防止程序运行多个例程 (2000年8月4日).txt

delphi 编程技巧

防止程序运行多个例程? (2000年8月4日) 

本站更新  分类:   作者:srw  推荐:   阅读次数:568  
(http://www.codesky.net)  

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More than one instance of program?
回答
This is copied direct from my *.dpr file. You can work it for your own
use.
var
hMutex : Thandle;
WaitResult : word;
BroadcastList : DWORD;
begin
MessageID := RegisterWindowMessage('Check For Choice Previous Inst');
// register a message to use later on
hMutex := createMutex(nil,false,pchar('App_Choice')); // grab a mutex
handle
WaitResult := WaitForSingleObject(hMutex,10); // wait to see
if we can have exclusive use of the mutex
if ( waitResult = WAIT_TIMEOUT ) then // if we can't then broadcast
the message to make the owner of the mutex respond
{ request that the running application takes focus }
begin
BroadcastList := BSM_APPLICATIONS;
BroadcastSystemMessage(
BSF_POSTMESSAGE,@BroadcastList,MessageID,0,0); //32 bit - broadcast the
message to all apps - only a prev inst will hear it.
end
else
begin
{ do the normal stuff}
Application.Title := 'Choice Organics Purchase & Sales System';
Application.CreateForm(TMainForm, MainForm);
Application.Run;
ReleaseMutex(hMutex); // release the mutex as a politeness
end;
CloseHandle(hMutex); // close the mutex handle
end.
This goes in the MainForm
procedure Tmainform.OnAppMessage(var Msg : TMsg ; Var Handled : Boolean);
begin
{ If it's the special message then focus on this window}
if Msg.Message = MessageID then // if we get the broadcast message from an
another instance of this app that is trying to start up
begin
show;
WindowState := wsMaximized;
BringToFront;
SetFocus;
Handled := true;
end;
end;
//And this goes in the TMainForm.FormCreate ;-
Application.OnMessage:= OnAppMessage;