Delphi MDI appliction 文档最大化显示、去掉最大化最小化等按钮

效果图

第一种方法：

        修改 CHILDWIN 单元,  太简单了, 不废话, 完整代码如下：

unit CHILDWIN;

interface

uses Winapi.Windows, System.Classes, Vcl.Graphics, Vcl.Forms, Vcl.Controls,
  Vcl.StdCtrls, Winapi.Messages, System.SysUtils;

type
  TMDIChild = class(TForm)
    Memo1: TMemo;
    procedure WMShowWindow(var Msg: TWMShowWindow); message WM_SHOWWINDOW;
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    // 重写 CreateParams
    procedure CreateParams(var Params: TCreateParams); override;
  private
    { Private declarations }
  public
    { Public declarations }
  end;

implementation

{$R *.dfm}

procedure TMDIChild.CreateParams(var Params: TCreateParams);
begin
  inherited;
  // 去掉 WS_BORDER WS_OVERLAPPEDWINDOW 等窗体样式
  Params.Style := Params.Style and not WS_OVERLAPPEDWINDOW or WS_BORDER;
end;

procedure TMDIChild.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Action := caFree;
end;

procedure TMDIChild.WMShowWindow(var Msg: TWMShowWindow);
begin
  // 自身最大化显示
  if Msg.Show then Self.Perform(WM_SYSCOMMAND, SC_MAXIMIZE, nil);
end;

end.

第二种方法：

        不动 CHILDWIN 单元, 在主窗口单元中创建 TMDIChild 对象时设置相关属性，相当简单。

        完整代码如下:

unit MAIN;

interface

uses Winapi.Windows, System.SysUtils, System.Classes, Vcl.Graphics, Vcl.Forms,
  Vcl.Controls, Vcl.Menus, Vcl.StdCtrls, Vcl.Dialogs, Vcl.Buttons, Winapi.Messages,
  Vcl.ExtCtrls, Vcl.ComCtrls, Vcl.StdActns, Vcl.ActnList, Vcl.ToolWin,
  Vcl.ImgList, System.ImageList, System.Actions;

type
  TMainForm = class(TForm)
    MainMenu1: TMainMenu;
    File1: TMenuItem;
    FileNewItem: TMenuItem;
    FileOpenItem: TMenuItem;
    FileCloseItem: TMenuItem;
    Window1: TMenuItem;
    Help1: TMenuItem;
    N1: TMenuItem;
    FileExitItem: TMenuItem;
    WindowCascadeItem: TMenuItem;
    WindowTileItem: TMenuItem;
    WindowArrangeItem: TMenuItem;
    HelpAboutItem: TMenuItem;
    OpenDialog: TOpenDialog;
    FileSaveItem: TMenuItem;
    FileSaveAsItem: TMenuItem;
    Edit1: TMenuItem;
    CutItem: TMenuItem;
    CopyItem: TMenuItem;
    PasteItem: TMenuItem;
    WindowMinimizeItem: TMenuItem;
    StatusBar: TStatusBar;
    ActionList1: TActionList;
    EditCut1: TEditCut;
    EditCopy1: TEditCopy;
    EditPaste1: TEditPaste;
    FileNew1: TAction;
    FileSave1: TAction;
    FileExit1: TAction;
    FileOpen1: TAction;
    FileSaveAs1: TAction;
    WindowCascade1: TWindowCascade;
    WindowTileHorizontal1: TWindowTileHorizontal;
    WindowArrangeAll1: TWindowArrange;
    WindowMinimizeAll1: TWindowMinimizeAll;
    HelpAbout1: TAction;
    FileClose1: TWindowClose;
    WindowTileVertical1: TWindowTileVertical;
    WindowTileItem2: TMenuItem;
    ToolBar2: TToolBar;
    ToolButton1: TToolButton;
    ToolButton2: TToolButton;
    ToolButton3: TToolButton;
    ToolButton4: TToolButton;
    ToolButton5: TToolButton;
    ToolButton6: TToolButton;
    ToolButton9: TToolButton;
    ToolButton7: TToolButton;
    ToolButton8: TToolButton;
    ToolButton10: TToolButton;
    ToolButton11: TToolButton;
    ImageList1: TImageList;
    procedure FileNew1Execute(Sender: TObject);
    procedure FileOpen1Execute(Sender: TObject);
    procedure HelpAbout1Execute(Sender: TObject);
    procedure FileExit1Execute(Sender: TObject);
  private
    { Private declarations }
    procedure CreateMDIChild(const Name: string);
  public
    { Public declarations }
  end;

var
  MainForm: TMainForm;

implementation

{$R *.dfm}

uses CHILDWIN, About;

procedure TMainForm.CreateMDIChild(const Name: string);
var
  Child: TMDIChild;
begin
  { create a new MDI child window }
  Child := TMDIChild.Create(Application);
  Child.Caption := Name;
  if FileExists(Name) then Child.Memo1.Lines.LoadFromFile(Name);

  // 去掉 WS_BORDER WS_OVERLAPPEDWINDOW 等窗体样式
  var style:= GetWindowLong(Child.Handle, GWL_STYLE);
  if style >0 then SetWindowLong(Child.Handle, GWL_STYLE, style and not (WS_OVERLAPPEDWINDOW + WS_BORDER));

  // 最大化显示
  SendMessage(Child.Handle, WM_SYSCOMMAND, SC_MAXIMIZE, 0);
  // 最大化显示
  //ShowWindow(Child.Handle, SW_SHOWMAXIMIZED);
  // 最大化显示
  //Child.perform(WM_SYSCOMMAND, SC_MAXIMIZE, nil);

end;

procedure TMainForm.FileNew1Execute(Sender: TObject);
begin
  CreateMDIChild('NONAME' + IntToStr(MDIChildCount + 1));
end;

procedure TMainForm.FileOpen1Execute(Sender: TObject);
begin
  if OpenDialog.Execute then
    CreateMDIChild(OpenDialog.FileName);
end;

procedure TMainForm.HelpAbout1Execute(Sender: TObject);
begin
  AboutBox.ShowModal;
end;

procedure TMainForm.FileExit1Execute(Sender: TObject);
begin
  Close;
end;

end.