For anyone who’s developed exclusively with UIViews on iOS may take the title of this post a bit oddly. “WHAT?!” they might say, “Are you insane? Core Graphics is not only a C-only API, but has confusing function names, and needs way more code to do the same thing I can do in less code in UIView”.  Yes, they might be right, but there’s a reason why Core Graphics exists. It’s FAST!

But using Core Graphics doesn’t mean that your code has to be confusing, or that you have to compromise flexibility for performance. You can have your cake and eat it too (aka you can have high-performing code that is easy to read). Read on to see what I mean.
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One of my pet peeves is Open Source iOS libraries distributed as just a collection of Objective-C classes, rather than being bundled as a static library. I know a lot of people prefer it that way, but from a maintainability standpoint it really doesn’t make much sense to me. So when I’m faced with another library I want to use that doesn’t have a static library readily available for it, I typically wrap it up in my own Xcode project, check it in to Github, and configure my Jenkins continuous integration build server to compile it for me.

I thought I’d walk you through the steps I go through to make this happen, so you can use this technique too. (more…)

With iOS 4.0 Apple introduced two new technologies to the iOS platform: Grand Central Dispatch, and blocks.  Simply put, it is to multi-threaded programming what fire is to a barbecue.  Sure you can do without it, but the end result is much better.

Despite all this, developers still seem to avoid using it. Some of the reasons for this, off the top of my head, could be backwards-compatibility for older versions of iOS, unfamiliarity with the funky syntax it uses, or simply a lack of practice.  The biggest thing I find however is a general misunderstanding about the importance of multi-threading among new developers, which was made worse by the difficulty of dealing with threads before blocks and GCD was released.

Fortunately there’s no reason to avoid multi-threaded programming in iOS, but before I dive into the specifics I’d like to point out just how important it is to use an asynchronous approach to development on iOS, or any mobile platform in general.
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One of the things I like most about Apple’s iOS SDK is the consistent and easy-to-use API they provide.  Across all their different frameworks there’s a pattern at work that makes using their classes easy to understand.  This is due in part to the simplicity for configuring those objects.  In most cases you don’t need to call cryptic methods to setup or teardown classes.  If you want to change a label’s font, you just set a property.  If you want to add a new set of tabs to a UITabBarController, you simply have to assign an array of view controllers to the “viewControllers” property and away you go.
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Following up on my previous post in this series, I’m going to continue talking about beginner topics that I and many other developers take for granted. So for this entry in my “Back To Basics” series I’d like to talk about UITableViews, and how to simply and easily construct one without convoluted or confusing code.

This topic in particular is something I’ve struggled over in the past and never managed to find a clear example for how to get started. Certainly there’s a lot of examples to show how to construct a table view, how to create a datasource for it, and the basics for how to construct cells. But hardly anyone tells you how to easily and conveniently construct a menu of options without going down a maze of twisty passages.

So today I’ll show you how you can use simple “typedef” structures to describe and control a simple menu of options.

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This is the fourth in a series of posts I’m writing on animating iOS interfaces using Core Animation. In the first post I created a planetary orbit demo using nested CALayer objects. The second post showed how to dress up a UI by animating an image. The third post shows how you can trigger animations in response to button actions.

This post will show how you can create the beginnings of a full game using Core Animation combined with CAShapeLayer and UIBezierPath objects.

Read on to see more

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This is the third in a series of posts I’m writing on animating iOS interfaces using Core Animation. In the first post I created a planetary orbit demo using nested CALayer objects. The second post showed how to dress up a UI by animating an image.

This time I’ll show how you can trigger animations in response to button actions to illustrate to the user that an action is taking place.

Read on to see more

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This is the second in a series of posts I’m writing on animating iOS interfaces using Core Animation. In the previous post I created a planetary orbit demo using nested CALayer objects.

This time I’m going to show how you can dress up a UI by creating a simple effect using an image and Core Animation.

Read on to see more

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One of the greatest things about the iOS platform and applications people see on it is its beauty. Smooth gradients, consistent transitions, and animations that illustrate the transition of UI elements from one state to another. Animations are more than flashy eye-candy; they tell the user what’s happening. If an element is being deleted, instead of it simply disappearing it fades or slides out of view. Unlike traditional desktop or web applications where a “2 items deleted” statusbar message is necessary, these animations are in many cases enough.

Knowing where to start with animations can be a problem for developers though, because there’s many different steps involved. Instead of walking you through it fully here in the blog, I highly recommend you watch the WWDC 2010 videos on the topic. I truly mean it; anything I do here will simply be a rehash of that material, and I don’t see the point in reproducing perfectly good documentation unnecessarily.

• WWDC 2010 Session 123 – Building Animation Driven Interfaces
• WWDC 2010 Session 424 – Core Animation in Practice, Part 1
• WWDC 2010 Session 425 – Core Animation in Practice, Part 2

Read on to see more

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Shadowed view using a rectangular shadowPath

I recently had to improve the performance of a few views that utilized CALayer-based shadows on rounded-rect UIView objects. On this particular iPad application, when the device was rotated, the views rotated quite a lot slower than we would have hoped. It wasn’t a show-stopper, but the jerky rotation animation made it look cheap and unpolished. The easiest way to have our cake, and eat it too, was to set a custom CGPath to the layer’s shadowPath property. This told UIKit to set the inside of the path to opaque, reducing the amount of work the rendering engine needed to perform.

// Add background tile
UIImage *bgImage = [UIImage imageNamed:@"embedded_bg.png"];
self.view.backgroundColor = [UIColor colorWithPatternImage:bgImage];
// Add the reference view
UIImage *image = [UIImage imageNamed:@"dccp.jpeg"];
UIImageView *imgView = [[UIImageView alloc] initWithImage:image];
[self.view addSubview:imgView];
imgView.center = self.view.center;
imgView.layer.shadowColor = [UIColor blackColor].CGColor;
imgView.layer.shadowOpacity = 0.7f;
imgView.layer.shadowOffset = CGSizeMake(10.0f, 10.0f);
imgView.layer.shadowRadius = 5.0f;
imgView.layer.masksToBounds = NO;
UIBezierPath *path = [UIBezierPath bezierPathWithRect:imgView.bounds];
imgView.layer.shadowPath = path.CGPath;
[imgView release];

The resulting image, as you can see above, has a shadow as you’d expect. But since we’ve declared the shape the path will have, the iPad can drastically improve its rendering performance.

Through that process however, I decided to see what sort of effects I could pull off by passing in a path other than the default rectangular bounds of the layer. Since you can create any sort of path you want, I considered the different effects I could get away with by making non-rectangular paths and using them as shadows. (more…)