CAGradientLayer的一些属性解析
CAGradientLayer的一些属性解析
iOS中Layer的坐标系统:
效果:
- (void)viewDidLoad { [super viewDidLoad]; CAGradientLayer *colorLayer = [CAGradientLayer layer]; colorLayer.frame = (CGRect){CGPointZero, CGSizeMake(200, 200)}; colorLayer.position = self.view.center; [self.view.layer addSublayer:colorLayer]; // 颜色分配 colorLayer.colors = @[(__bridge id)[UIColor redColor].CGColor, (__bridge id)[UIColor greenColor].CGColor, (__bridge id)[UIColor blueColor].CGColor]; // 颜色分割线 colorLayer.locations = @[@(0.25), @(0.5), @(0.75)]; // 起始点 colorLayer.startPoint = CGPointMake(0, 0); // 结束点 colorLayer.endPoint = CGPointMake(1, 0); }
颜色分配严格遵守Layer的坐标系统,locations,startPoint,endPoint都是以Layer坐标系统进行计算的.
而locations并不是表示颜色值所在位置,它表示的是颜色在Layer坐标系相对位置处要开始进行渐变颜色了.
CAGradientLayer 的这四个属性 colors locations startPoint endPoint 都是可以进行动画的哦.
附录:
稍微复杂点的动画效果
// // RootViewController.m // // Copyright (c) 2014年 Y.X. All rights reserved. // #import "RootViewController.h" #import "YXGCD.h" @interface RootViewController () @property (nonatomic, strong) GCDTimer *timer; @end @implementation RootViewController - (void)viewDidLoad { [super viewDidLoad]; CAGradientLayer *colorLayer = [CAGradientLayer layer]; colorLayer.backgroundColor = [UIColor blueColor].CGColor; colorLayer.frame = (CGRect){CGPointZero, CGSizeMake(200, 200)}; colorLayer.position = self.view.center; [self.view.layer addSublayer:colorLayer]; // 颜色分配 colorLayer.colors = @[(__bridge id)[UIColor cyanColor].CGColor, (__bridge id)[UIColor orangeColor].CGColor, (__bridge id)[UIColor magentaColor].CGColor]; // 起始点 colorLayer.startPoint = CGPointMake(0, 0); // 结束点 colorLayer.endPoint = CGPointMake(1, 0); _timer = [[GCDTimer alloc] initInQueue:[GCDQueue mainQueue]]; [_timer event:^{ static CGFloat test = - 0.1f; if (test >= 1.1) { test = - 0.1f; [CATransaction setDisableActions:YES]; colorLayer.locations = @[@(test), @(test + 0.05), @(test + 0.1)]; } else { [CATransaction setDisableActions:NO]; colorLayer.locations = @[@(test), @(test + 0.05), @(test + 0.1)]; } test += 0.1f; } timeInterval:NSEC_PER_SEC]; [_timer start]; } @end
_timer = [[GCDTimer alloc] initInQueue:[GCDQueue mainQueue]]; [_timer event:^{ static CGFloat test = - 0.1f; if (test >= 1.1) { test = - 0.1f; [CATransaction setDisableActions:NO]; colorLayer.locations = @[@(test), @(test + 0.01), @(test + 0.011)]; } else { [CATransaction setDisableActions:NO]; colorLayer.locations = @[@(test), @(test + 0.01), @(test + 0.011)]; } test += 0.1f; } timeInterval:NSEC_PER_SEC]; [_timer start];
配合CAShapeLayer使用
// // RootViewController.m // // Copyright (c) 2014年 Y.X. All rights reserved. // #import "RootViewController.h" #import "YXGCD.h" @interface RootViewController () @property (nonatomic, strong) GCDTimer *timer; @end // 将常数转换为度数 #define DEGREES(degrees) ((M_PI * (degrees))/ 180.f) @implementation RootViewController - (void)viewDidLoad { [super viewDidLoad]; self.view.backgroundColor = [UIColor blackColor]; CAGradientLayer *colorLayer = [CAGradientLayer layer]; colorLayer.backgroundColor = [UIColor blueColor].CGColor; colorLayer.frame = (CGRect){CGPointZero, CGSizeMake(200, 200)}; colorLayer.position = self.view.center; [self.view.layer addSublayer:colorLayer]; // 颜色分配 colorLayer.colors = @[(__bridge id)[UIColor redColor].CGColor, (__bridge id)[UIColor whiteColor].CGColor, (__bridge id)[UIColor redColor].CGColor]; colorLayer.locations = @[@(-0.2), @(-0.1), @(0)]; // 起始点 colorLayer.startPoint = CGPointMake(0, 0); // 结束点 colorLayer.endPoint = CGPointMake(1, 0); CAShapeLayer *circle = [RootViewController LayerWithCircleCenter:CGPointMake(102, 100) radius:80 startAngle:DEGREES(0) endAngle:DEGREES(360) clockwise:YES lineDashPattern:nil]; circle.strokeColor = [UIColor redColor].CGColor; [self.view.layer addSublayer:circle]; circle.strokeEnd = 1.f; colorLayer.mask = circle; _timer = [[GCDTimer alloc] initInQueue:[GCDQueue mainQueue]]; [_timer event:^{ static int i = 0; if (i++ % 2 == 0) { CABasicAnimation* fadeAnim = [CABasicAnimation animationWithKeyPath:@"locations"]; fadeAnim.fromValue = @[@(-0.2), @(-0.1), @(0)]; fadeAnim.toValue = @[@(1.0), @(1.1), @(1.2)]; fadeAnim.duration = 1.5; [colorLayer addAnimation:fadeAnim forKey:nil]; } } timeInterval:NSEC_PER_SEC]; [_timer start]; } + (CAShapeLayer *)LayerWithCircleCenter:(CGPoint)point radius:(CGFloat)radius startAngle:(CGFloat)startAngle endAngle:(CGFloat)endAngle clockwise:(BOOL)clockwise lineDashPattern:(NSArray *)lineDashPattern { CAShapeLayer *layer = [CAShapeLayer layer]; // 贝塞尔曲线(创建一个圆) UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(0, 0) radius:radius startAngle:startAngle endAngle:endAngle clockwise:clockwise]; // 获取path layer.path = path.CGPath; layer.position = point; // 设置填充颜色为透明 layer.fillColor = [UIColor clearColor].CGColor; // 获取曲线分段的方式 if (lineDashPattern) { layer.lineDashPattern = lineDashPattern; } return layer; } @end