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QTreeView Class Reference
[QtGui module]

The QTreeView class provides a default model/view implementation of a tree view. More...

 #include <QTreeView>

Inherits QAbstractItemView.

Inherited by QHelpContentWidget and QTreeWidget.

Properties

Public Functions

Public Slots

Signals

Protected Functions

Protected Slots

Additional Inherited Members


Detailed Description

The QTreeView class provides a default model/view implementation of a tree view.

A QTreeView implements a tree representation of items from a model. This class is used to provide standard hierarchical lists that were previously provided by the QListView class, but using the more flexible approach provided by Qt's model/view architecture.

The QTreeView class is one of the Model/View Classes and is part of Qt's model/view framework.

QTreeView implements the interfaces defined by the QAbstractItemView class to allow it to display data provided by models derived from the QAbstractItemModel class.

It is simple to construct a tree view displaying data from a model. In the following example, the contents of a directory are supplied by a QDirModel and displayed as a tree:

     QDirModel *model = new QDirModel;
     QTreeView *tree = new QTreeView(splitter);
     tree->setModel(model);

The model/view architecture ensures that the contents of the tree view are updated as the model changes.

Items that have children can be in an expanded (children are visible) or collapsed (children are hidden) state. When this state changes a collapsed() or expanded() signal is emitted with the model index of the relevant item.

The amount of indentation used to indicate levels of hierarchy is controlled by the indentation property.

Headers in tree views are constructed using the QHeaderView class and can be hidden using header()->hide(). Note that each header is configured with its stretchLastSection property set to true, ensuring that the view does not waste any of the space assigned to it for its header. If this value is set to true, this property will override the resize mode set on the last section in the header.

Key Bindings

QTreeView supports a set of key bindings that enable the user to navigate in the view and interact with the contents of items:

KeyAction
UpMoves the cursor to the item in the same column on the previous row. If the parent of the current item has no more rows to navigate to, the cursor moves to the relevant item in the last row of the sibling that precedes the parent.
DownMoves the cursor to the item in the same column on the next row. If the parent of the current item has no more rows to navigate to, the cursor moves to the relevant item in the first row of the sibling that follows the parent.
LeftHides the children of the current item (if present) by collapsing a branch.
MinusSame as LeftArrow.
RightReveals the children of the current item (if present) by expanding a branch.
PlusSame as RightArrow.
AsteriskExpands all children of the current item (if present).
PageUpMoves the cursor up one page.
PageDownMoves the cursor down one page.
HomeMoves the cursor to an item in the same column of the first row of the first top-level item in the model.
EndMoves the cursor to an item in the same column of the last row of the last top-level item in the model.
F2In editable models, this opens the current item for editing. The Escape key can be used to cancel the editing process and revert any changes to the data displayed.

Screenshot of a Windows XP style tree viewScreenshot of a Macintosh style tree viewScreenshot of a Plastique style tree view
A Windows XP style tree view.A Macintosh style tree view.A Plastique style tree view.

Improving Performance

It is possible to give the view hints about the data it is handling in order to improve its performance when displaying large numbers of items. One approach that can be taken for views that are intended to display items with equal heights is to set the uniformRowHeights property to true.

See also QListView, QTreeWidget, View Classes, QAbstractItemModel, QAbstractItemView, and Dir View Example.


Property Documentation

allColumnsShowFocus : bool

This property holds whether items should show keyboard focus using all columns.

If this property is true all columns will show focus, otherwise only one column will show focus.

The default is false.

This property was introduced in Qt 4.2.

Access functions:

animated : bool

This property holds whether animations are enabled.

If this property is true the treeview will animate expandsion and collasping of branches. If this property is false, the treeview will expand or collapse branches immediately without showing the animation.

By default, this property is false.

This property was introduced in Qt 4.2.

Access functions:

autoExpandDelay : int

This property holds the delay time before items in a tree are opened during a drag and drop operation.

This property holds the amount of time in milliseconds that the user must wait over a node before that node will automatically open or close. If the time is set to less then 0 then it will not be activated.

