Adding padding to an UIView

问题:

I'm looking for a way to add a padding property to an UIView. Ideally, I would like to avoid subclassing and putting it in a category. The usage would be something like:

myview.padding = UIEdgeInsetsMake(10, 10, 10, 10);

And maybe have a paddingBox property as well which would return a CGRect describing the size and position of the inner padding box.

Now, how would one implement in a category something like that. I initially though of using bounds, but unfortunately the size of the bounds is linked to the size of the frame (always the same) only the coordinates can differ.

回答1:

This is generally done by setting the bounds within the view. So if you wanted an inset of 10 all round you could do:

view.bounds = CGRectInset(view.frame, 10.0f, 10.0f);

The bounds defines the drawable area of the view, relative to the frame. So this should give in effect a padding. You can then get the 'paddingBox' just from the bounds.

Hope this helps! :)

回答2:

Update for Swift 3

view.bounds = view.frame.insetBy(dx: 10.0, dy: 10.0)

:)

回答3:

Since iOS 8, each view has now a layoutMargins property which corresponds to the padding.

myview.layoutMargins = UIEdgeInsetsMake(10, 10, 10, 10);

When you use AutoLayout, a format with |-[subview]-|, | will refer to the edges defined with layoutMargins.

Source: https://developer.apple.com/reference/uikit/uiview/1622566-layoutmargins?language=objc

回答4:

What you really have to do is create a view and add a subview to it. Make one view the background and give it the frame you want. Then make the second subview the frame you want with the edge insets.

UIView backgroundView = new UIView(CGRect.FromLTRB(0, 0, 100, 100))
{
    BackgroundColor = backgroundGray,
};

//Will have a right edge inset of 10
UIView edgyView = new UIView(CGRect.FromLTRB(0, 0, 90, 100))
{
    BackgroundColor = backgroundGray,
}

backgroundView.AddSubview(edgyView);

回答5:

You can override the alignmentRectInsets property. Here is an example in Swift 4

class YourCustomView: UIView {

    override var alignmentRectInsets: UIEdgeInsets {
        return UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)
    }
}