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POiPhone: Drawing a curved line until it becomes a circle animation
 

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  1. POiPhone: Drawing a curved line until it becomes a circle animation
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    <p>I wish to draw a curved line until it makes a full rotation and joins to become a complete circle, just the circle outline, not filled. This has to be animated over a number of seconds.</p> <p>Can anyone point me in the right direction? I already asked a <a href="https://stackoverflow.com/questions/7991086/iphone-core-animation-drawing-a-circle">similar question</a> to this but I worded it incorrectly so everyone had a hard time understanding what I meant and thus it got lost in the sea of questions.</p> <p>Many Thanks for any help</p> <p>[edit] </p> <p>I'm currently sub-classing UIView and overriding drawRect. I found code to draw a filled circle but I only require the stroke.</p> <pre><code>- (void)drawRect:(CGRect)rect { // Drawing code CGRect allRect = self.bounds; CGRect circleRect = CGRectInset(allRect, 2.0f, 2.0f); CGContextRef context = UIGraphicsGetCurrentContext(); // Draw background CGContextSetRGBStrokeColor(context, self.strokeValueRed, self.strokeValueGreen, self.strokeValueBlue, self.strokeValueAlpha); // white CGContextSetRGBFillColor(context, 1.0f, 1.0f, 1.0f, 0.1f); // translucent white CGContextSetLineWidth(context, self.lineWidth); CGContextFillEllipseInRect(context, circleRect); CGContextStrokeEllipseInRect(context, circleRect); // Draw progress CGPoint center = CGPointMake(allRect.size.width / 2, allRect.size.height / 2); CGFloat radius = (allRect.size.width - 4) / 2; CGFloat startAngle = - ((float)M_PI / 2); // 90 degrees CGFloat endAngle = (self.progress * 2 * (float)M_PI) + startAngle; CGContextSetRGBFillColor(context, 1.0f, 1.0f, 1.0f, 1.0f); // white CGContextMoveToPoint(context, center.x, center.y); CGContextAddArc(context, center.x, center.y, radius, startAngle, endAngle, 0); CGContextClosePath(context); CGContextFillPath(context); } </code></pre> <p>[edit #2]</p> <p>I changed the code to remove all the fill references but now its not drawing anything :( any ideas?</p> <pre><code>- (void)drawRect:(CGRect)rect { // Drawing code CGRect allRect = self.bounds; CGContextRef context = UIGraphicsGetCurrentContext(); // Draw background CGContextSetRGBStrokeColor(context, self.strokeValueRed, self.strokeValueGreen, self.strokeValueBlue, self.strokeValueAlpha); // white CGContextSetLineWidth(context, 5); // Draw progress CGPoint center = CGPointMake(allRect.size.width / 2, allRect.size.height / 2); CGFloat radius = (allRect.size.width - 4) / 2; CGFloat startAngle = - ((float)M_PI / 2); // 90 degrees CGFloat endAngle = (self.progress * 2 * (float)M_PI) + startAngle; CGContextAddArc(context, center.x, center.y, radius, startAngle, endAngle, 0); CGContextStrokePath(context); } </code></pre> <p>[edit #3] Solution</p> <p>Right I feel like a right dickhead! the problem was that the stroke colour values were not initialised meaning that line was being draw but obviously could not see it!! </p>
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