如何通过iphone中的时间间隔使用coregraphics快速绘制线条

Question

I am new to iphone programming.

In my app, I have to draw the lines very quickly according to my requirements. I am taking NSTimer with 0.01 as timing interval.

I am using the following code to draw the lines. How can I draw those lines quickly using NSTimer?

    UIGraphicsBeginImageContext(bgImage.frame.size);
    [bgImage.image drawInRect:CGRectMake(0, 0, bgImage.frame.size.width, bgImage.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(),5);
    CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(),([UIColor blueColor]).CGColor);
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), startPoint.x, startPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), endPoint.x, endPoint.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    bgImage.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    endpoint=startpoint;

can anybody help me?

Answer 1

If you want to present this in a view, you probably want to look at subclassing UIView , and placing this drawing code inside the drawRect: method.

drawRect: will have to re-draw the whole image each time, and may be called by the system whenever necessary. If you need to update it, call setNeedsDisplay: on the view, and it'll redraw at the end of the run loop.