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(, )};

    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(, );

    // 结束点

    colorLayer.endPoint   = CGPointMake(, );

}

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

#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(, )};

    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(, );

    // 结束点

    colorLayer.endPoint   = CGPointMake(, );

    _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

转http://www.cnblogs.com/YouXianMing/p/3793913.html