoke JavaScript upon the WebKit and henceforth do wonderful things
Multiple languages in one project. Whilst we mainly just wanted to take a static HTML file, and dynamically update various elements with application data (e.g. the surf and weather conditions in the example above), we needed to do that via JavaScript.
Why you may want to do it
WebKit for rapid prototyping: WebKit exists and it is awesome at rendering HTML and CSS, with access to the powerful CSS3 transformations and webkit-specific bonus features.
It is highly likely that your designer can make something beautiful looking in Photoshop and cut it up into HTML + CSS. Comparatively, its highly unlikely they can cut it up into native Objective-C code.
WebKit isn’t the holy grail for non-Objective-C developers, but if your grand-poobar level skills are in JavaScript and HTML, and your Objective-C/iPhone skills are still catching up, then its a wonderful prototyping platform. Especially for static, complicated displays of data. Especially if that data includes HTML content from an external feed which needs to be rendered.
For Oakley’s Surf Report app, Anthony is toying with replacing some of the WebKit usage with native UI elements (normal UITableView with custom UITableViewCells) so that we can get back those precious seconds and give them to the user as a Christmas present.
We’ve talked a bit about Apple’s extensions to HTML and CSS; <canvas> has of course gone on to much fame and fortune. Charles Ying pointed us to his CSS-VFX project which aims to be
a collection of components and code examples that illustrate the power of CSS Visual Effects. So far, only 1 gem that illustrates a popular RIA user interface demo, “Cover Flow” is currently available. If you’d like to see more, please don’t hesitate to suggest something you’d like to see.
Charles has a blog entry with a video showing off a mobile Safari demo of using Apple’s CSS Visual Effects to create a Cover Flow interface:
The demo makes use of a variety of these extensions:
* zflow starts by loading each image from the images array. When each image is loaded, we scale the image to fit in a square region, and apply 3D CSS transforms to scale it in place.
* Reflections - zflow then takes the scaled image and creates a Canvas element that contains a gradient alpha mask of the image’s reflection (using a “reflect” function to do this) and positions the canvas element in place.
* Touch Controller - zflow creates a TouchController object, who’s job is to field touch events from Mobile Safari and calculate an appropriate offset.
* Clicking - zflow detects when no move events have been made, and zooms + rotates the focused image forward by setting a “CSS Transition”ed 3D transform on the focused image. Clicking again transitions the image back.
* Inertia - zflow achieves inertia by setting the “transition timing function” of the “tray” to an “ease-out” function, which slows things down. On the touch end event, we calculate the projected velocity and set the tray’s target position to that location. CSS Transitions handles the decay in velocity as the transition timing function executes — slowing the tray down gradually.
It makes you wonder how many folks are going to need to learn the SDK in the future…
Now that the NDA has been released, book publishers are finally able to get out their wares. Christopher Allen and Shannon Appelcline have written iPhone in Action, and have kindly given the Ajaxian community free downloads of a couple of the early access chapters:
I hope to see books that focus on what you can do with the Web APIs too of course ;)
This article is based on iPhone in Action, to be published January 2009. It is being reproduced here by permission from Manning Publications. Manning early access books and ebooks are sold exclusively through Manning. Visit the book’s page for more information.
I am so happy that the NDA mess is over! Clancy has written about how you can have your iPhone Web app run in full screen and has a demo app that shows it off:
Ben Putman has put together a nice iPhone Safari 3D navigation menu example that shows off the transforms and events available on the latest mobile Safari.
Ben told us:
In thinking of an interesting test, I've created a menu that you can rotate across a fixed y-axis with touch, allowing you to spin the menu around and see the depth and back of elements. There are also some examples of how animations can be used as you click and the menu unfolds. I also added a lightbox to examine how one might view some photos although it's not really practical in this form.
Open up the demo in your iPhone / Touch and also take a peak at the source to see what is going on, with snippets like this:
Dave Johnson calls PhoneGap "AIR for the iPhone" because this nice little hack, first created at an iPhone BarCamp, wraps the Web view with a container. This container gives the view access to APIs available on the device, that may not be available yet via WebKit alone. AIR provides a similar container for Flash and Ajax content on the desktop.
