delphi - 如何制作一个透明背景的TScrollBox？

Question

我有一个带有 TImage 作为背景的 TFrame。

此框架是我在主 TForm 中放置在有限空间上的其他框架的祖先。所以它只是其他框架的用户界面基础。

我需要在这些框架内放置许多控件，因为它们将处理大型数据库表单。

由于主窗体空间有限，我需要在除标题栏之外的所有TFrame空间中放置一个TScrollBox。但这覆盖了背景图像。

如何使这个 ScrollBar 背景透明？

或者制作一个具有该功能的新组件是否更好，以及如何做到这一点？

我在其他网站上看到了一些示例，但它们在运行时有错误

谢谢!

编辑2:

我从 LMD Inovative 的 ElPack 中找到了 TElScrollBox。这是背景透明的，允许我们将图像作为背景。但同样的问题发生了:当我们在运行时滚动它时，它会移动其影响区域中祖先的背景。

编辑1:

我尝试制作一个后代，但滚动条仅在我们将鼠标悬停在应有的位置时显示，并且当我们滚动表单时，表单的背景在滚动框中移动。而且，它内部的控件出现了一些绘制错误......

interface

uses
  Windows, SysUtils, Messages, Classes, Graphics, Controls, Forms,
  Dialogs, Menus, StdCtrls, ExtCtrls;

type
  TTransScrollBox = class(TScrollBox)
  private
    { Private declarations }
  protected
    procedure CreateParams(var params: TCreateParams); override;
    procedure WMEraseBkGnd(var msg: TWMEraseBkGnd); message WM_ERASEBKGND;
  public
    { Public declarations }
  published
    { Published declarations }
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Eduardo', [TTransScrollBox]);
end;

procedure TTransScrollBox.CreateParams(var params: TCreateParams);
begin
  inherited CreateParams(params);
  params.ExStyle := params.ExStyle or WS_EX_TRANSPARENT;
end;

procedure TTransScrollBox.WMEraseBkGnd(var Msg: TWMEraseBkGnd); 
begin
  SetBkMode (Msg.DC, TRANSPARENT);
  Msg.Result := 1;
end;

Answer 1

如果你不想让图像滚动，你就必须滚动你自己的滚动条，这并不是太困难(英国这里还在下雨，所以我很无聊!)

为了测试，创建框架，将图像放在上面并与客户端对齐。将滚动条放在设置为垂直的框架上并右对齐。在设计时放大框架。将控件放在任意位置，然后将其缩小，以便某些控件不可见(底部下方)。在主窗体上的 form show 中(用于测试)，或者当您创建新框架时调用 Frame.BeforeShow 进行设置。

[稍后]编辑下雨了，但仍然很无聊，所以我为你完成了它!

unit ScrollingBaseFrameU;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, 
  Dialogs, jpeg, ExtCtrls, StdCtrls, contnrs, Generics.Collections, Grids,
  DBGrids;

const
  MaxLargeSteps = 5; // maximum large scroll clicks to scroll to max
  IgnoreTag = 99;   // Controls with this tag value are igored for scrolling
  TitleHeight = 23; // Height of title bar as we are dealing with the image mouse co-ordinates
  RightMargin = 25; // space after right-most control
  BottomMargin = 25; // space after bottom-most control
  StrControl = 'ControlName';  // prefix for controls with no name

type
  TControlPos = class(Tobject) // Little object to save initial control positions
  public
    Name: string;
    X,
    Y: Integer;
  end;

  TScrollingBaseFrame = class(TFrame)
    BackGroundImage: TImage;
    HorzScrollBar: TScrollBar;
    VertScrollBar: TScrollBar;
    pnlTitle: TPanel;
    procedure VertScrollBarChange(Sender: TObject);
    procedure BackGroundImageMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure FrameResize(Sender: TObject);
    procedure HorzScrollBarChange(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    ShowHScroller,
    ShowVScroller : Boolean;       // scroller needed at all?
    PosList: TList<TControlPos>;   // list of initial positions
    procedure BeforeShow; virtual; // override in descendants for specific behaviour
    procedure BeforeClose; virtual; // override in descendants for specific behaviour
    function IndexOfPos(AName:string): Integer;
  end;

