iOS CAGradientLayer 详解

//
//  ViewController.m
//  test_gradient_01
//
//  Created by admin on 2/3/16.
//  Copyright © 2016 jeffasd. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@property(nonatomic, strong)UIView *contentView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    _contentView = [UIView new];
    _contentView.frame = CGRectMake(100, 100, 100, 100);
    _contentView.backgroundColor = [UIColor redColor];
    [self.view addSubview:_contentView];
    
    CAGradientLayer *gradientLayer = [CAGradientLayer layer];
    gradientLayer.frame = self.contentView.bounds;
    [self.contentView.layer addSublayer:gradientLayer];
    
//    gradientLayer.colors = (__bridge NSArray * _Nullable)([UIColor blueColor].CGColor);
//    gradientLayer.colors = (__bridge NSArray * _Nullable)([UIColor cyanColor].CGColor);
    
    //渐变区域
    gradientLayer.locations = @[[NSNumber numberWithFloat:0.3], [NSNumber numberWithFloat:0.8]];
    
    gradientLayer.colors = @[(__bridge NSArray * _Nullable)([UIColor blueColor].CGColor), (__bridge NSArray * _Nullable)([UIColor redColor].CGColor)];
    
//    gradientLayer.startPoint = CGPointMake(0, 0);
    //最大值为 (1, 1),最小值为(0, 0)
    gradientLayer.startPoint = CGPointMake(1, 0);
    gradientLayer.endPoint = CGPointMake(1, 1);
    
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

print      ?                
1. <p class="p1">    gradientLayer.<span class="s1">locations</span> = <span class="s2">@[</span>[<span class="s1">NSNumber</span> <span class="s3">numberWithFloat</span>:<span class="s2">0.0</span>], [<span class="s1">NSNumber</span> <span class="s3">numberWithFloat</span>:<span class="s2">0.2</span>]<span class="s2">]</span>;</p>

1. gradientLayer.locations = @[[NSNumber numberWithFloat:0.5], [NSNumber numberWithFloat:0.7]];

1. - (void)viewDidLoad  
2. {  
3. super viewDidLoad];  
4.       
5. //create gradient layer and add it to our container view  
6. CAGradientLayer *gradientLayer = [CAGradientLayer layer];  
7. .frame = self.containerView.bounds;  
8. self.containerView.layer addSublayer:gradientLayer];  
9.       
10. //set gradient colors  
11. .colors = @[(__bridge id)[UIColor redColor].CGColor,  
12. id)[UIColor blueColor].CGColor];  
13.       
14. .locations = @[[NSNumber numberWithFloat:0.5], [NSNumber numberWithFloat:0.7]];  
15.   
16. //set gradient start and end points  
17. .startPoint = CGPointMake(0.75, 0.0);  
18. .endPoint = CGPointMake(1.0, 1.0);  
19. }