Values for touch locations fall out of view's bounds - iphone

Question

I am trying to record the locations of the touches. Below is my code. As far as I understand, a touch at the very far upper left corner would give me a location of (0,0), and the very far lower right corner would be (768, 1024) supposing I'm holding the iPad in portrait. However, I'm getting values like (-6, -18) for the upper left corner and (761,1003) for the lower right. It looks like the coordinates are shifted somehow. A trace of self.bounds does give me {{0,0}, {768, 1024}}. Can someone explain this to me? I would like to get x and y value that are between the bounds {{0,0}, {768, 1024}}. Thank you very much in advance.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGRect bounds = [self bounds];
NSLog(#"frame: %#", NSStringFromCGRect(bounds)); // this value was traced as frame: {{0, 0}, {768, 1024}}
UITouch* touch = [[event touchesForView:self] anyObject];
location = [touch locationInView:self];
NSLog(#"Location: %#", NSStringFromCGPoint(location));
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
CGRect bounds = [self bounds];
UITouch* touch = [[event touchesForView:self] anyObject];
location = [touch locationInView:self];
NSLog(#"Location: %#", NSStringFromCGPoint(location));
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
CGRect bounds = [self bounds];
UITouch* touch = [[event touchesForView:self] anyObject];
location = [touch locationInView:self];
NSLog(#"Location: %#", NSStringFromCGPoint(location));
}

Answer 1

Since I cannot comment yet, I have to post an answer. Have you tried setting the background color of the view to a different color so that you can see if its in the top left corner for sure?

Answer 2

Here's what I have for the view:
#implementation TouchesView
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self setUserInteractionEnabled:YES];
[self setBackgroundColor:[UIColor colorWithRed:1.0f green:0.6f blue:0.6f alpha:1.0f]];
}
return self;
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGPoint touch = [[touches anyObject] locationInView:self];
NSLog(#"(%.1f, %.1f)", touch.x, touch.y);
NSLog(#"%#", NSStringFromCGPoint(touch));
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event{}
#end
And this is the initialization and adding it to a view controller:
TouchesView *touchView = [[TouchesView alloc] initWithFrame:self.view.bounds];
[self.view addSubview:touchView];
This works fine for me.

Answer 3

The -20 offset on the y values is fixed by setting "Status bar is initially hidden" to YES. The rest of the problem looks like it's a hardware issue because I got a different range for x and y values each time I run the program on the iPad. I didn't get this problem while running the program on the simulator. On the simulator, x values range from 1 to 767 and y values range from 1 to 1023, which are pretty correct.