UISlider setMaximumTrackTintColor

Question

I\'m trying to dynamically configure the track color on a UISlider.

This line of code works perfectly for setting the low side of the slider track.

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Answer 1

For me the problem occurred because I had subclassed UISlider to create a custom trackRectForBounds that was returning a CGRect with an invalid size. My original implementation (and maybe some iOS version's implementations?) returned a track bounds with a zero or negative size depending on the UISlider's bounds. It appears that it is related to the fact that setting minimum/maximumTrackTintColor will call trackRectForBounds, possibly in order to create a track image.

The fix to the problem is making sure that the track bounds will be valid when setting minimum/maximum track tint colors.

Option 1: use initWithFrame that is sufficiently sized for the UISlider

UISlider *slider = [[UISlider alloc] initWithFrame:CGRectMake(0,0,100,38)];
slider.minimumTrackTintColor = [UIColor greenColor];
slider.maximumTrackTintColor = [UIColor orangeColor];
// ... rest of view setup ...

Option 2: add the slider and force auto-layout so that it is correctly sized before setting the tint colors

UISlider *slider = [[UISlider alloc] init]; // <-- problem, zero size
[view addSubview:slider];
// ... other view setup, including constraints ...
[view layoutIfNeeded]; // forced layout to give slider a non-zero size
slider.minimumTrackTintColor = [UIColor greenColor];
slider.maximumTrackTintColor = [UIColor orangeColor];

Option 3: fix the override to make sure that it will return a rectangle of non-zero size, regardless of bounds.

- (CGRect)trackRectForBounds:(CGRect)bounds {
     // example, inset left/right by 2 (thus width - 4)
     // track height is 5 pixels, centered in bounds.
     return CGRectMake(
         CGRectGetMinX(bounds) + 2,
         CGRectGetMinY(bounds) + (CGRectGetHeight(bounds) + 5)/2.0,
         MAX(10, CGRectGetWidth(bounds) - 4), // use max make sure positive.
         5)
}

Note: I am creating UISliders after the viewDidLoad so Ahufford's answer wouldn't work for me, but I presume this could also explain it. I would also guess Ahufford's answer will probably work best in most cases.