UISlider捕捉到固定数量的步骤（如iOS 7设置应用中的文字大小） [英] UISlider that snaps to a fixed number of steps (like Text Size in the iOS 7 Settings app)

问题描述

我正在尝试创建一个 UISlider ，它允许您从一组数字中进行选择。每个滑块位置应该是等距的，滑块应该对齐每个位置，而不是在它们之间平滑滑动。 （这是设置中滑块的行为> 常规> 文字大小，这是在iOS 7中引入的。）

I'm trying to create a UISlider that lets you choose from an array of numbers. Each slider position should be equidistant and the slider should snap to each position, rather than smoothly slide between them. (This is the behavior of the slider in Settings > General > Text Size, which was introduced in iOS 7.)

我想要选择的数字是： -3,0,2,4,7， 10和12。

The numbers I want to choose from are: -3, 0, 2, 4, 7, 10, and 12.

（我对Objective-C很新，所以一个完整的代码示例比一个完整的代码示例更有帮助代码片段。=）

(I'm very new to Objective-C, so a complete code example would be much more helpful than a code snippet. =)

推荐答案

其他一些答案有效，但这会给你在每个位置之间相同的固定空间你的滑块。在此示例中，您将滑块位置视为包含您感兴趣的实际数值的数组的索引。

Some of the other answers work, but this will give you the same fixed space between every position in your slider. In this example you treat the slider positions as indexes to an array which contains the actual numeric values you are interested in.

@interface MyViewController : UIViewController {
    UISlider *slider;
    NSArray *numbers;
}
@end

@implementation MyViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    slider = [[UISlider alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:slider];

    // These number values represent each slider position
    numbers = @[@(-3), @(0), @(2), @(4), @(7), @(10), @(12)];
    // slider values go from 0 to the number of values in your numbers array
    NSInteger numberOfSteps = ((float)[numbers count] - 1);
    slider.maximumValue = numberOfSteps;
    slider.minimumValue = 0;

    // As the slider moves it will continously call the -valueChanged: 
    slider.continuous = YES; // NO makes it call only once you let go
    [slider addTarget:self
               action:@selector(valueChanged:)
     forControlEvents:UIControlEventValueChanged];
}
- (void)valueChanged:(UISlider *)sender {
    // round the slider position to the nearest index of the numbers array
    NSUInteger index = (NSUInteger)(slider.value + 0.5);
    [slider setValue:index animated:NO];
    NSNumber *number = numbers[index]; // <-- This numeric value you want
    NSLog(@"sliderIndex: %i", (int)index);
    NSLog(@"number: %@", number);
}

我希望有所帮助，祝你好运。

I hope that helps, good luck.

class MySliderStepper: UISlider {
    private let values: [Float]
    private var lastIndex: Int? = nil
    let callback: (Float) -> Void

    init(frame: CGRect, values: [Float], callback: @escaping (_ newValue: Float) -> Void) {
        self.values = values
        self.callback = callback
        super.init(frame: frame)
        self.addTarget(self, action: #selector(handleValueChange(sender:)), for: .valueChanged)

        let steps = values.count - 1
        self.minimumValue = 0
        self.maximumValue = Float(steps)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    @objc func handleValueChange(sender: UISlider) {
        let newIndex = Int(sender.value + 0.5) // round up to next index
        self.setValue(Float(newIndex), animated: false) // snap to increments
        let didChange = lastIndex == nil || newIndex != lastIndex!
        if didChange {
            let actualValue = self.values[newIndex]
            self.callback(actualValue)
        }
    }
}

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