关于组件制作的问题：

2002-07-10 07:45:18 98 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

Excel COUNTIF函数精确统计全解析：从模糊匹配到精准计数在数据处理与办公自动化领域，条件计数是数据分析的基础操作，其核心原理在于对特定范围内满足设定条件的单元格进行识别与汇总。Excel中的COUNTIF函数是实现这一功能的常用工具，它通过文本匹配逻辑与通配符机制来执行条件判断。然而，其默认的模糊匹配行为常导致统计结果偏离预期，这正是精确统计的技术价值所在——确保数据汇总的准确性与可靠性，直接影响业务报告、薪酬核算、销售分析等应用场景的决策质量。本文聚焦COUNTIF函数的精确匹配技巧，深入剖析通配符（如星号*和问号?）的转义使用（通过波浪号~），并针对大小写敏阅读详情

我从TWinControl派生一个组件，目的是生成一个DBLookupComboBox,但问题出现了，当包编译，安装成功后。我将我的这个组件放到窗体上时，错误出现表现“control has no parent window"，但事实上我已经重载CreateWnd函数。令人奇怪的是，如果我不是生成TDBLookupCombobOX,而是其它则没有问题。附代码，希望大家讨论：
//---------------------------------------------------------------------------
#ifndef KingLookupH
#define KingLookupH
//---------------------------------------------------------------------------
#include <SysUtils.hpp>
#include <Controls.hpp>
#include <Classes.hpp>
#include <Forms.hpp>
#include <DBCtrls.hpp>
//---------------------------------------------------------------------------
class PACKAGE TKingLookup : public TWinControl
{
private:
TDBLookupComboBox FLookup;
protected:
virtual __fastcall ~TKingLookup();
virtual void __fastcall CreateWnd();
public:
__fastcall TKingLookup(TComponent* Owner);
__published:
};
//---------------------------------------------------------------------------
#endif
.cpp File
//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include "KingLookup.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(TKingLookup *)
{
new TKingLookup(NULL);
}
//---------------------------------------------------------------------------
__fastcall TKingLookup::TKingLookup(TComponent* Owner)
: TDBLookupComboBox(Owner)
{
FLookup=new TDBLookupComboBox(this);
FLookup->Parent=this;
FLookup->Font->Color=clWhite;
FLookup->Color=clBlack;
FLookup->Left=Left;
FLookup->Top=Top+21;
FLookup->Width=100;
FLookup->Height=21;

}
//---------------------------------------------------------------------------
__fastcall TKingLookup::~TKingLookup()
{
if(FLookup)
{
delete FLookup;
}
}
void __fastcall TKingLookup::CreateWnd()
{
TWinControl::CreateWnd();
}
namespace Kinglookup
{
void __fastcall PACKAGE Register()
{
TComponentClass classes[1] = {__classid(TKingLookup)};
RegisterComponents("AKing", classes, 0);
}
}
//---------------------------------------------------------------------------
奇怪的是，这么一个简单的代码，莫非TDBLookupComboBox这个类本身还有其它的问题？

...全文

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kingcaiyao

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Borlandor 2002-07-11

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OK，很不错，应该从TCustomControl中继承。

kingcaiyao 2002-07-11

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我将我的代码贴如下：
//---------------------------------------------------------------------------

#ifndef KingKingH
#define KingKingH
//---------------------------------------------------------------------------
#include <SysUtils.hpp>
#include <Controls.hpp>
#include <Classes.hpp>
#include <Forms.hpp>
#include <dsgnintf.hpp>
//---------------------------------------------------------------------------
class PACKAGE TKingKing : public TCustomControl
{
private:
TDBLookupComboBox *FLookup;
TEdit *FEdit;
TDataSource *FDataSource;
TDataSource *FListSource;
AnsiString FListField;
AnsiString FKeyField;
AnsiString FDataField;

protected:
virtual void __fastcall Paint();
virtual __fastcall ~TKingKing();
public:
__fastcall TKingKing(TComponent* Owner);
void __fastcall SetDataSource(TDataSource *DataSource);
void __fastcall SetListSource(TDataSource *DataSource);
void __fastcall SetKeyField(AnsiString Field);
void __fastcall SetDataField(AnsiString Field);
void __fastcall SetListField(AnsiString Field);

__published:
__property TDataSource* DataSource={read=FDataSource,write=SetDataSource};
__property TDataSource *ListSource={read=FListSource,write=SetListSource};
__property AnsiString KeyField={read=FKeyField,write=SetKeyField};
__property AnsiString ListField={read=FListField,write=SetListField};
__property AnsiString DataField={read=FDataField,write=SetDataField};
};
//DataField PropertyEditor
class TDataFieldProperty:public TStringProperty
{
public:
TPropertyAttributes __fastcall GetAttributes()
{
return TPropertyAttributes()<<paValueList;
}
void __fastcall GetValues(TGetStrProc Proc)
{
Proc("None");
TDataSet *pDataSet;
TKingKing *pDCBX=dynamic_cast<TKingKing*>(GetComponent(0));
if(pDCBX)
{ if(pDCBX->DataSource)
{
pDataSet=pDCBX->DataSource->DataSet;
if(pDataSet)
{
TStrings *pList=new TStringList();
pDataSet->GetFieldNames(pList);

