Symbian开发笔记(一)

CTest_1AppUi::HandleCommandL(TInt aCommand)     {     switch ( aCommand )         {         case EAknSoftkeyBack:         case EEikCmdExit:             {                           _LIT(KQueryDelete,"Are you sure to delete it?");                           CAknQueryDialog* dlg = new(ELeave) CAknQueryDialog(const_cast<TDesC&>(KQueryDelete()),CAknQueryDialog::EWarningTone);                           dlg->ExecuteLD(R_DIALOG_DELETE_QUERY);                           break;             }         case ETest_1CmdAppTest:             {                           // Info message shown only in the emulator                           iEikonEnv->InfoMsg(_L("test"));                               // Load localized message from the resource file                           HBufC* message = CEikonEnv::Static()->AllocReadResourceLC(R_MESSAGE_TEXT);                                                     // Show information note dialog                          CAknInformationNote* note = new (ELeave) CAknInformationNote;                          note->ExecuteLD(message->Des());                          CleanupStack::PopAndDestroy(message);                          break;             }         // TODO: Add Your command handling code here         default:             break;              }  这里面有几个知识点: 1:_LIT()宏所定义的常量并不是描述符,但可以通过使用一个重载的运算符()将其转换为const TDesC&类型的描述符。 2:CAknQueryDialog的第一个参数需要一个TDesC&类型的参数,所以我们需要把KQueryDelete()强制转换成非const类型的,这需要使用C++中的强制类型转换const_cast<TDesC&>。 3:千万注意要把const_cast<TDesC&>所接的数据加上()。

void CTest_1AppUi::HandleCommandL(TInt aCommand)     {     switch ( aCommand )         {         case EAknSoftkeyBack:         case EEikCmdExit:             {                   _LIT(KQueryDelete,"Are you sure to delete it?");                   CAknQueryDialog* dlg = new(ELeave) CAknQueryDialog(const_cast<TDesC&>(KQueryDelete()),CAknQueryDialog::EWarningTone);                   TInt temp = dlg->ExecuteLD(R_DIALOG_DELETE_QUERY);                   _LIT(KReturnValue,"the return value is :");                   HBufC* iBuf = HBufC::NewLC(100);                   iBuf->Des().Copy(KReturnValue);                   iBuf->Des().AppendNum(temp);                   CEikonEnv::Static()->InfoMsg(*iBuf);                   CleanupStack::PopAndDestroy(iBuf);                   break;             }         default:             break;              }     }            从程序执行中我们可以看到,当我们点dlg的NO按钮时,temp的值为一个正数(程序中是3005),而当我们点dlg 的OK的时候,temp的值为0。            所以我们在很多程序中可以看到类似下面的代码: if(dlg->ExecuteLD(R_DIALOG_DELETE_QUERY))     {         TInt index = iListBox->CurrentItemIndex();         TName name(db.iName);         iUi->iDB->iArrayDB->Delete(index);         iUi->iDB->SaveDBL();         CEikonEnv::Static()->ReadResource(info, R_STR_DELETE_TIPS);         tips.Format(info, &name);         ShowNotify(tips);         if(iUi->iDB->iArrayDB->Count()==0)         {             CEikonEnv::Static()->ReadResource(info, R_STR_NO_CD_TIPS);             ShowNotify(info);             CreateFunctionListBoxL();         }         else         {             CreateRecordListBoxL();         }     } 也就是判断我们是否点击了Dialog的OK按钮。

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