Question

I have a set of sliders, I’m using Value Changed to feed a number to a % indicator. I’m also using this value to check if the slider is below a certain point. If it is, I want to run a UIViewAnimation (which I am, it’s all working fine). However, the animation gets called constantly if the slider is moved below the threshold, meaning the items being animated go from point a to point b then back again over and over. So, can I trigger the animation once only at the threshold point?

This is how I get my value in pixels:

_sizeSliderRange = _sizeSlider.frame.size.width - _sizeSlider.currentThumbImage.size.width;
_sizeSliderOrigin = _sizeSlider.frame.origin.x + (_sizeSlider.currentThumbImage.size.width / 4.0);
_sizeSliderValueToPixels = (_sizeSlider.value * _sizeSliderRange) + _sizeSliderOrigin;

And I use a conditional inside the linked Value Changed IBAction function to checkt he value and do the work:

if (_sizeThumbX < 85) {  //if within 60px of the left margin we animate the label to sit float left
    [UIView transitionWithView:_sizeLabel duration:0.25f options:UIViewAnimationCurveEaseInOut animations:^(void) { etc etc

Thanks.

Answer 1

Like @Luis said, just use a BOOL property like this:

if (_sizeThumbX < 85) {  //if within 60px of the left margin we animate the label to sit float left
    if (!self.passedBelowThreshold) {
        [UIView transitionWithView:_sizeLabel duration:0.25f options:UIViewAnimationCurveEaseInOut animations:^(void) { /* ... */ }
    }
}
self.passedBelowThreshold = _sizeThumbX < 85;