Melvyn Hills melvynhills

Hacking UIView animation blocks for fun and profit

In this article, I'm going to explore a way that we can create views that implement custom Core Animation property animations in a natural way.

As we know, layers in iOS come in two flavours: Backing layers and hosted layers. The only difference between them is that the view acts as the layer delegate for its backing layer, but not for any hosted sublayers.

In order to implement the UIView transactional animation blocks, UIView disables all animations by default and then re-enables them individually as required. It does this using the actionForLayer:forKey: method.

Somewhat strangely, UIView doesn't enable animations for every property that CALayer does by default. A notable example is the layer.contents property, which is animatable by default for a hosted layer, but cannot be animated using a UIView animation block.

	#!/usr/bin/env sh

	##
	# This is script with usefull tips taken from:
	# https://github.com/mathiasbynens/dotfiles/blob/master/.osx
	#
	# install it:
	# curl -sL https://raw.github.com/gist/2108403/hack.sh \| sh
	#

	<!DOCTYPE html>
	<html>
	<head>

	<style>

	/* Core CSS */
	#box
	{
	background: white;

	So the model object can bind the event "change:#{field} to trigger event when the field value is changed.

	By default it's off and if need this feature, the model should extend Spine.Model.Dirty.

	A sample case.

	class User extends Spine.Model
	@extend Spine.Model.Dirty
	end

	$contrasted-default-dark: #000;
	$contrasted-default-light: #fff;

	@mixin contrasted($bg, $dark:$contrasted-default-dark, $light:$contrasted-default-light){
	background-color: $bg;
	color: get_contrast_yiq($bg, $dark, $light);
	}

	function whichTransitionEvent(){
	var t;
	var el = document.createElement('fakeelement');
	var transitions = {
	'transition':'transitionend',
	'MSTransition':'msTransitionEnd',
	'MozTransition':'transitionend',
	'WebkitTransition':'webkitTransitionEnd'
	}

	gifify() {
	if [[ -n "$1" ]]; then
	if [[ $2 == '--good' ]]; then
	ffmpeg -i $1 -r 10 -vcodec png out-static-%05d.png
	time convert -verbose +dither -layers Optimize -resize 600x600\> out-static*.png GIF:- \| gifsicle --colors 128 --delay=5 --loop --optimize=3 --multifile - > $1.gif
	rm out-static*.png
	else
	ffmpeg -i $1 -s 600x400 -pix_fmt rgb24 -r 10 -f gif - \| gifsicle --optimize=3 --delay=3 > $1.gif
	fi
	else

	# -- coding: utf-8 --
	$:.unshift("/Library/RubyMotion/lib")
	require 'motion/project'
	require 'motion-cocoapods'
	require 'bundler'
	Bundler.require

	Dir.glob('lib/tasks/*.rake').each { \|r\| import r }

	VERSION = "1.0.2"

	// Taken from http://PSPDFKit.com. This snippet is under public domain.
	#define UIKitVersionNumber_iOS_7_0 0xB57
	BOOL PSPDFIsUIKitFlatMode(void) {
	static BOOL isUIKitFlatMode = NO;
	static dispatch_once_t onceToken;
	dispatch_once(&onceToken, ^{
	// We get the modern UIKit if system is running >= iOS 7 and we were linked with >= SDK 7.
	if (kCFCoreFoundationVersionNumber >= kCFCoreFoundationVersionNumber_iOS_7_0) {
	isUIKitFlatMode = (NSVersionOfLinkTimeLibrary("UIKit") >> 16) >= UIKitVersionNumber_iOS_7_0;
	}

	/*
	`arc4random_uniform` is very useful but limited to `UInt32`.

	This defines a generic version of `arc4random` for any type
	expressible by an integer literal, and extends some numeric
	types with a `random` method that mitigates for modulo bias
	in the same manner as `arc4random`.

	`lower` is inclusive and `upper` is exclusive, thus: