缩放 SKNode 不一致

我已经创建了自己的解决方案，用于放大或缩小特定的 SKNode，而无需缩放整个场景，它似乎主要按照我期望的方式工作，有 2 个值得注意的例外，我希望在这里得到输入。首先是代码（该控制语句位于touchesMoved方法内）：

 if (touches.count == 2) {
        // this means there are two fingers on the screen
        NSArray *fingers = [touches allObjects];
        CGPoint fingOneCurr = [fingers[0] locationInNode:self];
        CGPoint fingOnePrev = [fingers[0] previousLocationInNode:self];
        CGPoint fingTwoCurr = [fingers[1] locationInNode:self];
        CGPoint fingTwoPrev = [fingers[1] previousLocationInNode:self];

        BOOL yPinch = fingOneCurr.y > fingOnePrev.y && fingTwoCurr.y < fingTwoPrev.y;
        BOOL yUnpinch = fingOneCurr.y < fingOnePrev.y && fingTwoCurr.y > fingTwoPrev.y;

        BOOL xPinch = fingOneCurr.x > fingOnePrev.x && fingTwoCurr.x < fingTwoPrev.x;
        BOOL xUnpinch = fingOneCurr.x < fingOnePrev.x && fingTwoCurr.x > fingTwoPrev.x;

        if (xUnpinch | yUnpinch) {
            if (YES) NSLog(@"This means an unpinch is happening");
            mapScale = mapScale +.02;
            [map setScale:mapScale];
        }

        if (xPinch | yPinch) {
            if (YES) NSLog(@"This means a pinch is happening");
            mapScale = mapScale - .02;
            [map setScale:mapScale];
        }
    }

现在的问题是：

1. 有时，捏合和松开并不总是正确的，当发生这种情况时，我无法完全准确地指出，捏合将表现为松开，反之亦然。

2. 当捏合和松开正确缩放 SKNode 时，它​​很少像我希望的那样平滑。它有一点生涩，我觉得很烦人。

谁能建议改进这种方法？谢谢！

这将解决您的问题，感谢 Steffen 的提示。

- (void)didMoveToView:(SKView *)view
{
    UIPinchGestureRecognizer *precog = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)];
    [self.scene.view addGestureRecognizer:precog];
}

- (void)handlePinch:(UIPinchGestureRecognizer *) recognizer
{
    //NSLog(@"Pinch %f", recognizer.scale);
    //[_bg setScale:recognizer.scale];
    [_bg runAction:[SKAction scaleBy:recognizer.scale duration:0]];
    recognizer.scale = 1;
}