delphi 关于禁止程序重复启动的另一种需要与实现

 手头的程序需要禁止重复启动, 但需要保留新的、关闭旧的.

我想还是从主窗口的类名下手吧; 写了一个函数, 在 OnCreate 中调用即可:
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{ 函数 }
procedure CloseSameClassNameWindow(ACurrentWindow: HWND; const AClassName: string);
var
h: HWND;
buf: array[0..255] of Char;
begin
h := ACurrentWindow;
while h > 0 do
begin
h := GetWindow(h, GW_HWNDNEXT);
GetClassName(h, buf, Length(buf));
if buf = AClassName then
begin
SendMessage(h, WM_CLOSE, 0, 0);
Break;
end;
end;
end;

{ 调用 }
procedure TForm1.FormCreate(Sender: TObject);
begin
CloseSameClassNameWindow(Handle, ClassName);
end;

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从程序文件中控制更简单, 一句话:
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program Project1;

uses
Forms, Windows, Messages,
Unit1 in 'Unit1.pas' {Form1};

{$R *.res}

begin
Application.Initialize;
SendMessage(FindWindow('TForm1', nil), WM_CLOSE, 0, 0); //假如主窗体的类名是 TForm1
Application.MainFormOnTaskbar := True;
Application.CreateForm(TForm1, Form1);
Application.Run;
end.

来源：http://www.cnblogs.com/del/archive/2011/10/12/2208036.html