Invalid Context Error! Please Advise..

[marioluig]

Anyone have any idea how to deal with the following console output?

<Error>: CGContextSetFillColorWithColor: invalid context
<Error>: CGContextSetStrokeColorWithColor: invalid context
<Error>: CGContextGetShouldSmoothFonts: invalid context
<Error>: CGContextSetFont: invalid context
<Error>: CGContextSetTextMatrix: invalid context
<Error>: CGContextSetFontSize: invalid context
<Error>: CGContextSetTextPosition: invalid context
<Error>: CGContextShowGlyphsWithAdvances: invalid context

The code generating this error message looks like this:

    CGPoint  location = CGPointMake(50, 200);
    UIFont   *font    = [UIFont systemFontOfSize:21];
    [[UIColor whiteColor] set];
	
    [hello drawAtPoint:location withFont:font];

Thanks in advance,
Mario Velasquez

[PhoneyDeveloper]

Is that code in some view's drawRect method? It has to be.

[marioluig]

Originally Posted by PhoneyDeveloper

Is that code in some view's drawRect method? It has to be.

Yeah, it is. Any advice?

[PhoneyDeveloper]

I assume you're not calling the drawRect yourself and this isn't happening in a secondary thread. There must be some other factor that you're not telling us.

Is this a simple UIView subclass? Does it ever draw correctly? Are you calling super drawRect? Does your app have unexplained crashes? Memory corruption might be the cause.

[marioluig]

Originally Posted by PhoneyDeveloper

I assume you're not calling the drawRect yourself and this isn't happening in a secondary thread. There must be some other factor that you're not telling us.

Yeah. It's being called using the following code:

	[stopButton addTarget:self action:@selector( drawSquare ) forControlEvents:UIControlEventTouchUpInside];

drawSquare is the method that calls the code in my first post.

Originally Posted by PhoneyDeveloper

Is this a simple UIView subclass? Does it ever draw correctly? Are you calling super drawRect? Does your app have unexplained crashes? Memory corruption might be the cause.

Yes.
It draws correctly when you call it from drawRect, but not when you hook it up to a button (see above code)
No explained crashes.

[PhoneyDeveloper]

OK, so you are calling drawRect or the code that you showed directly. You can't do that. To make a view draw itself send setNeedsDisplay. Update whatever state the view needs to draw itself and then send setNeedsDisplay.

You can't draw to a view outside drawRect and you can't call drawRect directly.

The invalid context that is mentioned in the error messages is the CGContext that is required for all drawing. When the framework calls a view's drawRect method it first sets up this context.

[entity2light]

Try:

setNeedsDisplay on the main thread

[self performSelectorOnMainThread:@selector(setNeedsDisp lay) withObject:0 waitUntilDone:YES];