<< Click to Display Table of Contents >> Navigation:  Create a PDF Editor > Delphi Example > Add code to initialize a PDF viewer

On the form there is a TWPViewPDF component - but it will never be used to load a PDF file.

 

Instead we create a new viewer automatically when we need to load a new file. This is done in the method NewPDFDocument which receives a filename.

 

It will create a new tab inside the PageControl. The tab will use the class TPDFTabSheet which holds additional variables and of course a reference to a TWPViewPDF component.

 

Create a custom TTabSheet class:

 

type TPDFTabSheet = class(TTabSheet)

  wpviewpdf : TWPViewPDF;

  image     : TImage; // uses Vcl.ExtCtrls, we use that later

end;

 

First we need an handler for the event which is used to update the state of all actions:

 

procedure TForm2.WPViewPDF_DoChangeViewPage(Sender: TObject; const PageNr: Integer);

var i : Integer;

begin

  for I := 0 to ActionList1.ActionCount-1 do

     ActionList1.UpdateAction(ActionList1.Actions[i])

end;

 

 

This method creates a new tab and the components on it.

 

procedure TForm2.NewPDFDocument( filename : string );

var

    newTab :TPDFTabSheet;

begin

    newTab := TPDFTabSheet.Create(PageControl1);

    newTab.wpviewpdf := TWPViewPDF.Create(newTab);

    try

      newTab.PageControl := PageControl1;

 

      // And move it to the page control

      newTab.wpviewpdf.Align := alClient;

      newTab.wpviewpdf.Parent := newTab;

 

      if not newTab.wpviewpdf.LoadFromFile(filename) then

        raise Exception.Create( filename + ' cannot be loaded.');

 

      // Make sure the annotations work interactively!

      newTab.wpviewpdf.Command(COMPDF_ACRO_MAKEDRAWOBJ,'', 8192 );  // 0=all Annots!

 

      // Enables saving of annotations which have been added to the page

      newTab.wpviewpdf.Command(COMPDF_Ann_SetAnnotSaveMode, 1);

 

      // Standard Action Mode 'Click + Pan'

      newTab.wpviewpdf.Command(COMPDF_SetActionMode,'',1);  

      // Set WPViewPDF Properties

      newTab.wpviewpdf.ViewOptions := [wpViewThumbnails,wpInteractiveThumbnails];

      newTab.wpviewpdf.ViewControls := [

            wpVertScrollBar,   // Scrollbar vertical

            wpHorzScrollBar,   // Scrollbar horizontal

            wpPropertyPanel,   // '?' Button

            wpNavigationPanel, // Up / down

            wpViewPanel,       // Zooming

            wpViewLeftPanel    // Thumbnails and Bookmarks -

         // also see COMPDF_ShowNavigation

          ];

 

      // assign the requires events

      newTab.wpviewpdf.OnChangeViewPage := WPViewPDF_DoChangeViewPage;

 

      // We need an image for optional background metafiles

      newTab.image := TImage.Create(newTab);

      newTab.image.Visible := false;

      newTab.image.Parent := newTab;

 

      // Add the tab to the page control

      newTab.Caption := ExtractFileName(filename);

      PageControl1.ActivePage := newTab;

    except

      newTab.PageControl := nil;

      // Loading failed, destroy the control!

      newTab.wpviewpdf.Parent := nil;

      newTab.wpviewpdf.Free;

      newTab.Free;

      raise;

    end;

end;

 

 

Consequently we add a function "pdf" which retrieves the WPViewPDF control which is currently active. If no tab has been added, the result will be nil.

 

function TForm2.pdf : TWPViewPDF;

begin

   Result := nil;

  if PageControl1.ActivePage<>nil then

  begin

     Result := TPDFTabSheet( PageControl1.ActivePage ).wpviewpdf;

  end;

end;