objective-c - 在 Mac OS X 下知道手指在触控板上的位置

Question

我正在开发一个 Mac 应用程序，我想知道触摸时手指在触控板上的位置。

这是否可能，如果可能，如何实现？

Answer 1

您的 View 需要设置为接受触摸 ([self setAcceptsTouchEvents:YES])。当你得到像 -touchesBeganWithEvent: 这样的触摸事件时，你可以通过查看它的 normalizedPosition(范围是 [0.0, 1.0] x [0.0, 1.0]) 鉴于其 deviceSize 大点(每英寸有 72 bp)。触控板的左下角被视为零原点。

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，而不是久经考验的真实示例代码；我只是将其直接写在评论框中。)