Animation when drawing with CGContext

Animation when drawing with CGContext

My question is how to animate the drawing process when drawing with
CGContextRef. Is it possible? Assuming it is, how?
I have two code snippets that I would like to animate. First one draws a
progress bar and the second one draws a simple line chart. The drawing is
done inside a subclass of UIView.
Progress bar is nice and easy. But I want it to sort of draw itself out
from the left. I am pretty sure that this will require using something
other than UIRectFill but I dont know how to accomplish it.
- (void)drawProgressLine
{
[bgColor set];
UIRectFill(self.bounds);
[graphColor set];
UIRectFill(CGRectMake(0, 0, self.frame.size.width / 100 * [[items
objectAtIndex:0] floatValue], self.frame.size.height));
}
The line chart is a bit more complex. I would really really like it to
start drawing itself from the left line by line slowly completing itself
towards the right but if that is too much how can I just slowly fade it
in? The code:
- (void)drawLineChart
{
[bgColor set];
UIRectFill(self.bounds);
[graphColor set];
if (items.count < 2) return;
CGRect bounds = CGRectMake(0, 50, self.bounds.size.width,
self.bounds.size.height - 100);
float max = -1;
for (GraphItem *item in items)
if (item.value > max)
max = item.value;
float xStep = (self.frame.size.width) / (items.count - 1);
for (int i = 0; i < items.count; i++)
{
if (i == items.count - 1) break;
float itemHeight = bounds.origin.y + bounds.size.height -
((GraphItem*)[items objectAtIndex:i]).value / max *
bounds.size.height;
float nextItemHeight = bounds.origin.y + bounds.size.height -
((GraphItem*)[items objectAtIndex:i + 1]).value / max *
bounds.size.height;
CGPoint start = CGPointMake(xStep * i, itemHeight);
CGPoint stop = CGPointMake(xStep * (i + 1), nextItemHeight);
[self drawLineFromPoint:start toPoint:stop lineWidth:1
color:graphColor shadow:YES];
}
}
Pretty simple I guess. If important the drawLineFromPoint..... is
implemented like:
- (void)drawLineFromPoint:(CGPoint)startPoint toPoint:(CGPoint)endPoint
lineWidth:(CGFloat)width color:(UIColor *)color shadow:(BOOL)shadow
{
if (shadow)
{
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat components[4] = {0.0, 0.0, 0.0, 1.0};
CGColorRef shadowColor = CGColorCreate(colorSpace, components);
CGContextSetShadowWithColor(UIGraphicsGetCurrentContext(),
CGSizeMake(1,1), 2.0, shadowColor);
}
CGContextBeginPath(context);
CGContextSetLineWidth(context, width);
CGContextMoveToPoint(context, startPoint.x, startPoint.y);
CGContextAddLineToPoint(context, endPoint.x, endPoint.y);
CGContextClosePath(context);
[color setStroke];
CGContextStrokePath(context);
CGContextSetShadowWithColor(context, CGSizeZero, 0, NULL);
}
I hope I made myself clear cause its 1 am in my country and this post is
the last thing that stands between me and my bed. Cheers, Jan.