ios - 如何像 Apple 一样突出显示 UIView

Question

当用户触摸 UIButton 时，它会变灰一点。苹果到底做了什么才能达到这样的效果呢？当我的自定义 UIButton 突出显示时，我需要相同的效果。

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    AppDelegate* appDelegate=(AppDelegate*)[UIApplication sharedApplication].delegate;
    if ([keyPath isEqualToString:@"highlighted"]){
        UIButton *button = object;
        if (button.isHighlighted) {
            self.backgroundColor=[UIColor colorWithRed:36.0/255.0 green:153.0/255.0 blue:116.0/255.0 alpha:1];
        }else{
            self.backgroundColor=appDelegate.currentAppColor;
        }
    }
}

我正在使用此代码，但更改背景颜色不会影响任何 subview 。我也需要它们变灰。

Answer 1

您可以使用自定义 View ，例如:

class HighlightView: UIView {

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        DispatchQueue.main.async {
            self.alpha = 1.0
            UIView.animate(withDuration: 0.4, delay: 0.0, options: .curveLinear, animations: {
                self.alpha = 0.5
            }, completion: nil)
        }
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        DispatchQueue.main.async {
            self.alpha = 0.5
            UIView.animate(withDuration: 0.4, delay: 0.0, options: .curveLinear, animations: {
                self.alpha = 1.0
            }, completion: nil)
        }
    }

    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        DispatchQueue.main.async {
            self.alpha = 0.5
            UIView.animate(withDuration: 0.4, delay: 0.0, options: .curveLinear, animations: {
                self.alpha = 1.0
            }, completion: nil)
        }
    }
}

然后您可以使用它来代替 UIView，每当您单击它时，它都会更改其 alpha 值，因此它看起来像一个突出显示。