How do I collect key input in a video-game style Cocoa app?

Question

I'm hacking on a simple Cocoa app to make blocks move around the screen like a video game. I need to detect key presses, but I'm not going to have text entry fields like a dialog box would have.

How do I get key presses without text controls? In particular, I need to get arrow keys.

Answer 1

In your game view, define the keyUp and keyDown methods:

@interface MyView : NSView
-(void)keyUp:(NSEvent*)event;
-(void)keyDown:(NSEvent*)event;
@end

@implementation MyView

-(void)keyUp:(NSEvent*)event
{
    NSLog(@"Key released: %@", event);
}

-(void)keyDown:(NSEvent*)event
{   
    // I added these based on the addition to your question :)
    switch( [event keyCode] ) {
     case 126: // up arrow
     case 125: // down arrow
     case 124: // right arrow
     case 123: // left arrow
      NSLog(@"Arrow key pressed!");
      break;
     default:
      NSLog(@"Key pressed: %@", event);
      break;
    }
}
@end

See the documentation for NSView and NSEvent for more info. Note that the keyDown and keyUp events are actually defined on NSResponder, the super class for NSView.