背景颜色渐变实现

项目名称：XDCalendarDemo-scroll

源码地址：https://github.com/xieyajie/XDCalendarDemo-scroll

用于控件：UIButton

类库引用：#import <QuartzCore/QuartzCore.h>

代码实现：

1、最开始使用以下方法，正确的实现了将button的背景颜色变成渐变色。但是在触发button点击事件时，背景不能变成在方法setBackgroundImage: forState:中设定好的图片。

1 - (void)gradientImageInRect:(CGRect)rect forView:(UIView *)view

2 {

3     CAGradientLayer *gradient = [CAGradientLayer layer];

4     gradient.frame = rect;

5     gradient.colors = [NSArray arrayWithObjects:(id)[UIColor redColor].CGColor, (id)[UIColor yellowColor].CGColor, (id)[UIColor greenColor].CGColor,nil];

6     [view.layer insertSublayer:gradient atIndex:0];

7 }

2、我需要的颜色R、G、B值都是相同的，选用这种方法，生成渐变色的image，在方法setBackgroundImage: forState:中设定image。

 1 /*

 2  *size:要生成图片的区域

 3  *start：颜色开始的值

 4  *end：颜色结束的值

 5  *centre：要绘制区域的中心点

 6  *radius：CGGradientDrawingOptions

 7  */

 8 - (UIImage *)radialGradientImage:(CGSize)size start:(float)start end:(float)end centre:(CGPoint)centre radius:(float)radius {

 9     // Initialise

10     UIGraphicsBeginImageContextWithOptions(size, YES, 1);

11     

12     // Create the gradient's colours

13     size_t num_locations = 2;

14     CGFloat locations[2] = { 0.0, 1.0 };

15     CGFloat components[8] = { start,start,start, 1.0,  // Start color

16         end,end,end, 1.0 }; // End color

17     

18     CGColorSpaceRef myColorspace = CGColorSpaceCreateDeviceRGB();

19     CGGradientRef myGradient = CGGradientCreateWithColorComponents (myColorspace, components, locations, num_locations);

20     

21     // Normalise the 0-1 ranged inputs to the width of the image

22     CGPoint myCentrePoint = CGPointMake(centre.x * size.width, centre.y * size.height);

23     float myRadius = MIN(size.width, size.height) * radius;

24     

25     // Draw

26     CGContextDrawRadialGradient (UIGraphicsGetCurrentContext(), myGradient, myCentrePoint,

27                                  0, myCentrePoint, myRadius,

28                                  kCGGradientDrawsAfterEndLocation);

29     

30     // Grab it as an autoreleased image

31     UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

32     

33     // Clean up

34     CGColorSpaceRelease(myColorspace); 

35     CGGradientRelease(myGradient); 

36     UIGraphicsEndImageContext();

37     return image;

38 }

3、如果R、G、B值各不相同，适当修改上面代码中的

CGFloat components[8] = { start,start,start, 1.0,  // Start color

         end,end,end, 1.0 };