On Fri, Oct 17, 2008 at 2:33 PM, James Walker <[EMAIL PROTECTED]> wrote:
> I'd like to be notified when the mouse button has been released after some
> live tracking of a slider. I can probably do it by subclassing NSSlider and
> NSSliderCell, for instance overriding [NSCell
> stopTracking:at:inView:mouseIsUp:], but is there an easier way?
There is indeed. Write your action like this:
- (IBAction)sliderMoved:(id)sender {
SEL trackingEndedSelector = @selector(sliderEnded:);
[NSObject cancelPreviousPerformRequestsWithTarget:self
selector:trackingEndedSelector object:sender];
[self performSelector:trackingEndedSelector withObject:sender
afterDelay:0.0];
// do whatever you want to do during tracking here
}
- (void)sliderEnded:(id)sender {
// do whatever you want to do when tracking ends here
}
It may not be immediately obvious why this works. Delayed performs
happen in the default runloop mode (unless you specify otherwise using
the variant that has modes: at the end). Event tracking happens in a
special event tracking runloop mode. So the delayed perform won't
happen until the user lets go of the mouse button.
To keep these delayed performs from piling up, this method first
cancels any previous ones before scheduling the new one. An alternate
method would be to have some sort of flag that guarantees you only
schedule one, but this way is simpler and doesn't require a flag.
This technique works for any control that uses the event tracking
mode, such as continuous buttons, menus, and other such things, but
it's most commonly used for sliders.
Mike
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