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Delphi对话框实现源码分析Delphi对话框实现源码分析

原作者: [db:作者] 来自: [db:来源] 收藏 邀请
 

 

简介

在这篇文章中，我将大概的从Delphi XE2 的Dialogs单元入手，分析ShowMessage，MessageBox等对话框运行原理，希望能帮助你理解Delphi，不求你爱上她，只求让你能快速地解决问题。

跟踪代码

为了了解这些对话框的运行原理，我们需要跟踪进源代码中去，为此，你需要做如下设置

1. 简单创建一个使用了ShowMessage的VCL应用程序

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unit Unit1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;
 
type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowMessage(Edit1.Text);
  MessageBox(Self.Handle,PChar(Edit1.Text),PChar(Application.Title),
    MB_ICONINFORMATION or MB_OK);
  MessageDlg(Edit1.Text,mtInformation,[mbOK,mbCancel],0);
end;
 
end.

 

2. 在29行里设置一个断点, 再在Edit里输入一些内容,按下Message Box按钮, 按F7跟踪到Dialogs单元, 经过一段时间的仔细跟踪, 你会发现程序运行到下面一段代码:

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function MessageDlgPosHelp(const Msg: string; DlgType: TMsgDlgType;
  Buttons: TMsgDlgButtons; HelpCtx: Longint; X, Y: Integer;
  const HelpFileName: string): Integer;
begin
  if (Win32MajorVersion >= 6) and UseLatestCommonDialogs and ThemeServices.ThemesEnabled then
    Result := DoTaskMessageDlgPosHelp('', Msg, DlgType, Buttons,
      HelpCtx, X, Y, HelpFileName)
  else
    Result := DoMessageDlgPosHelp(CreateMessageDialog(Msg, DlgType, Buttons),
      HelpCtx, X, Y, HelpFileName);
end;

函数MessageDlgPosHelp指出, 如果当前系统是Vista,sever2008或以上版本的系统,那就调用DoTaskMessageDlgPosHelp函数进行对话框显示, 否则调用DoMessageDlgPosHelp显示对话框. 继续跟踪DoTaskMessageDlgPosHelp函数, 你会发现如下一段代码:

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function TCustomTaskDialog.DoExecute(ParentWnd: HWND): Boolean;
const
  CTaskDlgFlags: array[TTaskDialogFlag] of Cardinal = (
    TDF_Enable_Hyperlinks, TDF_Use_Hicon_Main,
    tdf_Use_Hicon_Footer, TDF_ALLOW_DIALOG_CANCELLATION,
    TDF_USE_COMMAND_LINKS, TDF_USE_COMMAND_LINKS_NO_ICON,
    TDF_EXPAND_FOOTER_AREA, TDF_EXPANDED_BY_DEFAULT,
    TDF_VERIFICATION_FLAG_CHECKED, TDF_SHOW_PROGRESS_BAR,
    TDF_SHOW_MARQUEE_PROGRESS_BAR, TDF_CALLBACK_TIMER,
    TDF_POSITION_RELATIVE_TO_WINDOW, TDF_RTL_LAYOUT,
    TDF_NO_DEFAULT_RADIO_BUTTON, TDF_CAN_BE_MINIMIZED);
 
  CTaskDlgCommonButtons: array[TTaskDialogCommonButton] of Cardinal = (
    TDCBF_OK_BUTTON, TDCBF_YES_BUTTON, TDCBF_NO_BUTTON,
    TDCBF_CANCEL_BUTTON, TDCBF_RETRY_BUTTON, TDCBF_CLOSE_BUTTON);
 
  CTaskDlgDefaultButtons: array[TTaskDialogCommonButton] of Integer = (
    IDOK, IDYES, IDNO, IDCANCEL, IDRETRY, IDCLOSE);
 
var
  LWindowList: TTaskWindowList;
  LModalResult: Integer;
  LRadioButton: Integer;
  LFlag: TTaskDialogFlag;
  LFocusState: TFocusState;
  LVerificationChecked: LongBool;
  LTaskDialog: TTaskDialogConfig;
  LCommonButton: TTaskDialogCommonButton;
begin
  if Win32MajorVersion < 6 then
    raise EPlatformVersionException.CreateResFmt({$IFNDEF CLR}@{$ENDIF}SWindowsVistaRequired, [ClassName]);
  if not ThemeServices.ThemesEnabled then
    raise Exception.CreateResFmt({$IFNDEF CLR}@{$ENDIF}SXPThemesRequired, [ClassName]);
 
{$IF NOT DEFINED(CLR)}
  FillChar(LTaskDialog, SizeOf(LTaskDialog), 0);
{$IFEND}
  with LTaskDialog do
  begin
    // Set Size, Parent window, Flags
    cbSize := SizeOf(LTaskDialog);
    hwndParent := ParentWnd;
    dwFlags := 0;
    for LFlag := Low(TTaskDialogFlag) to High(TTaskDialogFlag) do
      if LFlag in FFlags then
        dwFlags := dwFlags or CTaskDlgFlags[LFlag];
 
