61

What would be the best way of selecting an item in a QT combo box out of a predefined list of enum based unique values.

In the past I have become accustomed to .NET's style of selection where the item can be selected by setting the selected property to the item's value you wish to select:

cboExample.SelectedValue = 2;

Is there anyway to do this with QT based on the item's data, if the data is a C++ enumeration?

Mohammad Kanan
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cweston
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3 Answers3

124

You lookup the value of the data with findData() and then use setCurrentIndex()

QComboBox* combo = new QComboBox;
combo->addItem("100",100.0);    // 2nd parameter can be any Qt type
combo->addItem .....

float value=100.0;
int index = combo->findData(value);
if ( index != -1 ) { // -1 for not found
   combo->setCurrentIndex(index);
}
AAEM
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Martin Beckett
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28

You can also have a look at the method findText(const QString & text) from QComboBox; it returns the index of the element which contains the given text, (-1 if not found). The advantage of using this method is that you don't need to set the second parameter when you add an item.

Here is a little example :

/* Create the comboBox */
QComboBox   *_comboBox = new QComboBox;

/* Create the ComboBox elements list (here we use QString) */
QList<QString> stringsList;
stringsList.append("Text1");
stringsList.append("Text3");
stringsList.append("Text4");
stringsList.append("Text2");
stringsList.append("Text5");

/* Populate the comboBox */
_comboBox->addItems(stringsList);

/* Create the label */
QLabel *label = new QLabel;

/* Search for "Text2" text */
int index = _comboBox->findText("Text2");
if( index == -1 )
    label->setText("Text2 not found !");
else
    label->setText(QString("Text2's index is ")
                   .append(QString::number(_comboBox->findText("Text2"))));

/* setup layout */
QVBoxLayout *layout = new QVBoxLayout(this);
layout->addWidget(_comboBox);
layout->addWidget(label);
Aloïké
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  • Using findText() is never good. findData() should be the preferred way. – hfrmobile Mar 07 '17 at 13:11
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    Your statement is contradictory. I agree that findData should be the "preferred" way, but not the only way. I'm writing logic for an existing system that sometimes creates "simple" combobox content with null data values. So usually findData is sufficient, but sometimes you need findText when there's no "data" to find. – TheGerm Jun 13 '17 at 22:14
11

If you know the text in the combo box that you want to select, just use the setCurrentText() method to select that item.

ui->comboBox->setCurrentText("choice 2");

From the Qt 5.7 documentation

The setter setCurrentText() simply calls setEditText() if the combo box is editable. Otherwise, if there is a matching text in the list, currentIndex is set to the corresponding index.

So as long as the combo box is not editable, the text specified in the function call will be selected in the combo box.

Reference: http://doc.qt.io/qt-5/qcombobox.html#currentText-prop

DowntownDev
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