防止多个实例-还能处理命令行参数？ [英] Preventing multiple instances - but also handle the command line parameters?

问题描述

我正在从Windows处理与我的应用程序相关的扩展文件。因此，当您双击Windows中的文件时，它将执行我的程序，然后我从那里处理该文件，例如：

I am handling from my Application associated extension files from Windows. So when you double click a file from Windows it will execute my program, and I handle the file from there, something like:

procedure TMainForm.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  for i := 0 to ParamCount -1 do
  begin
    if SameText(ExtractFileExt(ParamStr(i)), '.ext1') then
    begin
      // handle my file..

      // break if needed
    end else
    if SameText(ExtractFileExt(ParamStr(i)), '.ext2') then
    begin
      // handle my file..

      // break if needed
    end else
  end;
end;

这对我来说很有效，但是当我进行测试时，我意识到它并没有考虑

That works pretty much how I want it to, but when I was testing I realised it does not consider using only one instance of my program.

因此，例如，如果我从Windows中选择了多个文件并同时将其全部打开，则将创建相同数量的文件。

So for example, if I selected several Files from Windows and opened them all at the same time, this will create the same number of instances of my program with the number of Files being opened.

什么是解决此问题的好方法，因此除了打开程序的多个实例外，从Windows打开的其他文件将仅集中到一个实例，而我可以正常处理这些文件？

What would be a good way to approach this, so that instead of several instances of my program being opened, any additional Files from Windows being opened will simply focus back to the one and only instance, and I handle the Files as normal?

谢谢

更新

我在这里找到了一篇不错的文章： http://www.delphidabbler.com/articles?article=13&part=2 我认为这是我需要的，并且显示如rhool所述如何使用Windows API伊根我现在将通读它。.

I found a good article here: http://www.delphidabbler.com/articles?article=13&part=2 which I think is what I need, and shows how to work with the Windows API as mentioned by rhooligan. I am going to read through it now..

推荐答案

下面是一些简单的示例代码，可以完成工作。我希望它是不言自明的。

Here is some simple example code that gets the job done. I hope it is self-explanatory.

program StartupProject;

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

{$R *.res}

procedure Main;
var
  i: Integer;
  Arg: string;
  Window: HWND;
  CopyDataStruct: TCopyDataStruct;
begin
  Window := FindWindow(SWindowClassName, nil);
  if Window=0 then begin
    Application.Initialize;
    Application.MainFormOnTaskbar := True;
    Application.CreateForm(TMainForm, MainForm);
    Application.Run;
  end else begin
    FillChar(CopyDataStruct, Sizeof(CopyDataStruct), 0);
    for i := 1 to ParamCount do begin
      Arg := ParamStr(i);
      CopyDataStruct.cbData := (Length(Arg)+1)*SizeOf(Char);
      CopyDataStruct.lpData := PChar(Arg);
      SendMessage(Window, WM_COPYDATA, 0, NativeInt(@CopyDataStruct));
    end;
    SetForegroundWindow(Window);
  end;
end;

begin
  Main;
end.

 

unit uMainForm;

interface

uses
  Windows, Messages, SysUtils, Classes, Controls, Forms, StdCtrls;

type
  TMainForm = class(TForm)
    ListBox1: TListBox;
    procedure FormCreate(Sender: TObject);
  protected
    procedure CreateParams(var Params: TCreateParams); override;
    procedure WMCopyData(var Message: TWMCopyData); message WM_COPYDATA;
  public
    procedure ProcessArgument(const Arg: string);
  end;

var
  MainForm: TMainForm;

const
  SWindowClassName = 'VeryUniqueNameToAvoidUnexpectedCollisions';

implementation

{$R *.dfm}

{ TMainForm }

procedure TMainForm.CreateParams(var Params: TCreateParams);
begin
  inherited;
  Params.WinClassName := SWindowClassName;
end;

procedure TMainForm.FormCreate(Sender: TObject);
var
  i: Integer;
begin
  for i := 1 to ParamCount do begin
    ProcessArgument(ParamStr(i));
  end;
end;

procedure TMainForm.ProcessArgument(const Arg: string);
begin
  ListBox1.Items.Add(Arg);
end;

procedure TMainForm.WMCopyData(var Message: TWMCopyData);
var
  Arg: string;
begin
  SetString(Arg, PChar(Message.CopyDataStruct.lpData), (Message.CopyDataStruct.cbData div SizeOf(Char))-1);
  ProcessArgument(Arg);
  Application.Restore;
  Application.BringToFront;
end;

end.

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