Delphi实现判断网址是否存在及是否可以打开的方法
本例所述Delphi程序用于检测网址是否为404，也就是检测网址是否存在，或是否可以打开，针对不同的检查方法，会返回不同的结果。
程序主要代码如下：
unitaddress;
interface
uses
Windows,Messages,SysUtils,Classes,Graphics,Controls,Forms,Dialogs,
Psock,NMHttp,StdCtrls,ComCtrls;
type
TForm1=class(TForm)
Label1:TLabel;
Edit1:TEdit;
Button1:TButton;
NMHTTP1:TNMHTTP;
StatusBar1:TStatusBar;
procedureButton1Click(Sender:TObject);
procedureNMHTTP1Success(Cmd:CmdType);
procedureNMHTTP1Failure(Cmd:CmdType);
procedureNMHTTP1HostResolved(Sender:TComponent);
procedureNMHTTP1InvalidHost(varHandled:Boolean);
procedureNMHTTP1AuthenticationNeeded(Sender:TObject);
procedureNMHTTP1Connect(Sender:TObject);
procedureNMHTTP1ConnectionFailed(Sender:TObject);
procedureFormActivate(Sender:TObject);
procedureFormClose(Sender:TObject;varAction:TCloseAction);
procedureNMHTTP1Redirect(varHandled:Boolean);
procedureEdit1KeyDown(Sender:TObject;varKey:Word;
Shift:TShiftState);
private
{Privatedeclarations}
public
{Publicdeclarations}
end;
var
Form1:TForm1;
implementation
{$R*.DFM}
procedureTForm1.Button1Click(Sender:TObject);
var
url:string;
begin
url:=Edit1.Text;
StatusBar1.simpletext:='正在检验';
NMHTTP1.Head(url);
end;
procedureTForm1.NMHTTP1Success(Cmd:CmdType);
begin
casecmdof
CmdHEAD:
StatusBar1.SimpleText:='网址正确'
end;
end;
procedureTForm1.NMHTTP1Failure(Cmd:CmdType);
begin
casecmdof
CmdHEAD:
StatusBar1.SimpleText:='网址不正确，没有这个页面'
end;
end;
procedureTForm1.NMHTTP1HostResolved(Sender:TComponent);
begin
StatusBar1.SimpleText:='正确解析主机名';
end;
procedureTForm1.NMHTTP1InvalidHost(varHandled:Boolean);
begin
StatusBar1.SimpleText:='不能解析主机名';
end;
procedureTForm1.NMHTTP1AuthenticationNeeded(Sender:TObject);
begin
StatusBar1.SimpleText:='需要身份验证';
end;
procedureTForm1.NMHTTP1Connect(Sender:TObject);
begin
StatusBar1.SimpleText:='连接到主机';
end;
procedureTForm1.NMHTTP1ConnectionFailed(Sender:TObject);
begin
StatusBar1.SimpleText:='连接主机失败';
end;
procedureTForm1.FormActivate(Sender:TObject);
begin
Edit1.Text:='http://www.';
end;
procedureTForm1.FormClose(Sender:TObject;varAction:TCloseAction);
begin
NMHTTP1.Destroy;
end;
procedureTForm1.NMHTTP1Redirect(varHandled:Boolean);
begin
StatusBar1.SimpleText:='重定向到其它页面';
end;
procedureTForm1.Edit1KeyDown(Sender:TObject;varKey:Word;
Shift:TShiftState);
begin
ifKey=VK_RETURNthen
begin
StatusBar1.simpletext:='正在检验';
NMHTTP1.Head(Edit1.Text);
end;
end;
end.