xcode NSMenuItem 没有被启用？
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NSMenuItem not being enabled?
提问by user635064
I have an NSMenuItem called history which resides in a NSMenu called menu. When my program starts history doesn't have a submenu so its disabled. Then at some point, I need a submenu for history, so I create it, make it a submenu of history. An arrow appears beside history which tells me that the submenu is there. But history is still disabled. I have tried setEnabled but doesn't work. Please help. Here my code:
我有一个名为 history 的 NSMenuItem，它驻留在名为 menu 的 NSMenu 中。当我的程序启动历史没有子菜单时，它被禁用。然后在某个时候，我需要一个历史的子菜单，所以我创建了它，使它成为历史的子菜单。历史记录旁边会出现一个箭头，告诉我子菜单在那里。但是历史仍然是禁用的。我试过 setEnabled 但不起作用。请帮忙。这是我的代码：
This is when I create my menu, and history as you can see an NSMenuItem in menu.
这是我创建菜单和历史的时候，你可以在菜单中看到一个 NSMenuItem。
menu = [[NSMenu alloc] initWithTitle:@"Menu"];
[[menu addItemWithTitle:@"History" action:nil keyEquivalent:@""] setTarget:self];
[[menu addItemWithTitle:@"Settings" action:@selector(loadSettings:) keyEquivalent:@""] setTarget:self];
[[menu addItemWithTitle:@"Quit" action:@selector(terminateApp:) keyEquivalent:@""] setTarget:self];
At this point, history is disabled (greyed out). Then somewhere in the program I need to have a submenu for history so:
此时，历史记录被禁用（变灰）。然后在程序的某个地方我需要有一个历史子菜单，所以：
if (historyMenu == nil) {
historyMenu = [[NSMenu alloc] initWithTitle:@"Lyrics history"];
[menu setSubmenu:historyMenu forItem:[menu itemWithTitle:@"History"]];
}
I now see an arrow beside history, but it's still greyed out.
我现在在历史旁边看到一个箭头，但它仍然是灰色的。
Please help, I have been trying to figure this out for last 2 hours. Thanks.
请帮忙，我过去 2 小时一直在努力解决这个问题。谢谢。
回答by Jon Steinmetz
You are setting the target but have a nil action. Try not setting the target. This may leave it enabled all the time in which case you may have to manually enable or disable the menu item.
您正在设置目标但没有操作。尽量不要设定目标。这可能会一直启用它，在这种情况下，您可能必须手动启用或禁用菜单项。
Here is the documentationon how menu items get enabled.
回答by Adam Johns
I had to override the validateMenuItemmethod to return true:
我不得不将该validateMenuItem方法覆盖为return true：
override func validateMenuItem(menuItem: NSMenuItem) -> Bool {
return true
}
It didn't actually use the validation method until I set target to self though like you did with
它实际上并没有使用验证方法，直到我将目标设置为 self 虽然像你一样
menu.addItemWithTitle("An Item", action: #selector(itemPressed), keyEquivalent: "")?.target = self
