Xamarin ios - 如何在UIScrollView中放入大图像

Question

我正在使用在C＃中实现的Xamarin.iOS。我有一个图像列表。我正在尝试为Facebook或任何其他照片查看应用程序实现类似的功能。图像非常大但我想缩放它们以便它们总是适合滚动视图的边界 - 在这种情况下，scrollview符合屏幕边界。

我的挑战是：

1. 我的图片填满整个屏幕但未正确缩放。
2. 当我缩小时，我希望最小缩放比例返回到原始视图。

以下是我目前的代码：

public override void ViewDidLoad()
    {
        base.ViewDidLoad ();

        //Setting up the scrollView  

        ScrollViewMain.BouncesZoom = false;
        ScrollViewMain.ClipsToBounds = true;
        index = 0;

        AddImageInScrollView(index);

        btnClose.AddTarget (this, new Selector ("MySelector"), UIControlEvent.TouchDown);

        btnPrevious.TouchUpInside += (object sender, EventArgs e) => {
            index--;
            if(index < 0)
                index = 0;

            imageView.RemoveFromSuperview();
            AddImageInScrollView(index);

        } ;

        btnNext.TouchUpInside += (object sender, EventArgs e) => {
            index++;
            if((nuint)index > Car.allThumbnails.Count-1)
                index = (int)Car.allThumbnails.Count-1;

            imageView.RemoveFromSuperview();
            AddImageInScrollView(index);

        } ;


        var tapGestureRecognizer = new UITapGestureRecognizer (OnDoubleTap);
            tapGestureRecognizer.NumberOfTapsRequired = 2;

        ScrollViewMain.AddGestureRecognizer (tapGestureRecognizer);
}

public void AddImageInScrollView(int index)
    {

        //Setting up the imageView
        imageView = new UIImageView(Car.allThumbnails.GetItem<UIImage>((nuint)index));
        imageView.UserInteractionEnabled = true;
        imageView.ContentMode = UIViewContentMode.ScaleAspectFit;


        //Adding the imageView to the scrollView as subView
        ScrollViewMain.AddSubview(imageView);

        ScrollViewMain.DecelerationRate = UIScrollView.DecelerationRateFast;

        var scrollViewFrame = ScrollViewMain.Frame;
        var scaleWidth = scrollViewFrame.Size.Width / ScrollViewMain.ContentSize.Width;
        var scaleHeight = scrollViewFrame.Size.Height / ScrollViewMain.ContentSize.Height;

        ScrollViewMain.ContentSize = new System.Drawing.SizeF((float)ScrollViewMain.Bounds.Size.Width, (float)ScrollViewMain.Bounds.Size.Height);


        var minScale = Math.Min(scaleWidth, scaleHeight);
//Set the zoom properties
        ScrollViewMain.MaximumZoomScale = 3f;
        ScrollViewMain.MinimumZoomScale = (float)minScale;

        ScrollViewMain.ViewForZoomingInScrollView += (UIScrollView sv) => {
            return imageView;

        };
        ScrollViewMain.ZoomScale = 1.0f;
        ScrollViewMain.ContentMode = UIViewContentMode.ScaleAspectFit;
        imageView.ContentMode = UIViewContentMode.ScaleAspectFit;
        imageView.SizeToFit();
        ScrollViewMain.ContentSize = new System.Drawing.SizeF((float)imageView.Frame.Size.Width, (float)imageView.Frame.Size.Height);

}

这就是它的样子