C++Builder代码片断
本文中包含了一些常用的代码片断，看看想想或许有他山之石可以攻玉的可能。 CKER
| 删除别名中所有的表 | 纯虚函数 | 虚函数 | 启动页面 | 指针 |
| 为指针解除引用 | 表的For循环 | 变量与常量的声明 | 检查表是否存在 | 组件的类名 |
| 剪贴板中的文字 | 字符流 | 检查表是否已打开 | 表的状态操作 | 改变PageControl的标签 |
| 向Query传递参数 | 日期属性 | 绘制状态条 |
删除别名中所有的表 void TData::CleanTemp() { TStringList *myTables = new TStringList(); TTable *Table = new TTable(this); try { Session->GetTableNames("Temp", "", True, False, myTables); } catch (...) {} // AnsiString str = myTables->GetText(); // ShowMessage(str); for(int count=0; count < myTables->Count; count++) { Table->DatabaseName = "Temp"; Table->TableName = myTables->Strings[count]; Table->Close(); Table->DeleteTable(); } delete myTables; delete Table; } BACK 纯虚函数 //纯虚函数只在基类中出现，而在子类中必须有 //与其匹配的成员函数。程序中申明的子类的实例 file://必须为基类中的每一个纯虚函数提供一个重载的成员函数。 class TBaseClass { public: virtual void Display() = 0; }; class TDerivedClass : public TBaseClass { public: void Display() { ShowMessage("From Derived"); } }; class TSecondDerivedClass : public TDerivedClass { public: void Display() { ShowMessage("From Second Derived"); } }; void __fastcall TForm1::Button1Click(TObject *Sender) { TDerivedClass dc; dc.Display();// "From Derived" TSecondDerivedClass sc; TBaseClass* bc = ≻ bc->Display(); // "From Second Derived" } BACK 虚函数 //虚函数作为其他类的父类的成员函数。 //如果继承子类成员函数中存在与父类成员函数完全相同的函数， //子类中的成员函数永远有效。 class Base { public: virtual void Display() { ShowMessage("Base Class"); } }; class DerivedOne : public Base { public: void Display() { ShowMessage("DerivedOne"); } }; class DerivedTwo : public Base { public: void Display() { ShowMessage("DerivedTwo"); } }; Base* pBases[10]; int count = 0; DerivedOne aDerOne; DerivedTwo aDerTwo; pBases[count++] = &aDerOne; pBases[count++] = &aDerTwo; for( int i=0; i < count; i++ ) pBases[i]->Display(); BACK 启动页面 USEDATAMODULE("Datamod.cpp", DataModule); USEFORM("about.cpp", AboutBox); USEFORM("main.cpp", MainForm); USEFORM("splash.cpp", SplashForm); file://--------------------------------------------------------------------------- #include "splash.h" WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int) { try { SplashForm = new TSplashForm(Application); SplashForm->Show(); SplashForm->Update(); Application->Initialize(); Application->Title = "Example of Loading Splash Form"; Application->HelpFile = "SplashHelp.hlp"; Application->CreateForm(__classid(TMainForm), &MainForm); Application->CreateForm(__classid(TDataModule), &DataModule); Application->CreateForm(__classid(TAboutBox), &AboutBox); SplashForm->Hide(); SplashForm->Close(); Application->Run(); } catch (Exception &exception) { Application->ShowException(&exception); } return 0; } BACK 指针 int array[] = { 2, 4, 6, 8, 10} int myInteger = array[3]; // 值为 8 // ----使用指针可以实现同样的功能 ----- int array[] = { 2, 4, 6, 8, 10} int* myPtr = array; int myInteger = myPtr[3]; // 值为8 BACK 为指针解除引用 int x = 32; int* ptr = &x; //解除指针的引用 file://以获得内存位置的内容 int y = *ptr; // y = 32 BACK 表的For循环 void TDataModuleEmployee::ListNames( TStrings *Items ) { try { for ( TableAll->First(); !TableAll->Eof; TableAll->Next() ) if ( TableAll->FieldByName("Deleted")->AsBoolean == false ) Items->AddObject( TableAll->FieldByName("Name")->AsString, (TObject *)TableAll->FieldByName("Refnum")->AsInteger ); } catch (Exception &e) { Application->ShowException(&e); }; } BACK 变量与常量的声明 char ch; int count = 1; char* name = "csdn.net"; struct complex { float my, his;}; float real(complex* p) {return p->my}; const double pi = 3.1415926535897932385; templetate abc(T a) { return a < 0 ? -a : a; }; enum WebSite { one, two, three, four}; int* a; // * 指针 char* p[20]; // [ ] 数组 void myFunction(int); // ( )函数 struct str { short length; char* p; }; char ch1 = 'a'; char* p = &ch1; // &引用 ，p保持着ch1的地址 char ch2 = *p; // ch2 = 'a' BACK 检查表是否存在 #include "io.h" if (access(Table1->TableName.c_str(),0)) file://检查表是否存在 { // 若不存在就创建 ... Table1->Active = false; Table1->TableType = ttParadox; Table1->FieldDefs->Clear(); Table1->FieldDefs->Add("Myfield", ftString, 15, false); Table1->IndexDefs->Clear(); Table1->CreateTable(); Table1->Active = true; } else Table1->Active = true; BACK 组件的类名 //找出丢失的组件类名 for(int i=0; i < ComponentCount; i++) { if(String(dynamic_cast<TComponent&>(*Components[i]).Name) == "") { ShowMessage(Components[i]->ClassName()); } } BACK 剪贴板中的文字 #include "memory.h" // 包含 auto_ptr<> #include "clipbrd.hpp" file://包含 TClipboard & Clipboard() // 范例程序，包含了一个memo控件 __fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) { file://创建 TStringList对象 auto_ptr ClipText(new TStringList); file://得到剪贴板中的文字的拷贝 ClipText->Text = Clipboard()->AsText; file://然后加工一下... Memo1->Lines->AddStrings(ClipText.get()); } BACK 字符流 //范例一 #include "sstream" const char *name = "cker"; const char *email = "cker@sina.com"; // 生成 "cker"[SMTP:cker@sina.com] ostringstream ost; ost << "/"" << name << "/"[SMTP:" << email << "]"; Edit1->Text = ost.str().c_str(); file://范例二 void TDataModuleEmployee::FullReport(const char *title) { Report.header(title); Report << sformat( "Employee #-: %s%s/n", TableAllRefnum->Value, TableAllName->Text.c_str(), TableAllManagerFlag->Value ?"(Manager)" : "" ) << " Address: " << TableAllAddress->Text.c_str() << endl << " " << TableAllCityProvZip->Text.c_str() << endl << " " << NameCountry(TableAllCanada->Value) << endl; Report.footer(); } BACK 检查表是否已打开 void TData::CheckEdit() { for(int i=0; i < ComponentCount; i++) { if(dynamic_cast(Components[i])) { if(((TTable*)Components[i])->State == dsEdit) { String s = "Table " + Components[i]->Name + " is in edit mode" "/rWould you like to post it before entering new task?"; if(MessageBox(NULL,s.c_str(),"Table in Edit Mode",MB_YESNO | MB_ICONINFORMATION) == IDYES) ((TTable*)Components[i])->Post(); else ((TTable*)Components[i])->Cancel(); } } } } BACK 表的状态操作 //关闭已打开的表并将他们恢复成初始状态。 void TData::MyTables(TForm * sender) { int i; TTable * Table; bool *active = new bool[MyClass->ComponentCount];//在动态数组中存放每个表的初始状态，然后关闭所有的表 for(i = 0; i < MyClass->ComponentCount; i++) { try { if((Table = dynamic_cast(MyClass->Components[i])) != NULL) { active[i] = Table->Active; Table->Active = false; } } catch(...) {}; file://异常应该只来自于dynamic cast... } for(i = 0; i < MyClass->ComponentCount; i++) { try { if((Table = dynamic_cast(MyClass->Components[i])) != NULL) { if(Table->DatabaseName != OPTARDatabase->DatabaseName) continue; DBIResult result = DBIERR_NONE + 1; while(result != DBIERR_NONE) file://若希望的话，这样允许用户重试！ { result = DbiPackTable (OPTARDatabase->Handle,NULL,Table->TableName.c_str(),NULL, true); if(result != DBIERR_NONE) { AnsiString rsltText = "Unable to pack " + Table->TableName + "." ; char rslt[DBIMAXMSGLEN + 1]; DbiGetErrorString(result, rslt) rsltText += ". Try again?"; if(Application->MessageBox(rsltText.c_str(), "Error!",MB_YESNO) != IDYES) break; } } } } catch (...) {}; file://异常应该只来自于dynamic cast... } // 将所有的表设回初始状态。 for(i = 0; i < MyClass->ComponentCount; i++) { try { if((Table = dynamic_cast(MyClass->Components[i])) != NULL) Table->Active = active[i]; } catch(...) {}; } delete []active; } BACK 改变PageControl的标签 void __fastcall TfmMainForm::Cancel1Click(TObject *Sender) { int i; switch (PageControl1->ActivePage->Tag)) { case 1: for (i=0; i < ComponentCount; i++) { if (dynamic_cast(Components[i])) dynamic_cast(Components[i])->Enabled = false; } Data->tbDetail->Cancel(); break; case 2: for (i=0; i < ComponentCount; i++) { if (dynamic_cast(Components[i])) dynamic_cast(Components[i])->Enabled = false; } Data->tbDetail->Cancel(); break; case 3: for (i=0; i < ComponentCount; i++) { if (dynamic_cast(Components[i])) dynamic_cast(Components[i])->Text = ""; } break; } } BACK 向Query传递参数 // 直接从表向Query传递参数的一种方法 TQuery *Query = new TQuery(this); Query->DatabaseName = "dbServer"; Query->SQL->Clear(); Query->SQL->Add("DELETE FROM 'Events.DB' WHERE (TicketNo = " + Data->tbProblem->FieldByName("TicketNo")->AsString + ")" ); Query->ExecSQL(); Query->Close(); delete Query; BACK 日期属性 TMaskEdit *meOpen; TLabel *lbCount1; TDateTime Date2; void __fastcall TfmMainForm::CountOpen(TObject *Sender) { switch(dynamic_cast<TComponent&>(*Sender).Tag) { case 1: count1 = StrToInt(lbCount1->Caption); count1 += 1; Date2 = Now() + count1; meOpen->Text = Date2.DateString(); lbCount1->Caption = IntToStr(count1); break; case 2: count1 = StrToInt(lbCount1->Caption); count1 -= 1; Date2 = Now() + count1; meOpen->Text = Date2.DateString(); lbCount1->Caption = IntToStr(count1); break; } } BACK 绘制状态条 void __fastcall TForm1::StatusBar1DrawPanel(TStatusBar *StatusBar, TStatusPanel *Panel, const TRect &Rect) { TCanvas& c = *StatusBar->Canvas; switch (Panel->Index) { case 0 : { StatusBar1->Panels->Items[0]->Text = "Hello C++"; c.Brush->Style = bsClear; TRect temp = Rect; temp.Top += 1; temp.Left += 1; c.Font->Color = clWhite; DrawText(c.Handle, Panel->Text.c_str(), -1,(RECT*)&temp, DT_SINGLELINE | DT_CENTER); c.Font->Color = clBlack; DrawText(c.Handle, Panel->Text.c_str(), -1, (RECT*)&Rect, DT_SINGLELINE | DT_CENTER); break; } case 1: { c.Brush->Color = clYellow; c.FillRect(Rect); c.Font->Color = clRed; DrawText(c.Handle,"clYellow Color", -1, (RECT*)&Rect, DT_SINGLELINE | DT_CENTER); break; } case 2: { Graphics::TBitmap* bm = new Graphics::TBitmap; bm->Handle = LoadBitmap(NULL, MAKEINTRESOURCE(32760)); c.Draw(Rect.Left, Rect.Top, bm); delete bm; break; } } } BACK
