ios - UIStepper:如何知道用户点击了步进器的哪个按钮(减号或加号按钮)

Question

我怎么可能知道用户点击了步进器的哪个按钮(减号或加号按钮)？

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

谢谢:3

Answer 1

您可以代替 addTarget:action，观察步进器值属性并要求在更改字典中接收旧值和新值

{
    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;
    }
}

或子类化 UIStepper 并在覆盖的 -setValue 中进行计算: