CAGradientLayer处理颜色渐变效果

1、这个类很简单，下面简单介绍

/* CoreAnimation - CAGradientLayer.h   Copyright (c) 2008-2015, Apple Inc.   All rights reserved. *//* The gradient layer draws a color gradient over its background color, * filling the shape of the layer (i.e. including rounded corners). */#import <QuartzCore/CALayer.h>#import <Foundation/NSArray.h>NS_ASSUME_NONNULL_BEGIN@interface CAGradientLayer : CALayer/* The array of CGColorRef objects defining the color of each gradient * stop. Defaults to nil. Animatable. *///这个数组里面保存了用于渐变的颜色@property(nullable, copy) NSArray *colors;/* An optional array of NSNumber objects defining the location of each * gradient stop as a value in the range [0,1]. The values must be * monotonically increasing. If a nil array is given, the stops are * assumed to spread uniformly across the [0,1] range. When rendered, * the colors are mapped to the output colorspace before being * interpolated. Defaults to nil. Animatable. *///数值为0-1，用于设置颜色渐变的区间分布@property(nullable, copy) NSArray<NSNumber *> *locations;/* The start and end points of the gradient when drawn into the layer's * coordinate space. The start point corresponds to the first gradient * stop, the end point to the last gradient stop. Both points are * defined in a unit coordinate space that is then mapped to the * layer's bounds rectangle when drawn. (I.e. [0,0] is the bottom-left * corner of the layer, [1,1] is the top-right corner.) The default values * are [.5,0] and [.5,1] respectively. Both are animatable. *///对应locations中的第一个位置，默认值是(0.5,0.0)，下同@property CGPoint startPoint;@property CGPoint endPoint;/* The kind of gradient that will be drawn. Currently the only allowed * value is `axial' (the default value). *///<span class="s1">就一个默认值是kCAGradientLayerAxial，表示按像素均匀变化</span>@property(copy) NSString *type;@end/** `type' values. **/CA_EXTERN NSString * const kCAGradientLayerAxial    __OSX_AVAILABLE_STARTING (__MAC_10_6, __IPHONE_3_0);NS_ASSUME_NONNULL_END

2、代码实例：

在屏幕中间放一个view：

代码：

////  ViewController.m//  001-CAGradientLayer//#import "ViewController.h"@interface ViewController ()@property (weak, nonatomic) IBOutlet UIView *myView;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.        CAGradientLayer * gradLayer = [CAGradientLayer layer];        gradLayer.frame = _myView.layer.bounds;        gradLayer.colors = [NSArray arrayWithObjects:                         (id)[UIColor purpleColor].CGColor,                         (id)[UIColor yellowColor].CGColor,                         (id)[UIColor grayColor].CGColor,                         (id)[UIColor orangeColor].CGColor,                         (id)[UIColor blueColor].CGColor,                         nil];        //颜色渐变的区间分布，如果不设置，会平均分布    gradLayer.locations = [NSArray arrayWithObjects:                            [NSNumber numberWithFloat:0.0f],                            [NSNumber numberWithFloat:0.2f],                            [NSNumber numberWithFloat:0.5f],                            [NSNumber numberWithFloat:0.8f],                            [NSNumber numberWithFloat:1.0f],                            nil];    //    gradLayer.startPoint = CGPointMake(0, 0);//    //    gradLayer.endPoint = CGPointMake(1, 1);        [_myView.layer addSublayer:gradLayer];    }- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end

首先注释掉startPoint和endPoint：

去掉注释：