iPhone Rendering Question
- by slythic
Hi all,
I'm new to iPhone/Objective-C development. I "jumped the gun" and started reading and implementing some chapters from O'Reilly's iPhone Development. I was following the ebook's code exactly and my code was generating the following error:
CGContextSetFillColorWithColor: invalid context
CGContextFillRects: invalid context
CGContextSetFillColorWithColor: invalid context
CGContextGetShouldSmoothFonts: invalid context
However, when I downloaded the sample code for the same chapter the code is different.
Book Code:
- (void) Render {
CGContextRef g = UIGraphicsGetCurrentContext();
//fill background with gray
CGContextSetFillColorWithColor(g, [UIColor grayColor].CGColor);
CGContextFillRect(g, CGRectMake(0, 0, self.frame.size.width, self.frame.size.height));
//draw text in black.
CGContextSetFillColorWithColor(g, [UIColor blackColor].CGColor);
[@"O'Reilly Rules!" drawAtPoint:CGPointMake(10.0, 20.0) withFont:[UIFont systemFontOfSize:[UIFont systemFontSize]]];
}
Actual Project Code from the website (works):
- (void) Render {
[self setNeedsDisplay]; //this sets up a deferred call to drawRect.
}
- (void)drawRect:(CGRect)rect {
CGContextRef g = UIGraphicsGetCurrentContext();
//fill background with gray
CGContextSetFillColorWithColor(g, [UIColor grayColor].CGColor);
CGContextFillRect(g, CGRectMake(0, 0, self.frame.size.width, self.frame.size.height));
//draw text in black.
CGContextSetFillColorWithColor(g, [UIColor blackColor].CGColor);
[@"O'Reilly Rules!" drawAtPoint:CGPointMake(10.0, 20.0) withFont:[UIFont systemFontOfSize:[UIFont systemFontSize]]];
}
What is it about these lines of code that make the app render correctly?
- (void) Render {
[self setNeedsDisplay]; //this sets up a deferred call to drawRect.
}
- (void)drawRect:(CGRect)rect {
Thanks in advance for helping out a newbie!
