- Qt 5.15
- Qt Widgets
- C++ Classes
- QStackedLayout
- Qt 5.15.19 Reference Documentation

# QStackedLayout Class

The QStackedLayout class provides a stack of widgets where only one widget is visible at a time. More...

Header: | #include <QStackedLayout>
qmake: | QT += widgets
Inherits: | QLayout

- List of all members, including inherited members

## Public Types

enum | StackingMode { StackOne, StackAll }

## Properties

- count : const int
- currentIndex : int
- stackingMode : StackingMode

## Public Functions

| QStackedLayout(QLayout *parentLayout)
| QStackedLayout(QWidget *parent)
| QStackedLayout()
virtual | ~QStackedLayout()
int | addWidget(QWidget *widget)
int | currentIndex() const
QWidget * | currentWidget() const
int | insertWidget(int index, QWidget *widget)
void | setStackingMode(StackingMode stackingMode)
StackingMode | stackingMode() const
QWidget * | widget(int index) const

## Reimplemented Public Functions

virtual void | addItem(QLayoutItem *item) override
virtual int | count() const override
virtual bool | hasHeightForWidth() const override
virtual int | heightForWidth(int width) const override
virtual QLayoutItem * | itemAt(int index) const override
virtual QSize | minimumSize() const override
virtual void | setGeometry(const QRect &rect) override
virtual QSize | sizeHint() const override
virtual QLayoutItem * | takeAt(int index) override

## Public Slots

void | setCurrentIndex(int index)
void | setCurrentWidget(QWidget *widget)

## Signals

void | currentChanged(int index)
void | widgetRemoved(int index)

## Detailed Description

QStackedLayout can be used to create a user interface similar to the one provided by QTabWidget. There is also a convenience QStackedWidget class built on top of QStackedLayout.

A QStackedLayout can be populated with a number of child widgets ("pages"). For example:

         QWidget *firstPageWidget = new QWidget;
         QWidget *secondPageWidget = new QWidget;
         QWidget *thirdPageWidget = new QWidget;

         QStackedLayout *stackedLayout = new QStackedLayout;
         stackedLayout->addWidget(firstPageWidget);
         stackedLayout->addWidget(secondPageWidget);
         stackedLayout->addWidget(thirdPageWidget);

         QVBoxLayout *mainLayout = new QVBoxLayout;
         mainLayout->addLayout(stackedLayout);
         setLayout(mainLayout);

QStackedLayout provides no intrinsic means for the user to switch page. This is typically done through a QComboBox or a QListWidget that stores the titles of the QStackedLayout's pages. For example:

         QComboBox *pageComboBox = new QComboBox;
         pageComboBox->addItem(tr("Page 1"));
         pageComboBox->addItem(tr("Page 2"));
         pageComboBox->addItem(tr("Page 3"));
         connect(pageComboBox, QOverload<int>::of(&QComboBox::activated),
                 stackedLayout, &QStackedLayout::setCurrentIndex);

When populating a layout, the widgets are added to an internal list. The indexOf() function returns the index of a widget in that list. The widgets can either be added to the end of the list using the addWidget() function, or inserted at a given index using the insertWidget() function. The removeWidget() function removes the widget at the given index from the layout. The number of widgets contained in the layout, can be obtained using the count() function.

The widget() function returns the widget at a given index position. The index of the widget that is shown on screen is given by currentIndex() and can be changed using setCurrentIndex(). In a similar manner, the currently shown widget can be retrieved using the currentWidget() function, and altered using the setCurrentWidget() function.

Whenever the current widget in the layout changes or a widget is removed from the layout, the currentChanged() and widgetRemoved() signals are emitted respectively.

See also QStackedWidget and QTabWidget.

## Member Type Documentation

### enum QStackedLayout::StackingMode

This enum specifies how the layout handles its child widgets regarding their visibility.

Constant | Value | Description
--- | --- | ---
`QStackedLayout::StackOne` | `0` | Only the current widget is visible. This is the default.
`QStackedLayout::StackAll` | `1` | All widgets are visible. The current widget is merely raised.

This enum was introduced or modified in Qt 4.4.

## Property Documentation

### count : const int

This property holds the number of widgets contained in the layout

Access functions:

virtual int | count() const override

See also currentIndex() and widget().