By default, this property has a value of -1, meaning that auto-expansion is disabled.

This property was introduced in Qt 4.3.

Access functions:

expandsOnDoubleClick : bool

This property holds whether the items can be expanded by double-clicking.

This property holds whether the user can expand and collapse items by double-clicking. The default value is true.

This property was introduced in Qt 4.4.

Access functions:

See also itemsExpandable.

headerHidden : bool

This property holds whether the header is shown or not.

If this property is true, the header is not shown otherwise it is. The default value is false.

This property was introduced in Qt 4.4.

Access functions:

See also header().

indentation : int

This property holds indentation of the items in the tree view.

This property holds the indentation measured in pixels of the items for each level in the tree view. For top-level items, the indentation specifies the horizontal distance from the viewport edge to the items in the first column; for child items, it specifies their indentation from their parent items.

By default, this property has a value of 20.

Access functions:

itemsExpandable : bool

This property holds whether the items are expandable by the user.

This property holds whether the user can expand and collapse items interactively.

By default, this property is true.

Access functions:

rootIsDecorated : bool

This property holds whether to show controls for expanding and collapsing top-level items.

Items with children are typically shown with controls to expand and collapse them, allowing their children to be shown or hidden. If this property is false, these controls are not shown for top-level items. This can be used to make a single level tree structure appear like a simple list of items.

By default, this property is true.

Access functions:

sortingEnabled : bool

This property holds whether sorting is enabled.

If this property is true, sorting is enabled for the tree; if the property is false, sorting is not enabled. The default value is false.

Note: In order to avoid performance issues, it is recommended that sorting is enabled after inserting the items into the tree. Alternatively, you could also insert the items into a list before inserting the items into the tree.

This property was introduced in Qt 4.2.

Access functions:

See also sortByColumn().

uniformRowHeights : bool

This property holds whether all items in the treeview have the same height.

This property should only be set to true if it is guaranteed that all items in the view has the same height. This enables the view to do some optimizations.

The height is obtained from the first item in the view. It is updated when the data changes on that item.

By default, this property is false.

Access functions:

wordWrap : bool

This property holds the item text word-wrapping policy.

If this property is true then the item text is wrapped where necessary at word-breaks; otherwise it is not wrapped at all. This property is false by default.

Note that even if wrapping is enabled, the cell will not be expanded to fit all text. Ellipsis will be inserted according to the current textElideMode.

This property was introduced in Qt 4.3.

Access functions:


Member Function Documentation

QTreeView::QTreeView ( QWidget * parent = 0 )

Constructs a table view with a parent to represent a model's data. Use setModel() to set the model.

See also QAbstractItemModel.

QTreeView::~QTreeView ()

Destroys the tree view.

void QTreeView::collapse ( const QModelIndex & index )   [slot]

Collapses the model item specified by the index.

See also collapsed().

void QTreeView::collapseAll ()   [slot]

Collapses all expanded items.

This function was introduced in Qt 4.2.

See also expandAll(), expand(), collapse(), and setExpanded().

void QTreeView::collapsed ( const QModelIndex & index )   [signal]

This signal is emitted when the item specified by index is collapsed.

int QTreeView::columnAt ( int x ) const

Returns the column in the tree view whose header covers the x coordinate given.

void QTreeView::columnCountChanged ( int oldCount, int newCount )   [protected slot]

Informs the tree view that the number of columns in the tree view has changed from oldCount to newCount.

void QTreeView::columnMoved ()   [protected slot]

This slot is called whenever a column has been moved.

void QTreeView::columnResized ( int column, int oldSize, int newSize )   [protected slot]

This function is called whenever column's size is changed in the header. oldSize and newSize give the previous size and the new size in pixels.

See also setColumnWidth().

int QTreeView::columnViewportPosition ( int column ) const

Returns the horizontal position of the column in the viewport.

int QTreeView::columnWidth ( int column ) const

Returns the width of the column.

