Symbian开发笔记(一)

<iframe align="center" marginwidth="0" marginheight="0" src="http://www.zealware.com/csdnblog336280.html" frameborder="0" width="336" scrolling="no" height="280"></iframe>

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>(</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>。</tdesc>

3:千万注意要把const_cast<tdesc>所接的数据加上()。</tdesc>

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);</tdesc>

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。