implementation

{$R *.dfm}

procedure TScrollingBaseFrame.BeforeClose;
// Clean up
var
  p: TControlPos;
begin
  for p in PosList do
    p.free;
  PosList.Free;
end;

procedure TScrollingBaseFrame.BeforeShow;
//Setup scroller and save initial control positions
var
  i,XMax,YMax,Idx: Integer;
  AControl: TControl;
begin
  pnlTitle.Height := TitleHeight;
  PosList := TList<TControlpos>.Create;
  XMax := 0;
  YMax := 0;
  for i := 0 to ComponentCount - 1 do
  begin
    if Components[i] is TControl then
    begin
      AControl := TControl(Components[i]);
      if Acontrol.Tag <> IgnoreTag then
      begin
        Idx := PosList.Add(TcontrolPos.Create);
        if AControl.Name = '' then  // deal with empty names
          AControl.Name :=  StrControl + IntToStr(i);
        PosList[Idx].Name := AControl.Name;
        PosList[Idx].X := AControl.Left;
        PosList[Idx].Y := AControl.Top;
        if YMax < AControl.Top + AControl.Height then
         YMax := AControl.Top + AControl.Height;
        if XMax < AControl.Left + AControl.Width then
         XMax := AControl.Left + AControl.Width;
      end; // Ignored
    end; // is control
  end; // count
   VertScrollBar.Max := (YMax + BottomMargin) - Height; // bit of a bottom margin :)
   VertScrollBar.LargeChange := VertScrollBar.Max div MaxLargeSteps;
   ShowVScroller := VertScrollBar.Max > BottomMargin;
   VertScrollBar.Visible := ShowVScroller;
   HorzScrollBar.Max := (XMax + RightMargin) - Width; // bit of a Right margin :)
   HorzScrollBar.LargeChange := HorzScrollBar.Max div MaxLargeSteps;
   ShowHScroller := HorzScrollBar.Max > RightMargin;
   HorzScrollBar.Visible := ShowHScroller;
end;

procedure TScrollingBaseFrame.FrameResize(Sender: TObject);
begin
  BackGroundImage.Width := Width;
  BackGroundImage.Height := Height;
end;

procedure TScrollingBaseFrame.HorzScrollBarChange(Sender: TObject);
// Move the controls left and right relative to thier initail positions
var
  i,j: Integer;
  AControl: TControl;
begin
  for i := 0 to ComponentCount - 1 do
   begin
     if Components[i] is TControl then
     begin
       AControl :=  TControl(Components[i]);
       j := IndexOfPos(AControl.Name);
       if j >= 0 then  // could be ignored or the background image
         Acontrol.Left := PosList[j].X  - HorzScrollBar.Position;
     end;
   end;
end;

procedure TScrollingBaseFrame.BackGroundImageMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
// Show/Hide the scrollbars using mouse position
var
  ScrollBarWidth: Integer;
begin
  ScrollBarWidth := GetSystemmetrics(SM_CXVSCROLL);  // assume the same for horizontal
  VertScrollBar.Visible := (X > Width - ScrollBarWidth) and ShowVScroller;
  HorzScrollBar.Visible := (Y > (Height - TitleHeight) - ScrollBarWidth) and ShowHScroller;
end;

function TScrollingBaseFrame.IndexOfPos(AName:string): Integer;
// Find a control position in the list by name
var
  Idx: Integer;
begin
  Result := -1;
  Idx := 0;
  while (Result < 0) and (Idx < PosList.Count) do
  begin
    if PosList[idx].Name = AName then
      Result := idx;
    inc(idx);
  end;
end;

procedure TScrollingBaseFrame.VertScrollBarChange(Sender: TObject);
// Move the controls Up and down relative to thier initail positions
var
  i,j: Integer;
  AControl: TControl;
begin
  for i := 0 to ComponentCount - 1 do
   begin
     if Components[i] is TControl then
     begin
       AControl :=  TControl(Components[i]);
       j := IndexOfPos(AControl.Name);
       if j >= 0 then  // could be ignored
         Acontrol.Top := PosList[j].Y  - VertScrollBar.Position;
     end;
   end;
end;

end.

以及 DFM 的完整性:

object ScrollingBaseFrame: TScrollingBaseFrame
  Left = 0
  Top = 0
  Width = 830
  Height = 634
  DoubleBuffered = True
  ParentDoubleBuffered = False
  TabOrder = 0
  OnResize = FrameResize
  object BackGroundImage: TImage
    Tag = 99
    Left = 0
    Top = 23
    Width = 813
    Height = 594
    Align = alClient
    Picture.Data = { **Removed as it was so big!**}
    Transparent = True
    OnMouseMove = BackGroundImageMouseMove
    ExplicitTop = 0
    ExplicitWidth = 1600
    ExplicitHeight = 1200
  end
  object HorzScrollBar: TScrollBar
    Tag = 99
    Left = 0
    Top = 617
    Width = 830
    Height = 17
    Align = alBottom
    PageSize = 0
    TabOrder = 0
    OnChange = HorzScrollBarChange
    ExplicitLeft = 231
    ExplicitTop = 293
    ExplicitWidth = 121
  end
  object VertScrollBar: TScrollBar
    Tag = 99
    Left = 813
    Top = 23
    Width = 17
    Height = 594
    Align = alRight
    Kind = sbVertical
    PageSize = 0
    TabOrder = 1
    OnChange = VertScrollBarChange
    ExplicitTop = 29
  end
  object pnlTitle: TPanel
    Tag = 99
    Left = 0
    Top = 0
    Width = 830
    Height = 23
    Align = alTop
    Caption = 'pnlTitle'
    TabOrder = 2
    ExplicitLeft = 184
    ExplicitTop = 3
    ExplicitWidth = 185
  end
end

[第二次编辑] 好吧，不想浪费我的业余时间，下面的内容应该适用于 Delphi 6 及以上版本。

unit ScrollingBaseFrameU;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, 
  Dialogs, jpeg, ExtCtrls, StdCtrls, contnrs, Grids,
  DBGrids;

const
  MaxLargeSteps = 5; // maximum large scroll clicks to scroll to max
  IgnoreTag = 99;   // Controls with this tag value are igored for scrolling
  TitleHeight = 23; // Height of title bar as we are dealing with the image mouse co-ordinates
  RightMargin = 25; // space after right-most control
  BottomMargin = 25; // space after bottom-most control
  StrControl = 'ControlName';  // prefix for controls with no name

type
  TControlPos = class(Tobject) // Little object to save initial control positions
  public
    Name: string;
    X,
    Y: Integer;
  end;

  TControlPosList = class(TObject)
  private
    function GetCount: Integer;
    function GetItems(Index: Integer): TControlPos;
    procedure SetItems(Index: Integer; const Value: TControlPos);
  public
   TheList: TObjectList;
   Constructor Create; virtual;
   Destructor Destroy; override;
   function Add(APos: TControlPos): Integer;
   function IndexOfPos(AName: string): Integer;
   property Count: Integer read GetCount;
   property Items[Index: Integer]: TControlPos read GetItems write SetItems; default;
  end;

  TScrollingBaseFrame = class(TFrame)
    BackGroundImage: TImage;
    HorzScrollBar: TScrollBar;
    VertScrollBar: TScrollBar;
    pnlTitle: TPanel;
    procedure VertScrollBarChange(Sender: TObject);
    procedure BackGroundImageMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure FrameResize(Sender: TObject);
    procedure HorzScrollBarChange(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    ShowHScroller,
    ShowVScroller : Boolean;       // scroller needed at all?
    PosList: TControlPosList;   // list of initial positions
    procedure BeforeShow; virtual; // override in descendants for specific behaviour
    procedure BeforeClose; virtual; // override in descendants for specific behaviour
  end;

implementation

{$R *.dfm}

procedure TScrollingBaseFrame.BeforeClose;
// Clean up
begin
  PosList.Free;
end;

