delphi处理消息的几种方式

第一种：自定义处理单条消息

unit Unit2;

interface

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

type
  TForm2 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
  private
    { Private declarations }
    //直接用 TWMQueryEndSession
    procedure EndMsg(var nMsg: TWMQueryEndSession); Message WM_QUERYENDSESSION;
    //也可以用这种
    //procedure EndMsg(var nMsg: TMessage); Message WM_QUERYENDSESSION;
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

//收到WM_QUERYENDSESSION消息后就会触发这个过程
procedure TForm2.EndMsg(var nMsg: TWMQueryEndSession);
begin
  //0 可以取消关机操作
  nMsg.Result := 1;
  ShowMessage('注销、重启、关机');
end;

end.

第二种：利用Application.OnMessage处理消息

unit Unit2;

interface

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

type
  TForm2 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }

  public
    { Public declarations }
    procedure OnMsg(var nMsg: tagMSG; var nHandled: Boolean);
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

//消息处理过程
procedure TForm2.OnMsg(var nMsg: tagMSG; var nHandled: Boolean);
begin
  //处理……
  //这里会收到各种消息……经测试无法收到WM_QUERYENDSESSION消息
end;

procedure TForm2.FormCreate(Sender: TObject);
begin
  Application.OnMessage := OnMsg;
end;

end.

第三种：自己处理窗口函数，个人感觉这是最强大的，可以拦截一切发往窗口的消息！

unit Unit2;

interface

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

type
  TForm2 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }

  public
    { Public declarations }
    procedure WndProc(var nMsg: TMessage); override;
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

procedure TForm2.WndProc(var nMsg: TMessage);
begin

  //这里能收到发往窗口的所有消息

  inherited; // 注意这句不能少

  if nMsg.Msg = WM_QUERYENDSESSION then
  begin
    if nMsg.LParam = 0 then
      ShowMessage('关机或重启')
    else
      ShowMessage('注销');
  end;

end;

end.