Add a UIView to a PDF page

This tutorial only applies to Xamarin.iOS. See Xamarin.Android equivalent here .

This guide demonstrates how to make a `UIView` appear as if it is stuck to a page.

It is convenient for the user to make a UIView that is "stuck" to a page record its desired page location. To do this, you could add an extension/category to a UIView, or use a derived class, as shown below:

C#

public class FloatingView : UIView
{
    public FloatingView() : base()
    {
        
    }
    
    public int PageNumber { get; set; }

    public pdftron.PDF.Rect PdfPageRect { get; set; }
}

Swift

class FloatingView: UIView {
    // the page on which the UIView appears
    
    var pageNumber: Int32 = 0
    // the location, expressed in PDF coordinates, at which the view appears
    var pdfPageRect: PTPDFRect?
}

Obj-C

@interface FloatingView : UIView
// the page on which the UIView appears
@property (assign, nonatomic) int pageNumber;
// the location, expressed in PDF coordinates, at which the view appears
@property (strong, nonatomic) PTPDFRect* pdfPageRect;
@end
@implementation FloatingView
@end

A red `UIView` positioned near the bottom left hand corner of the first page.

In this example, we will add a red square to a location near the bottom left hand corner of the first page:

C#

var mCustomView = new FloatingView();
mCustomView.BackgroundColor = UIColor.Red;
mCustomView.PageNumber = 1;
mCustomView.PdfPageRect = new Rect(10, 10, 100, 100);
mPdfViewCtrl.OverlayView.AddSubview(mCustomView);

// position the view
positionFloatingViews();

Swift

// prepare the new view
let redRect = FloatingView()
redRect.backgroundColor = UIColor.red
redRect.pageNumber = 1
redRect.pdfPageRect = PTPDFRect(x1: 10, y1: 10, x2: 100, y2: 100)
// add the view to PTPDFViewCtrl's overlayView
self.pdfViewCtrl.overlayView.addSubview(redRect)
// position the view
positionFloatingViews()

Obj-C

// prepare the new view
FloatingView* redRect = [[FloatingView alloc] init];
[redRect setBackgroundColor:[UIColor redColor]];
redRect.pageNumber = 1;
redRect.pdfPageRect = [[PTPDFRect alloc] initWithX1:10 y1:10 x2:100 y2:100];
// add the view to PTPDFViewCtrl's overlayView
[self.pdfViewCtrl.overlayView addSubview:redRect];
// position the view
[self positionFloatingViews];

Without the last line in the code snippet above, the new view would not appear in the correct location. The following method will position it, and any others that have been added:

C#

void positionFloatingViews()
{
    foreach (UIView view in mPdfViewCtrl.OverlayView.Subviews)
    {
        if (view is FloatingView)
        {
            var overlayView = view as FloatingView;
            bool pageHidden = false;
            if (!mPdfViewCtrl.PagePresentationModeIsContinuous)
            {
                pageHidden = !mPdfViewCtrl.PageIsOnScreen(overlayView.PageNumber);
            }
            overlayView.Hidden = pageHidden;
            CGRect screenRect = mPdfViewCtrl.PDFRectPage2CGRectScreen(TypeConvertHelper.ConvRectToNative(overlayView.PdfPageRect), overlayView.PageNumber);
            screenRect.X += (nfloat)mPdfViewCtrl.GetHScrollPos();
            screenRect.Y += (nfloat)mPdfViewCtrl.GetVScrollPos();
            overlayView.Frame = screenRect;
        }
    }
}

Swift

func positionFloatingViews() {
    for case let overlayView as FloatingView in self.pdfViewCtrl.overlayView.subviews {
        // make sure this is a floating view
        if type(of: overlayView) === FloatingView.self {
            var pageHidden = false
            if !pdfViewCtrl.pagePresentationModeIsContinuous() {
                pageHidden = !pdfViewCtrl.pageIs(onScreen: overlayView.pageNumber)
            }
            overlayView.isHidden = pageHidden
            var screenRect: CGRect = pdfViewCtrl.pdfRectPage2CGRectScreen(overlayView.pdfPageRect, pageNumber: overlayView.pageNumber)
            screenRect.origin.x += CGFloat(pdfViewCtrl.getHScrollPos())
            screenRect.origin.y += CGFloat(pdfViewCtrl.getVScrollPos())
            overlayView.frame = screenRect
        }
    }
}

Obj-C

-(void)positionFloatingViews
{
    for(FloatingView* overlayView in self.pdfViewCtrl.overlayView.subviews)
    {
        // make sure this is a floating view
        if( [overlayView isMemberOfClass:[FloatingView class]])
        {
            BOOL pageHidden = NO;
            if( ![self.pdfViewCtrl pagePresentationModeIsContinuous] )
            {
                pageHidden = ![self.pdfViewCtrl pageIsOnScreen:overlayView.pageNumber];
            }
            overlayView.hidden = pageHidden;
            CGRect screenRect = [self.pdfViewCtrl PDFRectPage2CGRectScreen:overlayView.pdfPageRect PageNumber:overlayView.pageNumber];
            screenRect.origin.x += [self.pdfViewCtrl GetHScrollPos];
            screenRect.origin.y += [self.pdfViewCtrl GetVScrollPos];
            overlayView.frame = screenRect;
        }
    }
}

Whenever the PDF page shifts within the PTPDFViewCtrl, which may happen when changing the page presentation mode, zooming, and such, the views need to be re-positioned (positionFloatingViews needs to run again). To do this, implement the PTPDFViewCtrl delegate methods pdfScrollViewDidEndZooming: and onLayoutChanged, and in them, call positionFloatingViews:

C#

mPdfViewCtrl.PdfViewCtrlOnLayoutChanged += (sender, e) =>
{
    positionFloatingViews();
};
mPdfViewCtrl.PdfScrollViewDidEndZooming += (sender, e) =>
{
    positionFloatingViews();
};

Swift

func pdfViewCtrl(onLayoutChanged pdfViewCtrl: PTPDFViewCtrl!) {
    positionFloatingViews()
}
func pdfViewCtrl(_ pdfViewCtrl: PTPDFViewCtrl!, pdfScrollViewDidEndZooming scrollView: UIScrollView!, with view: UIView!, atScale scale: Float) {
    positionFloatingViews()
}

Obj-C

-(void)pdfViewCtrlOnLayoutChanged:(PTPDFViewCtrl *)pdfViewCtrl
{
    [self positionFloatingViews];
}
-(void)pdfViewCtrl:(PTPDFViewCtrl *)pdfViewCtrl pdfScrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale
{
    [self positionFloatingViews];
}