Delphi – 在运行时创建的TXMLDocument生成AV,表单上的组件正在

unit Unit1;

interface

uses
  Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,Dialogs,xmldom,XMLIntf,msxmldom,XMLDoc,StdCtrls;

type
  Txml = class(TForm)
//    XMLDocument1: TXMLDocument;
    Memo1: TMemo;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  xml: Txml;

implementation

{$R *.dfm}

procedure Txml.FormCreate(Sender: TObject);
var    i,j:integer;
       aNode:IXMLNode;
       ws:String;
       XMLDocument1:TXMLDocument;
begin
 Memo1.Lines.Clear;
 XMLDocument1 := TXMLDocument.Create(nil);
 try
  XMLDocument1.LoadFromFile('C:a.xml');
  XMLDocument1.Active := true;
  aNode := XMLDocument1.ChildNodes.First;
  while aNode<>nil do
  begin
   for i := 0 to aNode.ChildNodes.Count-1 do
    begin
     if aNode.ChildNodes[i].NodeName = 'Role' then
      begin
       Memo1.Lines.Add('Tag - '+aNode.ChildNodes[i].ChildNodes['Tag'].Text);
       for j := 0 to aNode.ChildNodes[i].ChildNodes.Count-1 do
        if aNode.ChildNodes[i].ChildNodes[j].HasChildNodes then
         begin
          ws :=  VarToStr(aNode.ChildNodes[i].ChildNodes[j].ChildValues['Tag']);
          if trim(ws)<>'' then
           Memo1.Lines.Add(ws);
          ws :=  VarToStr(aNode.ChildNodes[i].ChildNodes[j].ChildValues['Value']);
          if trim(ws)<>'' then
           Memo1.Lines.Add(ws);
         end;
      end;
    end;
   aNode := aNode.NextSibling;
  end;
  XMLDocument1.Active := false;
 finally
   FreeAndNil(XMLDocument1);
 end;
end;

end.

问题是这会产生AV.正如您可能已经看到的那样,组件在表单之前(// XMLDocument1：TXMLDocument;).

为什么当组件在代码工作的表单上时,但是当我在运行时创建它时它会生成AV？

LE：
解决方案：基于答案/评论和Delphi帮助：

XMLDocument1 : IXMLDocument;  //not TXMLDocument

XMLDocument1 := LoadXMLDocument(...);

FreeAndNil;// must be deleted