com.trolltech.qt.gui
Class QItemDelegate

java.lang.Object
  extended by com.trolltech.qt.internal.QSignalEmitterInternal
      extended by com.trolltech.qt.QSignalEmitter
          extended by com.trolltech.qt.QtJambiObject
              extended by com.trolltech.qt.core.QObject
                  extended by com.trolltech.qt.gui.QAbstractItemDelegate
                      extended by com.trolltech.qt.gui.QItemDelegate
All Implemented Interfaces:
QtJambiInterface
Direct Known Subclasses:
QSqlRelationalDelegate

public class QItemDelegate
extends QAbstractItemDelegate

The QItemDelegate class provides display and editing facilities for data items from a model. QItemDelegate can be used to provide custom display features and editor widgets for item views based on QAbstractItemView subclasses. Using a delegate for this purpose allows the display and editing mechanisms to be customized and developed independently from the model and view.

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

When displaying items from a custom model in a standard view, it is often sufficient to simply ensure that the model returns appropriate data for each of the roles that determine the appearance of items in views. The default delegate used by Qt's standard views uses this role information to display items in most of the common forms expected by users. However, it is sometimes necessary to have even more control over the appearance of items than the default delegate can provide.

This class provides default implementations of the functions for painting item data in a view and editing data from item models. Default implementations of the paint() and sizeHint() virtual functions, defined in QAbstractItemDelegate, are provided to ensure that the delegate implements the correct basic behavior expected by views. You can reimplement these functions in subclasses to customize the appearance of items.

When editing data in an item view, QItemDelegate provides an editor widget, which is a widget that is placed on top of the view while editing takes place. Editors are created with a QItemEditorFactory; a default static instance provided by QItemEditorFactory is installed on all item delagates. You can set a custom factory using setItemEditorFactory() or set a new default factory with QItemEditorFactory::setDefaultFactory(). It is the data stored in the item model with the Qt::EditRole that is edited.

Only the standard editing functions for widget-based delegates are reimplemented here:

The closeEditor() signal indicates that the user has completed editing the data, and that the editor widget can be destroyed.

Standard Roles and Data Types

The default delegate used by the standard views supplied with Qt associates each standard role (defined by
Qt::ItemDataRole ) with certain data types. Models that return data in these types can influence the appearance of the delegate as described in the following table.
Role
Accepted Types
Qt::BackgroundRole QBrush
Qt::BackgroundColorRole QColor (obsolete; use Qt::BackgroundRole instead)
Qt::CheckStateRole Qt::CheckState
Qt::DecorationRole QIcon and QColor
Qt::DisplayRole QString and types with a string representation
Qt::EditRole See QItemEditorFactory for details
Qt::FontRole QFont
Qt::SizeHintRole QSize
Qt::TextAlignmentRole Qt::Alignment
Qt::ForegroundRole QBrush
Qt::TextColorRole QColor (obsolete; use Qt::ForegroundRole instead)
If the default delegate does not allow the level of customization that you need, either for display purposes or for editing data, it is possible to subclass QItemDelegate to implement the desired behavior.

Subclassing

When subclassing QItemDelegate to create a delegate that displays items using a custom renderer, it is important to ensure that the delegate can render items suitably for all the required states; e.g. selected, disabled, checked. The documentation for the paint() function contains some hints to show how this can be achieved.

You can provide custom editors by using a QItemEditorFactory. The Color Editor Factory Example shows how a custom editor can be made available to delegates with the default item editor factory. This way, there is no need to subclass QItemDelegate. An alternative is to reimplement createEditor(), setEditorData(), setModelData(), and updateEditorGeometry(). This process is described in the Spin Box Delegate Example.

See also:
Delegate Classes, QStyledItemDelegate, QAbstractItemDelegate, Spin Box Delegate Example, Settings Editor Example, and Icons Example.


