drawing on the iPhone in objective c [duplicate] - iphone

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Closed 11 years ago.
Possible Duplicate:
Drawing on the iPhone in objective c
I have written this...
In the .h file:
#import <UIKit/UIKit.h>
#interface DrawView : UIView {
CGPoint gestureStartPoint,currentPosition;
CGContextRef c;
UIBezierPath *currentPath;
}
#property(nonatomic,retain)UIBezierPath *currentPath;
#end
And in the .m file:
#import "DrawView.h"
#implementation DrawView
#synthesize currentPath;
- (id)initWithFrame:(CGRect)frame {
[self drawRect:CGRectMake(0, 0, 320, 480)];
self = [super initWithFrame:frame];
if (self) {
currentPath = [[UIBezierPath alloc]init];
currentPath.lineWidth=3;
}
return self;
}
- (void)drawRect:(CGRect)rect {
[[UIColor redColor] set];
[currentPath strokeWithBlendMode:kCGBlendModeNormal alpha:1.0];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
currentPosition = [touch locationInView:self];
[currentPath addLineToPoint:(currentPosition)];
[self setNeedsDisplay];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
gestureStartPoint = [touch locationInView:self];
[currentPath moveToPoint:(gestureStartPoint)];
}
- (void)dealloc {
[super dealloc];
}
#end
I want to let the user draw an image on the iPhone screen and then use that image for the game... but this doesn't draw anything...

Answer 1

This is because your currentPath is not allocated.
If you instantiate the view in the resource [UIView initWithFrame:] will never be called.
Implement [UIView initWithCoder:] and allocate it there.
- (void)commonInit
{
currentPath = [[UIBezierPath alloc] init];
currentPath.lineWidth=3;
}
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self)
{
[self commonInit];
}
return self;
}
- (id)initWithCoder:(NSCoder*)aDecoder
{
self = [super initWithCoder:aDecoder];
if (self)
{
[self commonInit];
}
return self;
}
Alternatively you can make the path in the touchesBegan if it is nil.
- (UIBezierPath*)currentPath
{
if (currentPath = nil)
{
currentPath = [[UIBezierPath alloc] init];
currentPath.lineWidth=3;
}
return currentPath;
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
gestureStartPoint = [touch locationInView:self];
[[self currentPath] moveToPoint:(gestureStartPoint)];
}
However, there are some problems in the code.
You call [self drawRect:CGRectMake(0, 0, 320, 480)] before self = [super initWithFrame:frame]. You must not call any method there. You can write your code only inside
if (self ! =nil)
{
// your code
}
currentPath leaks. Release it in dealloc.
Never call drawRect directly. Call [UIView setNeedsDisplay] instead.