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前言 这个系列的本身不是为了写一些东西让读者拿过去就直接可以用的。过段时间我会在github上传一些拿去就可以用的。这个系列的本身是希望抛砖引玉，，提供一些自定义控件的思路。 本文的内容
阐述了实现自定义UIActivityIndicator的过程
希望通过本文，读者能够学会
CAShapeLayer的简单使用CAGradientLayer的简单使用
自定义控件的一些思路
一 demo效果
二 实现的过程
用_shapeLayer定义环形路径_shapeLayer = [CAShapeLayer layer];_shapeLayer.bounds = CGRectMake(0, 0, 100,100);_shapeLayer.position = CGPointMake(50,50);_shapeLayer.strokeColor = [UIColor blueColor].CGColor;_shapeLayer.fillColor = [UIColor clearColor].CGColor;CGMutablePathRef path = CGPathCreateMutable();_shapeLayer.lineWidth = 5.0;//_shapeLayer.backgroundColor = [UIColor purpleColor].CGColor;CGPathAddArc(path, nil,50, 50,45,0,2*M_PI,YES);_shapeLayer.path = path;
2 用CAGradientLayer定义渐变，用上文的环形路径去截取。
_indicatorLayer = [[CAGradientLayer alloc] init];_indicatorLayer.bounds = CGRectMake(0, 0, 100,100);_indicatorLayer.position = CGPointMake(50,50);_indicatorLayer.colors = @[(id)[UIColor blueColor].CGColor,(id)[UIColor greenColor].CGColor,(id)[UIColor blueColor].CGColor];_indicatorLayer.locations = @[@(0.25), @(0.5), @(0.75)];_indicatorLayer.startPoint = CGPointMake(0.0, 0.0);_indicatorLayer.endPoint = CGPointMake(1.0,1.0);_indicatorLayer.masksToBounds = YES;[_indicatorLayer setMask:self.shapeLayer];//截取
3 在Start函数中开始动画，stop结束动画
-(void)start{self.hidden = NO;[UIView animateWithDuration:1.0delay:0.0options:UIViewAnimationOptionRepeat | UIViewAnimationOptionCurveLinearanimations:^{self.transform = CGAffineTransformMakeRotation(M_PI);} completion:^(BOOL finished) {}];}-(void)stop{[self.indicatorLayer removeAllAnimations];self.hidden = YES;}
4 使用
– (IBAction)start:(id)sender {[self.spinner start];}- (IBAction)stop:(id)sender {[self.spinner stop];}- (void)viewDidLoad {[super viewDidLoad];self.spinner = [[WCActivityIndicicator alloc] init];= CGRectMake(0, 0, 100,100);= ;[];// Do any additional setup after loading the view, typically from a nib.}
最后，附上完整的demo代码，不要直接拿去用，很多地方我没有完善的，仅供学习使用。 WCActivityIndicicator.h
: UIView@property (strong,nonatomic) UIColor * color;-(instancetype)init;-(void)start;-(void)stop;@end
WCActivityIndicicator.m
(strong,nonatomic) CAGradientLayer * indicatorLayer;@property (strong,nonatomic) CAShapeLayer * shapeLayer;-(CAShapeLayer *)shapeLayer{if (!_shapeLayer) {_shapeLayer = [CAShapeLayer layer];_shapeLayer.bounds = CGRectMake(0, 0, 100,100);_shapeLayer.position = CGPointMake(50,50);_shapeLayer.strokeColor = [UIColor blueColor].CGColor;_shapeLayer.fillColor = [UIColor clearColor].CGColor;CGMutablePathRef path = CGPathCreateMutable();_shapeLayer.lineWidth = 5.0;//_shapeLayer.backgroundColor = [UIColor purpleColor].CGColor;CGPathAddArc(path, nil,50, 50,45,0,2*M_PI,YES);_shapeLayer.path = path;//roundShape.path}return _shapeLayer;}-(CAGradientLayer *)indicatorLayer{if (!_indicatorLayer){_indicatorLayer = [[CAGradientLayer alloc] init];_indicatorLayer.bounds = CGRectMake(0, 0, 100,100);_indicatorLayer.position = CGPointMake(50,50);_indicatorLayer.colors = @[(id)[UIColor blueColor].CGColor,(id)[UIColor greenColor].CGColor,(id)[UIColor blueColor].CGColor];// 颜色分割线_indicatorLayer.locations = @[@(0.25), @(0.5), @(0.75)];_indicatorLayer.startPoint = CGPointMake(0.0, 0.0);_indicatorLayer.endPoint = CGPointMake(1.0,1.0);_indicatorLayer.masksToBounds = YES;[_indicatorLayer setMask:self.shapeLayer];}return _indicatorLayer;}/*// Only override drawRect: if you perform custom drawing.// An empty implementation adversely affects performance during animation.- (void)drawRect:(CGRect)rect {// Drawing code}*/-(void)start{self.hidden = NO;[UIView animateWithDuration:1.0delay:0.0options:UIViewAnimationOptionRepeat | UIViewAnimationOptionCurveLinearanimations:^{self.transform = CGAffineTransformMakeRotation(M_PI);} completion:^(BOOL finished) {}];}-(void)stop{[self.indicatorLayer removeAllAnimations];self.hidden = YES;}-(void)setUp{self.bounds = CGRectMake(0, 0,100,100);[];self.hidden = YES;}-(instancetype)init{if (self = [super init]) {[self setUp];}return self;}@end在时间里面我们什么也不能留下，包括痛苦，快乐和生命。
