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How to use a XML File Viewer Turn on/off line numbers in source code. Switch to Orginial background IDE or DSP color Comment or reply to this aritlce/tip for discussion. Bookmark this article to my favorite article(s). Print this article
XML File Viewer 31-May-03
Category
XML
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Delphi 4.x
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Publisher:
DSP, Administrator
Reference URL:
DKB
			Author: Daniel Wischnewski 

How to create a simple XML File viewer, without worrying about the XML itself. The 
easiest solution is using the Microsoft XML Document Object Model, installed on 
every machine that run MS Internet Explorer 4 or higher.

Answer:

In this article I am showing you a simple XML file viewer, that may be extended to 
an XML editor with some work. You may enhance the editor by importing icons for the 
different node types, etc. That's up to you. 

My main idea is to show you how to import type libraries from readily available 
components installed on nearly every machine in the modern windows world. 

Note: The MS XML DOM is available for free download and redistribution at 
msdn.microsoft.comhttp://msdn.microsoft.com 

IMPORTING THE MS XML TYPE LIBRARY 

Start Delphi and create a new application, I you haven't done so already. In the 
Delphi menu go to Project|Import Type Library... A dialog will appear on your 
screen, with a list of all installed and registered COM libraries available for 
import. Take a moment and scroll through it, you might be surprised. 

Somewhere down the list you find Microsoft XML, version 2.0 (Version 2.0). This is 
the type library we are going to import. Additionally, you may see Microsoft XML, 
v3.0 (Version 3.0). This is a newer and faster version from MS, we are going to use 
the older version however, since it is more common. 

After selecting the MS XML, version 2.0 component object, select a Unit Directory, 
and press the Create Unit button. The Install button will install the component in 
your Component Pallete, additionally. 

PREPARING YOUR APPLICATION FORM 

Drop a MainMenu (Standard) component on your form, and insert a Open Menu item 
(name: Open1). 
Drop a TreeView (Win32) component on your form, set Align=alLeft and ReadOnly=True 
(name: trvStructure). 
Drop an OpenDialog (Dialogs) component on your form (name: OpenDialog1). 
Drop a Panel (Standard) component on your form, set Align=alClient and clear the 
Caption (name: Panel1). 
Drop a StringGrid (Additional) component on the Panel1 set Align=alTop, RowCount=2, 
ColCount=2, FixedCols=0, FixedRows=1 (name: grdAttributes). 
Drop a Memo (Standard) on the Panel1 set Align=alClient, ReadOnly=True (name 
mmoNodeContent). 

Note: The names I have used will appear in the source code again! 

A PSEUDO CLASS FOR THE XML INTERFACES 

Because mapping of interface via pointers introduces some problems I chose to 
create a simple class that contains only on variable holding the reference to the 
XML Node interface. 

1   type
2     TXMLNodeWrapper = class
3     private
4       FNode: IXMLDOMNode;
5     protected
6     public
7       constructor Create(aNode: IXMLDOMNode);
8       property Node: IXMLDOMNode read FNode;
9     end;


The constructor will save the reference in the FNode variable. 

CREATING THE XML DOM OBJECT 

Creating an instance of the object is rather simple. Having a variable FDocument of 
the type IXMLDOMDocument, defined in the imported MSXML_TLB. 
10  
11  FDocument := CoDOMDocument.Create;
12  
13  //Next you need to set up the component to your needs. 
14  
15  FDocument.async := False;
16  FDocument.validateOnParse := True;
17  FDocument.preserveWhiteSpace := True;

The first I want to do is inserting an base element into the document. Every XML 
document needs at least this base element. I have named it xmlstart. 

Note: Be careful, XML is case-sensitive. 
18  
19  FDocument.appendChild(FDocument.createNode(NODE_ELEMENT, 'xmlstart', ''));

PARSING THE XML DOCUMENT 

There are quite many ways of parsing XML. I want to show you two recursive ways, 
that are very similar, but have quite different results. 

(1) NodeList := Node.childNodes; 

Returns all children, inlcude some special node types, such as #text or #comment. 
These node types require special care. 

(2) NodeList := Node.selectNodes('*'); 

Returns all standard node types, that can be accessed via XSL (XML Structured 
Language). These node types are easy in use. 

ACCESSING THE NODE LIST 

Accessing any item in a Node List is very easy. The length returns the count of 
items in the list (equal to Delphis Count property). The Item array gives access to 
every Item of the node list. 

