class TMyEdit : public Vcl::Stdctrls::TEdit{    virtual void __fastcall CreateParams(TCreateParams& Params);    void __fastcall WMSize(TWMSize &Message);    virtual void __fastcall SetParent(TWinControl *AParent);public:    __fastcall TMyEdit(TComponent* Owner);    void __fastcall SetCenter(void);    inline __fastcall virtual ~TMyEdit(void)      {      }    inline __fastcall TMyEdit(HWND ParentWindow) : Vcl::Stdctrls::TEdit(ParentWindow)     {        }    BEGIN_MESSAGE_MAP        MESSAGE_HANDLER(WM_SIZE, TWMSize, WMSize);    END_MESSAGE_MAP(TEdit);};

// ---------------------------------------------------------------------------#include 
     
      #pragma hdrstop#include "Unit26.h"#include "Unit27.hpp"// ---------------------------------------------------------------------------#pragma package(smart_init)#pragma link "RzEdit"#pragma resource "*.dfm"TForm25 *Form25;// ---------------------------------------------------------------------------__fastcall TForm25::TForm25(TComponent* Owner)    : TForm(Owner){}__fastcall TMyEdit::TMyEdit(TComponent* Owner) : TEdit(Owner){}void __fastcall TMyEdit::CreateParams(TCreateParams& Params){    TEdit::CreateParams(Params);    Params.Style = Params.Style | ES_MULTILINE;}void __fastcall TMyEdit::SetParent(TWinControl *AParent){    TEdit::SetParent(AParent);    if (AParent != NULL)        SetCenter();}// ---------------------------------------------------------------------------void __fastcall TMyEdit::WMSize(TWMSize &Message){    TEdit::Dispatch(&Message);    SetCenter();}void __fastcall TMyEdit::SetCenter(void){    HDC DC;    HFONT SaveFont;    int Sin;    TTextMetric SysMetrics, Metrics;    TRect Rct;    DC = GetDC(0);    GetTextMetrics(DC, &SysMetrics);    SaveFont = (HFONT) SelectObject(DC, Font->Handle);    GetTextMetrics(DC, &Metrics);    SelectObject(DC, SaveFont);    ReleaseDC(0, DC);    if (Ctl3D)        Sin = 8;    else        Sin = 6;    Rct = ClientRect;    Sin = Height - Metrics.tmHeight - Sin;    Rct.Top = Sin / 2;    SendMessage(Handle, EM_SETRECT, 0, (LPARAM)(&Rct));}// ---------------------------------------------------------------------------void __fastcall TForm25::Button7Click(TObject *Sender){ // 起作用    // 首先把控件的属性设置为多行    RECT rect;    rect = myedt->ClientRect;    // 设置内容的,左边距与上边距    ::OffsetRect(&rect, 0, 5);    ::SendMessage(myedt->Handle, EM_SETRECT, 0, (LPARAM)&rect);}// ---------------------------------------------------------------------------void __fastcall TForm25::Button1Click(TObject *Sender){    SetWindowLong(myedt->Handle, GWL_STYLE,        GetWindowLong(myedt->Handle, GWL_STYLE) | ES_CENTER);}// ---------------------------------------------------------------------------void __fastcall TForm25::FormCreate(TObject *Sender){    myedt = new TMyEdit(this);    myedt->AutoSize = false;    myedt->Height = 50;    myedt->Parent = this;    myedt->Text = "hello";    myedt->Alignment = taCenter;}// ---------------------------------------------------------------------------void __fastcall TForm25::Button4Click(TObject *Sender){    myedt->SetCenter(); // 起作用}// ---------------------------------------------------------------------------
     

 

原帖是delphi的，转自

控件创建后不起作用，没有效果。显示调用SetCenter函数就有效果了。