How to tell when NSPanel gets focus or becomes key?

Question

I am writing a Cocoa/Objective-C app in XCode4, and I need to know when my preferences panel is opened. I need some callback like windowDidBecomeKey; I attempted to follow the solution provided in this question, but neither windowDidBecomeKey or windowDidExpose appear as delegate methods(but others, like windowDidLoad, windowWillLoad, etc do).

To clarify exactly what I mean by "don't appear as delegate methods", I mean they don't show up in the auto complete when I begin typing the method name. I did try defining them anyway, but they were never called.

Do NSPanel objects lack these methods, or is there something more I have to do?

Currently, I have an interface PrefWindowController:

PrefWindowController.h:

#import <Cocoa/Cocoa.h>

@interface PrefWindowController : NSWindowController
    //Delegate methods like windowDidBecomeKey appear to not be available here
@end

PrefWindowController.m:

@implementation PrefWindowController

- (id)initWithWindow:(NSWindow *)window
{
    self = [super initWithWindow:window];
    if (self) {
        NSAlert *alert = [[[NSAlert alloc] init] autorelease];
        [alert setMessageText:@".."];
        [alert runModal];
    }

    return self;
}

- (void)windowDidLoad
{
    NSAlert *alert = [[[NSAlert alloc] init] autorelease];
    [alert setMessageText:@"Loaded"];
    [alert runModal];
}

@end

When the window loads from the .xib as the application starts, windowDidLoad fires and the notification defined above is shown. I did this just to test that methods were actually getting called.

Any advice about how to get a callback for when the panel becomes key or takes focus would be very helpful.

Update:

I added a windowDidBecomeKey method to the window controller, like so:

PrefWindowController.h:

- (void)windowDidBecomeKey:(NSNotification *)notification;

PrefWindowController.m:

- (void)windowDidBecomeKey:(NSNotification *)notification
{
    NSLog(@"Test");
}

The test message gets logged the first time I open the window, but on the return line in my main.m file I get the error:

Thread 1: Program Received Signal: "EXC_BAD_ACCESS"

score 8 · Accepted Answer · answered Dec 02 '11 at 16:25

8

The NSWindowDelegate protocol has the following methods

- (void)windowDidBecomeKey:(NSNotification *)notification
- (void)windowDidResignKey:(NSNotification *)notification

so you can set your NSWindowController as the NSWindow delegate to get this callback. You can also register for these notifications:

NSWindowDidResignKeyNotification
NSWindowDidBecomeKeyNotification

NSPanel is an NSWindow subclass so all this behaviour applies in your case.

answered Dec 02 '11 at 16:25

jbat100

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the `windowDidBecomeKey` method seems to have worked - but see my update to the question. Could this have to do with the fact that I'm not using the window manager to open the window (and the window is set to release when closed)? I am sort of unclear how I would do that from another class, though. That is, obtain an instance of PrefWindowManager I could use to open the window with that. – WilHall Dec 02 '11 at 16:39
Do you have a log? kind of hard to say without more info. – jbat100 Dec 02 '11 at 18:07
I resolved the issue - it was in fact because the window was released on close. Thanks! – WilHall Dec 02 '11 at 18:35

How to tell when NSPanel gets focus or becomes key?

1 Answers1