    // Set CommonButtons
    dwCommonButtons := 0;
    for LCommonButton := Low(TTaskDialogCommonButton) to High(TTaskDialogCommonButton) do
      if LCommonButton in FCommonButtons then
        dwCommonButtons := dwCommonButtons or CTaskDlgCommonButtons[LCommonButton];
 
    // Set Content, MainInstruction, Title, MainIcon, DefaultButton
    if FText <> '' then
      pszContent := {$IFNDEF CLR}PWideChar{$ENDIF}(WideString(FText));
    if FTitle <> '' then
      pszMainInstruction := {$IFNDEF CLR}PWideChar{$ENDIF}(WideString(FTitle));
    if FCaption <> '' then
      pszWindowTitle := {$IFNDEF CLR}PWideChar{$ENDIF}(WideString(FCaption));
    if tfUseHiconMain in FFlags then
      hMainIcon := FCustomMainIcon.Handle
    else
    begin
      if FMainIcon in [tdiNone..tdiShield] then
        pszMainIcon := LPCWSTR(CTaskDlgIcons[FMainIcon])
      else
        pszMainIcon := LPCWSTR(MakeIntResourceW(Word(FMainIcon)));
    end;
    nDefaultButton := CTaskDlgDefaultButtons[FDefaultButton];
 
    // Set Footer, FooterIcon
    if FFooterText <> '' then
      pszFooter := {$IFNDEF CLR}PWideChar{$ENDIF}(WideString(FFooterText));
    if tfUseHiconFooter in FFlags then
      hFooterIcon := FCustomFooterIcon.Handle
    else
    begin
      if FFooterIcon in [tdiNone..tdiShield] then
        pszFooterIcon := LPCWSTR(CTaskDlgIcons[FFooterIcon])
      else
        pszFooterIcon := LPCWSTR(MakeIntResourceW(Word(FFooterIcon)));
    end;
 
    // Set VerificationText, ExpandedInformation, CollapsedControlText
    if FVerificationText <> '' then
      pszVerificationText := {$IFNDEF CLR}PWideChar{$ENDIF}(WideString(FVerificationText));
    if FExpandedText <> '' then
      pszExpandedInformation := {$IFNDEF CLR}PWideChar{$ENDIF}(WideString(FExpandedText));
    if FExpandButtonCaption <> '' then
      pszCollapsedControlText := {$IFNDEF CLR}PWideChar{$ENDIF}(WideString(FExpandButtonCaption));
 
    // Set Buttons
    cButtons := FButtons.Count;
    if cButtons > 0 then
      pButtons := FButtons.Buttons;
    if FButtons.DefaultButton <> nil then
      nDefaultButton := FButtons.DefaultButton.ModalResult;
 
    // Set RadioButtons
    cRadioButtons := FRadioButtons.Count;
    if cRadioButtons > 0 then
      pRadioButtons := FRadioButtons.Buttons;
    if not (tfNoDefaultRadioButton in FFlags) and (FRadioButtons.DefaultButton <> nil) then
      nDefaultRadioButton := FRadioButtons.DefaultButton.ModalResult;
 
    // Prepare callback
{$IF DEFINED(CLR)}
    pfCallBack := @CallbackProc;
{$ELSE}
    lpCallbackData := LONG_PTR(Self);
    pfCallback := @TaskDialogCallbackProc;
{$IFEND}
  end;
 
  LWindowList := DisableTaskWindows(ParentWnd);
  LFocusState := SaveFocusState;
  try
    Result := TaskDialogIndirect(LTaskDialog, {$IFNDEF CLR}@{$ENDIF}LModalResult,
      {$IFNDEF CLR}@{$ENDIF}LRadioButton, {$IFNDEF CLR}@{$ENDIF}LVerificationChecked) = S_OK;
    FModalResult := LModalResult;
    if Result then
    begin
      FButton := TTaskDialogButtonItem(FButtons.FindButton(FModalResult));
      FRadioButton := TTaskDialogRadioButtonItem(FRadioButtons.FindButton(LRadioButton));
      if LVerificationChecked then
        Include(FFlags, tfVerificationFlagChecked)
      else
        Exclude(FFlags, tfVerificationFlagChecked);
    end;
  finally
    EnableTaskWindows(LWindowList);
    SetActiveWindow(ParentWnd);
    RestoreFocusState(LFocusState);
  end;
end;

上面这段代码在Dialogs单元的第5407行, 该函数先进行可用性判断, 然后填充 

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LTaskDialog: TTaskDialogConfig;


一个TTaskDialogConfig的结构体, 该结构体定义在CommCtrl单元第9550行, 其定义如下:

