在 Core Animation 运行时,是否有一种简单的方法可以在其达到某些特定点时进行回调(例如,在完成的50%和66%处)?
我目前正在考虑设置一个 NSTimer,但这并不像我想要的那样精确。
在 Core Animation 运行时,是否有一种简单的方法可以在其达到某些特定点时进行回调(例如,在完成的50%和66%处)?
我目前正在考虑设置一个 NSTimer,但这并不像我想要的那样精确。
我终于为这个问题开发出了一种解决方案。
本质上,我希望每一帧都被回调并完成我需要做的事情。
没有明显的方法来观察动画的进度,但实际上是可能的:
首先,我们需要创建一个新的CALayer子类,其中包含一个可动画属性'progress'。
将该层添加到树中,然后创建一个动画,将驱动进度值从0到1,持续时间为整个动画的时间。
由于我们的progress属性可以进行动画处理,在动画的每一帧上,drawInContext函数会在我们的子类上被调用。虽然这个函数不需要重新绘制任何内容,但它可以用来调用一个委托函数 :)
下面是该类的接口:
@protocol TAProgressLayerProtocol <NSObject>
- (void)progressUpdatedTo:(CGFloat)progress;
@end
@interface TAProgressLayer : CALayer
@property CGFloat progress;
@property (weak) id<TAProgressLayerProtocol> delegate;
@end
实现代码如下:
@implementation TAProgressLayer
// We must copy across our custom properties since Core Animation makes a copy
// of the layer that it's animating.
- (id)initWithLayer:(id)layer
{
self = [super initWithLayer:layer];
if (self) {
TAProgressLayer *otherLayer = (TAProgressLayer *)layer;
self.progress = otherLayer.progress;
self.delegate = otherLayer.delegate;
}
return self;
}
// Override needsDisplayForKey so that we can define progress as being animatable.
+ (BOOL)needsDisplayForKey:(NSString*)key {
if ([key isEqualToString:@"progress"]) {
return YES;
} else {
return [super needsDisplayForKey:key];
}
}
// Call our callback
- (void)drawInContext:(CGContextRef)ctx
{
if (self.delegate)
{
[self.delegate progressUpdatedTo:self.progress];
}
}
@end
我们可以将此图层添加到我们的主要图层中:TAProgressLayer *progressLayer = [TAProgressLayer layer];
progressLayer.frame = CGRectMake(0, -1, 1, 1);
progressLayer.delegate = self;
[_sceneView.layer addSublayer:progressLayer];
同时与其他动画一起使其动起来:
CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:@"progress"];
anim.duration = 4.0;
anim.beginTime = 0;
anim.fromValue = @0;
anim.toValue = @1;
anim.fillMode = kCAFillModeForwards;
anim.removedOnCompletion = NO;
[progressLayer addAnimation:anim forKey:@"progress"];
最后,当动画进行时,将会回调委托对象:
- (void)progressUpdatedTo:(CGFloat)progress
{
// Do whatever you need to do...
}
drawInContext:
(在此过程中创建一个1x1pt位图)。相反,你可以重写[CALayer display]
,它会为零框架调用,并且默认不会创建位图上下文(稍微更加高效)。唯一的区别是你需要在draw
实现内读取self.presentationLayer.progress
而不是self.progress
。 - oztune// INTUAnimationEngine.h
// ...
+ (NSInteger)animateWithDuration:(NSTimeInterval)duration
delay:(NSTimeInterval)delay
animations:(void (^)(CGFloat percentage))animations
completion:(void (^)(BOOL finished))completion;
// ...
duration
和delay
值,然后对于每一帧动画,都会执行animations
块,并显示当前完成百分比。如果你想确保你的时间完美同步,可以完全使用INTUAnimationEngine驱动你的动画。我使用Swift (2.0)实现了tarmes在被接受的答案中建议的CALayer子类:
protocol TAProgressLayerProtocol {
func progressUpdated(progress: CGFloat)
}
class TAProgressLayer : CALayer {
// MARK: - Progress-related properties
var progress: CGFloat = 0.0
var progressDelegate: TAProgressLayerProtocol? = nil
// MARK: - Initialization & Encoding
// We must copy across our custom properties since Core Animation makes a copy
// of the layer that it's animating.
