Question

我有一个delphi应用程序，最小化运行到托盘图标。双击托盘图标后，应用程序将打开一个非模态用户界面表单。

我已经为应用添加了逻辑，以检测它是否已经在运行。如果它没有运行，它会启动并将自身减少到托盘。

如果它已经在运行，我希望它将控制权传递给它自己的第一个实例并打开非模态表单，然后退出（第二个实例）。最好的方法是什么？

TIA [R

Answer 1

检测给定应用程序的另一个实例的recommended方法是为该应用程序创建一个命名的互斥锁或在一个众所周知的位置锁定一个文件，以便第二个实例在您尝试时会触发错误创建相同的互斥锁或锁定相同的文件。一旦你知道另一个实例正在运行，你就可以找到该实例的进程句柄，并在最小化时向它发送一条消息进行恢复。

Answer 2

微软的方式并不完美，所以我更喜欢老学校：

const WM_KNOCK_KNOCK = WM_USER + 42;
{ or WM_USER + 265 or any number you like, consult PSDK documentation why WM_USER range }
{ or do RegisterWindowMessage }

{...}

procedure TMainForm.FormCreate(Sender: TObject);
var
  Window: HWND;
begin 
  Window := FindWindow(PChar({MainForm.}ClassName), nil);
  { 
  i neither remember how it works exactly nor have time to investigate right now, 
  so quick and dirty validity test follows:
  }
  Assert(not (HandleAllocated and (Window = Handle)), 'failed, use fallback');
  {
  if Window <> 0 then
  begin
    PostMessage(Window, WM_KNOCK_KNOCK, 0, 0);
    Halt;
  end;

  { regular initialization }

end;

现在，第一个实例的WM_KNOCK_KNOCK消息处理程序执行唤醒例程。

我很清楚你在Shell_NotifyIcon包装器中收到WM_LBUTTONUP（或者WM_LBUTTONDBLCLK）时究竟是怎么做的（可能是Application.Restore？）。正如克里斯桑顿所说，没有“最小化到托盘”这样的状态，这是人为的。

回退：如果断言失败，请注意哪些代码仅依赖于类函数ClassName，因此可以轻松地移出FormCreate并在应用程序创建它之前调用。

Answer 3

program Only_One_Mutex;

//undefine this   {.$define useMutex} to make it a multi instance app.
{$define useMutex}

uses
  Forms,
  Windows,
  Messages,
  MainForm in 'MainForm.pas' {frmMain};

{$R *.res}

{$ifdef useMutex}
var
  Mutex : THandle;
{$endif}


function pBuffStr( Var S1: String; S:String ): PChar;
begin
  FillChar(S1,SizeOf(S1),#0); {clear out the destination string}
  S1:= S+#0;                  {set it equal the source}
  Result:= @S1[1];            {result is a PChar pointer }
end;

procedure WindowToTop( WN: String );
  var
    iTitle: integer;
    S1,S  : String;
    Done: Boolean;
begin
  Done:= False;
  While NOT Done do begin
    if Pos(';',WN) > 0 then begin
      S:= Copy(WN,1,Pos(';',WN)-1);
      WN:= Copy(WN,Pos(';',WN)+1,Length(WN));
    end else begin
      S:= WN;
      Done:= True;
    end; {if Pos}
    iTitle:= FindWindow( nil, pBuffStr(S1,S) );
    if iTitle <> 0 then
      if NOT SetForegroundWindow( iTitle ) then
        GetLastError();
    Application.ProcessMessages;
  end; {while NOT Done}
end;

procedure RestoreWindow( WN: String );
  var
    iTitle: integer;
    Dest, S  : String;
    Done: Boolean;
begin
  Done:= False;
  While NOT Done do begin
    if Pos(';',WN) > 0 then begin             {is there more than ONE name}
      S:= Copy(WN,1,Pos(';',WN)-1);           {copy the first name of the original}
      WN:= Copy(WN,Pos(';',WN)+1,Length(WN)); {reduce the original string}
    end else begin
      S:= WN;                                 {only one name, so copy it}
      Done:= True;                            {this loop is done}
    end; {if Pos}
    iTitle:= FindWindow( nil, pBuffStr(Dest,S) ); {search for the window name}
    if iTitle <> 0 then                           {if found, then restore it}
      DefWindowProc(iTitle, WM_SYSCOMMAND, SC_RESTORE, SC_RESTORE);
  end; {while NOT Done}
end;


//=================================================================

procedure AppRun;
begin
  Application.Initialize;
  Application.Title := 'Only One Prog';
  Application.CreateForm(TfrmMain, frmMain);
  Application.Run;
end;

begin

{$ifdef useMutex}
  //global var declarations in the mainform.
  {=====================================================================}
  //ATitle MUST match the assigned Application.Title in AppRun
  //and Application.Title can "NOT" be a constant or var.
  ATitle   := 'Only One Prog';

  { THIS IS HOW IT KEEPS THE SECOND INSTANCE FROM STARTING,
    by using a MUTEX, and a MAINFORM window title  }
  //any text appender will work.
  AMutex   := ATitle + ' Mutex Thu, Jul/12/2012';

  //mainform's caption
  ACaption := ATitle + ', Mainform Caption';

  //a label on the mainform
  ALabel   := ATitle + ', MainForm Label-using mutex';
  {=====================================================================}

  Mutex := CreateMutex(nil, True, PAnsiChar( AMutex ));
  if (GetLastError = ERROR_ALREADY_EXISTS) then begin
    try
      RestoreWindow( ACaption );
      WindowToTop( ACaption );       //main form's name
    finally
      CloseHandle(Mutex);
    end;
  end else
    if  (Mutex <> 0)
    AND (GetLastError <> ERROR_ALREADY_EXISTS)
    then begin
     try
       AppRun;
     finally
       CloseHandle(Mutex);
     end;
    end;
{$else}
  //global var declarations in the mainform.
  {=====================================================================}
  ATitle   := 'More than One';                  //global declaration in the mainform.
  //mainform's caption - THIS IS HOW IT KEEPS THE SECOND INSTANCE FROM STARTING
  ACaption := ATitle + ', Mainform Caption';//global declaration in the mainform.
  //a label on the mainform
  ALabel   := ATitle + ', MainForm Label-multi exe';  //global declaration in the mainform.
  {=====================================================================}
  AppRun;
{$endif}

end.


unit MainForm;

interface

uses
  Windows, Messages, SysUtils,
  Variants, Classes, Graphics,
  Controls, Forms,   Dialogs, StdCtrls, LblEffct;


type
  TfrmMain = class(TForm)
    le1: TLabelEffect;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  frmMain: TfrmMain;

  //these GLOBAL vars, are assigned values in the program source (.dpr) file.
  ATitle,
  ACaption,
  ALabel,
  AMutex  :String;

implementation

{$R *.dfm}

procedure TfrmMain.FormCreate(Sender: TObject);
begin
  Caption     := ACaption;     //used to ID this form...
  le1.Caption := ALabel;
end;

end.

重新激活托盘中运行的应用的最佳方法是什么？

3 个答案: