CGContextFillEllipseInRect: invalid context - iphone

Question

when I launch my app, I keep getting this CGContextFillEllipseInRect: invalid context error. My app is simply to make the circle 'pinchable'.
The debugger shows me this:
[Session started at 2010-05-23 18:21:25 +0800.]
2010-05-23 18:21:27.140 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.144 Erase[8045:207] New value of counter is 1
2010-05-23 18:21:27.144 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.144 Erase[8045:207] New value of counter is 2
2010-05-23 18:21:27.144 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.144 Erase[8045:207] New value of counter is 3
2010-05-23 18:21:27.145 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.145 Erase[8045:207] New value of counter is 4
2010-05-23 18:21:27.148 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.149 Erase[8045:207] New value of counter is 5
2010-05-23 18:21:27.150 Erase[8045:207] I'm being redrawn.
Sun May 23 18:21:27 Sidwyn-Kohs-MacBook-Pro.local Erase[8045] <Error>: CGContextFillEllipseInRect: invalid context
2010-05-23 18:21:27.150 Erase[8045:207] New value of counter is 6
My implementation file is:
//
// ImageView.m
// Erase
//
#import "ImageView.h"
#import "EraseViewController.h"
#implementation ImageView
-(void)setNewRect:(CGRect)anotherRect{
newRect = anotherRect;
}
- (id)initWithFrame:(CGRect)frame {
if (self = [super initWithFrame:frame]) {
newRect = CGRectMake(0,0,0,0);
ref = UIGraphicsGetCurrentContext();
}
return self;
}
- (void)drawRect:(CGRect)rect {
static int counter = 0;
CGRect veryNewRect = CGRectMake(30.0, 210.0, 60.0, 60.0);
NSLog(#"I'm being redrawn.");
if (counter == 0){
CGContextFillEllipseInRect(ref, veryNewRect);
}
else{
CGContextFillEllipseInRect(ref, rect);
}
counter++;
NSLog(#"New value of counter is %d", counter);
}
- (void)setNeedsDisplay{
[super setNeedsDisplay];
[self drawRect:newRect];
}
- (void)dealloc {
[super dealloc];
}
#end
I've got two questions:
1) Why is it updating counter 6 times? I removed the line [super setNeedsDisplay]; but it becomes 4 times.
2) What is that invalid context error?
Thanks guys.

Answer 1

I'm not sure about the six calls, but at least two calls are happening because the framework is calling drawRect: and so are you. You don't need to call drawRect: yourself (and hence you don't need to override setNeedsDisplay:).
You should call UIGraphicsGetCurrentContext from inside drawRect:. Don't cache it. It may be failing because the framework doesn't guarantee to use the same context on each call, or because you are calling drawRect: directly, or both; I'm not sure which.