UIStepper:如何知道用户单击了步进器的哪个按钮(减号或加号按钮) [英] UIStepper: how to be aware which button (minus or plus button) of the stepper has been clicked by user

问题描述

我怎么可能知道用户单击了步进器的哪个按钮(减号或加号按钮)?

How do I possibly know which button(minus or plus button) of the stepper has been clicked by user?

- (IBAction)buttonStepper:(id)sender {
    int stepperValue = self.outletStepper.value;
    self.label.text = [NSString stringWithFormat:@"%d", stepperValue];
}

谢谢:3

推荐答案

您可以代替stepTarget属性来观察steppers值属性，并要求在更改字典中同时接收旧值和新值

You can, instead of addTarget:action, observe the steppers value property and ask to receive both old and new value in the change dictionary

{
    UIStepper *stepper = ...;
    [stepper addObserver:self forKeyPath:@"value"
                 options:NSKeyValueObservingOptionOld | NSKeyValueObservingOptionNew
                 context:0];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if (object == stepper) {
        double oldValue = change[NSKeyValueChangeOldKey];
        double newValue = change[NSKeyValueChangeNewKey];
        double change = newValue - oldValue;
    }
}

或子类UIStepper并在覆盖的-setValue中进行计算:

or subclass UIStepper and do the calculation in an overridden -setValue:

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