procedure TForm1.Button2Click(Sender: TObject);
var
  DC: HDC;
  C: TCanvas;
  R: TRect;
begin
  DC := GetDC(Edit1.Handle);
  try
    C := TCanvas.Create;
    try
      C.Handle := DC;
      C.Font.Assign(Edit1.Font);
      C.Brush.Color := Edit1.Color;
      R := Edit1.ClientRect;
      C.FillRect(R);
      DrawText(DC,
               PChar(Edit1.Text),
               Length(Edit1.Text),
               R,
               DT_CENTER or DT_VCENTER or DT_SINGLELINE);
    finally
      FreeAndNil(C);
    end;
  finally
    ReleaseDC(Edit1.Handle, DC);
  end;
end;    

 
// CenterEdit.h 部分內容    class PACKAGE TCenterEdit : public TEdit
{
private:
protected:
public:
    __fastcall TCenterEdit(TComponent* Owner);
    void __fastcall CreateParams(TCreateParams &Params);    __published:
};        //---------------------------------------------------------------------------    // CenterEdit.cpp 部分內容        #include     #pragma hdrstop    #include "CenterEdit.h"
#pragma package(smart_init)
//---------------------------------------------------------------------------
// ValidCtrCheck is used to assure that the components created do not have
// any pure virtual functions.
//    static inline void ValidCtrCheck(TCenterEdit*)
{
    new TCenterEdit(NULL);
}
//---------------------------------------------------------------------------
__fastcall TCenterEdit::TCenterEdit(TComponent* Owner)
    : TEdit(Owner)
{
}    //---------------------------------------------------------------------------
void __fastcall TCenterEdit::CreateParams(TCreateParams &Params)
{
    TEdit::CreateParams(Params);        // 最重要的就是下面這一行而已
    Params.Style = Params.Style | ES_CENTER;// ES_MULTILINE; 
}    //---------------------------------------------------------------------------
namespace CenterEdit
{
    void __fastcall PACKAGE Register()
    {
         TComponentClass classes[1] = {__classid(TCenterEdit)};
         RegisterComponents("Standard", classes, 0);
    }
}
//---------------------------------------------------------------------------

引言: 如何让 TEdit 的内容居中显示?