Cocoa, NSTextField not noticing lost focus when pressing Tab?

Question

I can't seem to find a way to get notified when an NSTextField loses focus by pressing the Tab key. I get a nice textDidEndEditing when clicking another control or when pressing Enter, but not if I change the focus by pressing the Tab key.

Also tried to yank KeyDown and doCommandBySelector for this purpose but I got nowhere.

Any ideas?

Thanks in advance

Edit:

Forgot to mention, but I tried resignFirstResponder too. This is the code I tried:

- (BOOL)resignFirstResponder
{
    NSRunAlertPanel(@"", @"Lost Focus",@"OK", nil, nil);
    return [super resignFirstResponder];
}
- (BOOL)becomeFirstResponder
{
    NSRunAlertPanel(@"", @"Got focus",@"OK", nil, nil);
    return [super becomeFirstResponder];
}

Strangely, what happens here is that when getting focus, both becomeFirstResponder and resignFirstResponder are called one after the other. But when changing focus away from the control, neither are.

Answer 1

NSTextField is a subclass of NSResponder. NSResponder has a method - (BOOL)resignFirstResponder. That will notify you when the NSTextField is no longer first responder... ie. loses focus. So subclass your NSTextField and do your stuff in there.

Answer 2

With the understanding that I mentioned in my other post, I figured out an answer. It's a little convoluted but it works. You have to subclass both the NSTextField and the NSWindow because you need information from both to set this up. Here's the subclasses: HMTextField.h

#import <Foundation/Foundation.h>

@interface HMTextField : NSTextField {

}

@end

HMTextField.m

#import "HMTextField.h"
#import "HMWindow.h"

@implementation HMTextField

- (BOOL)becomeFirstResponder {
    [(HMWindow*)[self window] setTfBecameFirstResponder:YES];
    return [super becomeFirstResponder];
}

@end

HMWindow.h

#import <Foundation/Foundation.h>

@interface HMWindow : NSWindow {
    BOOL tfIsFirstResponder, tfBecameFirstResponder;
}

@property (nonatomic, readwrite, assign) BOOL tfBecameFirstResponder;

@end

HMWindow.m

#import "HMWindow.h"

@implementation HMWindow

@synthesize tfBecameFirstResponder;

-(id)init {
    if (self = [super init]) {
        tfIsFirstResponder = NO;
    }
    return self;
}

- (NSResponder *)firstResponder {
    id fr = [super firstResponder];

    if ([fr isEqualTo:[self fieldEditor:NO forObject:nil]]) {
        tfIsFirstResponder = YES;
    } else {
        if (tfIsFirstResponder && tfBecameFirstResponder) {
            NSLog(@"the text field stopped being first responder");
            tfBecameFirstResponder = NO;
        }
        tfIsFirstResponder = NO;
    }

    return fr;
}

@end

Make the classes and make your objects their class. You'll be notified of the first responder change from your text field where the NSLog message is in the HMWindow.m file. If you need help understanding how it works let me know.

Answer 3

Ok, I've found a way to do it: use a window delegate to make the window return a custom field editor. This field editor keeps track of the last TextField that's been activated and calls its textDidEndEditting method when losing firstResponder itself. Here's an example of how to do it:

#import <Cocoa/Cocoa.h>
#import <AppKit/AppKit.h>


@interface MyTextField : NSTextField
- (BOOL)resignFirstResponder;
- (void)textDidEndEditing:(NSNotification *)notification;
@end

@interface MyFieldEditor : NSTextView
{
    MyTextField * lastBox;
}
-(void) setLastEditBox:(MyTextField*) box;
@end

@interface MyWindowDelegate : NSWindowController 
{
    MyFieldEditor *fieldEditor;
}
@end



@implementation MyFieldEditor

-(void) setLastEditBox:(MyTextField*) box{ lastBox = box; }

-(id)init
{
    if (self = [super init]) 
        [self setFieldEditor:YES];

    return self;
}

- (BOOL)resignFirstResponder
{
    // Activate the last active editbox editting-end event
    if(lastBox != nil)
    {
        [lastBox textShouldEndEditing:self];
        lastBox = nil;
    }

    return [super resignFirstResponder];
}

@end


@implementation MyWindowDelegate

-(id)windowWillReturnFieldEditor:(NSWindow *)sender toObject:(id)client
{
    if(fieldEditor == nil)  // Return our special field editor
        fieldEditor = [[[MyFieldEditor alloc] autorelease] init];
    return fieldEditor;
}
@end


@implementation MyTextField

- (BOOL)resignFirstResponder
{
    // We're losing first responder, inform the field editor that this was the last edit box activated
    MyFieldEditor* myTf = (MyFieldEditor*) [[self window] fieldEditor:YES forObject:self];
    [myTf setLastEditBox:self];
    return [super resignFirstResponder];
}

- (void)textDidEndEditing:(NSNotification *)notification;
{
    [super textDidEndEditing:notification];
    [self setStringValue:@"RECEIVED ENDEDITING"];
}

@end




int main(int argc, char *argv[])
{   
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    NSApplication *app = [NSApplication sharedApplication];

    NSRect frame = NSMakeRect(100, 100, 200, 150);

    // Create the window
    NSWindow* window  = [[[NSWindow alloc] autorelease ] initWithContentRect:frame styleMask:NSClosableWindowMask|NSResizableWindowMask
                                                      backing:NSBackingStoreBuffered defer:NO];

    [window setDelegate:[[MyWindowDelegate alloc] autorelease]];


    MyTextField * tf = [ [[ MyTextField alloc ] autorelease] initWithFrame: NSMakeRect( 30.0, 100.0, 150.0, 22.0 ) ];
    [ [ window contentView ] addSubview: tf ];

    MyTextField * tf2 = [ [[ MyTextField alloc ] autorelease] initWithFrame: NSMakeRect( 30.0, 40.0, 150.0, 22.0 ) ];
    [ [ window contentView ] addSubview: tf2 ];

    [window makeKeyAndOrderFront: window];  

    [app run];
    [pool release];

    return 0;
}