speed（CAMediaTiming）控制动画暂停和结束

//
//  ViewController.m
//  MediaTiming
//
//  Created by apple on 17/8/18.
//  Copyright © 2017年 Wang. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()
@property (nonatomic, strong) CALayer *layer;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    CALayer *layer = [CALayer layer];
    layer.backgroundColor = [UIColor purpleColor].CGColor;
    layer.frame = CGRectMake(0, 0, 100, 100);
    [self.view.layer addSublayer:layer];
    self.layer = layer;
    
    CABasicAnimation *basicAnimation = [CABasicAnimation animationWithKeyPath:@"position"];
    basicAnimation.duration = 4.f;
    basicAnimation.repeatCount = HUGE;
    basicAnimation.toValue = [NSValue valueWithCGPoint:CGPointMake(50, 400)];
    [layer addAnimation:basicAnimation forKey:nil];
}

- (void) pauseLayer: (CALayer *) theLayer
{
    CFTimeInterval mediaTime = CACurrentMediaTime();
    CFTimeInterval pausedTime = [theLayer convertTime: mediaTime fromLayer: nil];
    theLayer.speed = 0.0;
    theLayer.timeOffset = pausedTime;
}

//-----------------------------------------------------------------------------

- (void) removePauseForLayer: (CALayer *) theLayer;
{
    theLayer.speed = 1.0;
    theLayer.timeOffset = 0.0;
    theLayer.beginTime = 0.0;
}

//-----------------------------------------------------------------------------

- (void) resumeLayer: (CALayer *) theLayer;
{
    CFTimeInterval pausedTime = [theLayer timeOffset];
    [self removePauseForLayer: theLayer];
    CFTimeInterval mediaTime = CACurrentMediaTime();
    CFTimeInterval timeSincePause =
    [theLayer convertTime: mediaTime fromLayer: nil] - pausedTime;
    theLayer.beginTime = timeSincePause;
}

- (IBAction)pauseClick:(UIButton *)sender {
    [self pauseLayer:self.layer];
    
}

- (IBAction)resumeClick:(UIButton *)sender {
    [self resumeLayer:self.layer];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


@end

参考:How To Pause & Resume Animation - KDCircularProgress Circular Bar