QCombobox信号和槽

A QComboBox is a widget in Qt that provides a dropdown menu with a list of items. Signals and slots are used in Qt for communication between objects.

A signal is emitted by an object when a particular event occurs. In the case of QComboBox, it emits signals when the current item is changed, or when the user selects an item from the dropdown menu.

A slot is a function that is connected to a signal and gets executed when the signal is emitted. You can connect a slot to a signal using the QObject::connect() function.
For example, if you have a QComboBox named "comboBox", you can connect its currentIndexChanged() signal to a slot using the following syntax:

connect(comboBox, SIGNAL(currentIndexChanged(int)), this, SLOT(handleIndexChanged(int)));

In this example, the handleIndexChanged() slot will be called whenever the current item in the QComboBox changes. The int parameter passed to the slot represents the index of the new current item.

You can define the handleIndexChanged() slot in your class as follows:

void MyClass::handleIndexChanged(int index) {
    // Do something with the new index
}

By connecting signals and slots, you can easily handle user interactions with a QComboBox and perform actions based on the selected item.