A headache-inducing scenario: I’m working on a view controller, and I realise that in order to support landscape and portrait modes, I’m going to need to provide two different layouts.
So, I create two different views within the nib, one portrait, one landscape, each with the same view hierarchy, but with a different layout.
When the orientation changes, I set self.view to the appropriate view. I initialise both views on load, and keep both of them synced to properly reflect the app’s state — basically, I’m double-handling everything, which bloats my code and increases the chance I’ll make a mistake.
So, here’s an easier way: Rather than maintaining two separate view hierarchies and switching between them when the orientation changes, why not just change the layout of one single view hierarchy? The only changes between the portrait and landscape views are layout changes, so if we can extract just the layout information from each view, then we don’t have to worry about maintaining both view hierarchies.
Basically, we’re talking about using each view version as a layout template only.
That’s what TPMultiLayoutViewController class does. It’s a drop-in UIViewController subclass that automatically manages switching between different view layouts for portrait and landscape orientations, without the need to maintain view state across two different view hierarchies.
It works by defining portraitView and landscapeView outlets which it traverses upon loading the nib. It matches each subview element to its counterpart in the other layout (based on tag, target/action, title, etc.), and stores just the layout attributes of each element.
Then, when the orientation changes, the view hierarchy is traversed and these layouts are applied to each subview.
To use it,
- Set the superclass for your view controller to
TPMultiLayoutViewController. - In Interface Builder, create two different views: one for portrait orientation, and one for landscape orientation.
- Attach your portrait orientation root view to the “portraitView” outlet, and the landscape orientation root view to the “landscapeView” outlet.
- Attach one of the views (whichever you prefer) to the “view” outlet, and connect any actions and outlets from that view.
Grab it from the TPMultiLayoutViewController GitHub repository, and let me know what you think.
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Compiling Image Resources into a Static Library
I’ve recently been working on a static library for distribution to other developers — Audiobus — and I need to include a couple of graphical resources with the distribution. The usual solution to this is to include the resources separately in a bundle, and require the user to drop them in to their project along with the static library.
I thought I’d see if I could make the process just a little neater, and successfully devised a way to compile the images straight into the library, so the distribution remains nice and clean — just the library itself and a few header files.
Now, I can pop image resources into a folder, and after compiling, access them within the static library with:
It automatically handles “@2x” Retina images (although it doesn’t currently do “~ipad” versions).
Here’s how it’s done.
The magic is in a shell script which uses the
xxdhex dump tool to create C code that represents the image data as a byte array, then creates around it a set of utilities to turn those arrays into UIImages on demand.Along with it is a couple of template files — a header and implementation file — that describe the format of the derived code.
Finally, a little tweaking of the project in Xcode (with a brief foray into a text editor to work around some Xcode shortcomings) puts it all together. Read More »