【iOS开发系列】颜色渐变

记录：

//Transparent Gradient Layer  
- (void) insertTransparentGradient {  
    UIColor *colorOne = [UIColor colorWithRed:(33/255.0)  green:(33/255.0)  blue:(33/255.0)  alpha:0.0];  
    UIColor *colorTwo = [UIColor colorWithRed:(33/255.0)  green:(33/255.0)  blue:(33/255.0)  alpha:1.0];  
    NSArray *colors = [NSArray arrayWithObjects:(id)colorOne.CGColor, colorTwo.CGColor, nil nil];  
    NSNumber *stopOne = [NSNumber numberWithFloat:0.0];  
    NSNumber *stopTwo = [NSNumber numberWithFloat:1.0];  
    NSArray *locations = [NSArray arrayWithObjects:stopOne, stopTwo, nil nil];  
      
    //crate gradient layer  
    CAGradientLayer *headerLayer = [CAGradientLayer layer];  
      
    headerLayer.colors = colors;  
    headerLayer.locations = locations;  
    headerLayer.frame = self.bounds;  
      
    [self.layer insertSublayer:headerLayer atIndex:0];  
}  
  
  
//color gradient layer  
- (void) insertColorGradient {  
      
    UIColor *colorOne = [UIColor colorWithRed:(255/255.0) green:(255/255.0) blue:(255/255.0) alpha:1.0];  
    UIColor *colorTwo = [UIColor colorWithRed:(33/255.0)  green:(33/255.0)  blue:(33/255.0)  alpha:1.0];  
      
    NSArray *colors = [NSArray arrayWithObjects:(id)colorOne.CGColor, colorTwo.CGColor, nil nil];  
    NSNumber *stopOne = [NSNumber numberWithFloat:0.0];  
    NSNumber *stopTwo = [NSNumber numberWithFloat:1.0];  
      
    NSArray *locations = [NSArray arrayWithObjects:stopOne, stopTwo, nil nil];  
    CAGradientLayer *headerLayer = [CAGradientLayer layer];  
    headerLayer.colors = colors;  
    headerLayer.locations = locations;  
    headerLayer.frame = self.bounds;  
      
    [self.layer insertSublayer:headerLayer above:0];  
      
}