iOS setNeedsDisplay won't call drawRect:

[chauhan4]

hi,
I am trying to complete assignment 3 from the Stanford lectures on iTunes U. They're real interesting but I've run into a problem. I'm trying to update a subview in a window to display the shape of a polygon but setNeedsDisplay is called once and never again. Could someone please help me resolve this bug. Thanks

//PolygonView header file
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#import "PolygonShape.h"

@interface PolygonView : UIView/* Specify a superclass (eg: NSObject or NSView) */ {
    IBOutlet PolygonShape *polyShape;
}

@property (retain) PolygonShape *polyShape;

+ (NSArray *)pointsForPolygonInRect:(CGRect)rect numberOfSides:(int)numberOfSides;

@end

//PolygonView implementation file
#import "PolygonView.h"

@implementation PolygonView

@synthesize polyShape;

+ (NSArray *)pointsForPolygonInRect:(CGRect)rect numberOfSides:(int)numberOfSides
{
	CGPoint center = CGPointMake(rect.size.width / 2.0, rect.size.height / 2.0);
	float radius = 0.9 * center.x;
	NSMutableArray *result = [NSMutableArray array];
	float angle = (2.0 * M_PI) / numberOfSides;
	float exteriorAngle = M_PI - angle;
	float rotationDelta = angle - (0.5 * exteriorAngle);
	
	for (int currentAngle = 0; currentAngle < numberOfSides; currentAngle++)
	{
		float newAngle = (angle * currentAngle) - rotationDelta;
		float curX = cos(newAngle) * radius;
		float curY = sin(newAngle) * radius;
		[result addObject:[NSValue valueWithCGPoint:CGPointMake(center.x + curX, center.y + curY)]];
	}
	return result;
}
[B]- (void)drawRect:(CGRect)rect[/B]
{
	NSLog(@"Entering drawRect function");
	CGRect bounds = [self bounds];//Here bounds is reference to the subview that was created
	[[UIColor blueColor] set];
	UIRectFill(bounds);//fills the color of the bounds
	NSArray *arraypoints = [PolygonView pointsForPolygonInRect:bounds numberOfSides:polyShape.numberOfSides];//we don't use self here as this is a class method that begins with a '+' (I think)
	//The above statement returns an array with and x and y coordinates of the polygon that is generated using information of numberOfSides	
	CGContextRef context = UIGraphicsGetCurrentContext();//gets the current graphic context which is what we use when you're overriding the drawRect funtion
	CGContextBeginPath(context);//begin drawing the polygon
	CGPoint currentPoint = [[arraypoints objectAtIndex:0] CGPointValue];//retrieve the first coordinate point of the polygon from the array
	CGContextMoveToPoint(context, currentPoint.x, currentPoint.y);//move to the first point of the array
	//Found this code in the documentation to enumerate through an array using NSEnumerator
	NSEnumerator *enumerator = [arraypoints objectEnumerator];
	id object;
	while((object = [enumerator nextObject]))
	{
		currentPoint = [object CGPointValue];
		CGContextAddLineToPoint(context, currentPoint.x, currentPoint.y);
	}
	CGContextClosePath(context);
	[[UIColor redColor] setFill];
	[[UIColor blackColor] setStroke];
	CGContextDrawPath(context, kCGPathFillStroke);
	NSLog(@"drawRect is being called");
	return;
}
	
@end

//Controller header file
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>
#import "PolygonShape.h"
#import "PolygonView.h"

@interface Controller : NSObject/* Specify a superclass (eg: NSObject or NSView) */ {
    IBOutlet UIButton *decreaseButton;
    IBOutlet UIButton *increaseButton;
    IBOutlet UILabel *numberOfSidesLabel;
    IBOutlet PolygonShape *polygon;
    IBOutlet PolygonView *polyview;
}

- (IBAction)decrease;
- (IBAction)increase;
- (void)awakeFromNib;
- (void)updateInterface;

@end

//Controller implementation file
#import "Controller.h"
#import "PolygonShape.h"
#import "PolygonView.h"

@implementation Controller

- (IBAction)decrease 
{
    //NSLog(@"I'm in the decrease method");
	polygon.numberOfSides = polygon.numberOfSides - 1;
	[B][self updateInterface];[/B]
	NSLog(@"Polygon: %@", polygon);
	//NSLog(@"The number of sides is %d", polygon.numberOfSides);
}

- (IBAction)increase 
{
	polygon.numberOfSides = polygon.numberOfSides + 1;
	[B][self updateInterface];[/B]
	NSLog(@"Polygon: %@", polygon);
	//NSLog(@"I'm in the increase method");
	//NSLog(@"The number of sides is %d", polygon.numberOfSides);
}

[B]- (void)updateInterface[/B]
{
	NSLog(@"Updating");
	if(polygon.numberOfSides > polygon.minimumNumberOfSides)
	{
		decreaseButton.enabled = YES;
	}
	else
	{
		decreaseButton.enabled = NO;
	}
	
	if(polygon.numberOfSides < polygon.maximumNumberOfSides)
		increaseButton.enabled = YES;
	else
		increaseButton.enabled = NO;
	
	numberOfSidesLabel.text = [NSString stringWithFormat:@"%d", polygon.numberOfSides];
	NSLog(@"The number of sides is %d", polygon.numberOfSides);
	[B][polyview setNeedsDisplay];[/B]
}

- (void)awakeFromNib
{
	//PolygonShape *poly = [PolygonShape alloc]; 
	//[polygon initWithNumberOfSides:numberOfSidesLabel.text.integerValue minimumNumberOfSides:3 maximumNumberOfSides:12];
	[self updateInterface];
	NSLog(@"My polygon = %@", polygon);
	//numberOfSidesLabel.text = [NSString stringWithFormat:@"%@", polygon.numberOfSides];
	//[polygon release];
}
@end

Thanks for your help in advance...

 

[jeremy.king]

Did you remember to connect the polygon view to your outlet instance variable?

 

[chauhan4]

Oh, i'm sorry I forgot to update this....I fixed the problem, one of my connections had broken in IB for some reason and thats why it wouldn't display.....Thanks anyway.....

 

[akdude]

I'm working my way though this class as well, but I'm running into a semi-issue. I was having the same issue as the OP where setNeedsDisplay wasn't doing anything. I then linked the PolyView to the controller (or the other way around, still kinda confused about that). This made the call take place, but the polygon was never updating. If I add the line of code

[polygonView setPolygon:polygon];

then the polygon in the view updates and everything draws correctly. I might be wrong, but shouldn't this line of code never be needed? I have

PolygonView with a polygon instance variable linked to the polygon object in the mainview.xib

Controller with a polygon and polygonView instance variables linked to the polygon object and the view respectively.

and finally

Polygon linked to both the controller and polygonview.

I figure with all these links there should only be the ONE polygon ever in existence, and that pointers are passed around correctly, but like I said, if I don't call that line of code above, the updating draw method is called, but nothing changes (did a

NSLog(@"%@", polygon)

and it was the same polygon I started with (5 sides, 3 min, 12 max)).