IOS绘制渐变颜色

第一种：参考自：http://www.mgenware.com/blog/?p=2396

第二种：使用QuartzCore库

CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = self.bounds;
    gradient.colors = [NSArray arrayWithObjects:(id)[UIColor colorWithHexString:@"#292931"].CGColor,(id)[UIColor colorWithHexString:@"#343a46"].CGColor, nil];
    [self.layer insertSublayer:gradient above:0];