Question

我编写的代码会让我在iOS中的视图放大屏幕并限制我可以缩小的数量。我不希望用户能够缩小开始屏幕。问题是，下面的代码将让我放大，但一旦我在某一点，我无法缩小到开始屏幕。我不确定我做错了什么。

float _currentScale = 1.0f;

public override void ViewDidLoad()
{
    base.ViewDidLoad();
    UIPinchGestureRecognizer twoFingerPinch = new UIPinchGestureRecognizer();
    twoFingerPinch.Delegate = new GestureDelegate();
    View.AddGestureRecognizer(twoFingerPinch);

}


class GestureDelegate : UIGestureRecognizerDelegate
{

    public override bool ShouldReceiveTouch(UIGestureRecognizer aRecogniser, UITouch aTouch)
    {
        return true;
    }

    // Ensure that the pinch, pan and rotate gestures are all recognized simultaneously
    public override bool ShouldRecognizeSimultaneously(UIGestureRecognizer gestureRecognizer, UIGestureRecognizer otherGestureRecognizer)
    {
        // if the gesture recognizers views differ, don't recognize
        if (gestureRecognizer.View != otherGestureRecognizer.View)
            return false;

        // if either of the gesture recognizers is a long press, don't recognize
        if (gestureRecognizer is UILongPressGestureRecognizer || otherGestureRecognizer is UILongPressGestureRecognizer)
            return false;

        return true;
    }
}

void ScaleScreen(UIPinchGestureRecognizer gestureRecognizer)
{
    AdjustAnchorPointForGestureRecognizer(gestureRecognizer);
    if (gestureRecognizer.State == UIGestureRecognizerState.Began || gestureRecognizer.State == UIGestureRecognizerState.Changed)
    {
        float minScale = 1.0f;
        float maxScale = 3.0f;
        float zoomSpeed = .5f;

        float deltaScale = (float)gestureRecognizer.Scale;

        deltaScale = ((deltaScale - 1) * zoomSpeed) + 1;

        deltaScale = Math.Min(deltaScale, maxScale / _currentScale);
        deltaScale = Math.Max(deltaScale, minScale / _currentScale);
        _currentScale = deltaScale;


        gestureRecognizer.View.Transform *= CGAffineTransform.MakeScale(deltaScale, deltaScale);

        // Reset the gesture recognizer's scale - the next callback will get a delta from the current scale.
        gestureRecognizer.Scale = 1;
    }
}

void AdjustAnchorPointForGestureRecognizer(UIGestureRecognizer gestureRecognizer)
{
    if (gestureRecognizer.State == UIGestureRecognizerState.Began)
    {
        var image = gestureRecognizer.View;
        var locationInView = gestureRecognizer.LocationInView(image);
        var locationInSuperview = gestureRecognizer.LocationInView(image.Superview);

        image.Layer.AnchorPoint = new CGPoint(locationInView.X / image.Bounds.Size.Width, locationInView.Y / image.Bounds.Size.Height);
        image.Center = locationInSuperview;
    }
}

Answer 1

我会将这个条件添加到ScaleScreen

中的if语句中

void ScaleScreen(UIPinchGestureRecognizer gestureRecognizer)
{
    AdjustAnchorPointForGestureRecognizer(gestureRecognizer);
    if (gestureRecognizer.State == UIGestureRecognizerState.Began ||       gestureRecognizer.State == UIGestureRecognizerState.Changed)
       //...
    else {
        if (gestureRecognizer.View.Transform.xx < 1)
            UIView.Animate(0.4, () => {
                gestureRecognizer.View.Transform = CGAffineTransform.MakeIdentity();
             }, null);
         }
    }
}

UIPinchGestureRecognizer在Xamarin放大但不放弃

1 个答案: