How to draw a rectangle?

Question

I want to draw a filled rectangle in my viewContoller's view. I wrote the code below in viewDidLoad. But there is no change. What is wrong?

CGRect rectangle = CGRectMake(0, 100, 320, 100);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextFillRect(context, rectangle);

please note, for this **extremely old question**, I've put in the modern answer, 2018 — Fattie, Mar 10 '18 at 16:36

score 45 · Accepted Answer · answered Nov 19 '11 at 15:50

45

You can't do it in a viewController. You need to extend your View and add the code under "drawRect:"

this will change the drawing logic of your view.

-(void) drawRect:(CGRect)rect{    
[super drawRect:rect];  
    CGRect rectangle = CGRectMake(0, 100, 320, 100);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);
    CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
    CGContextFillRect(context, rectangle);
}

answered Nov 19 '11 at 15:50

Guy Ephraim

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+1 for correct answer - though I would not ignore the CGRect parameter of drawRect.... – Till Nov 19 '11 at 15:51
Right, I guess a better solution is to first verify that the area that needs to be re-drawn is part of the rectangle, and only then do it. – Guy Ephraim Nov 19 '11 at 15:55
What do you mean extend view? – charly Nov 19 '11 at 15:57
Create a new class for your view extending UIView – Guy Ephraim Nov 19 '11 at 15:58
1

No need to call super here; as it says in the Apple UIView class reference: "If you subclass UIView directly, your implementation of this method does not need to call super." – jpswain Feb 24 '13 at 08:46

score 6 · Answer 2 · edited Jun 20 '20 at 09:12

6

modern 2018 solution..

override func draw(_ rect: CGRect) {

    let r = CGRect(x: 5, y: 5, width: 10, height: 10)

    UIColor.yellow.set()
    UIRectFill(r)
}

that's it.

edited Jun 20 '20 at 09:12

Community

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answered Mar 10 '18 at 16:38

Fattie

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score 4 · Answer 3 · answered Mar 04 '14 at 12:15

Just for clarity:

If You need to draw a rectangle which has the same fill and border color, then You can replace:

CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);
CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);

with:

 [[UIColor redColor] set];

score 3 · Answer 4 · answered Nov 19 '11 at 15:52

You can't render directly in viewDidLoad; it's the views themselves that would have to run this in their drawRect method.

The easiest way to "draw" a rectangle is to place a UIView with a background color & border in your view. (You can set the border via the view's CALayer's methods. i.e. myView.layer.borderColor = [[UIColor redColor] CGColor];)

How to draw a rectangle?

4 Answers4

modern 2018 solution..

Linked

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