C++博客-笔记-文章分类-C++Builder

OnClose

EiN — Tue, 06 Jan 2009 08:26:00 GMT

Occurs when the form closes.

enum TCloseAction { caNone, caHide, caFree, caMinimize };
typedef void __fastcall (__closure *TCloseEvent)(System::TObject* Sender, TCloseAction &Action);
__property TCloseEvent OnClose = {read=FOnClose, write=FOnClose, stored=IsForm};

Description

Use OnClose to perform special processing when the form closes. The OnClose event specifies which event handler to call when a form is about to close. The handler specified by OnClose might, for example, test to make sure all fields in a data-entry form have valid contents before allowing the form to close.

A form is closed by the Close method or when the user chooses Close from the form's system menu.

The TCloseEvent type points to a method that handles the closing of a form. The value of the Action parameter determines if the form actually closes. These are the possible values of Action:

Value    Meaning

caNone    The form is not allowed to close, so nothing happens.
caHide    The form is not closed, but just hidden. Your application can still access a hidden form.
caFree    The form is closed and all allocated memory for the form is freed.
caMinimize    The form is minimized, rather than closed. This is the default action for MDI child forms.

If a form is an MDI child form, and its BorderIcons property is biMinimize, then the default Action is caMinimize. If a MDI child form does not have these settings, the default Action is caNone, meaning that nothing happens when the user attempts to close the form.

If a form is an SDI child form, Action defaults to caHide.

To close the form and free it in an OnClose event, set Action to caFree.

Note:    When the application shuts down, the main form receives an OnClose event, but any child forms do not receive the OnClose event.

EiN 2009-01-06 16:26 发表评论

小观构件

EiN — Fri, 02 Jan 2009 14:21:00 GMT

摘自BCB的例子,越看越有点迷糊,还越觉得niubility.像观察者又肯定不是,实在是牛...

Main.cpp:

//----------------------------------------------------------------------------
//Borland C++Builder
//Copyright (c) 1987, 1998-2002 Borland International Inc. All Rights Reserved.
//----------------------------------------------------------------------------
//-------------------------------------------------------------------------
//    minicomp.cpp - uses the TCounter example component
//-------------------------------------------------------------------------
#include "minicomp.h"
#include <stdio.h>
#include <stdlib.h>
#include <condefs.h>
//-------------------------------------------------------------------------
USEUNIT("counter.cpp");
//---------------------------------------------------------------------------
main()
{
  TExample example;

  return 0;
}
//-------------------------------------------------------------------------
TExample::TExample()
{
  TCounter Counter(7);
  int i;
  //把控件Counter的接口FMultiple和外部实现MultipleReached连接上
  Counter.OnMultiple = MultipleReached;

  for (i=0; i < 100; i++)
    Counter.Increment();
}
//-------------------------------------------------------------------------
void TExample::MultipleReached(TCounter *Sender)
{
  printf("Multiple=%d reached with val=%d\n", Sender->Multiple, Sender->Val);
}
//-------------------------------------------------------------------------

minicomp.h:

//-------------------------------------------------------------------------
//    minicomp.h - uses the TCounter example component
//-------------------------------------------------------------------------
#include "counter.h"
//-------------------------------------------------------------------------
class TExample
{
private:
  void MultipleReached(TCounter *Sender);
public:
  TExample();
};
//-------------------------------------------------------------------------

counter.h:

//-------------------------------------------------------------------------
//    counter.h. - example of a small, non-visual counter component
//-------------------------------------------------------------------------
class TCounter;         // forward

typedef void (__closure *TCounterEvent)(TCounter *Sender);
//-------------------------------------------------------------------------
class TCounter
{
private:
  TCounterEvent FOnMultiple; //这就是个函数接口
  int FVal;
  int FMultiple;
public:
  __property int Val = {read=FVal, write=FVal};
  __property int Multiple = {read=FMultiple};
  __property TCounterEvent OnMultiple = {read=FOnMultiple, write=FOnMultiple};
  void Clear();
  void Increment();
  TCounter(int Multiple);
};
//-------------------------------------------------------------------------

counter.cpp:

//-------------------------------------------------------------------------
//    counter.cpp - example of a small, non-visual counter component
//-------------------------------------------------------------------------
#include "counter.h"
//-------------------------------------------------------------------------
TCounter::TCounter(int Multiple)
{
  FMultiple = Multiple;
}
//-------------------------------------------------------------------------
void TCounter::Clear()
{
  FVal = 0;
}
//-------------------------------------------------------------------------
void TCounter::Increment()
{
  //这句执行时都是外部来调用的,此时OnMultiple已经和外面那个函数接口连接上了
  //也就是调用的其实是外面进来的那个函数,把this传出去,让外部那个函数操作
  //TExample::MultipleReached(this)
  if (((++FVal) % FMultiple) == 0)
      OnMultiple(this);
}
//-------------------------------------------------------------------------

