164检测屏幕中动画的状态

效果如下：

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
@property (strong, nonatomic) UIImageView *imgVAnimation;

@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()
- (void)layoutUI;
- (void)startAnimation;
- (void)animationWillStart:(NSString *)animationID context:(void *)context;
- (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self layoutUI];
}

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

- (void)layoutUI {
    self.view.backgroundColor = [UIColor blackColor];
    
    _imgVAnimation = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"ImageForAnimation"]];
    _imgVAnimation.center = CGPointMake(self.view.center.x, 100);
    [self.view addSubview:_imgVAnimation];
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    
    [self startAnimation];
}

- (void)startAnimation {
    _imgVAnimation.center = CGPointMake(self.view.center.x, 100);
    _imgVAnimation.alpha = 1.0;
    _imgVAnimation.transform = CGAffineTransformIdentity;
    
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; //设置动画弧度；默认值为UIViewAnimationCurveEaseInOut
    [UIView setAnimationDuration:2.0];
    [UIView setAnimationRepeatCount:1.0]; //设置动画播放重复次数；默认值为0，表示不循环只执行一次（区别于UIImageView.animationRepeatCount=0为无限循环）
    [UIView setAnimationRepeatAutoreverses:YES]; //设置自动倒退，即动画回放；默认值为NO，只在动画起码执行一次的情况下有效
    [UIView setAnimationDelegate:self];
    [UIView setAnimationWillStartSelector:@selector(animationWillStart:context:)]; //设置动画将开始时执行委托方法；在设置好委托前提下，默认就是绑定animationWillStart:context:
    [UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:context:)]; //设置动画结束后执行委托方法；在设置好委托前提下，默认就是绑定animationDidStop:finished:context:
    
    _imgVAnimation.center = CGPointMake(self.view.center.x, 300);
    _imgVAnimation.alpha = 0.2;
    //设置放大和旋转
    CGAffineTransform transformScale = CGAffineTransformScale(CGAffineTransformIdentity, 3, 3);
    CGAffineTransform transformRotate = CGAffineTransformRotate(CGAffineTransformIdentity, M_PI); //M_PI表示180度
    _imgVAnimation.transform = CGAffineTransformConcat(transformScale, transformRotate);
    
    [UIView commitAnimations];
}

- (void)animationWillStart:(NSString *)animationID context:(void *)context {
    static BOOL isFirstTime = YES;
    if (isFirstTime) {
        UIAlertView *alertVAnimation = [[UIAlertView alloc] initWithTitle:@"提示信息"
                                                                  message:@"开始动画了"
                                                                 delegate:nil
                                                        cancelButtonTitle:nil
                                                        otherButtonTitles:@"确定", nil];
        [alertVAnimation show];
        
        isFirstTime = NO;
    }
}

- (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {
    //如果动画正常结束时（非强制取消），就再次开始动画
    if ([finished boolValue]) {
        [self startAnimation];
    }
}

@end