iOS drawRect with custom height - ios

Question

I have placed a view on a viewController and I want to draw a rectangle in this view, but with a custom height. I determine the height based on a parameter in my viewController.
So for example. If my parameter is 50, I want the rectangle to have the height of 50% of the UIView.
2 questions:
how can I pass the height to the custom drawRect?
how do I make the rectangle be placed on the bottom of the UIView?
I have placed the view using Interface Builder and I have implemented the drawRect in a subclass of UIView and used this as Custom Class for my UIView.
So in the custom class I have:
- (void)drawRect:(CGRect)rect
{
// Drawing code
CGContextRef context = UIGraphicsGetCurrentContext();
UIColor * lightGrayColor = [UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0];
CGRect paperRect = self.bounds;
drawLinearGradient(context, paperRect, lightGrayColor.CGColor, [UIColor clearColor].CGColor);
}
void drawLinearGradient(CGContextRef context, CGRect rect, CGColorRef startColor, CGColorRef endColor)
{
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[] = { 0.0, 1.0 };
NSArray *colors = #[(__bridge id) startColor, (__bridge id) endColor];
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) colors, locations);
CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect));
CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect));
CGContextSaveGState(context);
CGContextAddRect(context, rect);
CGContextClip(context);
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGContextRestoreGState(context);
CGGradientRelease(gradient);
CGColorSpaceRelease(colorSpace);
}
This draws a nice gradient rectangle in my view but it fills the complete UIView.
This is because of the self.bounds.
I have added a property *height to my custom class, but I don't know how to fill this from my viewController. So I want it to start at the bottom off the UIView, and make it as high as I have determined (a % of the real height).
Anybody knows how I can achieve this?

Answer 1

have you set your custom view class in identity inspector in interface builder?
you can set the height property from your viewController:
((MyViewClass *) self.myView).height = myCalculatedValue;
then implement drawRect:
- (void)drawRect:(CGRect)rect
{
// Drawing code
CGContextRef context = UIGraphicsGetCurrentContext();
UIColor * lightGrayColor = [UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0];
CGRect paperRect = self.bounds;
paperRect.origin.y = paperRect.size.height - self.height;
paperRect.size.height = self.height;
//assuming your height property is of CGFloat type
drawLinearGradient(context, paperRect, lightGrayColor.CGColor, [UIColor clearColor].CGColor);
}
this will draw your gradient from (height) points above the bottom to the bottom

Answer 2

I think you can get calculate 50% of screen height and then substract new view height from the full screen Height
youParameter = 50; // Lets assume this is your parametere
int heightOfView = ([UIScreen mainScreen].bounds.size.height * yourParameter) / 100;
// For placing the view to the bottom;
CGRect newFrame;
frame.origin.y = [UIScreen mainScreen].bounds.size.height - heightOfView;
frame.origin.x = 0;
frame.size.width = [UIScreen mainScreen].bounds.size.width; // assuming it will take full width
frame.size.height = heightOfView;
youViewToChange.frame = newFrame; // normally do this or
To pass the value to drawRect you can do:
[self drawRect:newFrame];