1。
#import <QuartzCore/QuartzCore.h>
CAGradientLayer *gradient = [CAGradientLayer layer];
gradient.frame = rect;
gradient.colors = [NSArray arrayWithObjects:(id)[UIColor redColor].CGColor,
(id)[UIColor
yellowColor].CGColor,
(id)[UIColor
greenColor].CGColor,nil];
[self.layer insertSublayer:gradient atIndex:0];
2。
CGRect barRect=CGRectMake(xPosition, self.bounds.size.height - 180
-13, 30, 180);
CGColorRef upColor = [UIColor colorWithRed:254/255.0 green:186/
255.0 blue:187/255.0 alpha:1.0].CGColor;
CGColorRef downColor = [UIColor colorWithRed:255/255.0 green:91/
255.0 blue:92/255.0 alpha:1.0].CGColor;
drawLinearGradient(context, barRect, upColor, downColor);