Gradient alpha not working in drawRect

Question

I'm using a slightly modified version of code I grabbed from the top answer here: Modern technique of adding gradient to UIView

My modified code:

- (void)drawRect:(CGRect)rect
{
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = UIGraphicsGetCurrentContext();

    // The if statements are surely a crappy way of setting the locations, but whatever
    CGGradientRef gradient;
    if ([self.colors count] == 3) {
        CGFloat gradientLocations[] = {0, 0.5, 1};
        gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef)self.colors, gradientLocations);
    } else {
        CGFloat gradientLocations[] = {0, 1};
        gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef)self.colors, gradientLocations);
    }

    CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect));
    CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect));    

    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
}

I have put that into a class called Gradient_View, and I am attempting to subclass it. In my subclass's init method, I have this:

self.colors = [NSArray arrayWithObjects:
            (id)[UIColor colorWithRed:1.0f green:1.0f blue:1.0f alpha:1.0f].CGColor,
             [UIColor colorWithRed:1.0f green:1.0f blue:1.0f alpha:0.0f].CGColor,
              nil];

Note that the second color in that final array has an alpha value of 0, so the gradient should become see-through. However, the result I get in my simulator is totally opaque:

How can I get the transparency to work?

Answer 1

Check and see if your UIView is opaque or not. Make sure opaque is set to NO.