Quartz custom drawing and UIViews. Cannot see the quartz drawing.

Question

Hello everyone,

I am drawing on a UIview several other subviews. Then in the DrawRect method of this UIView I am drawing a bezier curve.

UNFORTUNATELY, the bezier curve never shows up. I have checked that the bezier curve is behind the background of the view (when I remove the background view I can see it).

How can I combine custom drawing with Quartz and other UISubviews?

The UIViews of the view are kept in a xib. I load the xib and then I draw the curve in the Drawrect method of the view.

This is the implementation code of the UIView I am talking about:

#import "DandiGameView.h"
#import "SeedView.h"
#import "Defines.h"

@implementation DandiGameView

@synthesize flowerHeadPosition, blowVolume, seedArray, trunkTop;

- (void)awakeFromNib {
 [super awakeFromNib];
 //self.clearsContextBeforeDrawing = YES;
 [self animateTrunk:1 andWindVolume:1.0];
 self.seedArray = [NSMutableArray array];
 UIImageView *tmpImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"TRUNKTOP.PNG"]];
 [tmpImageView setCenter:flowerHeadPosition];
 self.trunkTop = tmpImageView;
 [tmpImageView release];
 //[tmpImageView sett]
 [self addSubview:self.trunkTop];
 [tmpImageView release];
}

- (id)initWithCoder:(NSCoder *)decoder
{
    if (self = [super initWithCoder:decoder])
    {
  // Initialization code
  float pointX =  FLOWER_POSITION_HOR - FLOWER_TRUNK_WIDTH / 2.0;
  float topPointY =  self.bounds.size.height - FLOWER_POSITION_VER;
  flowerHeadPosition = CGPointMake(pointX, topPointY);
  s = CGPointMake(pointX, self.bounds.size.height);
  e = flowerHeadPosition;
  cp1 = CGPointMake(pointX + 10.0, self.bounds.size.height - FLOWER_LOWER_CONTROLPOINT);
  cp2 = CGPointMake(pointX - 10.0, self.bounds.size.height - FLOWER_UPPER_CONTROLPOINT);
    }
    return self;
}

- (void) animateTrunk:(double)time andWindVolume: (double) windVolume {
 randOne = sin(0.2 * time * windVolume) + sin(0.5 * time* windVolume);
 randTwo = sin(0.35 * time* windVolume) - sin(0.15 * time * windVolume);
 flowerHeadPosition.x = FLOWER_POSITION_HOR - FLOWER_TRUNK_WIDTH / 2.0 - randTwo * randOne * FLOWER_CURVITY_CONTROL;
 cp1.x = FLOWER_POSITION_HOR - FLOWER_TRUNK_WIDTH / 2.0 + 10 + randTwo * randOne * 2.0;
 [self.trunkTop setCenter:flowerHeadPosition];
 [self bringSubviewToFront:trunkTop];
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.

- (void)drawRect:(CGRect)rect {
    // Drawing code
 CGContextRef c = UIGraphicsGetCurrentContext();

    // Drawing with a GREEN stroke color
 CGContextSetRGBStrokeColor(c, 141.0/255.0, 198.0/255.0, 63.0/255.0, 1.0);
 // Draw them with a FLOWER_TRUNK_WIDTH stroke width so they are a bit more visible.
 CGContextSetLineWidth(c, FLOWER_TRUNK_WIDTH);
 // Draw a bezier curve with end points s,e and control points cp1,cp2
 e = flowerHeadPosition;
 CGContextMoveToPoint(c, s.x, s.y);
 CGContextAddCurveToPoint(c, cp1.x, cp1.y, cp2.x, cp2.y, e.x, e.y);
 CGContextStrokePath(c);
}

-(void)onElementTouch:(id)sender {

}

- (void) onTimeTick:(id)sender {
 static float runningTime = 0.0;
 runningTime += ANIMATION_TIME_STEP;
 [self animateTrunk:runningTime andWindVolume:pow(blowVolume, 5.0)];
}


- (void)dealloc {
 [trunkTop release];
 [delegate release];
    [super dealloc];
}


@end

Answer 1

Do the subviews of the view you're drawing into have their opaque property set to YES? If so (which is the default) and they entirely cover the view you are drawing into, then I would not expect to see any of your drawing.

EDIT with further suggestion:

If the other views have opaque=NO, perhaps also set their background color to clear? If they are created in Interface Builder you can set their background color there to "Clear Color". If they are created in code you can do view.backgroundColor = [UIColor clearColor].