macos - 使用 nextKeyView 在 NSTextField 之间切换

Question

我有一个具有以下布局的 NSViewController，使用 Storyboard 进行设置:

每个 NSTextField 的 nextKeyView 导出被配置为按照屏幕截图中显示的顺序的下一个 NSTextField。例如，我在IB中选择了服务器NSTextField，并从Connectivity检查器中的nextKeyView socket 拖动到登录NSTextField，并对其余字段执行相同的操作。

当应用程序启动时，在任何字段上按下任何选项卡都会将选择移动到第一个 NSTextField。如何在字段之间实现所需的选项卡切换？

我在相应的 WindowController 中尝试了此操作，但没有成功:

- (void)windowDidLoad {
    [super windowDidLoad];

    self.window.initialFirstResponder = self.serverTextField;
}

Answer 1

这个好像是最详细的answer ，来自 Justin Bur，发布到 cocoa-dev 邮件列表(2007 年 1 月 31 日)。

On several occasions over the years, people have asked why their key view loop doesn't work properly. Most of these queries never get answered on the list. After failing to find help for my key view loop problems either on this list or on web sites, I did some experimenting.

The key view loop can be problematic to deal with. It is designed to just work magically, so in most cases it's not an issue. But if it doesn't work, it's pretty difficult to figure out why not. Here are some guidelines for getting a working key view loop.

1. Consider whether you can settle for an automatically generated key view loop. Each responder's top left corner determines its placement in the loop. The loop proceeds from upper left to lower right, row by row (at least for left-to-right scripts). This is by far the easiest solution. To enable this, make sure the window's initialFirstResponder is nil. See also -[NSWindow recalculateKeyViewLoop].

2. If the automatic key view loop is not suitable, set up your own key view loop using Interface Builder as much as possible. The window's initialFirstResponder outlet must be set, in order to disable automatic key loop generation. From that responder around the loop, set the nextKeyView outlet of each item in the loop. (If desired, the last item's nextKeyView can be set to the first item, thus closing the loop.) For any view with scrollbars (NSTextView, NSTableView, etc.), you should use the enclosing NSScrollView when setting nextKeyView.

3. If you have any responders created in code, splice them into the key view loop early (preferably in awakeFromNib or maybe -[NSWindowController windowDidLoad]). For each (sequence of) new item(s), you must use call -[NSView setNextKeyView:] thus: once to make the previous item point to the (first) new one, (calls to make each new item point to the next), and finally to make the (last) new item point to its successor.

4. If your window has a toolbar, toolbar items that are interested in becoming key view will automatically add and remove themselves as the toolbar is shown or hidden. The toolbar does not take into account the return value of -[NSWindow autorecalculatesKeyViewLoop]. Toolbar items are always placed in the loop before the top leftmost item. There is no easy way to change this.

5. Once the window has been displayed, it can be extremely difficult to modify the key view loop - in particular if you are using NSScrollView or NSTabView. These (and others?) are special cases because they insert their contained views into the loop automatically. For information on the initialFirstResponder and key view loop of an NSTabViewItem, see the AppKit release notes for OS X 10.1 .

6. If you have items that should sometimes be in the loop and other times not, it is not advisable to attempt to splice them in and out of the loop. Instead, subclass -[NSResponder acceptsFirstResponder] for these items. If an item returns NO from this method, it will be left out of the loop (temporarily); if it returns YES, it will come back into the loop. Alternately, if the item is derived from NSControl (it probably is), you can call setRefusesFirstResponder: on it.

7. If you make a mistake, your key view loop will cease to function, either in one direction or in both. Once it breaks it stays broken. To debug, comment out calls to setNextKeyView: or setInitialFirstResponder: until it works again. The offending call is likely trying to modify the key view loop in the presence of NSScrollView or NSTabView, after these objects have already done their behind-the-scenes loop-munging. Move the calls to an earlier point, or do without. (If you have no calls to setNextKeyView:, then check your nib - make sure the window's initialFirstResponder is set and that nextKeyView outlets are chained together the way you want.)

8. In System Preferences/Keyboard & Mouse/Keyboard Shortcuts, at the bottom of the pane under "Full keyboard access", you can control whether key view loops include all controls or only text fields and scrolling lists (^F7 to toggle). You should test your key view loops with this setting in each state.

These guidelines were determined by experiment and may not be entirely accurate. Corrections and further explanations are most welcome.