需求 - 11 - 等待動畫 - 2

可以用單純的 圖層加核心動畫實現一個等待旋轉的效果：

#import "LoadingCircleButton.h"

@interface LoadingCircleButton ()

@property (nonatomic,strong) CAShapeLayer *loadingLayer;

@property (nonatomic,strong) UIButton *button;


@end

@implementation LoadingCircleButton


- (instancetype)initWithFrame:(CGRect)frame
{
    if(self = [super initWithFrame:frame])
    {
        _button = [UIButton buttonWithType:UIButtonTypeCustom];
        _button.frame = self.bounds;
        [_button setTitle:@" " forState:UIControlStateNormal];
        [_button setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
        _button.titleLabel.font = [UIFont systemFontOfSize:13.f];
        [self addSubview:_button];
        [_button addTarget:self action:@selector(clickBtn) forControlEvents:UIControlEventTouchUpInside];
    }
    return self;
}


- (void)clickBtn
{
    [self loadingAnimation];
}


- (void)loadingAnimation
{
    _loadingLayer = [CAShapeLayer layer];
    _loadingLayer.position = CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2);
    _loadingLayer.fillColor = [UIColor clearColor].CGColor;
    _loadingLayer.strokeColor = [UIColor whiteColor].CGColor;
    _loadingLayer.lineWidth = 2;
    _loadingLayer.path = [self drawLoadingBezierPath].CGPath;
    [self.layer addSublayer:_loadingLayer];
    
    CABasicAnimation *basicAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
    basicAnimation.fromValue = @(0);
    basicAnimation.toValue = @(M_PI*2);
    basicAnimation.duration = 0.5;
    basicAnimation.repeatCount = LONG_MAX;
    [_loadingLayer addAnimation:basicAnimation forKey:@"loadingAnimation"];
    
    [self performSelector:@selector(stopLoadingAnimation) withObject:self afterDelay:5];
}


- (void)stopLoadingAnimation
{
    [_loadingLayer removeFromSuperlayer];
}


- (UIBezierPath *)drawLoadingBezierPath
{
    CGFloat radius = self.bounds.size.height/2 - 3;
    UIBezierPath *bezierPath = [UIBezierPath bezierPath];
    [bezierPath addArcWithCenter:CGPointMake(0,0) radius:radius startAngle:M_PI/2 endAngle:M_PI/2+M_PI/2 clockwise:YES];
    return bezierPath;
}

@end