override init(layer: AnyObject) {
super.init(layer: layer)
if let other = layer as? TAProgressLayerProtocol {
self.progress = other.progress
self.progressDelegate = other.progressDelegate
}
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
progressDelegate = aDecoder.decodeObjectForKey("progressDelegate") as? CALayerProgressProtocol
progress = CGFloat(aDecoder.decodeFloatForKey("progress"))
}
override func encodeWithCoder(aCoder: NSCoder) {
super.encodeWithCoder(aCoder)
aCoder.encodeFloat(Float(progress), forKey: "progress")
aCoder.encodeObject(progressDelegate as! AnyObject?, forKey: "progressDelegate")
}
init(progressDelegate: TAProgressLayerProtocol?) {
super.init()
self.progressDelegate = progressDelegate
}
// MARK: - Progress Reporting
// Override needsDisplayForKey so that we can define progress as being animatable.
class override func needsDisplayForKey(key: String) -> Bool {
if (key == "progress") {
return true
} else {
return super.needsDisplayForKey(key)
}
}
// Call our callback
override func drawInContext(ctx: CGContext) {
if let del = self.progressDelegate {
del.progressUpdated(progress)
}
}
}
protocol CAProgressLayerDelegate: CALayerDelegate {
func progressDidChange(to progress: CGFloat)
}
extension CAProgressLayerDelegate {
func progressDidChange(to progress: CGFloat) {}
}
class CAProgressLayer: CALayer {
private struct Const {
static let animationKey: String = "progress"
}
@NSManaged private(set) var progress: CGFloat
private var previousProgress: CGFloat?
private var progressDelegate: CAProgressLayerDelegate? { return self.delegate as? CAProgressLayerDelegate }
override init() {
super.init()
}
init(frame: CGRect) {
super.init()
self.frame = frame
}
override init(layer: Any) {
super.init(layer: layer)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.progress = CGFloat(aDecoder.decodeFloat(forKey: Const.animationKey))
}
override func encode(with aCoder: NSCoder) {
super.encode(with: aCoder)
aCoder.encode(Float(self.progress), forKey: Const.animationKey)
}
override class func needsDisplay(forKey key: String) -> Bool {
if key == Const.animationKey { return true }
return super.needsDisplay(forKey: key)
}
override func display() {
super.display()
guard let layer: CAProgressLayer = self.presentation() else { return }
self.progress = layer.progress
if self.progress != self.previousProgress {
self.progressDelegate?.progressDidChange(to: self.progress)
}
self.previousProgress = self.progress
}
}
class ProgressView: UIView {
override class var layerClass: AnyClass {
return CAProgressLayer.self
}
}
class ExampleViewController: UIViewController, CAProgressLayerDelegate {
override func viewDidLoad() {
super.viewDidLoad()
let progressView = ProgressView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
progressView.layer.delegate = self
view.addSubview(progressView)
var animations = [CAAnimation]()
let opacityAnimation = CABasicAnimation(keyPath: "opacity")
opacityAnimation.fromValue = 0
opacityAnimation.toValue = 1
opacityAnimation.duration = 1
animations.append(opacityAnimation)
let progressAnimation = CABasicAnimation(keyPath: "progress")
progressAnimation.fromValue = 0
progressAnimation.toValue = 1
progressAnimation.duration = 1
animations.append(progressAnimation)
let group = CAAnimationGroup()
group.duration = 1
group.beginTime = CACurrentMediaTime()
group.animations = animations
progressView.layer.add(group, forKey: nil)
}
func progressDidChange(to progress: CGFloat) {
print(progress)
}
}