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CAKeyframeAnimation Class Reference

Inherits from
CAPropertyAnimation : CAAnimation : NSObject
Conforms to
NSCoding (CAAnimation)
NSCopying (CAAnimation)
CAAction (CAAnimation)
CAMediaTiming (CAAnimation)
NSObject (NSObject)
Framework
/System/Library/Frameworks/QuartzCore.framework
Availability
Available in iOS 2.0 and later.
Declared in
CAAnimation.h
Companion guides
Core Animation Programming Guide
Core Animation Cookbook

Overview

CAKeyframeAnimation provides generic keyframe animation capabilities for a layer property in the render tree. You create an CAKeyframeAnimation instance using the inherited animationWithKeyPath: method, specifying the key path of the property updated in the render tree during the animation. The animation provides a series of keyframe values, either as an array or a series of points in a CGPathRef. While animating, it updates the value of the property in the render tree with values calculated using the specified interpolation calculation mode.

Tasks

Providing Keyframe Values

Keyframe Timing

Rotation Mode Attribute

Cubic Mode Attributes

Properties

For more about Objective-C properties, see “Properties” in The Objective-C Programming Language.

biasValues

An array of NSNumber objects that define the position of the curve relative to a control point.

@property(copy) NSArray *biasValues

Discussion

This property is used only for the cubic calculation modes. Positive values move the curve before the control point while negative values move it after the control point. The first value defines the behavior of the tangent to the first control point, the second value controls the second point’s tangents, and so on. If you do not specify a value for a given control point, the value 0 is used.

Availability
  • Available in iOS 4.0 and later.
Declared In
CAAnimation.h

calculationMode

Specifies how intermediate keyframe values are calculated by the receiver.

@property(copy) NSString *calculationMode

Discussion

The possible values are described in “Value calculation modes”. The default is kCAAnimationLinear.

Availability
  • Available in iOS 2.0 and later.
Declared In
CAAnimation.h

continuityValues

An array of NSNumber objects that define the sharpness of the timing curve’s corners.

@property(copy) NSArray *continuityValues

Discussion

This property is used only for the cubic calculation modes. Positive values result in sharper corners while negative values create inverted corners. The first value defines the behavior of the tangent to the first control point, the second value controls the second point’s tangents, and so on. If you do not specify a value for a given control point, the value 0 is used.

Availability
  • Available in iOS 4.0 and later.
Declared In
CAAnimation.h

keyTimes

An optional array of NSNumber objects that define the duration of each keyframe segment.

@property(copy) NSArray *keyTimes

Discussion

Each value in the array is a floating point number between 0.0 and 1.0 and corresponds to one element in the values array. Each element in the keyTimes array defines the duration of the corresponding keyframe value as a fraction of the total duration of the animation. Each element value must be greater than, or equal to, the previous value.

The appropriate values in the keyTimes array are dependent on the calculationMode property.

  • If the calculationMode is set to kCAAnimationLinear, the first value in the array must be 0.0 and the last value must be 1.0. Values are interpolated between the specified key times.

  • If the calculationMode is set to kCAAnimationDiscrete, the first value in the array must be 0.0.

  • If the calculationMode is set to kCAAnimationPaced or kCAAnimationCubicPaced, the keyTimes array is ignored.

If the values in the keyTimes array are invalid or inappropriate for the calculationMode, the keyTimes array is ignored.

Availability
  • Available in iOS 2.0 and later.
Declared In
CAAnimation.h

path

An optional CGPathRef that provides the keyframe values for the receiver.

@property CGPathRef path;

Discussion

Defaults to nil. Specifying a path overrides the values property. Each point in the path, except for move-to points, defines a single keyframe segment for the purpose of timing and interpolation. For constant velocity animation along the path, calculationMode should be set to kCAAnimationPaced.

Availability
  • Available in iOS 2.0 and later.
See Also
Declared In
CAAnimation.h

rotationMode

Determines whether objects animating along the path rotate to match the path tangent.

@property(copy) NSString *rotationMode

Discussion

Possible values are described in “Rotation Mode Values”. The default is nil, which indicates that objects should not rotate to follow the path.

The effect of setting this property to a non-nil value when no path object is supplied is undefined.

Availability
  • Available in iOS 2.0 and later.
See Also
Declared In
CAAnimation.h

tensionValues

An array of NSNumber objects that define the tightness of the curve.

@property(copy) NSArray *tensionValues

Discussion

This property is used only for the cubic calculation modes. Positive values indicate a tighter curve while negative values indicate a rounder curve. The first value defines the behavior of the tangent to the first control point, the second value controls the second point’s tangents, and so on. If you do not specify a value for a given control point, the value 0 is used.

Availability
  • Available in iOS 4.0 and later.
Declared In
CAAnimation.h

timingFunctions

An optional array of CAMediaTimingFunction instances that defines the pacing of the each keyframe segment.

@property(copy) NSArray *timingFunctions

Discussion

If the receiver defines n keyframes, there must be n-1 objects in the timingFunctions array. Each timing function describes the pacing of one keyframe to keyframe segment.

Special Considerations

The inherited timingFunction value is always ignored.

Availability
  • Available in iOS 2.0 and later.
Declared In
CAAnimation.h

values

An array of objects that provide the keyframe values for the receiver.

@property(copy) NSArray *values

Discussion

The values property is ignored when the path property is used.

Availability
  • Available in iOS 2.0 and later.
Declared In
CAAnimation.h

Constants

Rotation Mode Values

These constants are used by the rotationMode property.

NSString * const kCAAnimationRotateAuto
NSString * const kCAAnimationRotateAutoReverse
Constants
kCAAnimationRotateAuto

The objects travel on a tangent to the path.

Available in iOS 2.0 and later.

Declared in CAAnimation.h.

kCAAnimationRotateAutoReverse

The objects travel at a 180 degree tangent to the path.

Available in iOS 2.0 and later.

Declared in CAAnimation.h.

Value calculation modes

These constants are used by the calculationMode property.

NSString * const kCAAnimationLinear;
NSString * const kCAAnimationDiscrete;
NSString * const kCAAnimationPaced;
NSString * const kCAAnimationCubic;
NSString * const kCAAnimationCubicPaced;
Constants
kCAAnimationLinear

Simple linear calculation between keyframe values.

Available in iOS 2.0 and later.

Declared in CAAnimation.h.

kCAAnimationDiscrete

Each keyframe value is used in turn, no interpolated values are calculated.

Available in iOS 2.0 and later.

Declared in CAAnimation.h.

kCAAnimationPaced

Keyframe values are interpolated to produce an even pace throughout the animation.

Available in iOS 2.0 and later.

Declared in CAAnimation.h.

kCAAnimationCubic

Intermediate frames are computed using a Catmull-Rom spline that passes through the keyframes. You can adjust the shape of the spline by specifying an optional set of tension, continuity, and bias values, which modify the spline using the standard Kochanek-Bartels form.

Available in iOS 4.0 and later.

Declared in CAAnimation.h.

kCAAnimationCubicPaced

Intermediate frames are computed using the cubic scheme but the keyTimes and timingFunctions properties of the animation are ignored. Instead, timing parameters are calculated implicitly to give the animation a constant velocity.

Available in iOS 4.0 and later.

Declared in CAAnimation.h.



Last updated: 2010-05-25

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