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type
  { $EXTERNALSYM TASKDIALOGCONFIG}
  TASKDIALOGCONFIG = packed record
    cbSize: UINT;
    hwndParent: HWND;
    hInstance: HINST;                     // used for MAKEINTRESOURCE() strings
    dwFlags: DWORD;                       // TASKDIALOG_FLAGS (TDF_XXX) flags
    dwCommonButtons: DWORD;               // TASKDIALOG_COMMON_BUTTON (TDCBF_XXX) flags
    pszWindowTitle: LPCWSTR;              // string or MAKEINTRESOURCE()
    case Integer of
      0: (hMainIcon: HICON);
      1: (pszMainIcon: LPCWSTR;
          pszMainInstruction: LPCWSTR;
          pszContent: LPCWSTR;
          cButtons: UINT;
          pButtons: PTaskDialogButton;
          nDefaultButton: Integer;
          cRadioButtons: UINT;
          pRadioButtons: PTaskDialogButton;
          nDefaultRadioButton: Integer;
          pszVerificationText: LPCWSTR;
          pszExpandedInformation: LPCWSTR;
          pszExpandedControlText: LPCWSTR;
          pszCollapsedControlText: LPCWSTR;
          case Integer of
            0: (hFooterIcon: HICON);
            1: (pszFooterIcon: LPCWSTR;
                pszFooter: LPCWSTR;
                pfCallback: TFTaskDialogCallback;
                lpCallbackData: LONG_PTR;
                cxWidth: UINT  // width of the Task Dialog's client area in DLU's.
                               // If 0, Task Dialog will calculate the ideal width.
              );
          );
  end;
  {$EXTERNALSYM _TASKDIALOGCONFIG}
  _TASKDIALOGCONFIG = TASKDIALOGCONFIG;
  PTaskDialogConfig = ^TTaskDialogConfig;
  TTaskDialogConfig = TASKDIALOGCONFIG;

 

该结构体其实是从MSDN里翻译过来的, 定义在CommCtrl.h 头文件里(需要Windows Vista, Windows Server 2008及以上版本, 我是用Windows 7 64位进行的测试), 详细说明可以查看MSDN.

TCustomTaskDialog.DoExecute 填充完LTaskDialog结构体后, 直接调用:

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Result := TaskDialogIndirect(LTaskDialog, {$IFNDEF CLR}@{$ENDIF}LModalResult,
      {$IFNDEF CLR}@{$ENDIF}LRadioButton, {$IFNDEF CLR}@{$ENDIF}LVerificationChecked) = S_OK;

TaskDialogIndirect显示对话框, TaskDialogIndirect定义在CommCtrl单元, 其代码如下:

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{ Task Dialog }
 
var
  _TaskDialogIndirect: function(const pTaskConfig: TTaskDialogConfig;
    pnButton: PInteger; pnRadioButton: PInteger;
    pfVerificationFlagChecked: PBOOL): HRESULT; stdcall;
 
  _TaskDialog: function(hwndParent: HWND; hInstance: HINST;
    pszWindowTitle: LPCWSTR; pszMainInstruction: LPCWSTR; pszContent: LPCWSTR;
    dwCommonButtons: DWORD; pszIcon: LPCWSTR; pnButton: PInteger): HRESULT; stdcall;
 
function TaskDialogIndirect(const pTaskConfig: TTaskDialogConfig;
  pnButton: PInteger; pnRadioButton: PInteger; pfVerificationFlagChecked: PBOOL): HRESULT;
begin
  if Assigned(_TaskDialogIndirect) then
    Result := _TaskDialogIndirect(pTaskConfig, pnButton, pnRadioButton,
      pfVerificationFlagChecked)
  else
  begin
    InitComCtl;
    Result := E_NOTIMPL;
    if ComCtl32DLL <> 0 then
    begin
      @_TaskDialogIndirect := GetProcAddress(ComCtl32DLL, 'TaskDialogIndirect');
      if Assigned(_TaskDialogIndirect) then
        Result := _TaskDialogIndirect(pTaskConfig, pnButton, pnRadioButton,
          pfVerificationFlagChecked)
    end;
  end;
end;

查看代码知道, TaskDialogIndirect 直接调用ComCtrl32.Dll里的函数:TaskDialogIndirect  显示对话框. 通过查询MSDN了解TaskDialogIndirect API的用途与用法:

The TaskDialogIndirect function creates, displays, and operates a task dialog. The task dialog contains application-defined icons, messages, title, verification check box, command links, push buttons, and radio buttons. This function can register a callback function to receive notification messages.

函数TaskDialogIndirect 用于创建, 显示, 运行一个任务对话框, 这个任务对话框可以包括由应用程序定义的图标,消息,标题,复选框,按钮,单选框. 该函数还可以接收一个回调函数用于接收通知信息

看到这里你或许会问:

如果我的系统是xp或其他低于Vista, server2008的系统呢? 由上文中可知, 如果是低版本的系统, 则调用DoMessageDlgPosHelp 函数进行对话框显示, 调用代码如下:

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Result := DoMessageDlgPosHelp(CreateMessageDialog(Msg, DlgType, Buttons),

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