What signal is raised by QLineEdit when you click on the 'clearButton'?

[Dougf9]

Using Qt 5.12 on Windows 10
I have a QLineEdit widget with setClearButtonEnabled(true).
I want to do something when the user clicks on the clear button. I can find nothing in the documents about a signal. I see there is a reference to a QAction, so I added one to capture the triggered signal, but none came.

There is a signal textChanged which probably gets sent but I only want the act on 'returnPressed", not a keystroke. How can I capture clearButton pressed?

[J.Hilk]

hi @dougf9 and welcome

I can find nothing in the documents about a signal. I see there is a reference to a QAction, so I added one to capture the triggered signal, but none came.

How did you do that exactly, because from what I can see, a QAction is added automatically by the setClearButtonEnabled

I'm not quite sure, how you would explicitly search/get the auto created QAction. but until someone else suggest something different, this could work:

auto list = myLineEdit->findChildren();
for(QObject *obj : list){
     QAction *a = qobject_cast<QAction*>(obj);
     if(a){
        your connect goes here, not sure if there are other QActions already on the QLineEdit or not. Some more testing required I guess.
     }
}

[Dougf9]

Thanks for the suggestion. I coded this:

auto list = m_search->children();  //  findChildren();
qDebug() << "LE list size:" << list.size();
for(QObject *obj : list)
{
    QAction *a = qobject_cast<QAction*>(obj);
    qDebug() << "LE child: obj/a" << obj << a;
    if (a)
    {
        //your connect goes here, not sure if there are other QActions already on the QLineEdit or not. Some more testing required I guess.
        connect(a, &QAction::triggered,
                [this]()
        {
            qDebug()<<"LE triggered  .text:" << m_search->text();
            m_search->setText(tr(""));
            emit m_search->returnPressed();;
        });
        break;
    }
}

When I ran it, here is the debug output:

LE list size: 3
LE child: obj/a QWidgetLineControl(0x207691e05f0) QAction(0x00)
LE child: obj/a QAction(0x2076920ebd0, name = "_q_qlineeditclearaction") QAction(0x2076920ebd0 text="" menuRole=TextHeuristicRole visible=true)
LE child: obj/a QLineEditIconButton(0x20768e447d0) QAction(0x00)

When the action is triggered, the text() is unchanged (much surprise!). So I cleared it and generated the returnPressed() signal. That worked like a charm!

However did you know to look for actions? Did you write the Qt code? Why did they provide a button to push and no (obvious) was to capture the button press?

Please close this issue as SOLVED. Thanks!

[Pablo J. Rogina]

@dougf9 said in What signal is raised by QLineEdit when you click on the 'clearButton'?:

Please close this issue as SOLVED. Thanks!

You need to do that please. Thanks.

[Cobra91151]

@J-Hilk

Hello!

I came across this thread to find a better solution to clearBtn click event. Previously, I used textChanged signal and check if data is empty to execute my code. Your code works well but I have changed it. Instead of qobject_cast I find only QAction.

Code Example 1:

  QList<QAction*> actionList = myLineEdit->findChildren<QAction*>();

   for (QAction *clearBtnAction : actionList) {
        if (clearBtnAction) {
            connect(clearBtnAction, &QAction::triggered, this, [this]() {
                qDebug() << "Clicked!";
            });
        }
   }

My code works, but it is still a bit odd. Since, I have checked the actionList.count(); and it returns only 1 item in the list. Here is my second code example.

Code Example 2:

QList<QAction*> actionList = myLineEdit->findChildren<QAction*>();

if (!actionList.isEmpty()) {
    connect(actionList.first(), &QAction::triggered, this, [this]() {
	qDebug() << "Clicked!";
    });
}

So, in my second example, it only takes the 1st item from the list and no need to set for loop anymore. Happy coding!

[J.Hilk]

@Cobra91151 probably the better solution :D

however, I would advice to firstly check if the returned list has an entry. If (for what ever reason) it doesn't, your program will crash on the call to first()

[Cobra91151]

@J-Hilk

Yes, you are right. I changed the Code Example 2. Now, it checks if the actionList has an entry. Thanks.