### currentIndex : int

This property holds the index position of the widget that is visible

The current index is -1 if there is no current widget.

Access functions:

int | currentIndex() const
void | setCurrentIndex(int index)

Notifier signal:

void | currentChanged(int index)

See also currentWidget() and indexOf().

### stackingMode : StackingMode

determines the way visibility of child widgets are handled.

The default value is StackOne. Setting the property to StackAll allows you to make use of the layout for overlay widgets that do additional drawing on top of other widgets, for example, graphical editors.

This property was introduced in Qt 4.4.

Access functions:

StackingMode | stackingMode() const
void | setStackingMode(StackingMode stackingMode)

## Member Function Documentation

### QStackedLayout::QStackedLayout(QLayout *parentLayout)

Constructs a new QStackedLayout and inserts it into the given parentLayout.

### QStackedLayout::QStackedLayout(QWidget *parent)

Constructs a new QStackedLayout with the given parent.

This layout will install itself on the parent widget and manage the geometry of its children.

### QStackedLayout::QStackedLayout()

Constructs a QStackedLayout with no parent.

This QStackedLayout must be installed on a widget later on to become effective.

See also addWidget() and insertWidget().

### `[signal]` void QStackedLayout::currentChanged(int index)

This signal is emitted whenever the current widget in the layout changes. The index specifies the index of the new current widget, or -1 if there isn't a new one (for example, if there are no widgets in the QStackedLayout)

Note: Notifier signal for property currentIndex.

See also currentWidget() and setCurrentWidget().

### `[slot]` void QStackedLayout::setCurrentWidget(QWidget *widget)

Sets the current widget to be the specified widget. The new current widget must already be contained in this stacked layout.

See also setCurrentIndex() and currentWidget().

### `[signal]` void QStackedLayout::widgetRemoved(int index)

This signal is emitted whenever a widget is removed from the layout. The widget's index is passed as parameter.

See also removeWidget().

### `[virtual]` QStackedLayout::~QStackedLayout()

Destroys this QStackedLayout. Note that the layout's widgets are not destroyed.

### `[override virtual]` void QStackedLayout::addItem(QLayoutItem *item)

Reimplements: QLayout::addItem(QLayoutItem *item).

### int QStackedLayout::addWidget(QWidget *widget)

Adds the given widget to the end of this layout and returns the index position of the widget.

If the QStackedLayout is empty before this function is called, the given widget becomes the current widget.

See also insertWidget(), removeWidget(), and setCurrentWidget().

### QWidget *QStackedLayout::currentWidget() const

Returns the current widget, or `nullptr` if there are no widgets in this layout.

See also currentIndex() and setCurrentWidget().

### `[override virtual]` bool QStackedLayout::hasHeightForWidth() const

Reimplements: QLayoutItem::hasHeightForWidth() const.

### `[override virtual]` int QStackedLayout::heightForWidth(int width) const

Reimplements: QLayoutItem::heightForWidth(int ) const.

### int QStackedLayout::insertWidget(int index, QWidget *widget)

Inserts the given widget at the given index in this QStackedLayout. If index is out of range, the widget is appended (in which case it is the actual index of the widget that is returned).

If the QStackedLayout is empty before this function is called, the given widget becomes the current widget.

Inserting a new widget at an index less than or equal to the current index will increment the current index, but keep the current widget.

See also addWidget(), removeWidget(), and setCurrentWidget().

### `[override virtual]` QLayoutItem *QStackedLayout::itemAt(int index) const

Reimplements: QLayout::itemAt(int index) const.

### `[override virtual]` QSize QStackedLayout::minimumSize() const

Reimplements: QLayout::minimumSize() const.

### `[override virtual]` void QStackedLayout::setGeometry(const QRect &rect)

Reimplements: QLayout::setGeometry(const QRect &r).

### `[override virtual]` QSize QStackedLayout::sizeHint() const

Reimplements: QLayoutItem::sizeHint() const.

### `[override virtual]` QLayoutItem *QStackedLayout::takeAt(int index)

Reimplements: QLayout::takeAt(int index).

### QWidget *QStackedLayout::widget(int index) const

Returns the widget at the given index, or `nullptr` if there is no widget at the given position.

See also currentWidget() and indexOf().