ios – 如何在Swift中使用字符串初始化NSTextStorage

为了将 another problem分解成更小的部分,我试图设置所有的TextKit组件.但是,在更改初始化NSTextStorage的方式后,我遇到了崩溃.出于测试目的,我已将项目简化为以下内容：

import UIKit

class ViewController3: UIViewController {

    @IBOutlet weak var textView: UITextView!
    @IBOutlet weak var myTextView: MyTextView!

    override func viewDidLoad() {
        super.viewDidLoad()

        let container = NSTextContainer(size: myTextView.bounds.size)
        let layoutManager = NSLayoutManager()
        let textStorage = NSTextStorage(string: "This is a test")
        layoutManager.addTextContainer(container)

        //layoutManager.textStorage = textView.textStorage  // This works
        layoutManager.textStorage = textStorage  // This doesn't work

        myTextView.layoutManager = layoutManager

    }
}

class MyTextView: UIView {

    var layoutManager: NSLayoutManager?

    override func drawRect(rect: CGRect) {
        let context = UIGraphicsGetCurrentContext();

        // Enumerate all the line fragments in the text
        layoutManager?.enumerateLineFragmentsForGlyphRange(NSMakeRange(0,layoutManager!.numberOfGlyphs),usingBlock: {
            (lineRect: CGRect,usedRect: CGRect,textContainer: NSTextContainer!,glyphRange: NSRange,stop: UnsafeMutablePointer<ObjCBool>) -> Void in

            // Draw the line fragment
            self.layoutManager?.drawGlyphsForGlyphRange(glyphRange,atPoint: CGPointMake(0,0))

        })
    }
}

它在enumerateLineFragmentsForGlyphRange崩溃,异常代码为EXC_I386_GPFLT.该代码不是很解释.基本问题似乎归结为我如何初始化NSTextStorage.

如果我更换

let textStorage = NSTextStorage(string: "This is a test")
layoutManager.textStorage = textStorage

有了这个

layoutManager.textStorage = textView.textStorage

然后它工作.我究竟做错了什么？

解决方法

这似乎是做事的方法,是将NSLayoutManager添加到NSTextStorage对象,(使用addLayoutManager :)而不是在布局管理器上设置textStorage属性.

来自Apple的文件：

This method is invoked automatically when you add an NSLayoutManager to an NSTextStorage object; you should never need to invoke it directly,but you might want to override it. If you want to replace the NSTextStorage object for an established group of text-system objects containing the receiver,use replaceTextStorage:.

Link to setTextStorage: for NSLayoutManager

大概是在’addLayoutManager：’中完成了一些事情,这在setTextStorage中没有完成,导致崩溃.

您可能还希望增加textStorage变量的范围,如果它看起来在viewDidLoad完成后被清除.