cocoa - 将文本容器添加到 NSLayoutManager 会导致异常

Question

在我的 cocoa 应用程序(用 Swift 编写)中，我试图创建一个分页系统，其中每个页面都是 CASTextView(NSTextView 的子类)的一个实例。此外，每个 CASTextView 都保留一个 CASTextContainer(NSTextContainer 的子类)的实例。为了完成分页，我通过单例模式使 CASTextView 的所有实例共享同一个 NSLayoutManager 实例。

我已经实现了方法 - (void)layoutManager:(NSLayoutManager *)aLayoutManager didCompleteLayoutForTextContainer:(NSTextContainer *)aTextContainer atEnd:(BOOL)flag 如下:

func layoutManager(layoutManager: NSLayoutManager!,
    didCompleteLayoutForTextContainer textContainer: NSTextContainer!,
    atEnd layoutFinishedFlag: Bool)
{
    let containers = layoutManager.textContainers
    if !layoutFinishedFlag || !textContainer {
        let lastContainer = containers[containers.count - 1] as NSTextContainer
        if !textContainer || textContainer == lastContainer {
            if layoutManager.glyphRangeForTextContainer(lastContainer).length > 0 {
                addPage(nil)
            }
        }
    }
}

下面是接收 NSLayoutManager 单例实例的代码(CASTextView.sharedLayoutManager):

class var sharedLayoutManager: NSLayoutManager {
        struct Singleton {
            static let instance = NSLayoutManager()
        }

        return Singleton.instance // All text containers share the same layout manager.
    }

addPage 方法初始化一个 TextView ，将文本容器替换为 CASTextContainer 类型之一，然后将布局管理器替换为共享布局管理器，如下所示:

func addPage(sender: NSNotification?) {
    let midpoint = NSWidth(mainView.frame) / 2
    let firstEndpoint = midpoint - 500
    var rect: NSRect = NSZeroRect
    let yValue: CGFloat = 50 + 1425 * CGFloat(pages.count)
    mainView.frame.size = NSMakeSize(NSWidth(mainView.frame), yValue + 1675) // extend the scrolling size to account for new subview.
    let origin = NSMakePoint(firstEndpoint, yValue)
    let size = NSMakeSize(1000, 1375)
    rect.origin = origin
    rect.size = size
    var nextView = CASTextView(frame: rect)
    var nextContainer = CASTextContainer(containerSize: containerSize)
    nextContainer.mainView = nextView
    nextView.replaceTextContainer(nextContainer)
    nextContainer.replaceLayoutManager(CASTextView.sharedLayoutManager)
    nextView.autoresizingMask = NSAutoresizingMaskOptions.ViewNotSizable
    nextView.delegate = nextView
    nextView.usesFindPanel = true
    mainView.addSubview(nextView)
    pages.append(nextView)
    for var i = 0; i < pages.count - 1; ++i {
        pages[i].nextPage = pages[i + 1] // reset nextPage variable
    }
}

每个 CASTextView 都保留对下一页(也是 CASTextView 类型)的引用，最后一个 CASTextView 要将这个引用(称为 nextPage)设置为 nil。变量“pages”是 NSLayoutManagerDelegate(NSViewController 的子类)保留的所有页面的数组。

问题:对 addPage 的调用完全按预期执行(当一页的文本容器无法再容纳所有文本时)，但导致在方法如下:

 -[NSBigMutableString _getBlockStart:end:contentsEnd:forRange:stopAtLineSeparators:]: Range {0, 98} out of bounds; string length 0

我在任何地方都找不到有关此方法的文档；前导下划线似乎暗示它是 NSString 的私有(private)方法，但堆栈跟踪显示它正在由 -[NSString paragraphRangeForRange:] 调用。有趣的是，堆栈跟踪并未显示 addPage 方法位于堆栈上。这是堆栈跟踪:

