objective-c – 在Mac OS X上的触控板中知道手指的位置

您的视图需要设置为接受触摸([self setAcceptsTouchEvents：YES]).当你得到一个触摸事件,如-touchesBeganWithEvent：,你可以通过查看它的normalizedPosition(范围是[0.0,1.0] x [0.0,1.0]),根据它的deviceSize的大点来确定手指的位置(有72磅/英寸).触控板的左下角被视为零起点.

所以,例如：

- (id)initWithFrame:(NSRect)frameRect {
   self = [super initWithFrame:frameRect];
   if (!self) return nil;

   /* You need to set this to receive any touch event messages. */
   [self setAcceptsTouchEvents:YES];

   /* You only need to set this if you actually want resting touches.
    * If you don't,a touch will "end" when it starts resting and
    * "begin" again if it starts moving again. */
   [self setWantsRestingTouches:YES]
   return self;
}

/* One of many touch event handling methods. */
- (void)touchesBeganWithEvent:(NSEvent *)ev {
   NSSet *touches = [ev touchesMatchingPhase:NSTouchPhaseBegan inView:self];

   for (NSTouch *touch in touches) {
      /* Once you have a touch,getting the position is dead simple. */
      NSPoint fraction = touch.normalizedPosition;
      NSSize whole = touch.deviceSize;
      NSPoint wholeInches = {whole.width / 72.0,whole.height / 72.0};
      NSPoint pos = wholeInches;
      pos.x *= fraction.x;
      pos.y *= fraction.y;
      NSLog(@"%s: Finger is touching %g inches right and %g inches up "
            @"from lower left corner of trackpad.",__func__,pos.x,pos.y);
   }
}

(将此代码视为示例,而不是尝试和真实的,战斗的示例代码;我只是将其直接写入注释框中.)