Ios 在UITextView中垂直居中NSTextAttachment

我有一个自定义的

NSTextAttachment

类，用于缩放

UITextView

中的图像（基于）。这在

纵向

模式下非常有效。在

横向

模式下，图像不会覆盖整个屏幕，我希望将它们置于

文本视图

的中心位置

---

更改自定义类中的边界（在

attachmentBoundsForTextContainer:

中）没有任何区别（尝试更改边界中的

x

和

y

）。这还有什么可以改变的？谢谢。

将UITextView的内容垂直居中。

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

在视图中，将显示UIViewController的名称

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

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

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
    }
}

在视图中，UIViewController的图标将消失

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

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

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
    }
}

覆盖UIViewController中的observeValueForKeyPath

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

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

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
    }
}