NSLayoutManager with multiple NSTextContainers causes UITextViews to not be selectable/editable

问题

I am trying to achieve a multi page text editing layout, as in Pages, MS Word, ... . On OS X I can achieve this by creating one NSLayoutManager with one NSTextStorage for multiple NSTextViews. Each NSTextView has its own NSTextContainer. See below code for OS X. A simple example with text spreading between two NSTextViews:

import Cocoa

class ViewController: NSViewController {

let layoutManager = NSLayoutManager()
let textStorage = NSTextStorage(attributedString: NSAttributedString(string: "This is a test"))
let textContainer1 = NSTextContainer()
let textContainer2 = NSTextContainer()

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.

    textStorage.addLayoutManager(layoutManager)

    textContainer1.widthTracksTextView = true
    textContainer1.heightTracksTextView = true
    textContainer2.widthTracksTextView = true
    textContainer2.heightTracksTextView = true

    let textView1 = NSTextView(frame: CGRectMake(0, 100, 100, 100), textContainer: textContainer1)
    textView1.backgroundColor = NSColor.greenColor()
    self.view.addSubview(textView1)
    layoutManager.addTextContainer(textContainer1)


    let textView2 = NSTextView(frame: CGRectMake(200, 100, 100, 100), textContainer: textContainer2)
    textView2.backgroundColor = NSColor.greenColor()
    self.view.addSubview(textView2)
    layoutManager.addTextContainer(textContainer2)
}
}

This works.

However, when I try to do the same on iOS with UITextView, the UITextViews become not selectable or editable. See my code for iOS:

import UIKit

class ViewController: UIViewController, UITextViewDelegate {

let layoutManager = NSLayoutManager()
let textStorage = NSTextStorage(attributedString: NSAttributedString(string: "This is a test. This text should spread over two UITextViews. Bla bla bla bla bla bla bla bla bla bla bla bla bla"))
let textContainer1 = NSTextContainer()
let textContainer2 = NSTextContainer()

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.        

    textStorage.addLayoutManager(layoutManager)

    textContainer1.heightTracksTextView = true
    textContainer1.widthTracksTextView = true
    textContainer2.heightTracksTextView = true
    textContainer2.widthTracksTextView = true

    let textView1 = UITextView(frame: CGRectMake(0, 100, 100, 100), textContainer: textContainer1)
    textView1.scrollEnabled = false
    textView1.delegate = self
    textView1.editable = true
    textView1.selectable = true
    textView1.backgroundColor = UIColor.greenColor()
    self.view.addSubview(textView1)
    layoutManager.addTextContainer(textContainer1)

    let textView2 = UITextView(frame: CGRectMake(200, 100, 100, 100), textContainer: textContainer2)
    textView2.scrollEnabled = false
    textView2.delegate = self
    textView2.editable = true
    textView2.selectable = true
    textView2.backgroundColor = UIColor.greenColor()
    self.view.addSubview(textView2)
    layoutManager.addTextContainer(textContainer2)

}
}

The text flows from one UITextView to the other, but it is not editable. I would be extremely thankful for any advice. I googled the issue and found other people experiencing the same problem, but found no solutions.

回答1:

I've been searching for an answer too, and it seems that when a UITextView shares a layout manager with other text views, the text view unfortunately becomes static.

This issue is outlined in iOS 7 Programming Pushing the Limits: Develop Advance Applications for Apple, page 375:

Because you can easily add additional text containers to a layout manager, and because UITextView uses a layout manager, you may think it would be easy to create a multicolumn, editable UITextView. Unfortunately, this is not the case. If a UITextView is assigned multiple text containers [sic], it becomes static and cannot respond to user interaction such as editing or selection. This is a known issue and is currently "as designed".

来源：https://stackoverflow.com/questions/32645312/nslayoutmanager-with-multiple-nstextcontainers-causes-uitextviews-to-not-be-sele