CODEWITHSUNDEEP
iphoneobjective-ciosipad
adit
adit

Reputation: 33644

calling drawRect in a UIView subclass

I have subclassed a UIView and I have a drawRect implemented. I basically want this drawRect to be called after I've set the CGPoint, which is a property of this UIView. How do I do this? Here's my code:

-(id) initWithCoder:(NSCoder *)aDecoder
{
    if(self = [super initWithCoder:aDecoder]) {
        point_.x = 0;
        self.page_ = [UIImage imageNamed:@"pages"];
    }
    return self;
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    if (point_.x != 0){
        [self.page_ drawInRect:rect];
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
        CGContextSetLineWidth(context, 1.0f);
        CGContextMoveToPoint(context, 40, point_.y); 
        CGContextAddLineToPoint(context, 420, point_.y);
        CGContextStrokePath(context);
    }
}

When I've set the point of this UIView and I call drawRect in my other UIViewController like follows:

 self.page_.point_ = CGPointMake(-100, self.title_.frameHeight + self.title_.frameX + 40);
    [self.page_ drawRect:self.page_.frame];

It gives me all of these errors:

  <Error>: CGContextSaveGState: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextSetBlendMode: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextSetAlpha: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextTranslateCTM: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextScaleCTM: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextDrawImage: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextRestoreGState: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextSetStrokeColorWithColor: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextSetLineWidth: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextMoveToPoint: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextAddLineToPoint: invalid context 0x0
    Feb 22 20:24:38 <Error>: CGContextDrawPath: invalid context 0x0

Why is this?

Upvotes: 0

Views: 3276

Answers (3)

Ievgen
Ievgen

Reputation: 1596

Wrap your drawing code into UIGraphicsPushContext( context ) and UIGraphicsPopContext() to avoid this error messages.

Upvotes: 0

Darshan Kunjadiya
Darshan Kunjadiya

Reputation: 3329

- (id)initWithCoder:(NSCoder *)aDecoder // (1)
{
if (self = [super initWithCoder:aDecoder])
{
    [self setMultipleTouchEnabled:NO]; // (2)
    [self setBackgroundColor:[UIColor whiteColor]];
    path = [UIBezierPath bezierPath];
    [path setLineWidth:2.0]; 
}
return self;
}


- (void) drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 0.0, 0.0, 0.0, 1.0);
CGContextSetLineWidth(context, 3.0);
CGContextDrawPath(context, kCGPathFillStroke);    //CGContextSetRGBFillColor doesn't work either
CGContextBeginPath(context);
CGContextMoveToPoint(context, 100.0, 60.0);
CGRect rectangle = {100.0, 60.0, 120.0, 120.0};
CGContextAddRect(context, rectangle);

CGContextStrokePath(context);
CGContextFillPath(context);
}
this code implement in create new uiview and add this code i hope that code you usefull.

Upvotes: 2

Jacob Relkin
Jacob Relkin

Reputation: 163228

You should never, ever call -drawRect: directly.

Use -setNeedsDisplay instead:

self.page_.point_ = CGPointMake(-100, self.title_.frameHeight + self.title_.frameX + 40);
[self.page_ setNeedsDisplay];

If you need to customize the drawing area (aka the CGRect that will be passed to -drawRect:), you can use -setNeedsDisplayInRect:

As @rob mayoff has suggested, you can override the setter for the point_ property:

- (void)setPoint_:(CGPoint)point {
   if(!CGPointEqualToPoint(point_, point)) {
      point_ = point;
      [self setNeedsDisplay];
   }
}

Upvotes: 4

Related Questions