如何让一个Panel始终居中(相对于Parent)
当Parent的Size变化时，要能获取到这个信息，并即时改变自身的Postion.

有没有哪个控件，或如何处理消息？

小弟先谢谢啦！

繼承 TControl 以下都有一個屬性為 Align 的屬性, 裏面有一項對齊的方式為 alCustom
( 開發者自訂對齊方式, 就像是你所提到的特殊對齊方式, 這須要寫程式碼控制 )

1. 假設 Panel 的 Parent 為 Form1
2. 設定 Pane1.Align = alCustom
3. 在 Form1 的 Proected 區塊中覆寫 CustomAlignPosition 函式


[code delphi]
type
TForm1 = class(TForm)
Panel1: TPanel
protected
procedure CustomAlignPosition(Control: TControl; var NewLeft, NewTop, NewWidth,
NewHeight: Integer; var AlignRect: TRect; AlignInfo: TAlignInfo); override;
public
end

implementation

procedure TForm1.CustomAlignPosition(Control: TControl; var NewLeft,
NewTop, NewWidth, NewHeight: Integer; var AlignRect: TRect;
AlignInfo: TAlignInfo);
begin
inherited;
if ( Control = Panel1 ) then
begin
NewLeft := ( AlignRect.Right - NewWidth ) div 2;
end;
end;

[/code]

編輯記錄

感谢Osx大哥的指点, 不过,我想做成一个控件,这样,不用影响其它地方的源代码. 我做了一个控件,不过,很丑,没有过滤,(不知道怎么过滤消息)(效率很低) 帮看看,哪里可以改时一下. 

感谢Osx大哥的指点, 不过,我想做成一个控件,这样,不用影响其它地方的源代码. 我做了一个控件,不过,很丑,没有过滤,(不知道怎么过滤消息)(效率很低) 帮看看,哪里可以改进一下.

unit kCPal;
interface
uses
Windows, Messages, Classes, ExtCtrls,Graphics,Controls,AppEvnts,SysUtils;
type
TkCPal = class(TPanel)
private
FkAutoCenterPosition:Boolean;
FApplicationEvents: TApplicationEvents;
protected
procedure pSetPalCenter;
procedure pSetkAutoCenterPosition(aAutoCenterPosition:Boolean);
procedure ApplicationEventsMessage(var Msg: tagMSG;var Handled: Boolean);
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
procedure Paint;override;
published
property kAutoCenterPosition:Boolean read FkAutoCenterPosition write pSetkAutoCenterPosition;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('kERP', [TkCPal]);
end;
constructor TkCPal.Create(AOwner: TComponent);
begin
inherited;
if not (csDesigning in ComponentState) then
begin
FApplicationEvents:=TApplicationEvents.Create(aOwner);
FApplicationEvents.OnMessage:=ApplicationEventsMessage;
end;
kAutoCenterPosition:=False;
Alignment:=taCenter;
BevelOuter:=bvNone;
end;
procedure TkCPal.ApplicationEventsMessage(var Msg: tagMSG;var Handled: Boolean);
begin
pSetPalCenter;
end;

destructor TkCPal.Destroy;
begin
if not (csDesigning in ComponentState) then
FApplicationEvents.Free;
inherited;
end;
procedure TkCPal.pSetPalCenter;
begin
if (Parent<>nil) and FkAutoCenterPosition then
begin
Top :=(Parent.ClientHeight-Height) div 2;
Left:=(Parent.ClientWidth -Width ) div 2;
end;
end;
procedure TkCPal.pSetkAutoCenterPosition(aAutoCenterPosition:Boolean);
begin
FkAutoCenterPosition:=aAutoCenterPosition;
pSetPalCenter;
end;
procedure TkCPal.Paint;
begin
Caption:='';
if (csDesigning in ComponentState) then
pSetPalCenter;
inherited;
end;
initialization
registerClasses([TApplicationEvents]);
end.

編輯記錄

感谢Osx大哥的指点, 不过,我想做成一个控件,这样,不用影响其它地方的源代码. 我做了一个控件,不过,很丑,没有过滤,(不知道怎么过滤消息)(效率很低) 帮看看,哪里可以改进一下. 

unit kCPal;
interface
uses
Windows, Messages, Classes, ExtCtrls,Graphics,Controls,AppEvnts,SysUtils;
type
TkCPal = class(TPanel)
private
FkAutoCenterPosition:Boolean;
FApplicationEvents: TApplicationEvents;
protected
procedure pSetPalCenter;
procedure pSetkAutoCenterPosition(aAutoCenterPosition:Boolean);
procedure ApplicationEventsMessage(var Msg: tagMSG;var Handled: Boolean);
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
procedure Paint;override;
published
property kAutoCenterPosition:Boolean read FkAutoCenterPosition write pSetkAutoCenterPosition;
end;
procedure Register;
implementation
procedure Register;
begin
RegisterComponents('kERP', [TkCPal]);
end;
constructor TkCPal.Create(AOwner: TComponent);
begin
inherited;
if not (csDesigning in ComponentState) then
begin
FApplicationEvents:=TApplicationEvents.Create(aOwner);
FApplicationEvents.OnMessage:=ApplicationEventsMessage;
end;
kAutoCenterPosition:=False;
Alignment:=taCenter;
BevelOuter:=bvNone;
end;
procedure TkCPal.ApplicationEventsMessage(var Msg: tagMSG;var Handled: Boolean);
begin
pSetPalCenter;
end;

destructor TkCPal.Destroy;
begin
if not (csDesigning in ComponentState) then
FApplicationEvents.Free;
inherited;
end;
procedure TkCPal.pSetPalCenter;
begin
if (Parent<>nil) and FkAutoCenterPosition then
begin
Top :=(Parent.ClientHeight-Height) div 2;
Left:=(Parent.ClientWidth -Width ) div 2;
end;
end;
procedure TkCPal.pSetkAutoCenterPosition(aAutoCenterPosition:Boolean);
begin
FkAutoCenterPosition:=aAutoCenterPosition;
pSetPalCenter;
end;
procedure TkCPal.Paint;
begin
Caption:='';
if (csDesigning in ComponentState) then
pSetPalCenter;
inherited;
end;
initialization
registerClasses([TApplicationEvents]);
end.