See also resizeColumnToContents() and setColumnWidth().

void QTreeView::drawBranches ( QPainter * painter, const QRect & rect, const QModelIndex & index ) const   [virtual protected]

Draws the branches in the tree view on the same row as the model item index, using the painter given. The branches are drawn in the rectangle specified by rect.

void QTreeView::drawRow ( QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const   [virtual protected]

Draws the row in the tree view that contains the model item index, using the painter given. The option control how the item is displayed.

See also setAlternatingRowColors().

void QTreeView::drawTree ( QPainter * painter, const QRegion & region ) const   [protected]

Draws the part of the tree intersecting the given region using the specified painter.

This function was introduced in Qt 4.2.

See also paintEvent().

void QTreeView::expand ( const QModelIndex & index )   [slot]

Expands the model item specified by the index.

See also expanded().

void QTreeView::expandAll ()   [slot]

Expands all expandable items.

Warning: if the model contains a large number of items, this function will take some time to execute.

This function was introduced in Qt 4.2.

See also collapseAll(), expand(), collapse(), and setExpanded().

void QTreeView::expandToDepth ( int depth )   [slot]

Expands all expandable items to the given depth.

This function was introduced in Qt 4.3.

See also expandAll(), collapseAll(), expand(), collapse(), and setExpanded().

void QTreeView::expanded ( const QModelIndex & index )   [signal]

This signal is emitted when the item specified by index is expanded.

See also setExpanded().

QHeaderView * QTreeView::header () const

Returns the header for the tree view.

See also setHeader() and QAbstractItemModel::headerData().

void QTreeView::hideColumn ( int column )   [slot]

Hides the column given.

Note: This function should only be called after the model has been initialized, as the view needs to know the number of columns in order to hide column.

See also showColumn() and setColumnHidden().

int QTreeView::horizontalOffset () const   [virtual protected]

Returns the horizontal offset of the items in the treeview.

Note that the tree view uses the horizontal header section positions to determine the positions of columns in the view.

Reimplemented from QAbstractItemView.

See also verticalOffset().

QModelIndex QTreeView::indexAbove ( const QModelIndex & index ) const

Returns the model index of the item above index.

QModelIndex QTreeView::indexBelow ( const QModelIndex & index ) const

Returns the model index of the item below index.

int QTreeView::indexRowSizeHint ( const QModelIndex & index ) const   [protected]

Returns the size hint for the row indicated by index.

See also sizeHintForColumn() and uniformRowHeights().

bool QTreeView::isColumnHidden ( int column ) const

Returns true if the column is hidden; otherwise returns false.

See also hideColumn() and isRowHidden().

bool QTreeView::isExpanded ( const QModelIndex & index ) const

Returns true if the model item index is expanded; otherwise returns false.

See also expand(), expanded(), and setExpanded().

bool QTreeView::isFirstColumnSpanned ( int row, const QModelIndex & parent ) const

Returns true if the item in first column in the given row of the parent is spanning all the columns; otherwise returns false.

This function was introduced in Qt 4.3.

See also setFirstColumnSpanned().

bool QTreeView::isRowHidden ( int row, const QModelIndex & parent ) const

Returns true if the item in the given row of the parent is hidden; otherwise returns false.

See also setRowHidden() and isColumnHidden().

QModelIndex QTreeView::moveCursor ( CursorAction cursorAction, Qt::KeyboardModifiers modifiers )   [virtual protected]

Move the cursor in the way described by cursorAction, using the information provided by the button modifiers.

Reimplemented from QAbstractItemView.

void QTreeView::resizeColumnToContents ( int column )   [slot]

Resizes the column given to the size of its contents.

See also columnWidth() and setColumnWidth().

int QTreeView::rowHeight ( const QModelIndex & index ) const   [protected]

Returns the height of the row indicated by the given index.

This function was introduced in Qt 4.3.

See also indexRowSizeHint().

void QTreeView::rowsAboutToBeRemoved ( const QModelIndex & parent, int start, int end )   [virtual protected]

Informs the view that the rows from the start row to the end row inclusive are about to removed from the given parent model item.

Reimplemented from QAbstractItemView.

void QTreeView::rowsInserted ( const QModelIndex & parent, int start, int end )   [virtual protected]

Informs the view that the rows from the start row to the end row inclusive have been inserted into the parent model item.

