UIView Doesn't Appear and drawRect Method Never Called - objective-c

Question

I've made a UIView subclass called MiniView.
I try adding it to my viewController as follows:
#interface SomeViewController ()
#property (strong, nonatomic) MiniView *miniView;
#end
- (void)viewDidLoad
{
[super viewDidLoad];
self.miniView = [[MiniView alloc] initWithFrame:CGRectMake(20.f, 20.f, 200.f, 200.f)];
_miniView.backgroundColor = [UIColor blackColor];
[self.view addSubview:_miniView];
}
The MiniView class looks like this:
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
- (void)drawRect:(CGRect)rect
{
NSLog(#"DRAW RECT");
CGContextRef context = UIGraphicsGetCurrentContext();
UIColor * redColor = [UIColor colorWithRed:1.0 green:0.0 blue:0.0 alpha:1.0];
CGContextSetFillColorWithColor(context, redColor.CGColor);
CGContextFillRect(context, self.bounds);
}
But drawRect never gets called, unless I explicity call it, from within the setNeedsLayout method. It also doesn't draw anything. I've tried just adding a UIImageView in the drawRect method, and this appears fine. But the above code produces nothing.
I also get the error:
: CGContextSetFillColorWithColor: invalid context 0x0. This is
a serious error. This application, or a library it uses, is using an
invalid context and is thereby contributing to an overall degradation
of system stability and reliability. This notice is a courtesy: please
fix this problem. It will become a fatal error in an upcoming update.
If I print a log statement in the drawRect method and output the 'rect' values, it's correct at 200 x 200, so I don't know why the context is 0x0.
So one problem is that drawRect is never called, and the other problem is that if I call it explicitly, nothing is displayed...

Answer 1

You probably need to call setNeedsDisplay on your custom UIView subclass:
- (void)viewDidLoad {
[super viewDidLoad];
self.miniView = [[MiniView alloc] initWithFrame:CGRectMake(20.f, 20.f, 200.f, 200.f)];
_miniView.backgroundColor = [UIColor blackColor];
[_miniView setNeedsDisplay]; // Added this
[self.view addSubview:_miniView];
}
This is basically a prod to tell the system your UIView needs to be redrawn. See the docs for more info.

Answer 2

Posting as a separate answer as requested:
The actual problem was that I had redefined the setNeedsDisplay method in the MiniView class, like so:
- (void)setNeedsDisplay
{
NSLog(#"Redrawing info: %#", [_info description]);
}
Because I had neglected to make a call to [super setNeedsDisplay], drawRect was never being called and nothing was drawing. So this fixed it:
- (void)setNeedsDisplay
{
[super setNeedsDisplay];
NSLog(#"Redrawing info: %#", [_info description]);
}

Answer 3

Never call drawRect explicity, try this:
- (void)viewDidLoad
{
[super viewDidLoad];
self.miniView = [[MiniView alloc] initWithFrame:CGRectMake(20.f, 20.f, 200.f, 200.f)];
_miniView.backgroundColor = [UIColor blackColor];
[self.view addSubview:_miniView];
[_miniView setNeedsDisplay];
}

Answer 4

Well in your drawrect method include this line:-
[super drawRect:rect];