Hide UISlider track when behind transparent thumb image - xcode

Question

I'm currently creating a custom UISlider in Xcode. I am setting the thumb Image, min Image, and max Image for the slider. Everything works great. The design calls for the thumb image to be transparent to the background of the view. This is where my problem comes in, you can see the two sides of the slider coming together in the middle of the thumb image. I don't want it to look like this. I want the slider bars to stop a the edge of the thumb image. Any ideas as to how I can accomplish this? Any and all suggestions are welcome. Thanks.
This is the Code I'm using so far.
UIImage *thumbImage = [UIImage imageNamed:#"thumb.png"];
UIImage *minImage = [UIImage imageNamed:#"min.png"];
UIImage *maxImage = [UIImage imageNamed:#"max.png"];
minImage = [minImage resizableImageWithCapInsets:UIEdgeInsetsMake(0,0,0,0)];
maxImage = [maxImage resizableImageWithCapInsets:UIEdgeInsetsMake(0,0,0,0)];
[_slider setMinimumTrackImage:minImage forState:UIControlStateNormal];
[_slider setMaximumTrackImage:maxImage forState:UIControlStateNormal];
[_slider setThumbImage:thumbImageforState:UIControlStateNormal];
I can't Post an image because I don't have enough reputation. I'll try to explain a little better. I have a Thumb Image that is a circle. The center of the circle is transparent and you can see right to the background image of my view. The track for the slider continues all the way to the center of the circle. I'd prefer if the track stopped at the outline of the circle. I hope that makes more sense.

Answer 1

I have not received any suggestions as to how to hide the slider track when it is behind the thumb image so I am posting my solution incase someone else has this problem. If anyone has a better way of doing this please let me know.
In order to have a transparent thumb image and not have the track connect in the center of it I had to set the slider track images to blank images and setup my own slider track image that is just going to be resized every time the value of the slider changes. Not only will I be changing the width of the custom slider track but I also will have to update the X position of the image every time I resize it so that it will connect with the end image of my slider track.
In my case I have a slider that is set to 0 and its Max is set to the Width of the slider. My custom slider track is only going to appear on the right side of the thumb image. So as you slide the thumb image to the right the bar shrinks and the left side is clear.
First I setup my Slider Thumb Image and Set the Slider Track to Blank Images.
- (void)viewDidLoad {
[super viewDidLoad];
UIImage *thumbImage =[UIImage imageNamed:#"answerSlider.png"];
[_slider setMinimumTrackImage:[UIImage new] forState:UIControlStateNormal];
[_slider setMaximumTrackImage:[UIImage new] forState:UIControlStateNormal];
[_slider setThumbImage:thumbImage forState:UIControlStateNormal];
thumbImage = nil;
_slider.value = 0;
}
In the ViewWillApear I have a call to setup my custom SLider track that I will create.
- (void)viewDidAppear:(BOOL)animated{
[self updateSlideBarLength];
}
Inside updateSLideBarLength I Use the value of the slider to help determine the width of my slider track Image.
- (void)updateSlideBarLength{
// Get Position Of Slider
CGFloat sliderValue = _slider.value;
CGFloat thumbImageWidth = 58; // this is the width of my thumb image
CGFloat sliderControlWidth = 288.0f; // This is a constant number in my case
CGFloat sliderWidth = sliderControlWidth - thumbImageWidth - sliderValue;
CGFloat sliderBarHeight = 2.0f;
// Reset Width Of aFrame
CGFloat sliderEndY = _sliderEnd.frame.origin.y;
CGFloat sliderEndX = _sliderEnd.frame.origin.x;
CGFloat sliderBarY = sliderEndY + (_sliderEnd.frame.size.height / 2 - 1);
CGFloat sliderBarX = sliderEndX - sliderWidth + (_sliderEnd.frame.size.width/2);
CGRect aframe = CGRectMake(sliderBarX, sliderBarY, sliderWidth, sliderBarHeight);
if (_sliderBar == nil) {
NSLog(#"Slider Bar Doesnt Exist");
_sliderBar = [[UIImageView alloc] initWithFrame:aframe];
_sliderBar.image = [UIImage imageNamed:#"sliderBar.png"];
[self.view addSubview:_sliderBar];
[self.view bringSubviewToFront:_sliderBar];
}
_sliderBar.frame = aframe;
}
Lastly I make sure the updateSliderBarLength is called every time the slider value changes.
- (IBAction)sliderMoved:(id)sender {
[self updateSlideBarLength];
}
This works although I had to adjust the Max value of my slider so that the custom slider track image I created always lines up with the edge of the thumb Image. While sliding the thumb image as the value increased the more the slider track started to infringe on my thumb image. By increasing the slider value I was able to stop this from happening. Again, I'm not convinced this is the best way to do this but it works for me. Later when I have more Rep and can post Pictures I will edit this post to help everyone visualize what I am describing.

Answer 2

I did something similar to Sean Marraffa, although I found it easier to subclass UISlider and update the frames of my image views in thumbRectForBounds:trackRect:value using something like this:
var trackHeight: CGFloat = 2
override func thumbRectForBounds(bounds: CGRect, trackRect rect: CGRect, value: Float) -> CGRect
{
let superValue = super.thumbRectForBounds(bounds, trackRect: rect, value: value)
let originY = (bounds.height-trackHeight)/2.0
minTrackImageView?.frame = CGRectMake(0, originY, superValue.minX, trackHeight)
maxTrackImageView?.frame = CGRectMake(superValue.maxX, originY, bounds.width-superValue.maxX, trackHeight)
return superValue
}
minTrackImageView and maxTrackImageView are image views I set up in viewDidLoad.