cocoa - 对于某些击键，performKeyEquivalent 被调用两次

Question

按“Command +”会导致两次 -performKeyEquivalent 调用。这是第一次调用的堆栈跟踪片段:

1   AppKit                              0x00007fff903da2f9 -[NSView _performKeyEquivalent:conditionally:] + 41
2   AppKit                              0x00007fff903da442 -[NSView performKeyEquivalent:] + 166
3   AppKit                              0x00007fff903da2f9 -[NSView _performKeyEquivalent:conditionally:] + 41
4   AppKit                              0x00007fff903da259 -[NSWindow performKeyEquivalent:] + 64
5   AppKit                              0x00007fff903da044 -[NSApplication _handleKeyEquivalent:] + 462
6   AppKit                              0x00007fff90297173 -[NSApplication sendEvent:] + 4480

第二次调用:

1   AppKit                              0x00007fff903da2f9 -[NSView _performKeyEquivalent:conditionally:] + 41
2   AppKit                              0x00007fff903da442 -[NSView performKeyEquivalent:] + 166
3   AppKit                              0x00007fff903da2f9 -[NSView _performKeyEquivalent:conditionally:] + 41
4   AppKit                              0x00007fff903da259 -[NSWindow performKeyEquivalent:] + 64
5   AppKit                              0x00007fff903da044 -[NSApplication _handleKeyEquivalent:] + 462
6   AppKit                              0x00007fff900e3927 -[NSApplication _handleSpecialAlternateKeyEquivalent:] + 656
7   AppKit                              0x00007fff9029718e -[NSApplication sendEvent:] + 4507

如您所见，第二个 -performKeyEquivalent 调用是由 -[NSApplication _handleSpecialAlternateKeyEquivalent:] 发起的。那么，谁能告诉我“Command +”击键有什么特别之处，以至于它不需要一次而是两次 -performKeyEquivalent 调用，以及如何过滤掉第二个调用？

Answer 1

最可能的原因是第一次调用返回NO，因此 AppKit 使用略有不同的事件再次尝试。您是否覆盖performKeyEquivalent:？您第一次返回NO吗？

<小时/>

来自Cocoa Event Handling Guide: Handling Key Events的笔记:

NSWindow subclasses are discouraged from overriding performKeyEquivalent:.

Note: Beginning with OS X v10.5, if a key equivalent is not recognized, NSWindow sends it as an NSKeyDown event to the first responder. This behavior enables custom key-binding entries with Command-key modifiers. In addition, NSApplication sends a Control-key event to the key window via performKeyEquivalent: before sending it as an NSKeyDown event through the responder chain. This behavior allows more reliable use of Control-key events as menu key equivalents.