for(int i=0;i<pList->Count;i++)
{
Proc(pList->Strings[i]);
}
delete pList;
}
}
}
}
};
//ListField PropertyEditor
class TListFieldProperty:public TStringProperty
{
public:
TPropertyAttributes __fastcall GetAttributes()
{
return TPropertyAttributes()<<paValueList;
}
void __fastcall GetValues(TGetStrProc Proc)
{
Proc("None");
TDataSet *pDataSet;
TKingKing *pDCBX=dynamic_cast<TKingKing*>(GetComponent(0));
if(pDCBX)
{ if(pDCBX->ListSource)
{
pDataSet=pDCBX->ListSource->DataSet;
if(pDataSet)
{
TStrings *pList=new TStringList();
pDataSet->GetFieldNames(pList);
for(int i=0;i<pList->Count;i++)
{
Proc(pList->Strings[i]);
}
delete pList;
}
}
}
}
};
//KeyField PropertyEditor
class TKeyFieldProperty:public TStringProperty
{
public:
TPropertyAttributes __fastcall GetAttributes()
{
return TPropertyAttributes()<<paValueList;
}
void __fastcall GetValues(TGetStrProc Proc)
{
Proc("None");
TDataSet *pDataSet;
TKingKing *pDCBX=dynamic_cast<TKingKing*>(GetComponent(0));
if(pDCBX)
{ if(pDCBX->ListSource)
{
pDataSet=pDCBX->ListSource->DataSet;
if(pDataSet)
{
TStrings *pList=new TStringList();
pDataSet->GetFieldNames(pList);
for(int i=0;i<pList->Count;i++)
{
Proc(pList->Strings[i]);
}
delete pList;
}
}
}
}
};

//---------------------------------------------------------------------------
#endif
.cpp File
//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include "KingKing.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(TKingKing *)
{
new TKingKing(NULL);
}
//---------------------------------------------------------------------------
TTypeInfo *AnsiStringInfo()
{
TTypeInfo *pTypeInfo=new TTypeInfo;
pTypeInfo->Kind=tkLString;
pTypeInfo->Name="AnsiString";
return pTypeInfo;
}

__fastcall TKingKing::TKingKing(TComponent* Owner)
: TCustomControl(Owner)
{
FLookup=new TDBLookupComboBox(this);
FEdit=new TEdit(this);
Width = 150;
Height=46;

}
//---------------------------------------------------------------------------
void __fastcall TKingKing::Paint()
{

Width = 150;
Height=46;
FLookup->Parent=this;
FLookup->Left=0;
FLookup->Top=0;
FLookup->Width=145;
FLookup->Height=21;

FEdit->Parent=this;
FEdit->Left=0;
FEdit->Top=FLookup->Height;
FEdit->Width=80;
FEdit->Height=21;
}
void __fastcall TKingKing::SetDataSource(TDataSource *DataSource)
{
FDataSource=DataSource;
}
//--------------------------------------------------------------------------
void __fastcall TKingKing::SetListSource(TDataSource *DataSource)
{
FListSource=DataSource;
}
//--------------------------------------------------------------------------
void __fastcall TKingKing::SetKeyField(AnsiString Field)
{
FKeyField=Field;
}
void __fastcall TKingKing::SetListField(AnsiString Field)
{
FListField=Field;
}
void __fastcall TKingKing::SetDataField(AnsiString Field)
{
FDataField=Field;
}

__fastcall TKingKing::~TKingKing()
{
if(FLookup)
{
delete FLookup;
}
if(FEdit)
{
delete FEdit;
}

}

namespace Kingking
{
void __fastcall PACKAGE Register()
{
TComponentClass classes[1] = {__classid(TKingKing)};
RegisterPropertyEditor(AnsiStringInfo(),__classid(TKingKing),"DataField",__classid(TDataFieldProperty));
RegisterPropertyEditor(AnsiStringInfo(),__classid(TKingKing),"ListField",__classid(TListFieldProperty));
RegisterPropertyEditor(AnsiStringInfo(),__classid(TKingKing),"KeyField",__classid(TKeyFieldProperty));
RegisterComponents("AKing", classes, 0);
}
}
//---------------------------------------------------------------------------

kingcaiyao 2002-07-11

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问题差不多已被我找到了。因为我对两个组件进行比较发现：TDBLookupComboBox和TDBComboBox发现，首先它们的继承的类层次不同，其中TDBComboBox的继承层次有TCustomComboBox（而这个类是TComboBox的父类），而TDBLookupComboBox的最直接父类就是TCustomControl，这恰恰证明TDBLookupComboBox是放在Paint函数中被画出来的。而我的错误代码是从TWinControl继承下来的，而父类为TWinControl控件的最大特点就是自已能够画出自已，而TCustomControl则需要自已画自已（用Paint方法）,据此可以判断TDBLookupComboBox为什么在设计期间就已经有了句柄的理由就是在从TCustomControl继承的过程序，TDBLookupComboBox不仅重载了Paint方法，还重载了CreateWnd方法。而如果你从TWinControl继承，再动态生成一个TDBLookupComboBox就会出现错误提示”该控件没有父窗口“。
欢迎各位网友参与讨论。

kingcaiyao 2002-07-10

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看来c++ builder和Delphi论坛对组件有研究的人比较少。

dupenf 2002-07-10

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代码没看到阿

netlib 2002-07-10

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老大，帖错论坛了。

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