How to draw a triangle programmatically

问题:

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.

回答1:

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); } 

回答2:

Swift 3 equivalent for progrmr's answer:

override func draw(_ rect: CGRect) {      guard let context = UIGraphicsGetCurrentContext() else { return }      context.beginPath()     context.move(to: CGPoint(x: rect.minX, y: rect.minY))     context.addLine(to: CGPoint(x: rect.maxX, y: rect.midY))     context.addLine(to: CGPoint(x: (rect.minX), y: rect.maxY))     context.closePath()      context.setFillColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 1.0)     context.fillPath() } 

回答3:

- (void)drawRect:(CGRect)rect {       CGContextRef ctx = UIGraphicsGetCurrentContext();     CGContextClearRect(ctx, rect);      // Draw a triangle     CGContextSetRGBFillColor(ctx, 255, 160, 122, 1);      CGContextBeginPath(ctx);     CGContextMoveToPoint   (ctx, 290, 35);  // top     CGContextAddLineToPoint(ctx, 350, 165);  // right     CGContextAddLineToPoint(ctx, 230,165);  // left     CGContextClosePath(ctx);      CGContextSetRGBFillColor(ctx, 1, 1, 1, 1);     CGContextFillPath(ctx); } 

文章来源: How to draw a triangle programmatically