{"id":61,"date":"2012-01-07T15:40:13","date_gmt":"2012-01-07T07:40:13","guid":{"rendered":"http:\/\/hoo.onpech.net\/?p=61"},"modified":"2012-01-10T13:30:10","modified_gmt":"2012-01-10T05:30:10","slug":"calayer-implicit-animation-of-a-custom-property","status":"publish","type":"post","link":"https:\/\/hoo.onpech.net\/?p=61","title":{"rendered":"CALayer: Implicit animation of a custom property"},"content":{"rendered":"

For Apple’s iOS, below is the code to implicitly animate a custom property, using float as an example, in a subclass of CALayer:
\n

\/* MyLayer.m *\/\n@interface MyLayer() {\n    BOOL _isPresenting; \/* TRUE for presentation layer *\/\n}\n@property (nonatomic) float property; \/* normally defined in MyLayer.h *\/\n@end\n@implementation MyLayer\n@synthesize property = _property;\n- (void)setProperty:(float)property {\n    if (_isPresenting) {\n        NSLog(@"Presenting layer");\n        _property = property;\n        return;\n    }\n    NSLog(@"Setting value");\n    if ([self animationForKey:@"animateProperty"]) {\n        _property = [[self presentationLayer] property];\n        [self removeAnimationForKey:@"animateProperty"];\n    }\n    CABasicAnimation *a = [CABasicAnimation animationWithKeyPath:@"property"];\n    [a setFromValue:[NSNumber numberWithFloat:_property]];\n    [a setToValue:[NSNumber numberWithFloat:property]];\n    \/* Set other animation properties *\/\n    [self addAnimation:a forKey:@"animateProperty"];\n    _property = property;\n}\n+ (BOOL)needsDisplayForKey:(NSString *)key {\n    if ([key isEqualToString:@"property"]) {\n        return YES;\n    }\n    return [super needsDisplayForKey:key];\n}\n- (id)init {\n    if (self = [super init]) {\n        _property = 10; \/* initial value *\/\n    }\n    return  self;\n}\n- (id)initWithLayer:(id)layer {\n    if (self = [super initWithLayer:layer]) {\n        MyLayer *l = (MyLayer *)layer;\n        _isPresenting = TRUE;\n        _property = l.property;\n    }\n    return self;\n}\n- (void)drawInContext:(CGContextRef)ctx {\n    NSLog(@"%f", _property);\n    \/* Add drawing code *\/\n}\n@end\n<\/code><\/pre>Then, setting the custom property with:
\n
myLayer.property = 50;\n<\/code><\/pre>gives the following in the log:
\n
Setting value\nPresenting layer\n18.953653\nPresenting layer\n25.723625\nPresenting layer\n..\n..\n..\nPresenting layer\n49.999870\n50.000000\n50.000000\n<\/code><\/pre>The animation is working, but it cannot be overridden.  It is time to change that by adding:
\n
+ (id<CAAction>)defaultActionForKey:(NSString *)key {\n    if ([key isEqualToString:@"property"]) {\n        CABasicAnimation *a = [CABasicAnimation animationWithKeyPath:@"property"];\n        [a setValue:@"defaultAction" forKey:@"animationType"];\n        return a;\n    }\n    return [super defaultActionForKey:key];\n}\n<\/code><\/pre>and modifying the setter to:
\n
- (void)setProperty:(float)property {\n    if (_isPresenting) {\n        NSLog(@"Presenting layer");\n        _property = property;\n        return;\n    }\n    NSLog(@"Setting value");\n    if ([self animationForKey:@"animateProperty"]) {\n        _property = [[self presentationLayer] property];\n        [self removeAnimationForKey:@"animateProperty"];\n    }\n    CABasicAnimation *a = (CABasicAnimation *)[self actionForKey:@"property"];\n    if (a) {\n        if ([[a valueForKey:@"animationType"] isEqualToString:@"defaultAction"]) {\n            [a setFromValue:[NSNumber numberWithFloat:_property]];\n            [a setToValue:[NSNumber numberWithFloat:property]];\n            \/* Set other animation properties *\/\n        }\n        [self addAnimation:a forKey:@"animateProperty"];\n    }\n    _property = property;\n}\n<\/code><\/pre>Now, all is good.<\/p>\n","protected":false},"excerpt":{"rendered":"
For Apple’s iOS, below is the code to implicitly animate a custom property, using float as an example, in a subclass of CALayer: \/* MyLayer.m *\/ @interface MyLayer() {     BOOL _isPresenting; \/* TRUE for presentation layer *\/ } @property (nonatomic) float property; \/* normally defined in MyLayer.h *\/ @end @implementation MyLayer @synthesize property = _property; […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[10],"class_list":["post-61","post","type-post","status-publish","format-standard","hentry","category-programming","tag-ios"],"_links":{"self":[{"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=\/wp\/v2\/posts\/61","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=61"}],"version-history":[{"count":15,"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=\/wp\/v2\/posts\/61\/revisions"}],"predecessor-version":[{"id":78,"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=\/wp\/v2\/posts\/61\/revisions\/78"}],"wp:attachment":[{"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=61"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=61"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hoo.onpech.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=61"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}