Vertically center NSTextAttachment in a UITextView

Question

I have an custom NSTextAttachment class which I use to scale images inside a UITextView (based on the answer here). This works great in portrait mode. In landscape mode, the images do not cover the whole screen and I want to center them in the textview.

Making changes to the bounds in the custom class (in attachmentBoundsForTextContainer:) does not make a difference (tried changing both x and y in the bounds). How else can this be changed? Thanks.

Answer 1

Vertically center the content of a UITextView.

In viewWillAppear of your UIViewController.

textView.addObserver(self, forKeyPath: "contentSize", options: .New, context: nil)

In viewWillDisappear of your UIViewController.

textView.removeObserver(self, forKeyPath: "contentSize")

Override observeValueForKeyPath in your UIViewController.

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {

    if keyPath == "contentSize" {

        let height = textView.bounds.size.height
        let contentHeight = textView.contentSize.height
        let zoom = textView.zoomScale
        let top = (height - contentHeight * zoom) / 2.0
        textView.contentInset.top = top < 0.0 ? 0.0 : top
    }
}

Horizontally center the content of an NSAttributtedString inside a UITextView.

let attachment = NSTextAttachment()
let attachmentAttrString = NSAttributedString(attachment: attachment)
let result = NSMutableAttributedString(attributedString: attachmentAttrString)

let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = .Center

let attrs:[String:AnyObject] = [NSParagraphStyleAttributeName: paragraphStyle]
let range = NSMakeRange(0, result.length)
result.addAttributes(attrs, range: range)

textView.attributedText = result