Question

我有一个调用UIView类的UIViewController，我正在使用CGAffine Transform使用以下代码放大我的UIView类实例

CGAffineTransform transform = CGAffineTransformMakeScale(recognizer.scale,    recognizer.scale);
NSLog(@"Pinch scale: %f", recognizer.scale);
float scale = recognizer.scale;
float SCALE_MIN = 1.0f;
float SCALE_MAX = 3.0f;
. . .

这个基本代码，有效！（某些代码已被省略）

现在的问题是无论屏幕上的哪个位置“捏”，文件总是从文件的中间放大，而不是在我捏的位置。。

有关如何让它缩放到精确位置的任何建议吗？

Answer 1

在locationInView:的实例上调用时，UIGestureRecognizers方法可用于所有UIPinchGestureRecognizer，它将为您提供构成捏合的两个触摸之间的中点。这是我认为你会得到的最接近的东西“确切的位置。”

首次识别手势时，保存locationInView以获取您想要缩放的点。我不会尝试在夹点过程中更新缩放中心，因为我认为你最终会得到一个不直观的复杂实现。您需要缩放以保持中心点的固定，并且您应该可以通过设置要转换的视图的anchorPoint的{{1}}来实现此目的。请注意，layer坐标已标准化 - 默认为anchorPoint，即视图的中心。

Answer 2

- (void)pinchDetected:(UIPinchGestureRecognizer *)gestureRecognizer {

if([gestureRecognizer state] == UIGestureRecognizerStateBegan) {
    // Reset the last scale, necessary if there are multiple objects with different scales
    lastScale = [gestureRecognizer scale];
}

if ([gestureRecognizer state] == UIGestureRecognizerStateBegan ||
    [gestureRecognizer state] == UIGestureRecognizerStateChanged) {

    CGFloat currentScale = [[[gestureRecognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];

    // Constants to adjust the max/min values of zoom
    const CGFloat kMaxScale = 2.2;
    const CGFloat kMinScale = 0.64;

    CGFloat newScale = 1 -  (lastScale - [gestureRecognizer scale]);
    newScale = MIN(newScale, kMaxScale / currentScale);
    newScale = MAX(newScale, kMinScale / currentScale);
    CGAffineTransform transform = CGAffineTransformScale([[gestureRecognizer view] transform], newScale, newScale);
    [gestureRecognizer view].transform = transform;

    [gestureRecognizer setScale:1.0];

    lastScale = [gestureRecognizer scale];  // Store the previous scale factor for the next pinch gesture call
}
}

Answer 3

希望这对你有所帮助，这对我来说就像魅力一样......

- (void)pinchDetected:(UIPinchGestureRecognizer *)pinchRecognizer
{
    CGAffineTransform transform = CGAffineTransformScale(pinchRecognizer.view.transform, pinchRecognizer.scale,pinchRecognizer.scale);
    _designImage.transform = transform;
    _Zoomscale = pinchRecognizer.scale;

    NSLog(@"image Pinch scale: %2ff", _Zoomscale);
}

iOS - 使用CGAffineTransform缩放到缩放点

3 个答案: