Size of default thumb image for iOS slider?

问题:

What is the exact size (width, height) of the (default) thumb image for the iOS slider? Is there perhaps some clever way to coax this out of the system (XCode, iOS)?

I tried

int thumbWidth = slider.currentThumbImage.size.width;

which I found here on this site, but it comes back with 0.

Additional question: The Xcode debugger shows this undocumented variable in the UISlider: CGFloat _hitOffset. Does anyone by chance know what it is and what it's for?

回答1:

What about this? Works for me:

CGRect trackRect = [self trackRectForBounds:self.bounds];
CGRect thumbRect = [self thumbRectForBounds:self.bounds trackRect:trackRect value:0];
CGSize thumbSize = thumbRect.size;

回答2:

If you want change UISlider appearance then use below method

[[UISlider appearance] setThumbImage:[UIImage imageNamed:@"yoursliderimage.png"] forState:UIControlStateNormal];

as well as below code would change you slider track also

UIImage *white = [UIImage imageNamed:@"16x16white.png"];

[movieTimeControl setMinimumTrackImage:[white stretchableImageWithLeftCapWidth:3.0 topCapHeight:0.0] forState:UIControlStateNormal];

[movieTimeControl setMaximumTrackImage:[white stretchableImageWithLeftCapWidth:3.0 topCapHeight:0.0] forState:UIControlStateNormal];

Aplle HIG document doesn't define any size for UISlider thumb image but it should be under normal image size.

回答3:

The best way is using a Resizable Image. But the slider thumb size is 23x23 if you don't want to make the image resizable

回答4:

There is a session video about UI customization in the WWDC 2012 collection:

https://developer.apple.com/videos/wwdc/2012/?id=216

You might find your answer here. Its about UISlider customization too

回答5:

Here is the swift 4 version:

yourSlider.setThumbImage(UIImage(named: "Knob"), for: .normal)