EiN 2009-01-02 22:21 发表评论

New Application

EiN — Wed, 31 Dec 2008 15:10:00 GMT

Project1.cpp:

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop
//---------------------------------------------------------------------------
USEFORM("Unit1.cpp", Form1); //调用这个vcl模块,详见Unit1.cpp
//---------------------------------------------------------------------------
//这里很搞笑,没给参数名重写,不知道这样函数里面能不能用到这几个参数
//不过好像也就没用
WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
{
    try
    {
         Application->Initialize();
         //The owner of the new form is the Application object
         //__classid返回一个指向TForm1的vtable的指针,这点还要再看看实现过程
         Application->CreateForm(__classid(TForm1), &Form1);
         Application->Run();
    }
    catch (Exception &exception)
    {
         Application->ShowException(&exception);
    }
    catch ()
    {
         try
         {
             throw Exception("");
         }
         catch (Exception &exception)
         {
             Application->ShowException(&exception);
         }
    }
    return 0;
}
//---------------------------------------------------------------------------

Unit1.h:

//---------------------------------------------------------------------------

#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
//都只是些声明部分,所以包含在头文件里面
#include <Classes.hpp> //TPersistent, TComponent
#include <Controls.hpp> //TControl, TWinControl
#include <StdCtrls.hpp> //TButton
#include <Forms.hpp> //TApplication, TForm
//---------------------------------------------------------------------------
/*
TObject(RTTI,垃圾回收等最基本的)
    |
    |--TList(stores an array of pointers)
    |
    |--TStream(read and write to some media)
    |   |
    |   |--TFileStream,TStringStream,TWinSocketStrem
    |
    |--TFiler(读写控件[objects]属性:比如保存dfm文件信息,在内存中暂存控件信息等)
    |   |
    |   |--TReader
    |   |--TWriter(具体实现Filer功能)
    |
    |--TPersistent(have assignment and streaming capabilities)
        |
        |--TStrings(for objects that represent a list of strings)
        |   |
        |   |--TStringList(具体实现)
        |
        |--TComponent(控件父类,包括可显示和不可显示)
            |
            |--TApplication(抽象WindowsGUI环境,消息机制当然还有针对web的环境)
            |
            |--TControl(可视控件)
                |
                |--TWinControl(针对Windows的可视控件)
                    |
                    |--TButtonControl(Button的抽象)
                    |   |
                    |   |--TButton(Button的具体实现)
                    |
                    |--TScrollingWinControl(支持滚动条的Windows控件)
                        |
                        |--TCustomForm
                            |
                            |--TForm
*/
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:    // IDE-managed Components
private:    // User declarations
public:        // User declarations
    __fastcall TForm1(TComponent* Owner); //Owner是创造者,Parent是呈现者(只对于可视控件)
};
//---------------------------------------------------------------------------
/*
把这个vcl(Form1)导出,其他模块使用这个头文件时就告诉编译器,这个vcl在别处具体定义
*/
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

Unit1.cpp:

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop //之前的头文件可以使用头文件缓存技术,其他包含vcl.h的编译块就编译一次

#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
/*
这里的疑问在于,头文件里面已经有一个extern的指针,这里为何还要再次搞出个指针.
注意在Project1.cpp里面有个USEFORM的宏,这个宏的具体定义在vcl\sysclass.h文件中
如下:

#ifdef BCBVER1
  #define USEFORM(FileName, FormName) \
    class DELPHICLASS T##FormName;       \
    extern T##FormName *FormName;
#else
  #define USEFORM(FileName, FormName) \
    class DELPHICLASS T##FormName;       \
    extern PACKAGE T##FormName *FormName;
#endif

可以看出这里FileName根本没用上,所以"既然给了cpp也就给了.h也就给了那个extern指针"
的想法是错误的,cpp文件根本就没有起到任何作用,还是完全依赖连接时靠extern的存储
属性在obj里面去找.这也就是为什么cpp里面如果没有下面这个指针声明,报错的不是Unit1
而是Project1,因为是在Project1调用了这么个没有定义个指针.还有一点就是,之所以会这
样是因为.h是不会编译的,Project1在Unit1.cpp对应的obj里面去找,当然找不到.所以这里
必须要再次写上一句.
*/
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
{
}
//---------------------------------------------------------------------------

EiN 2008-12-31 23:10 发表评论