Understanding QToolBox::setCurrentWidget() in Qt Widgets

Purpose

• It essentially switches between the different widgets that have been added to the QToolBox using the addItem() or insertItem() methods.
• This function is used to make a specific widget within a QToolBox the currently visible one.

Functionality

1. Input Argument
   It takes a single argument, which is a pointer to a QWidget object.
2. Widget Validation
   
   • The function first checks if the provided widget is actually an item within the QToolBox. It does this using the indexOf() method internally.
   • If the widget is not found in the tool box (i.e., indexOf() returns -1), a warning message is issued using qWarning() to indicate that you're trying to set a widget that's not part of the tool box.
3. Setting Current Widget
   
   • If the widget is valid, the function retrieves its index within the tool box.
   • It then sets the internal state of the QToolBox to display that particular widget.

Example

#include <QApplication>
#include <QToolBox>
#include <QWidget>
#include <QLabel>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);

    // Create a QToolBox
    QToolBox *toolbox = new QToolBox;

    // Create some widgets to add to the toolbox
    QWidget *widget1 = new QWidget;
    widget1->setLayout(new QVBoxLayout);
    widget1->layout()->addWidget(new QLabel("Widget 1"));

    QWidget *widget2 = new QWidget;
    widget2->setLayout(new QVBoxLayout);
    widget2->layout()->addWidget(new QLabel("Widget 2"));

    // Add the widgets to the toolbox
    toolbox->addItem(widget1, "Tab 1");
    toolbox->addItem(widget2, "Tab 2");

    // Initially, widget1 will be displayed (index 0)

    // Programmatically switch to widget2 (index 1)
    toolbox->setCurrentWidget(widget2);

    toolbox->show();

    return app.exec();
}

• The currentChanged(int index) signal is emitted whenever the current widget is changed, allowing you to connect it to custom slots for further actions.
• You can also use the currentIndex() or currentWidget() functions to get information about the currently displayed widget in the QToolBox.

---

Setting Current Widget by Index

#include <QApplication>
#include <QToolBox>
#include <QWidget>
#include <QLabel>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);

    // Create a QToolBox
    QToolBox *toolbox = new QToolBox;

    // Create some widgets
    QWidget *widget1 = new QWidget;
    widget1->setLayout(new QVBoxLayout);
    widget1->layout()->addWidget(new QLabel("Widget 1"));

    QWidget *widget2 = new QWidget;
    widget2->setLayout(new QVBoxLayout);
    widget2->layout()->addWidget(new QLabel("Widget 2"));

    // Add widgets to the toolbox
    toolbox->addItem(widget1, "Tab 1");
    toolbox->addItem(widget2, "Tab 2");

    // Set the current widget by index (0 for widget1, 1 for widget2)
    toolbox->setCurrentWidget(1);  // Display widget2

    toolbox->show();

    return app.exec();
}

#include <QApplication>
#include <QToolBox>
#include <QWidget>
#include <QLabel>

void handleCurrentWidgetChange(int index) {
    qDebug() << "Current widget changed to index:" << index;
}

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);

    // Create a QToolBox
    QToolBox *toolbox = new QToolBox;

    // Create some widgets
    QWidget *widget1 = new QWidget;
    widget1->setLayout(new QVBoxLayout);
    widget1->layout()->addWidget(new QLabel("Widget 1"));

    QWidget *widget2 = new QWidget;
    widget2->setLayout(new QVBoxLayout);
    widget2->layout()->addWidget(new QLabel("Widget 2"));

    // Add widgets and connect the currentChanged signal
    toolbox->addItem(widget1, "Tab 1");
    toolbox->addItem(widget2, "Tab 2");
    connect(toolbox, SIGNAL(currentChanged(int)), handleCurrentWidgetChange, Qt::QueuedConnection);

    // Set the initial widget
    toolbox->setCurrentWidget(widget1);

    toolbox->show();

    return app.exec();
}

---

QStackedWidget

• Unlike QToolBox, QStackedWidget doesn't provide visual tabs or labels for each widget.
• It allows you to add and remove widgets dynamically, and you can switch between them using setCurrentIndex().
• Use QStackedWidget if you need a more flexible container for managing multiple widgets.

#include <QApplication>
#include <QStackedWidget>
#include <QWidget>
#include <QLabel>

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);

    // Create a QStackedWidget
    QStackedWidget *stackedWidget = new QStackedWidget;

    // Create some widgets
    QWidget *widget1 = new QWidget;
    widget1->setLayout(new QVBoxLayout);
    widget1->layout()->addWidget(new QLabel("Widget 1"));

    QWidget *widget2 = new QWidget;
    widget2->setLayout(new QVBoxLayout);
    widget2->layout()->addWidget(new QLabel("Widget 2"));

    // Add widgets to the stacked widget
    stackedWidget->addWidget(widget1);
    stackedWidget->addWidget(widget2);

    // Initially, widget1 will be displayed (index 0)

    // Switch to widget2 (index 1)
    stackedWidget->setCurrentIndex(1);

    stackedWidget->show();

    return app.exec();
}

QTabWidget

• It provides similar functionality to QToolBox but offers more flexibility in customizing tab appearance and behavior.
• If you need a tabbed interface with visual labels for each widget, use QTabWidget.

Custom Layout Management

• It requires more manual work compared to using pre-built widgets like QToolBox or QStackedWidget.
• This approach allows you to dynamically show and hide widgets based on your application logic.
• For more granular control over widget visibility, you can use a custom layout manager class.

• If you require a high degree of customization, explore QTabWidget or a custom layout manager.
• For more dynamic management of multiple widgets without tabs, QStackedWidget is suitable.
• If you need a simple tabbed interface with a fixed set of widgets, QToolBox is a good choice.