I meant to say -touchesMoved instead of -touchesBegan below.
- Carl
On Oct 3, 2013, at 12:47 PM, Carl Hoefs <newsli...@autonomy.caltech.edu> wrote:
> iOS 6.1.3 & 7.0.2, newb!
>
> I'm seeing an unacceptable lag in my iOS app on drag touches, from when a
> finger is dragged across the screen to when my code updates the screen. I
> can't figure out what is causing the lag.
>
> Here's my setup. I have a -touchesBegan:withEvent: method in my view
> controller that gets invoked via callback from the GUI when a finger touch
> occurs. My code displays a tiny dot on the GUI beneath the user's fingertip
> that is supposed to track with the user's touch in real time.
>
> -(void) -touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
> {
> CGPoint apoint=[[touches anyObject] locationInView:[self view]];
> [layer setPosition:apoint];
> }
>
> The 'layer' variable is defined as:
>
> CALayer *layer=[[CALayer alloc]init];
> [layer setDelegate:self];
> [layer setBounds:CGRectMake(0,0,5,5)]; // a tiny "dot"
>
> This all works well except when the user makes large, sweeping touches (say
> dragging a fingertip across the entire screen). In this case, the update
> drawing of the dot lags a second or two behind, which is unacceptable.
>
> So I'm wondering how to handle this. FWIW, adding a [super
> touchesBegan:touches withEvent:event] to the above callback method didn't
> change the behavior.
>
> - Carl
>
>
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