0   CoreFoundation                      0x00007fff90ef3f1c __exceptionPreprocess + 172
    1   libobjc.A.dylib                     0x00007fff869b274e objc_exception_throw + 43
    2   CoreFoundation                      0x00007fff90ef3dcd +[NSException raise:format:] + 205
    3   Foundation                          0x00007fff8d480b5c -[NSString _getBlockStart:end:contentsEnd:forRange:stopAtLineSeparators:] + 239
    4   Foundation                          0x00007fff8d4a699c -[NSString paragraphRangeForRange:] + 57
    5   AppKit                              0x00007fff8ea8a7fe -[NSTextView _markTextEditedForRange:] + 1405
    6   AppKit                              0x00007fff8ea852a0 -[NSTextView insertText:replacementRange:] + 2800
    7   AppKit                              0x00007fff8eaba451 -[NSTextView insertText:] + 318
    8   AppKit                              0x00007fff8eade292 -[NSTextView(NSKeyBindingCommands) insertNewline:] + 239
    9   AppKit                              0x00007fff8ea8f544 -[NSTextView doCommandBySelector:] + 195
    10  AppKit                              0x00007fff8f0b6a71 -[NSTextInputContext(NSInputContext_WithCompletion) doCommandBySelector:completionHandler:] + 118
    11  AppKit                              0x00007fff8ea64c9b -[NSKeyBindingManager(NSKeyBindingManager_MultiClients) interpretEventAsCommand:forClient:] + 1899
    12  AppKit                              0x00007fff8f0b54a2 __61-[NSTextInputContext _handleEvent:options:completionHandler:]_block_invoke968 + 335
    13  AppKit                              0x00007fff8f0b6edf -[NSTextInputContext(NSInputContext_WithCompletion) hasMarkedTextWithCompletionHandler:] + 76
    14  AppKit                              0x00007fff8f0b52c3 __61-[NSTextInputContext _handleEvent:options:completionHandler:]_block_invoke_3 + 95
    15  AppKit                              0x00007fff8f0b45d8 -[NSTextInputContext tryHandleEvent_HasMarkedText_withDispatchCondition:dispatchWork:continuation:] + 101
    16  AppKit                              0x00007fff8f0b5234 __61-[NSTextInputContext _handleEvent:options:completionHandler:]_block_invoke956 + 321
    17  HIToolbox                           0x00007fff8e0e204f __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke_5 + 70
    18  AppKit                              0x00007fff8f0ae056 __55-[NSTextInputContext handleTSMEvent:completionHandler:]_block_invoke174 + 2387
    19  AppKit                              0x00007fff8f0b6edf -[NSTextInputContext(NSInputContext_WithCompletion) hasMarkedTextWithCompletionHandler:] + 76
    20  AppKit                              0x00007fff8f0ad674 __55-[NSTextInputContext handleTSMEvent:completionHandler:]_block_invoke_2 + 95
    21  AppKit                              0x00007fff8f0ab3c8 -[NSTextInputContext tryHandleTSMEvent_HasMarkedText_withDispatchCondition:dispatchWork:continuation:] + 101
    22  AppKit                              0x00007fff8f0ad3d0 -[NSTextInputContext handleTSMEvent:completionHandler:] + 3293
    23  AppKit                              0x00007fff8ea8410e _NSTSMEventHandler + 324
    24  HIToolbox                           0x00007fff8decd6c8 _ZL23DispatchEventToHandlersP14EventTargetRecP14OpaqueEventRefP14HandlerCallRec + 1128
    25  HIToolbox                           0x00007fff8deccb8e _ZL30SendEventToEventTargetInternalP14OpaqueEventRefP20OpaqueEventTargetRefP14HandlerCallRec + 386
    26  HIToolbox                           0x00007fff8decca02 SendEventToEventTargetWithOptions + 43
    27  HIToolbox                           0x00007fff8e0db37c SendTSMEvent_WithCompletionHandler + 417
    28  HIToolbox                           0x00007fff8e0db87c __SendUnicodeTextAEToUnicodeDoc_WithCompletionHandler_block_invoke + 400
    29  HIToolbox                           0x00007fff8e0dbb36 __SendFilterTextEvent_WithCompletionHandler_block_invoke + 189
    30  HIToolbox                           0x00007fff8e0db3d0 SendTSMEvent_WithCompletionHandler + 501
    31  HIToolbox                           0x00007fff8e0db6bf SendFilterTextEvent_WithCompletionHandler + 236
    32  HIToolbox                           0x00007fff8e0d8a31 SendUnicodeTextAEToUnicodeDoc_WithCompletionHandler + 295
    33  HIToolbox                           0x00007fff8e0dd329 __utDeliverTSMEvent_WithCompletionHandler_block_invoke_2 + 296
    34  HIToolbox                           0x00007fff8e0dd1f8 __utDeliverTSMEvent_WithCompletionHandler_block_invoke + 437
    35  HIToolbox                           0x00007fff8e0d84ad TSMKeyEvent_WithCompletionHandler + 701
    36  HIToolbox                           0x00007fff8e0e1fd0 __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke_4 + 251
    37  HIToolbox                           0x00007fff8e0e1ec6 __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke_3 + 330
    38  HIToolbox                           0x00007fff8e0e1d02 __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke_2 + 259
    39  HIToolbox                           0x00007fff8e0e1b85 __TSMProcessRawKeyEventWithOptionsAndCompletionHandler_block_invoke + 251
    40  HIToolbox                           0x00007fff8e0e198f TSMProcessRawKeyEventWithOptionsAndCompletionHandler + 3068
    41  AppKit                              0x00007fff8f0b5046 __61-[NSTextInputContext _handleEvent:options:completionHandler:]_block_invoke945 + 131
    42  AppKit                              0x00007fff8f0b4502 -[NSTextInputContext tryTSMProcessRawKeyEvent:dispatchCondition:setupForDispatch:furtherCondition:dispatchWork:continuation:] + 127
    43  AppKit                              0x00007fff8f0b4b35 -[NSTextInputContext _handleEvent:options:completionHandler:] + 1266
    44  AppKit                              0x00007fff8ea8394e -[NSTextInputContext handleEvent:] + 109
    45  AppKit                              0x00007fff8ea63368 -[NSView interpretKeyEvents:] + 207
    46  AppKit                              0x00007fff8ea837cd -[NSTextView keyDown:] + 695
    47  AppKit                              0x00007fff8efa2d7b -[NSWindow _reallySendEvent:] + 1959
    48  AppKit                              0x00007fff8ea337bc -[NSWindow sendEvent:] + 368
    49  AppKit                              0x00007fff8e9e5dc0 -[NSApplication sendEvent:] + 4008
    50  AppKit                              0x00007fff8e871b48 -[NSApplication run] + 711
    51  AppKit                              0x00007fff8e85d2de NSApplicationMain + 1778
    52  Application                           0x000000010000e2a5 top_level_code + 37
    53  Application                         0x000000010000e2da main + 42
    54  libdyld.dylib                       0x00007fff9422d5c9 start + 1
    55  ???                                 0x0000000000000003 0x0 + 3
)

Answer 1

该错误是由于我调用 replaceLayoutManager 而发生的。我改变了初始化 TextView 的方式。我没有使用 init(frame: frameRect) 构造函数，而是通过单独初始化文本容器来利用指定的初始化程序，如下所示:

var nextContainer = CASTextContainer(containerSize: containerSize)
var nextView = CASTextView(frame: rect, textContainer: nextContainer)

然后我继续调用mainView.addSubview(nextView)，添加 subview 后，我调用了以下内容:

CASTextView.sharedLayoutManager.addTextContainer(nextContainer)

然后允许发生分页效果。