PhoneGap is a free open source development tool and framework that allows web developers to take advantage of the powerful features in the iPhone SDK from HTML and JavaScript. We're trying to make iPhone app development easy and open. For many applications a web application is the way to but in Safari you don't get access to the native iPhone APIs, and the that's the problem we're trying to solve.
It is written in Objective-C and allows developers to embed their web app (HTML, JavaScript, CSS) in Webkit within a native iPhone app. We're big advocates of the Open Web and want JavaScript developers to be able to get access iPhone features such as a spring board icon, background processing, push, geo location, camera, local sqlLite and accelerometers without the burden of learning Objective-C and Cocoa.
PhoneGap also has a web app that allows web developers to quickly package their web app into a native iPhone app by providing a URL, a name and icon graphic the web service with automagically create a native iPhone application. We haven't open sourced that code but we're going to soon.
PhoneGap was conceived at iPhoneDevCamp II by Nitobi developer Brock Whitten, Rob Ellis, freelance designer Colin Toomey and Eric Oesterle.
There are a few APIs available now, and others pending:
Dylan Schiemann wrote about how disappointing it was that the iPhone didn't support SVG:
Safari on the iPhone does not currently have support for SVG. Safari 3 beta on Mac and Windows is currently the best browser on the planet for SVG performance, so this is a somewhat disappointing omission. We are hopeful that by the end of the year, the iPhone will receive the Safari 3 upgrade, and along with that native support for SVG. For now, we’ll have to wait on dynamic charting and drawing tools due to no SVG and the lack of mousemove event handlers.
It appears that if you point your iPhone 2.1 browser to SVG content and tests it now works!
iPhone apps get a lot of attention and press and understandably so. For a lot of iPhone app developers, these tiny apps can turn into a tremendous cash cow making development for the phone platform invaluable. But considering that the iPhone is running Safari on it, it's surprising that we haven't seen a whole lot more buzz surrounding the use of the new Webkit functionality available to the browser.
So I wasn’t content with the things I’ve tried doing in Safari, and recently began digging through the documentation of the iPhone SDK and the actual CSS Transforms spec.
I was a bit skeptical when I first read about all the cool functions that work in Webkit iPhone, but nowhere else, because there was little documentation, and literally nothing done by other developers, no demos, no tests. I thought, surely, some students with too much free time must have jumped on that immediately?
Seems like Paul was on the right track as finding information on taking advantage of there features for the iPhone was scarce. So by using a iPhone simulator, Paul was able to start hacking at some of the built-in Webkit features, especially the 2D CSS Transforms.
Here comes the cool stuff: The perspective function seems to define how the other primitive functions behave.
Let’s have a look at a practical example: Take a look at the following three functions:
* rotateX - Rotates the element on the X axis.
* rotateY - Rotates the element on the Y axis.
* rotateZ - Rotates the element on the Z axis (By default, same as “rotate”)
Try these out - all three will give you flat, 2d animations, although they are, in fact, functions that use a 3D matrix. However, now change the -webkit-perspective property to 200, and try again. Now, you established virtual depth, and all three functions will give you incredible results.
The end result of Paul's tinkering is a very cool flip effect that is handled within the iPhone's browser and similar to that found in typical iPhone applications. While only a small demo, this opens up possibilities in how browser-based applications can react within the iPhone and what can be presented to mobile web users.
To see the demo, you will need an iPhone or an iPhone simulator.
What about iPhone limits though? David Golightly tests the limits on the iPhone with a script that keeps downloading tiles until it can no longer do so:
After downloading about 210 images, the iPhone simply stops downloading new ones. This is probably due to hitting the hard 30MB same-page resource limit.
Matthew Congrove took some time to play with the iPhone SDK, but it wasn't his bag, so he decided to go back to building a Web application for the iPhone, and was pleasantly surprised with the updates to Safari that enabled new things:
In the midst of all my research for help I stumbled across something that I, like most, had completely forgotten about; the iPhone update wasn't just for native third-party applications, but it also upgraded the existing applications. Yes, that includes Safari. The upgrade for the iPhone's on-board browser added in support for CSS animations and transitions, a JavaScript accessible database, a few new DOM selectors and more. For me this meant that the myDailyPhoto web application could look and feel more like it was a native Cocoa Touch enabled experience. As soon as the idea crossed my mind I sat down to churn out this little test app.
To get the flick effect Matthew wrote the following CSS:
