ios - 如何在 UITextView 中水平和垂直对齐文本？

Question

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Answer 1

这是一个 Swift 解决方案，现在有所不同，因为内容插入和偏移量已略有变化。此解决方案适用于 Xcode 7 beta 6。

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    textView.addObserver(self, forKeyPath: "contentSize", options: NSKeyValueObservingOptions.New, context: nil)
}

override func viewWillDisappear(animated: Bool) {
    super.viewWillDisappear(animated)
    textView.removeObserver(self, forKeyPath: "contentSize")
}

Apple 已经更改了内容偏移和插图的工作方式，现在需要这个稍微修改过的解决方案来设置内容插图的顶部而不是偏移。

/// Force the text in a UITextView to always center itself.
override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
    let textView = object as! UITextView
    var topCorrect = (textView.bounds.size.height - textView.contentSize.height * textView.zoomScale) / 2
    topCorrect = topCorrect < 0.0 ? 0.0 : topCorrect;
    textView.contentInset.top = topCorrect
}