ios - CATransform3D.MakeScale 正在移动层

Question

我正在开发适用于 iOS 的 Xamarin.Forms 应用程序。此应用程序由 UIView 组成，其中包含 CALayers 子层。它们的添加方式如下:

// draw all the pins from the list
foreach (var pin in _control.PinsSource)
{
    var point = new CGPoint
    {
        X = pin.Longitude,
        Y = pin.Latitude
    };

    var shapeLayer = new CAShapeLayer
    {
        Name = nameof(MapItem),
        Path = MakeCircleAtLocation(point, PinRadius).CGPath,
        FillColor = UIColor.Red.CGColor
    };

    Layer.AddSublayer(shapeLayer);
}

// Create a UIBezierPath which is a circle at a certain location of a certain radius.
private static UIBezierPath MakeCircleAtLocation(CGPoint location, nfloat radius)
{
    var path = new UIBezierPath();
    path.AddArc(location, radius, 0, (float)(Math.PI * 2.0), true);
    return path;
}

然后我有一个 UIPinchGestureRecognizer ，它可以缩放 UIView 和其他一些 GestureRecognizers (如平移)。

缩放和平移基础 View 效果很好。 UIView 使用名为 _currentScale 的变量进行缩放。请参阅此处的完整方法:

private void HandlePinch(UIPinchGestureRecognizer recognizer)
{
    // Prevent the object to become too large or too small
    var newScale = (nfloat)Math.Max(MinZoomLevel, Math.Min(_currentScale * recognizer.Scale, MaxZoomLevel));

    if (_currentScale != newScale)
    {
        _currentScale = newScale;

        Transform = CGAffineTransform.MakeScale(_currentScale, _currentScale);

        foreach (var subLayer in Layer.Sublayers)
        {
            if (subLayer.Name == nameof(MapItem))
                subLayer.Transform = CATransform3D.MakeScale(PinRadius / _currentScale, PinRadius / _currentScale, 1);
        }
    }
    recognizer.Scale = 1;
}

如果子图层是 map 图钉，我确实不使用_currentScale对其进行缩放，因此这就是我使用PinRadius/划分比例的原因_currentScale。

缩放工作正常，但是图钉在 map 上移动，这很奇怪。请参阅此处:

我该如何解决这个问题？

Answer 1

不幸的是，我找不到另一种方法，然后在每次捏合时重新创建一个新的CAShapeLayer。虽然很丑陋，但它确实有效。

private void HandlePinch(UIPinchGestureRecognizer recognizer)
{
    // Prevent the object to become too large or too small
    var newScale = (nfloat)Math.Max(MinZoomLevel, Math.Min(_currentScale * recognizer.Scale, _maxZoomLevel));

    if (_currentScale != newScale)
    {
        _currentScale = newScale;
        _currentPinRadius = _pinRadius / _currentScale;

        Transform = CGAffineTransform.MakeScale(_currentScale, _currentScale);

        // First layer is a CALayer, so start at 1
        for (var i = 1; i < Layer.Sublayers.Length; i++)
        {
            var caLayer = ((CAShapeLayer)Layer.Sublayers[i]);

            var cgPoint = new CGPoint
            {
                X = _control.PinsSource[i - 1].Longitude,
                Y = _control.PinsSource[i - 1].Latitude
            };

            caLayer.Path = CreateCircle(cgPoint, _currentPinRadius);
        }
    }
    recognizer.Scale = 1;
}