How to change UISlider background color with slide

Question

I want to change UISlider background color with slide like this

I have tried this code but it is not like this type view

@property (strong, nonatomic) IBOutlet UISlider *r;
@property (strong, nonatomic) IBOutlet UISlider *g;
@property (strong, nonatomic) IBOutlet UISlider *b;

-(void)blueSlider:(UISlider*)slider {
    UIColor *newColor = [UIColor colorWithRed:_r.value green:_g.value blue:_b.value alpha:1];
   _b.backgroundColor=newColor;
}

-(void)greenSlider:(UISlider*)slider {
    UIColor *newColor = [UIColor colorWithRed:_r.value green:_g.value blue:_b.value alpha:1];
    _g.backgroundColor=newColor;
}

-(void)redSlider:(UISlider*)slider  {
    UIColor *newColor = [UIColor colorWithRed:_r.value green:_g.value blue:_b.value alpha:1];
   _r.backgroundColor=newColor;
}

I want particular this look.

Answer 1

in header file import quartzCore and define layer instances as

#import <QuartzCore/QuartzCore.h>

@interface ViewController : UIViewController
{
    CAGradientLayer *red_gradient;
    CAGradientLayer *green_gradient;
    CAGradientLayer *blue_gradient;
}

@property (strong, nonatomic) IBOutlet UISlider *r;
@property (strong, nonatomic) IBOutlet UISlider *g;
@property (strong, nonatomic) IBOutlet UISlider *b;
@property (strong, nonatomic) IBOutlet UILabel *colorLabel;
-(IBAction)sliderValue:(UISlider*)sender;
@end

In implementation file initialize layers and set frames of UISliders as given below

- (void)viewDidLoad
{
    red_gradient =[CAGradientLayer layer];
    green_gradient =[CAGradientLayer layer];
    blue_gradient=[CAGradientLayer layer];

    CGRect rect=_r.frame;
    rect.size.height=10;
    [_r setFrame:rect];

    rect=_g.frame;
    rect.size.height=10;
    [_g setFrame:rect];

    rect=_b.frame;
    rect.size.height=10;
    [_b setFrame:rect];

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

In view did appear method call addLayers method as

-(void)viewDidAppear:(BOOL)animated
{
    [self addLayers];
}

On value change slider method call addSubLayers method as

-(IBAction)sliderValue:(UISlider*)sender
{
    [self addLayers];
    UIColor *newColor = [UIColor colorWithRed:_r.value green:_g.value blue:_b.value alpha:1];
   _colorLabel.backgroundColor = newColor;
}

And At last here is your addLayers Method :---

-(void)addLayers
{
    UIColor *startColor=[UIColor colorWithRed:0 green:_g.value blue:_b.value alpha:1];
    UIColor *endColor=[UIColor colorWithRed:1 green:_g.value blue:_b.value alpha:1];

    red_gradient.frame = _r.bounds;
    red_gradient.colors = [NSArray arrayWithObjects:(id)[startColor CGColor], (id)[endColor CGColor], nil];

    [red_gradient setStartPoint:CGPointMake(0.0, 0.5)];
    [red_gradient setEndPoint:CGPointMake(1.0, 0.5)];

    [_r.layer insertSublayer:red_gradient atIndex:2];

    startColor=[UIColor colorWithRed:_r.value green:0 blue:_b.value alpha:1];
    endColor=[UIColor colorWithRed:_r.value green:1 blue:_b.value alpha:1];

    green_gradient.frame = _g.bounds;
    green_gradient.colors = [NSArray arrayWithObjects:(id)[startColor CGColor], (id)[endColor CGColor], nil];

    [green_gradient setStartPoint:CGPointMake(0.0, 0.5)];
    [green_gradient setEndPoint:CGPointMake(1.0, 0.5)];

    [_g.layer insertSublayer:green_gradient atIndex:2];

    startColor=[UIColor colorWithRed:_r.value green:_g.value blue:0 alpha:1];
    endColor=[UIColor colorWithRed:_r.value green:_g.value blue:1 alpha:1];

    blue_gradient.frame = _b.bounds;
    blue_gradient.colors = [NSArray arrayWithObjects:(id)[startColor CGColor], (id)[endColor CGColor], nil];

    [blue_gradient setStartPoint:CGPointMake(0.0, 0.5)];
    [blue_gradient setEndPoint:CGPointMake(1.0, 0.5)];

    [_b.layer insertSublayer:blue_gradient atIndex:2];
}

it would look like :--------

Answer 2

Your code does not achieve the desired look because you are setting the background color of the slider all together.

Take a look at the CGGradient reference to learn how to use gradients.

Also, what you pictured is not looking like a slider at all, but rather like an object within the bounds of a gradient that changes the value through a panGestureRecognizer .

To learn about that, visit the UIPanGestureRecognizer Class Reference