Delphi拖动可以"升级"到对接吗？

Question

我有一个TPageControl页面都是使用附加的各种形式ManualDock().用户应该能够通过拖动来重新排列选项卡,这已经有效.然而,也应该可以移除停靠的表格.

现在我有以下代码:

procedure TMainForm.PageControlMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  if (Button = mbLeft) and (Shift * [ssShift, ssCtrl] = [])
    and PageControl.DockSite
  then begin
    PageControl.BeginDrag(False, 32);
  end;
end;

如果按住键Shift或Ctrl键,则将启动对接操作,否则可以通过拖动来重新排列选项卡.

使用键作为修饰符是很尴尬的.当鼠标光标位于页面控件的选项卡区域之外时,有没有办法取消活动拖动操作,并开始对接子窗体？这是Delphi 2009.

Answer 1

我现在有一个适合我的解决方案,所以我会自己回答 - 也许有人也可以使用它.

让我们从一个小样本应用程序开始,该应用程序创建一个TPageControl带有8个停靠窗体的代码,其代码允许运行时重新排序选项卡.选项卡将被实时移动,当拖动被取消时,活动选项卡索引将恢复为其原始值:

unit uDragDockTest;

interface

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

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    fPageControl: TPageControl;
    fPageControlOriginalPageIndex: integer;
    function GetPageControlTabIndex(APosition: TPoint): integer;
  public
    procedure PageControlDragDrop(Sender, Source: TObject; X, Y: Integer);
    procedure PageControlDragOver(Sender, Source: TObject; X, Y: Integer;
      AState: TDragState; var AAccept: Boolean);
    procedure PageControlEndDrag(Sender, Target: TObject; X, Y: Integer);
    procedure PageControlMouseDown(Sender: TObject; AButton: TMouseButton;
      AShift: TShiftState; X, Y: Integer);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
const
  FormColors: array[1..8] of TColor = (
    clRed, clGreen, clBlue, clYellow, clLime, clMaroon, clTeal, clAqua);
var
  i: integer;
  F: TForm;
begin
  fPageControlOriginalPageIndex := -1;

  fPageControl := TPageControl.Create(Self);
  fPageControl.Align := alClient;
  // set to False to enable tab reordering but disable form docking
  fPageControl.DockSite := True;
  fPageControl.Parent := Self;

  fPageControl.OnDragDrop := PageControlDragDrop;
  fPageControl.OnDragOver := PageControlDragOver;
  fPageControl.OnEndDrag := PageControlEndDrag;
  fPageControl.OnMouseDown := PageControlMouseDown;

  for i := Low(FormColors) to High(FormColors) do begin
    F := TForm.Create(Self);
    F.Caption := Format('Form %d', [i]);
    F.Color := FormColors[i];
    F.DragKind := dkDock;
    F.BorderStyle := bsSizeToolWin;
    F.FormStyle := fsStayOnTop;
    F.ManualDock(fPageControl);
    F.Show;
  end;
end;

const
  TCM_GETITEMRECT = $130A;

function TForm1.GetPageControlTabIndex(APosition: TPoint): integer;
var
  i: Integer;
  TabRect: TRect;
begin
  for i := 0 to fPageControl.PageCount - 1 do begin
    fPageControl.Perform(TCM_GETITEMRECT, i, LPARAM(@TabRect));
    if PtInRect(TabRect, APosition) then
      Exit(i);
  end;
  Result := -1;
end;

procedure TForm1.PageControlDragDrop(Sender, Source: TObject; X, Y: Integer);
var
  Index: integer;
begin
  if Sender = fPageControl then begin
    Index := GetPageControlTabIndex(Point(X, Y));
    if (Index <> -1) and (Index <> fPageControl.ActivePage.PageIndex) then
      fPageControl.ActivePage.PageIndex := Index;
  end;
end;

procedure TForm1.PageControlDragOver(Sender, Source: TObject; X, Y: Integer;
  AState: TDragState; var AAccept: Boolean);
var
  Index: integer;
begin
  AAccept := Sender = fPageControl;
  if AAccept then begin
    Index := GetPageControlTabIndex(Point(X, Y));
    if (Index <> -1) and (Index <> fPageControl.ActivePage.PageIndex) then
      fPageControl.ActivePage.PageIndex := Index;
  end;
end;

