How to draw a triangle programmatically

user804306 picture user804306 · Jul 14, 2011 · Viewed 29k times · Source

I have a triangle solver, I want a way to use the values I get from the answer to draw a triangle to the screen that matches it.

Answer

progrmr picture progrmr · Jul 14, 2011

If you subclass a UIView you can implement something like this in drawRect to draw a triangle:

-(void)drawRect:(CGRect)rect
{
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    CGContextBeginPath(ctx);
    CGContextMoveToPoint   (ctx, CGRectGetMinX(rect), CGRectGetMinY(rect));  // top left
    CGContextAddLineToPoint(ctx, CGRectGetMaxX(rect), CGRectGetMidY(rect));  // mid right
    CGContextAddLineToPoint(ctx, CGRectGetMinX(rect), CGRectGetMaxY(rect));  // bottom left
    CGContextClosePath(ctx);

    CGContextSetRGBFillColor(ctx, 1, 1, 0, 1);
    CGContextFillPath(ctx);
}