I'm trying to position an additional UIView centered above the thumb in a UISlider. To do this, I need the width of the thumb image. In iOS6, this works fine. I can use:
CGFloat thumbWidth = self.navSlider.currentThumbImage.size.width;
(As seen in this answer: How to get the center of the thumb image of UISlider)
This returns 0.0f in iOS7. I've also tried reading it using:
UIImage *thumb = [self.navSlider thumbImageForState:UIControlStateNormal];
But thumb ends up nil.
Is it possible to read the size of the default slider thumb image? Or will I have to find it, set a constant, and how Apple doesn't change it later?
The docs on the currentThumbImage property say:
If no custom thumb images have been set using the setThumbImage:forState: method, this property contains the value nil. In that situation, the receiver uses the default thumb image for drawing.
The docs on thumbImageForState: are less clear:
Return Value The thumb image associated with the specified state, or nil if an appropriate image could not be retrieved.
I think you might be out of luck trying to figure out the default thumb size. How about installing a "custom" thumb image that looks exactly like the system image? That would solve the problem of Apple changing it out from under you.