procedure TScrollingBaseFrame.BeforeShow;
//Setup scroller and save initial control positions
var
  i,XMax,YMax,Idx: Integer;
  AControl: TControl;
begin
  pnlTitle.Height := TitleHeight;
  PosList := TControlPosList.Create;
  XMax := 0;
  YMax := 0;
  for i := 0 to ComponentCount - 1 do
  begin
    if Components[i] is TControl then
    begin
      AControl := TControl(Components[i]);
      if Acontrol.Tag <> IgnoreTag then
      begin
        Idx := PosList.Add(TcontrolPos.Create);
        if AControl.Name = '' then  // deal with empty names
          AControl.Name :=  StrControl + IntToStr(i);
        PosList[Idx].Name := AControl.Name;
        PosList[Idx].X := AControl.Left;
        PosList[Idx].Y := AControl.Top;
        if YMax < AControl.Top + AControl.Height then
         YMax := AControl.Top + AControl.Height;
        if XMax < AControl.Left + AControl.Width then
         XMax := AControl.Left + AControl.Width;
      end; // Ignored
    end; // is control
  end; // count
   VertScrollBar.Max := (YMax + BottomMargin) - Height; // bit of a bottom margin :)
   VertScrollBar.LargeChange := VertScrollBar.Max div MaxLargeSteps;
   ShowVScroller := VertScrollBar.Max > BottomMargin;
   VertScrollBar.Visible := ShowVScroller;
   HorzScrollBar.Max := (XMax + RightMargin) - Width; // bit of a Right margin :)
   HorzScrollBar.LargeChange := HorzScrollBar.Max div MaxLargeSteps;
   ShowHScroller := HorzScrollBar.Max > RightMargin;
   HorzScrollBar.Visible := ShowHScroller;
end;

procedure TScrollingBaseFrame.FrameResize(Sender: TObject);
begin
  BackGroundImage.Width := Width;
  BackGroundImage.Height := Height;
end;

procedure TScrollingBaseFrame.HorzScrollBarChange(Sender: TObject);
// Move the controls left and right relative to thier initail positions
var
  i,j: Integer;
  AControl: TControl;
begin
  for i := 0 to ComponentCount - 1 do
   begin
     if Components[i] is TControl then
     begin
       AControl :=  TControl(Components[i]);
       j := PosList.IndexOfPos(AControl.Name);
       if j >= 0 then  // could be ignored
         Acontrol.Left := PosList[j].X  - HorzScrollBar.Position;
     end;
   end;
end;

procedure TScrollingBaseFrame.BackGroundImageMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
// Show/Hide the scrollbars using mouse position
var
  ScrollBarWidth: Integer;
begin
  ScrollBarWidth := GetSystemmetrics(SM_CXVSCROLL);  // assume the same for horizontal
  VertScrollBar.Visible := (X > Width - ScrollBarWidth) and ShowVScroller;
  HorzScrollBar.Visible := (Y > (Height - TitleHeight) - ScrollBarWidth) and ShowHScroller;
end;


procedure TScrollingBaseFrame.VertScrollBarChange(Sender: TObject);
// Move the controls Up and down relative to thier initail positions
var
  i,j: Integer;
  AControl: TControl;
begin
  for i := 0 to ComponentCount - 1 do
   begin
     if Components[i] is TControl then
     begin
       AControl :=  TControl(Components[i]);
       j := PosList.IndexOfPos(AControl.Name);
       if j >= 0 then  // could be ignored
         Acontrol.Top := PosList[j].Y  - VertScrollBar.Position;
     end;
   end;
end;

{ TcontrolPosList }

function TControlPosList.Add(APos: TControlPos): Integer;
begin
  Result := TheList.Add(APos);
end;

constructor TControlPosList.Create;
begin
  TheList := TObjectList.Create;
  TheList.OwnsObjects := True;
end;

destructor TControlPosList.Destroy;
begin
  TheList.Free;
  inherited;
end;

function TControlPosList.GetCount: Integer;
begin
  Result := TheList.Count;
end;

function TControlPosList.GetItems(Index: Integer): TControlPos;
begin
  Result := TControlPos(TheList[Index]);
end;

function TControlPosList.IndexOfPos(AName: string): Integer;
// Find a control position in the list by name
var
  Idx: Integer;
begin
  Result := -1;
  Idx := 0;
  while (Result < 0) and (Idx < TheList.Count) do
  begin
    if Items[idx].Name = AName then
      Result := idx;
    inc(idx);
  end;
end;

procedure TControlPosList.SetItems(Index: Integer; const Value: TControlPos);
begin
  TheList[Index] := Value;
end;

end.