Objective c NSWindow不'；无法接收键盘事件

我以编程方式创建NSWindow，无法接收任何键盘消息。我没有这样做，而是在Xcode编辑器中键入，但此时我的窗口处于焦点位置。我如何拦截这些事件

这是我的密码：

//// delegate
@interface MyDelegate : NSObject
@end
@implementation MyDelegate
@end

//// view
@interface MyView : NSView
@end

@implementation MyView

- (BOOL)isOpaque { return YES;}
- (BOOL)canBecomeKeyView { return YES;}
- (BOOL)acceptsFirstResponder { return YES;}

- (void)keyDown:(NSEvent *)event
{
    printf("PRESS\n"); // it's ignoring
}

@end

//// main
int main(int argc, const char **argv){
    [NSApplication sharedApplication];

    NSWindow *window = [[NSWindow alloc]
              initWithContentRect:NSMakeRect( 0, 0, 100, 100 )
              styleMask:NSTitledWindowMask | NSClosableWindowMask | NSMiniaturizableWindowMask
              backing:NSBackingStoreBuffered
              defer:NO];
    [window setContentView: [[MyView alloc] init]];
    [window setDelegate: [[MyDelegate alloc] init] ];
    [window setAcceptsMouseMovedEvents:YES];
    [window setLevel: NSFloatingWindowLevel];
    [window makeKeyAndOrderFront: nil];

    [NSApp run];
    return 0;
}

---

您需要使应用程序成为前台应用程序。这是主窗口接收关键事件所必需的

ProcessSerialNumber psn = {0, kCurrentProcess};
OSStatus status =
  TransformProcessType(&psn, kProcessTransformToForegroundApplication);

---

这对我有帮助。不知道为什么进程在默认情况下不是前台应用程序。。。