无法获得UIView sizeToFit来做任何有意义的事情

Question

当我向a添加子视图UIView时,或者当我调整现有子视图的大小时,我希望[view sizeToFit]并[view sizeThatFits]反映出这种变化.但是,我的经验是sizeToFit什么都不做,并sizeThatFits在更改之前和之后返回相同的值.

我的测试项目有一个包含单个按钮的视图.单击该按钮会向视图添加另一个按钮,然后调用sizeToFit包含视图.在添加子视图之前和之后,视图的边界将转储到控制台.

- (void) logSizes {
 NSLog(@"theView.bounds: %@", NSStringFromCGRect(theView.bounds));
 NSLog(@"theView.sizeThatFits: %@", NSStringFromCGSize([theView sizeThatFits:CGSizeZero])); 
}

- (void) buttonTouched { 
 [self logSizes];
 UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
 btn.frame = CGRectMake(10.0f, 100.0f, 400.0f, 600.0f);
 [theView addSubview:btn];
 [theView sizeToFit];
 [self performSelector:@selector(logSizes) withObject:nil afterDelay:1.0];
}

输出是:

2010-10-15 15:40:42.359 SizeToFit[14953:207] theView.bounds: {{0, 0}, {322, 240}}
2010-10-15 15:40:42.387 SizeToFit[14953:207] theView.sizeThatFits: {322, 240}
2010-10-15 15:40:43.389 SizeToFit[14953:207] theView.bounds: {{0, 0}, {322, 240}}
2010-10-15 15:40:43.391 SizeToFit[14953:207] theView.sizeThatFits: {322, 240}

我必须在这里遗漏一些东西.

谢谢.

Answer 1

文档非常明确.-sizeToFit几乎调用-sizeThatFits:(可能以视图的当前大小作为参数),默认实现-sizeThatFits:几乎没有(它只返回其参数).

一些UIView子类覆盖-sizeThatFits:了更有用的东西(例如UILabel).如果您想要任何其他功能(例如调整视图大小以适合其子视图),您应该继承UIView并覆盖-sizeThatFits:.

Answer 2

如果你不覆盖 UIView，你可以只使用扩展。

迅速：

extension UIView {

    func sizeToFitCustom () {
        var size = CGSize(width: 0, height: 0)
        for view in self.subviews {
            let frame = view.frame
            let newW = frame.origin.x + frame.width
            let newH = frame.origin.y + frame.height
            if newW > size.width {
                size.width = newW
            }
            if newH > size.height {
                size.height = newH
            }
        }
        self.frame.size = size
    }

}

相同的代码，但速度提高了 3 倍：

extension UIView {
    final func sizeToFitCustom() {
        var w: CGFloat = 0,
            h: CGFloat = 0
        for view in subviews {
            if view.frame.origin.x + view.frame.width > w { w = view.frame.origin.x + view.frame.width }
            if view.frame.origin.y + view.frame.height > h { h = view.frame.origin.y + view.frame.height }
        }
        frame.size = CGSize(width: w, height: h)
    }
}