How to change a UISlider value using a single touc

问题:

I'm developing my first iOS app which contains a UISlider. I know how to get the value when the UISlider is dragged. But for my app I need to get the slider's value in a single touch; i.e. if I touch somewhere in the UISlider, a UILabel should display its correct value.

Is it possible to this way. Any tutorial or code will very helpful.

回答1:

Please Write Following Code may be helpful for you :)

Here tapCount is int variable that declare in .h file

- (void)viewDidLoad
{
  tapCount = 0; // Count tap on Slider 

 UITapGestureRecognizer *gr = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(sliderTapped:)];
    [slider addGestureRecognizer:gr];

}

 - (void)sliderTapped:(UIGestureRecognizer *)g 
    {
/////////////// For TapCount////////////

        tapCount = tapCount + 1;
        NSLog(@"Tap Count -- %d",tapCount);

/////////////// For TapCount////////////

        UISlider* s = (UISlider*)g.view;
        if (s.highlighted)
            return; // tap on thumb, let slider deal with it
        CGPoint pt = [g locationInView: s];
        CGFloat percentage = pt.x / s.bounds.size.width;
        CGFloat delta = percentage * (s.maximumValue - s.minimumValue);
        CGFloat value = s.minimumValue + delta;
        [s setValue:value animated:YES];

        NSString *str=[NSString stringWithFormat:@"%.f",[self.slider value]];
        self.lbl.text=str;
    }

For Swift User

override func viewDidLoad()
{
    super.viewDidLoad()

    tapCount = 0
    let gr = UITapGestureRecognizer(target: self, action: #selector(self.sliderTapped(_:)))
    slider.addGestureRecognizer(gr)

}

func sliderTapped(_ g: UIGestureRecognizer) {

    /////////////// For TapCount////////////
    tapCount = tapCount + 1
    print("Tap Count -- \(tapCount)")
    /////////////// For TapCount////////////

    let s: UISlider? = (g.view as? UISlider)
    if (s?.isHighlighted)! {
        return
    }

    // tap on thumb, let slider deal with it
    let pt: CGPoint = g.location(in: s)
    let percentage = pt.x / (s?.bounds.size.width)!
    let delta = Float(percentage) * Float((s?.maximumValue)! - (s?.minimumValue)!)
    let value = (s?.minimumValue)! + delta
    s?.setValue(Float(value), animated: true)
    let str = String(format: "%.f", slider.value)
    lbl.text = str
}

回答2:

Correction @ipatel: Math in previous answers is incomplete and causes jitter due to missing thumb width considerations.

Here is what it should look like if you choose to subclass UISlider:

- (BOOL)beginTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event
{
    [super beginTrackingWithTouch:touch withEvent:event];
    CGPoint touchLocation = [touch locationInView:self];
    CGFloat value = self.minimumValue + (self.maximumValue - self.minimumValue) *
        ((touchLocation.x - self.currentThumbImage.size.width/2) /
        (self.frame.size.width-self.currentThumbImage.size.width));
    [self setValue:value animated:YES];

    return YES;
}

回答3:

Swift version for accepted answer,

@IBAction func sliderTappedAction(sender: UITapGestureRecognizer)
{
    if let slider = sender.view as? UISlider {

        if slider.highlighted { return }

        let point = sender.locationInView(slider)
        let percentage = Float(point.x / CGRectGetWidth(slider.bounds))
        let delta = percentage * (slider.maximumValue - slider.minimumValue)
        let value = slider.minimumValue + delta
        slider.setValue(value, animated: true)
    }
}

回答4:

You can display the current value of UISlider with its action method like below.

- (IBAction) sliderValueChanged:(UISlider *)sender {  
    yourLable.text = [NSString stringWithFormat:@"%.1f", [sender value]];  
} 

See these tutorials and examples of UISlider:

1. UISlider-tutorial-example-how-to-use-slider-in-iphone-sdk-xcode.
2. iphone-slider-control-uislider-control-tutorial.

This second tutorial with example which display the current (Latest) value of UISlider in UILable see the image below for example.