title: UISlider thumbTintColor doesn't change on iOS 7 (fine on iOS 6)
body: <p>I have an app that runs perfectly on iOS 6. I've set a blinking effect to a UISlider's thumb this way:</p>
  
  <pre><code>-(void)startBlinkingSlider{
      isSliderBlinking = YES;
      isSliderTinted = NO;
      [self performSelector:@selector(toggleSliderColor) withObject:nil afterDelay:0.2];
  }
  
  -(void)toggleSliderColor{
      if(isSliderBlinking){
          if(isSliderTinted){
              self.effectAmountSlider.thumbTintColor = [UIColor colorWithRed:0 green:0 blue:0 alpha:1];
          }else{
              self.effectAmountSlider.thumbTintColor = [UIColor colorWithRed:255 green:0 blue:0 alpha:1];
          }
          isSliderTinted = !isSliderTinted;
          [self performSelector:@selector(toggleSliderColor) withObject:nil afterDelay:0.2];
      }
  }
  
  -(void)stopBlinkingSlider{
      isSliderBlinking = NO;
      isSliderTinted = NO;
      self.effectAmountSlider.thumbTintColor = [UIColor colorWithRed:0 green:0 blue:0 alpha:1];
  }
  </code></pre>
  
  <p>When I call <code>startBlinkingSlider</code> my slider starts blinking red in iOS 6. If I run the same exact app on my iOS 7 device, nothing happens. The slider's thumb retains its original white color. I've set a breakpoint on the line where I set the <code>thumbTintColor</code>. In debugger, here is what I'm getting:</p>
  
  <pre><code>(lldb) po self.effectAmountSlider.thumbTintColor
  error: failed to get API lock
  (lldb) po self.effectAmountSlider.thumbTintColor
  UIDeviceRGBColorSpace 0 0 0 1
  (lldb) 
  </code></pre>
  
  <p>I typed the exact same code and got a weird message in the first one. However, the second result is correct. Then after setting it to red I'm also getting the correct result:</p>
  
  <pre><code>(lldb) po self.effectAmountSlider.thumbTintColor
  UIDeviceRGBColorSpace 1 0 0 1
  </code></pre>
  
  <p>Even though the debugger shows the correct value, I'm getting no visual change in the slider. It's still white, color doesn't change in any way. I've searched Apple's documents here: <a href="https://developer.apple.com/library/ios/documentation/userexperience/conceptual/TransitionGuide/Controls.html">https://developer.apple.com/library/ios/documentation/userexperience/conceptual/TransitionGuide/Controls.html</a></p>
  
  <p>It doesn't say anything about UISlider's thumbTintColor not working as iOS 6. It should stay working as expected. I've checked the thread and everything is running on the main thread. <code>toggleSliderColor</code> is always on the main thread so it's not a threading issue. Why is my thumb color not working?</p>
  
  <p>Thanks, Can.</p>