UISlider and UIScrollView

Question

I have a UISlider as part of a view that is loaded into a UIScrollView with paging enabled. I\'ve noticed an unexpected behavior. If the user tries

Answer 1

My problem was a superset of this issue - I've got UISliders inside UITableViewCells and the whole UITableView is a page inside a UIScrollView. The sliders were wreaking havoc on the interactions with the other two and the subclassing solutions did not work. Here's what I came up with that's working great: send notifications when the sliders move and have the UITableView and UIScrollView disableScrolling on during this time. Note in the picture below: my sliders are horizontal, my tableview is vertical, and my UIScrollView has horizontal pages.



The UITableViewCell picks up events for the programmatically-created slider:

self.numberSlider = [[UISlider alloc] init];
[self.numberSlider addTarget:self action:@selector(sliderValueChanged:) forControlEvents:UIControlEventValueChanged];
[self.numberSlider addTarget:self action:@selector(sliderTouchDown:) forControlEvents:UIControlEventTouchDown];
[self.numberSlider addTarget:self action:@selector(sliderTouchUp:) forControlEvents:UIControlEventTouchUpInside];
[self.numberSlider addTarget:self action:@selector(sliderTouchUp:) forControlEvents:UIControlEventTouchUpOutside];

For the purposes of this tutorial, we only care about touchDown and Up:

- (void)sliderTouchDown:(UISlider *)sender
{
    [[NSNotificationCenter defaultCenter] postNotificationName:NOTIFY_SLIDER_TOUCH_BEGAN object:nil];
}

- (void)sliderTouchUp:(UISlider *)sender
{
    [[NSNotificationCenter defaultCenter] postNotificationName:NOTIFY_SLIDER_TOUCH_ENDED object:nil];
}

Now, we catch in these notifications in both the UITableView (note that the tableview is in a VC but I'm sure this would work if you subclassed):

- (void)viewDidLoad
{
    // other stuff
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sliderTouchDown:) name:NOTIFY_SLIDER_TOUCH_BEGAN object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sliderTouchUp:) name:NOTIFY_SLIDER_TOUCH_ENDED object:nil];
}

- (void)sliderTouchDown:(NSNotification *)notify
{
    self.treatmentTableView.scrollEnabled = NO;
}

- (void)sliderTouchUp:(NSNotification *)notify
{
    self.treatmentTableView.scrollEnabled = YES;
}

and the UIScrollView (same as above, enclosed in a VC):

- (void)viewDidLoad
{
    // other stuff

    // Register for slider notifications
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(disableScrolling:) name:NOTIFY_SLIDER_TOUCH_BEGAN object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(enableScrolling:) name:NOTIFY_SLIDER_TOUCH_ENDED object:nil];
}

- (void)disableScrolling:(NSNotification *)notify
{
    self.scrollView.scrollEnabled = NO;
}

- (void)enableScrolling:(NSNotification *)notify
{
    self.scrollView.scrollEnabled = YES;
}

I'd love to hear a more elegant solution, but this one definitely gets the job done. When you use a slider, the table and scrollviews hold still and when you click outside the sliders, the tableview and scrollviews move as expected. Also - notice that I could use non-subclassed instances of all 3 components in this solution. Hope this helps someone!