ios - UIScrollView 页面宽度不等于 self.view 宽度

Question

我有代码:

为什么 UIScrollView 的页面宽度不等于 self.view 宽度？

如果我认为正确，self.view.frame.size.width 必须等于 scroll.bounds.width 和 scroll.contentSize 必须是 self.view.frame.size.width*4(在这种情况下)，是对吗？

非常感谢!!

class ViewController: UIViewController {

    @IBOutlet weak var scroll: UIScrollView!
    var frame: CGRect = CGRectMake(0, 0, 0, 0)

    override func viewDidLoad() {
        super.viewDidLoad()
        scroll.bounds = self.view.bounds
        scroll.frame = self.view.frame

        NSLog("%@", UIScreen.mainScreen().bounds.width);
        NSLog("%@", scroll.bounds.width);
                NSLog("%@", self.view.bounds.width);
        NSLog("%@", scroll.contentSize.width);


        let colors = [UIColor.redColor(), UIColor.greenColor(), UIColor.yellowColor(), UIColor.magentaColor()];

        for index in 0..<colors.count {

            frame.origin.x = self.view.frame.size.width * CGFloat(index)
            frame.size = self.view.frame.size

            var subView = UIView(frame: frame)
            subView.backgroundColor = colors[index]
            subView.layer.borderColor = UIColor.blackColor().CGColor
            subView.layer.borderWidth = 1.0;
            self.scroll .addSubview(subView)
        }

        scroll.contentSize = CGSizeMake(self.view.frame.size.width * CGFloat(colors.count), self.view.frame.size.height)          
    }
...  
}

我在第二页看到的:

Answer 1

(1) 如果您要在一行之后设置框架，则无需设置边界，因此您可以完全删除这一行:scroll.bounds = self.view.bounds

(2) 将 viewDidLoad 中的所有其他内容移动到 viewDidLayoutSubviews，因为您设置的框架取决于 View 的宽度，这可以改变一个 subview 布局以适本地适合屏幕。但我也建议只使用条件执行此代码一次，因为 viewDidLayoutSubviews 可以多次调用，您应该只运行此代码一次，以免不必要地添加额外的 subview ，例如:

@IBOutlet weak var scroll: UIScrollView!
var frame: CGRect = CGRectMake(0, 0, 0, 0)
var viewLaidout:Bool = false

override func viewDidLayoutSubviews() {

    if !viewLaidout {
        scroll.frame = self.view.frame

        let colors = [UIColor.redColor(), UIColor.greenColor(), UIColor.yellowColor(), UIColor.magentaColor()];

        for index in 0..<colors.count {

            frame.origin.x = self.view.frame.size.width * CGFloat(index)
            frame.size = self.view.frame.size

            var subView = UIView(frame: frame)
            subView.backgroundColor = colors[index]
            subView.layer.borderColor = UIColor.blackColor().CGColor
            subView.layer.borderWidth = 1.0;
            self.scroll.addSubview(subView)
        }

        scroll.contentSize = CGSizeMake(self.view.frame.size.width * CGFloat(colors.count), self.view.frame.size.height)
        viewLaidout = true
    }
}