Reimplemented from QAbstractItemView.

void QTreeView::rowsRemoved ( const QModelIndex & parent, int start, int end )   [protected slot]

Informs the view that the rows from the start row to the end row inclusive have been removed from the given parent model item.

This function was introduced in Qt 4.1.

void QTreeView::scrollContentsBy ( int dx, int dy )   [virtual protected]

Scrolls the contents of the tree view by (dx, dy).

Reimplemented from QAbstractScrollArea.

void QTreeView::scrollTo ( const QModelIndex & index, ScrollHint hint = EnsureVisible )   [virtual]

Scroll the contents of the tree view until the given model item index is visible. The hint parameter specifies more precisely where the item should be located after the operation. If any of the parents of the model item are collapsed, they will be expanded to ensure that the model item is visible.

Reimplemented from QAbstractItemView.

void QTreeView::setColumnHidden ( int column, bool hide )

If hide is true the column is hidden, otherwise the column is shown.

See also isColumnHidden(), hideColumn(), and setRowHidden().

void QTreeView::setColumnWidth ( int column, int width )

Sets the width of the given column to the width specified.

This function was introduced in Qt 4.2.

See also columnWidth() and resizeColumnToContents().

void QTreeView::setExpanded ( const QModelIndex & index, bool expanded )

Sets the item referred to by index to either collapse or expanded, depending on the value of expanded.

See also expanded(), expand(), and isExpanded().

void QTreeView::setFirstColumnSpanned ( int row, const QModelIndex & parent, bool span )

If span is true the item in the first column in the row with the given parent is set to span all columns, otherwise all items on the row are shown.

This function was introduced in Qt 4.3.

See also isFirstColumnSpanned().

void QTreeView::setHeader ( QHeaderView * header )

Sets the header for the tree view, to the given header.

The view takes ownership over the given header and deletes it when a new header is set.

See also QAbstractItemModel::headerData().

void QTreeView::setRowHidden ( int row, const QModelIndex & parent, bool hide )

If hide is true the row with the given parent is hidden, otherwise the row is shown.

See also isRowHidden() and setColumnHidden().

void QTreeView::setSelection ( const QRect & rect, QItemSelectionModel::SelectionFlags command )   [virtual protected]

Applies the selection command to the items in or touched by the rectangle, rect.

Reimplemented from QAbstractItemView.

See also selectionCommand().

void QTreeView::showColumn ( int column )   [slot]

Shows the given column in the tree view.

See also hideColumn() and setColumnHidden().

int QTreeView::sizeHintForColumn ( int column ) const   [virtual protected]

Returns the size hint for the column's width or -1 if there is no model.

If you need to set the width of a given column to a fixed value, call QHeaderView::resizeSection() on the view's header.

If you reimplement this function in a subclass, note that the value you return is only used when resizeColumnToContents() is called. In that case, if a larger column width is required by either the view's header or the item delegate, that width will be used instead.

Reimplemented from QAbstractItemView.

See also QWidget::sizeHint and header().

void QTreeView::sortByColumn ( int column, Qt::SortOrder order )

Sets the model up for sorting by the values in the given column and order.

column may be -1, in which case no sort indicator will be shown and the model will return to its natural, unsorted order. Note that not all models support this and may even crash in this case.

This function was introduced in Qt 4.2.

See also sortingEnabled.

int QTreeView::verticalOffset () const   [virtual protected]

Returns the vertical offset of the items in the tree view.

Reimplemented from QAbstractItemView.

See also horizontalOffset().

QRect QTreeView::visualRect ( const QModelIndex & index ) const   [virtual]

Returns the rectangle on the viewport occupied by the item at index. If the index is not visible or explicitly hidden, the returned rectangle is invalid.

Reimplemented from QAbstractItemView.

QRegion QTreeView::visualRegionForSelection ( const QItemSelection & selection ) const   [virtual protected]

Returns the rectangle from the viewport of the items in the given selection.

Reimplemented from QAbstractItemView.


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