A trick for capturing all touch input for the duration of a touch

If you’ve ever tried to implement an interactive control that makes use of gestures within a UITableView, or tried to implement a view that you can drag around, like pins on a MKMapView, you’ll know that you’re either generally thwarted by the scroll view (and the table view will just scroll, instead of your control getting the vertical drag gesture), or as soon as the touch moves outside the bounds of your view, you’ll get no more touchesMoved events, making for a very frustrating dragging interaction.

Some platforms give you a way to capture all pointer input for a time, but this doesn’t appear to be available out of the box on the iPhone — at least, I haven’t found it.

Here’s a way to make it work:

  • Subclass UIWindow and replace sendEvent: with your own method
  • Provide a way for objects to be registered with your UIWindow subclass to gain ‘touch priority’ – either add a property that taken a UIView/UIResponder, or add a mutable array to be able to register multiple views.
  • When you receive a touch began event, check to see if the touch was within the bounds of any ‘priority’ views – if they are, the view subsequently gets all events until the touch ended event.
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iPhone/Mac animation for custom classes: Property animation for more than just CALayer

I recently wrote a custom view — a 3D vintage-looking pull lever — that provided a continuous property to control the state. I wanted to animated this smoothly, a-la CABasicAnimation, but couldn’t find a built-in way to do so.

So, I wrote a class that provides similar functionality to CABasicAnimation, but works on any object. I thought I’d share it.

Features:

  • From/to value settings (currently only supports NSNumber and scalar numeric types, but easily extendable)
  • Duration, delay settings
  • Timing functions: Linear, ease out, ease in, and ease in/ease out
  • Animation chaining (specify another configured animation for chainedAnimation, and it’ll be fired once the first animation completes)
  • Delegate notification of animation completion
  • Uses a single timer for smooth lock-step animation
  • Uses CADisplayLink if available, to update in sync with screen updates

Use it like this:

- (void)startMyAnimation {
  TPPropertyAnimation *animation = [TPPropertyAnimation propertyAnimationWithKeyPath:@"state"];
  animation.toValue = [NSNumber numberWithFloat:1.0]; // fromValue is taken from current value if not specified
  animation.duration = 1.0;
  animation.timing = TPPropertyAnimationTimingEaseIn;
  [animation beginWithTarget:self];
}

Make sure you also include the QuartzCore framework, used to access CADisplayLink, if it’s available.

It’s BSD-licensed.

Grab it here:
TPPropertyAnimation.zip

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Links for May 30th through August 8th

Links for May 30th through August 8th:

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Achieve smaller app downloads by replacing large PNGs with JPEG + mask

I’m using a transparent overlay on top of a fairly common interface element to make it look awesome. I originally did this with a transparent PNG, until I realised the PNG in question for the iPhone 4’s Retina display was truly massive, clocking in at 1 Mb.

Why we don’t have common image format with both transparency and lossy compression is beyond me, but there’s a relatively easy alternative: Using a JPEG and masking it with another JPEG.

Based on Rodney Aiglstorfer’s solution on how to mask an image, I derived a category on UIImage which would apply a mask to an image. The method required a little tweaking to work with JPEG images — the CGImageCreateWithMask function won’t work correctly on source images that don’t have an alpha channel, so one has to create one first, from the original. Jean Regisser figured out the solution which he presents in a comment on the above article, but it needs one more addition: A check on line 37 for kCGImageAlphaNoneSkipLast. Update: Oh, and one more – kCGImageAlphaNoneSkipFirst

So, the complete category for applying a mask to a JPEG image, to achieve the same result as using a PNG but with less download time for your users:

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Reginald RegEx explorer

With a desperate need to debug a lengthy regular expression destined for use with the excellent RegexKitLite library, I have quickly put together a Mac OS X application.

Reginald icon
Reginald is a kindly old gentleman devoted to assisting you with those tricky regular expressions.

Provide some sample input, and your regular expression, and Reginald will provide you with colour-coded output and a list of all your matches and the corresponding capture groups for your exploration. Select a match or capture group in the list to the right, and the corresponding text will be selected in the panel to the left.

Reginald is built on RegexKitLite, and so uses the ICU syntax.

It will run on Mac OS X 10.6 and above.

Download Reginald here, or access the source on GitHub.

Reginald screenshot

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Making UIToolbar and UINavigationBar’s background totally transparent

I have an upcoming iPhone application, Cartographer, that is highly stylised and requires high customisation of the interface to achieve a convincing, beautiful vintage look. To make it work, I needed transparent toolbars and navigation bars for my UIViewController-based views.

The solution I came up with for this was to implement a category on UINavigationBar and UIToolbar, and overriding drawRect: with a method that does absolutely nothing. Then I can place my own textures behind the bar, and they’ll be seen, instead of the default bar background.

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UIImage, resolution independence and the iPhone 4’s Retina display

iOS4 caters for the high-resolution Retina display that comes with the iPhone 4 by some rather clever abstraction, that moves away from the concept of ‘pixels’, and instead uses ‘points’, which are resolution-independent.

So, when you display an image that’s been prepared for the Retina display, it’s represented with a scale factor of 2, meaning that to your code, it appears to have the same dimensions, but in fact contains twice the information density.

iOS4’s UIImage makes it work by automatically looking for high-res images located alongside the prior ‘standard resolution’ ones — identified by a “@2x” suffix to the filename.

This works great with +[UIImage imageNamed:], but although the API documentation says that other image loading methods will automatically load the @2x versions, they actually don’t. Yeah. Apple are working on it.

Until they sort themselves out, I’m using a convenience method sitting inside a UIImage category. So, where I would previously use something like [UIImage imageWithContentsOfFile:], I now use [UIImage imageWithContentsOfResolutionIndependentFile:].

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