procedure TForm1.PageControlEndDrag(Sender, Target: TObject; X, Y: Integer);
begin
  // restore original index of active page if dragging was canceled
  if (Target <> fPageControl) and (fPageControlOriginalPageIndex > -1)
    and (fPageControlOriginalPageIndex < fPageControl.PageCount)
  then
    fPageControl.ActivePage.PageIndex := fPageControlOriginalPageIndex;
  fPageControlOriginalPageIndex := -1;
end;

procedure TForm1.PageControlMouseDown(Sender: TObject; AButton: TMouseButton;
  AShift: TShiftState; X, Y: Integer);
begin
  if (AButton = mbLeft)
    // undock single docked form or reorder multiple tabs
    and (fPageControl.DockSite or (fPageControl.PageCount > 1))
  then begin
    // save current active page index for restoring when dragging is canceled
    fPageControlOriginalPageIndex := fPageControl.ActivePageIndex;
    fPageControl.BeginDrag(False);
  end;
end;

end.

将其粘贴到编辑器中并运行它,将在运行时创建和设置所有必需的组件及其属性.

请注意,只有双击选项卡才能取消停靠表单.无论与标签的距离如何,只有在释放鼠标左键时才会显示拖动光标,这也有点难看.当鼠标位于具有几个像素边距的页面控制选项卡区域之外时,如果拖动被自动取消并且表格被取消停靠将会好得多.

这可以通过在页面控件DragObject的OnStartDrag处理程序中创建自定义来实现.在此对象中捕获鼠标,因此可以在其中处理拖动时的所有鼠标消息.当鼠标光标位于选项卡影响矩形之外时,将取消拖动,并启动活动页面控制表中表单的停靠操作:

type
  TConvertDragToDockHelper = class(TDragControlObjectEx)
  strict private
    fPageControl: TPageControl;
    fPageControlTabArea: TRect;
  protected
    procedure WndProc(var AMsg: TMessage); override;
  public
    constructor Create(AControl: TControl); override;
  end;

constructor TConvertDragToDockHelper.Create(AControl: TControl);
const
  MarginX = 32;
  MarginY = 12;
var
  Item0Rect, ItemLastRect: TRect;
begin
  inherited;
  fPageControl := AControl as TPageControl;
  if fPageControl.PageCount > 0 then begin
    // get rects of first and last tab
    fPageControl.Perform(TCM_GETITEMRECT, 0, LPARAM(@Item0Rect));
    fPageControl.Perform(TCM_GETITEMRECT, fPageControl.PageCount - 1,
      LPARAM(@ItemLastRect));
    // calculate rect valid for dragging (includes some margin around tabs)
    // when this area is left dragging will be canceled and docking will start
    fPageControlTabArea := Rect(
      Min(Item0Rect.Left, ItemLastRect.Left) - MarginX,
      Min(Item0Rect.Top, ItemLastRect.Top) - MarginY,
      Max(Item0Rect.Right, ItemLastRect.Right) + MarginX,
      Max(Item0Rect.Bottom, ItemLastRect.Bottom) + MarginY);
  end;
end;

procedure TConvertDragToDockHelper.WndProc(var AMsg: TMessage);
var
  MousePos: TPoint;
  CanUndock: boolean;
begin
  inherited;
  if AMsg.Msg = WM_MOUSEMOVE then begin
    MousePos := fPageControl.ScreenToClient(Mouse.CursorPos);
    // cancel dragging if outside of tab area with margins
    // optionally start undocking the docked form (can be canceled with [ESC])
    if not PtInRect(fPageControlTabArea, MousePos) then begin
      fPageControl.EndDrag(False);
      CanUndock := fPageControl.DockSite and (fPageControl.ActivePage <> nil)
        and (fPageControl.ActivePage.ControlCount > 0)
        and (fPageControl.ActivePage.Controls[0] is TForm)
        and (TForm(fPageControl.ActivePage.Controls[0]).DragKind = dkDock);
      if CanUndock then
        fPageControl.ActivePage.Controls[0].BeginDrag(False);
    end;
  end;
end;

该类从而TDragControlObjectEx不是TDragControlObject从而下降,以便自动释放.现在,如果TPageControl创建了示例应用程序中的处理程序(并为页面控件对象设置):

procedure TForm1.PageControlStartDrag(Sender: TObject;
  var ADragObject: TDragObject);
begin
  // do not cancel dragging unless page control has docking enabled
  if (ADragObject = nil) and fPageControl.DockSite then
    ADragObject := TConvertDragToDockHelper.Create(fPageControl);
end;

然后当鼠标移动远离选项卡时,将取消选项卡拖动,如果活动页面是可停靠的表单,则将启动它的停靠操作,仍然可以使用该ESC键取消.