Drawing on the iPhone in objective c [closed] - iphone

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Closed 11 years ago.
I´m quite new to programming and i have sort of half made my (simple) app but i want to know how to draw an picture on the screen (the user draws the picture) and then use that image for the game to just move left and right (and to check if it is colliding with another image).
I've got this..
float pointx;
float pointy;
- (void)drawRect:(CGRect)rect {
CGColorRef blue = [[UIColor blueColor] CGColor];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextClearRect(context, self.bounds);
CGContextSetFillColorWithColor(context, blue);
CGContextFillRect(context, CGRectMake(pointx, pointy, 10, 10));
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch=[[event allTouches]anyObject];
CGPoint point = [touch locationInView:touch.view];
pointx = point.x;
pointy = point.y;
[self setNeedsDisplay];
}
but then when i press on the screen a blue square goes to the finger, but dues not draw anything...

Answer 1

Create a class which is a subclass of UIView... then add these lines of code in tat...
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
gestureStartPoint = [touch locationInView:self];
[currentPath moveToPoint:(gestureStartPoint)];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
currentPosition = [touch locationInView:self];
[currentPath addLineToPoint:(currentPosition)];
[self setNeedsDisplay];
}
- (void)drawRect:(CGRect)rect {
[[UIColor redColor] set];
[currentPath strokeWithBlendMode:kCGBlendModeNormal alpha:1.0];
}
in the header file declare the following.....
CGPoint gestureStartPoint,currentPosition;
UIBezierPath *currentPath;
and declare a property...
#property(nonatomic,retain)UIBezierPath *currentPath;
in the initWIthFrame method inside if block add these lines
currentPath = [[UIBezierPath alloc]init];
currentPath.lineWidth=3;
Create a viewcontroler class then add these lines of code in loadVIew method..
mainView=[[sampleView alloc]initWithFrame:CGRectMake(0, 0, 320, 480)];
mainView.backgroundColor=[UIColor whiteColor];
self.view=mainView;
where sampleView is the UIView subclass u created b4....
Hope this helps...

Answer 2

Drawing user generated pictures with Cocoa Touch is a 2 step process. A UIView will only draw the latest touch you hand it after clearing all the previously user drawn stuff.
One possible solution is to save all the user touches in a history array and (re)draw all of them into the view after any new touch is added. But this can be very slow, depending on the amount of drawing required.
Another possible 2 step method is to create your own bitmap drawing context. First draw your new latest thing into this context, which will have kept the older portions of the drawing if configured correctly, then draw this context into the UIView (or convert the bitmap to an image displayed in a layer over the view).