user1293618 user1293618 - 10 months ago 62
iOS Question

Increasing a thumbs "click area" in UISlider

I am creating a custom UISlider and wonder, how do you increase a thumb image's "click area" ? The code below works great, except the thumb's "click area" remains unchanged. If I am not wrong, I believe the standard thumb area is 19 px ? Lets say I would like to increase it to 35px with the following code below, what steps do I need to take? Keep in mind I am not an expert within this area at all.

EDIT The code below is corrected and ready for copy pasta! Hope it helps you!


#import "MyUISlider.h"

@interface main : MLUIViewController <UITableViewDelegate, UITableViewDataSource, UISearchBarDelegate, UIActionSheetDelegate, UIAlertViewDelegate, MFMailComposeViewControllerDelegate, UIGestureRecognizerDelegate, MLSearchTaskDelegate, MLDeactivateDelegate, MLReceiptDelegate>


- (void)create_Custom_UISlider;


- (void)viewDidLoad

[self create_Custom_UISlider];
[self.view addSubview: customSlider];


- (void)create_Custom_UISlider
CGRect frame = CGRectMake(20.0, 320.0, 280, 0.0);

customSlider = [[MyUISlider alloc] initWithFrame:frame];

[customSlider addTarget:self action:@selector(sliderAction:) forControlEvents:UIControlEventValueChanged];
// in case the parent view draws with a custom color or gradient, use a transparent color

customSlider.backgroundColor = [UIColor clearColor];

UIImage *stetchLeftTrack = [[UIImage imageNamed:@"blue_slider08.png"]
stretchableImageWithLeftCapWidth: 10.0 topCapHeight:0.0];
UIImage *stetchRightTrack = [[UIImage imageNamed:@"blue_slider08.png"]
stretchableImageWithLeftCapWidth: 260.0 topCapHeight:0.0];

[customSlider setThumbImage: [UIImage imageNamed:@"slider_button00"] forState:UIControlStateNormal];
[customSlider setMinimumTrackImage:stetchLeftTrack forState:UIControlStateNormal];
[customSlider setMaximumTrackImage:stetchRightTrack forState:UIControlStateNormal];

customSlider.minimumValue = 0.0;
customSlider.maximumValue = 1.0;
customSlider.continuous = NO;
customSlider.value = 0.00;


-(void) sliderAction: (UISlider *) sender{

if(sender.value !=1.0){
[sender setValue: 0.00 animated: YES];
[sender setValue 0.00 animated: YES];
// add some code here depending on what you want to do!

EDIT (trying to subclass with the code below)


#import <UIKit/UIKit.h>

@interface MyUISlider : UISlider {




#import "MyUISlider.h"

@implementation MyUISlider

- (CGRect)thumbRectForBounds:(CGRect)bounds trackRect:(CGRect)rect value:(float)value

return CGRectInset ([super thumbRectForBounds:bounds trackRect:rect value:value], 10 , 10);



Answer Source

You have to override thumbRectForBounds:trackRect:value: in a custom subclass (instead of calling the method yourself like you do in your code, which does nothing except returning a value that you don't even bother to retrieve).

thumbRectForBounds:trackRect:value: is not a method to set the tumb rect, but to get it. The slider will internally call this thumbRectForBounds:trackRect:value: method to know where to draw the thumb image, so you need to override it — as explained in the documentation — to return the CGRect you want (so that it will be 35x35px as you wish).