CGContext line drawing: CGContextFillPath not work

Question

Anyone have any idea why CGContextFillPath won't work in the code snippet below? I'm using the following code to draw to a UIImageView. It's stroking the path correctly, but ignoring CGContextFillPath.

UIGraphicsBeginImageContext(self.frame.size);
[drawingView.image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0);
CGContextSetAllowsAntialiasing(UIGraphicsGetCurrentContext(), YES);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
CGContextSetRGBFillColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), firstMovedTouch.x, firstMovedTouch.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFillPath(UIGraphicsGetCurrentContext());
drawingView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Answer 1

To solve this problem, use the following code:

CGContextRef context = UIGraphicsGetCurrentContext(); 

CGContextSetRGBStrokeColor(context, 0.0, 0.0, 0.0, 1.0);
CGContextSetRGBFillColor(context, 0.0, 0.0, 0.0, 1.0);
CGContextSetLineJoin(context, kCGLineJoinRound);
CGContextSetLineWidth(context, 8.0);

CGMutablePathRef pathRef = CGPathCreateMutable();

/* do something with pathRef. For example:*/
CGPathMoveToPoint(pathRef, NULL, x, y);
CGPathAddLineToPoint(pathRef, NULL, x, y+100);
CGPathAddLineToPoint(pathRef, NULL, x+100, y+100);
CGPathAddLineToPoint(pathRef, NULL, x+100, y);
CGPathCloseSubpath(pathRef);

CGContextAddPath(context, pathRef);
CGContextFillPath(context);

CGContextAddPath(context, pathRef);
CGContextStrokePath(context);

CGPathRelease(pathRef);

Answer 2

I had the same trouble. I found that you can not use

CGContextStrokePath( UIGraphicsGetCurrentContext() ) 
CGContextFillPath( UIGraphicsGetCurrentContext() ) 

consecutively: the latter will not work because after committing the stroke on the path, the path is removed from the context.

So, I used the same path twice; one for stroke，the other for fill.

// ... create a path of CGMutablePathRef ....

CGContextSaveGState( context );
//....fill the path .....
CGContextRestoreGState( context );

CGContextSaveGState ( context );
//....stroke the path .....
CGContextRestoreGState( context );

CFRelease( path );

Answer 3

I think you need to call CGContextClosePath before you can fill the path. I am not sure what you are trying to draw, but CGContextFillPath will fill the area inside the path and I only see single line here.

Answer 4

I believe that the best way to stroke and fill your path is to add the following line of code after you've finished setting up your path:

    CGContextDrawPath(myContext, kCGPathFillStroke);