20  for I := 0 to Pred(XMLNodeList.length) do
21    ShowMessage(XMLNodeList.item[I].nodeName);


MORE INFORMATION ABOUT THE MS XML DOM 

The most important web addresses for the MS XML DOM are: 

http://msdn.microsoft.com/xmlhttp://msdn.microsoft.com/xml  (all about XML) 
http://msdn.microsoft.com/downloads/default.asp?URL=/code/topic.asp?URL=/msdn-files/
028/000/072/topic.xml  
http://msdn.microsoft.com/downloads/default.asp?URL=/code/topic.asp?URL=/msdn-files/
028/000/072/topic.xml(Downloads) 

THE SOURCE CODE FOR THE XML VIEWER 

22  unit uMainForm;
23  
24  interface
25  
26  uses
27    Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
28    MSXML_TLB, ComCtrls, Menus, Grids, ExtCtrls, StdCtrls;
29  
30  type
31    TXMLNodeWrapper = class
32    private
33      FNode: IXMLDOMNode;
34    protected
35    public
36      constructor Create(aNode: IXMLDOMNode);
37      property Node: IXMLDOMNode read FNode;
38    end;
39  
40    TfrmMain = class(TForm)
41      MainMenu1: TMainMenu;
42      File1: TMenuItem;
43      Open1: TMenuItem;
44      trvStructure: TTreeView;
45      OpenDialog1: TOpenDialog;
46      Panel1: TPanel;
47      grdAttributes: TStringGrid;
48      mmoNodeContent: TMemo;
49      procedure FormCreate(Sender: TObject);
50      procedure Open1Click(Sender: TObject);
51      procedure trvStructureChange(Sender: TObject; Node: TTreeNode);
52    private
53      FDocument: IXMLDOMDocument;
54      FFileName: string;
55      procedure LoadXML;
56    public
57    end;
58  
59  var
60    frmMain: TfrmMain;
61  
62  implementation
63  
64  {$R *.DFM}
65  
66  { TXMLNodeWrapper }
67  
68  constructor TXMLNodeWrapper.Create(aNode: IXMLDOMNode);
69  begin
70    inherited Create;
71    FNode := aNode;
72  end;
73  
74  { TFrmMain }
75  
76  procedure TfrmMain.FormCreate(Sender: TObject);
77  begin
78    FDocument := CoDOMDocument.Create;
79    FDocument.async := False;
80    FDocument.validateOnParse := True;
81    FDocument.preserveWhiteSpace := True;
82    FDocument.appendChild(FDocument.createNode(NODE_ELEMENT, 'xmlstart', ''));
83  
84    grdAttributes.Cells[0, 0] := 'Attribute name';
85    grdAttributes.Cells[1, 0] := 'Attribute value';
86  end;
87  
88  procedure TfrmMain.LoadXML;
89    procedure EnterNode(const XMLNode: IXMLDOMNode; TreeNode: TTreeNode);
90    var
91      I: Integer;
92      XMLNodeList: IXMLDOMNodeList;
93      NewTreeNode: TTreeNode;
94    begin
95      NewTreeNode := trvStructure.Items.AddChild(TreeNode, XMLNode.nodeName);
96      NewTreeNode.Data := TXMLNodeWrapper.Create(XMLNode);
97      // use XMLNode.childNodes to get all nodes (incl. special types)
98      XMLNodeList := XMLNode.selectNodes('*');
99      for I := 0 to Pred(XMLNodeList.length) do
100       EnterNode(XMLNodeList.item[I], NewTreeNode);
101   end;
102 begin
103   for I := 0 to trvStructure.Items.Count - 1 do
104     TXMLNodeWrapper(trvStructure.Items.Item[I].Data).Destroy;
105   trvStructure.Items.BeginUpdate;
106   try
107     trvStructure.Items.Clear;
108     EnterNode(FDocument.documentElement, nil);
109   finally
110     trvStructure.Items.EndUpdate;
111   end;
112 end;
113 
114 procedure TfrmMain.Open1Click(Sender: TObject);
115 begin
116   if OpenDialog1.Execute then
117   begin
118     FDocument.load(OpenDialog1.FileName);
119     FFileName := OpenDialog1.FileName;
120     LoadXML;
121   end;
122 end;
123 
124 procedure TfrmMain.trvStructureChange(Sender: TObject; Node: TTreeNode);
125 var
126   I: Integer;
127   CurrentNode: IXMLDOMNode;
128 begin
129   CurrentNode := TXMLNodeWrapper(Node.Data).Node;
130   Caption := CurrentNode.nodeName;
131   if CurrentNode.selectNodes('*').length = 0 then
132     mmoNodeContent.Text := CurrentNode.text
133   else
134     mmoNodeContent.Text := '';
135   if CurrentNode.attributes.length > 0 then
136   begin
137     grdAttributes.RowCount := Succ(CurrentNode.attributes.length);
138     grdAttributes.FixedRows := 1;
139     for I := 0 to Pred(CurrentNode.attributes.length) do
140     begin
141       grdAttributes.Cells[0, Succ(I)] := CurrentNode.attributes.item[I].nodeName;
142       grdAttributes.Cells[1, Succ(I)] := CurrentNode.attributes.item[I].text;
143     end;
144   end
145   else
146   begin
147     grdAttributes.RowCount := 2;
148     grdAttributes.Cells[0, 1] := '';
149     grdAttributes.Cells[1, 1] := '';
150   end;
151 end;
152 
153 end.


			
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