Nested Class Summary
 
Nested classes/interfaces inherited from class com.trolltech.qt.gui.QAbstractItemDelegate
QAbstractItemDelegate.EndEditHint
 
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
QSignalEmitter.AbstractSignal, QSignalEmitter.PrivateSignal0, QSignalEmitter.PrivateSignal1, QSignalEmitter.PrivateSignal2, QSignalEmitter.PrivateSignal3, QSignalEmitter.PrivateSignal4, QSignalEmitter.PrivateSignal5, QSignalEmitter.PrivateSignal6, QSignalEmitter.PrivateSignal7, QSignalEmitter.PrivateSignal8, QSignalEmitter.PrivateSignal9, QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9
 
Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal
 
Field Summary
 
Fields inherited from class com.trolltech.qt.gui.QAbstractItemDelegate
closeEditor, commitData, sizeHintChanged
 
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
currentSender
 
Constructor Summary
QItemDelegate()
          Constructs an item delegate with the given parent.
QItemDelegate(QObject parent)
          Constructs an item delegate with the given parent.
 
Method Summary
protected  void drawBackground(QPainter painter, QStyleOptionViewItem option, com.trolltech.qt.core.QModelIndex index)
          Renders the item background for the given index, using the given painter and style option.
protected  void drawCheck(QPainter painter, QStyleOptionViewItem option, QRect rect, Qt.CheckState state)
          Renders a check indicator within the rectangle specified by rect, using the given painter and style option, using the given state.
protected  void drawDecoration(QPainter painter, QStyleOptionViewItem option, QRect rect, QPixmap pixmap)
          Renders the decoration pixmap within the rectangle specified by rect using the given painter and style option.
protected  void drawDisplay(QPainter painter, QStyleOptionViewItem option, QRect rect, java.lang.String text)
          Renders the item view text within the rectangle specified by rect using the given painter and style option.
protected  void drawFocus(QPainter painter, QStyleOptionViewItem option, QRect rect)
          Renders the region within the rectangle specified by rect, indicating that it has the focus, using the given painter and style option.
 boolean hasClipping()
          This property holds if the delegate should clip the paint events.
 QItemEditorFactory itemEditorFactory()
          Returns the editor factory used by the item delegate.
 void setClipping(boolean clip)
          This property holds if the delegate should clip the paint events.
 void setItemEditorFactory(QItemEditorFactory factory)
          Sets the editor factory to be used by the item delegate to be the factory specified.
 
Methods inherited from class com.trolltech.qt.gui.QAbstractItemDelegate
createEditor, editorEvent, helpEvent, paint, setEditorData, setModelData, sizeHint, updateEditorGeometry
 
Methods inherited from class com.trolltech.qt.core.QObject
childEvent, children, connectSlotsByName, customEvent, disposeLater, dumpObjectInfo, dumpObjectTree, dynamicPropertyNames, event, eventFilter, findChild, findChild, findChild, findChildren, findChildren, findChildren, findChildren, indexOfProperty, installEventFilter, isWidgetType, killTimer, moveToThread, objectName, parent, properties, property, removeEventFilter, setObjectName, setParent, setProperty, startTimer, timerEvent, toString, userProperty
 
Methods inherited from class com.trolltech.qt.QtJambiObject
dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr
 
Methods inherited from class com.trolltech.qt.QSignalEmitter
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread
 
Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
__qt_signalInitialization
 
Methods inherited from class java.lang.Object
clone, getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface com.trolltech.qt.QtJambiInterface
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership
 

Constructor Detail

QItemDelegate

public QItemDelegate()
Constructs an item delegate with the given parent.


QItemDelegate

public QItemDelegate(QObject parent)
Constructs an item delegate with the given parent.

Method Detail

drawBackground

protected final void drawBackground(QPainter painter,
                                    QStyleOptionViewItem option,
                                    com.trolltech.qt.core.QModelIndex index)
Renders the item background for the given index, using the given painter and style option.


hasClipping

public final boolean hasClipping()
This property holds if the delegate should clip the paint events. This property will set the paint clip to the size of the item. The default value is on. It is useful for cases such as when images are larger than the size of the item.


itemEditorFactory

public final QItemEditorFactory itemEditorFactory()
Returns the editor factory used by the item delegate. If no editor factory is set, the function will return null.

See also:
setItemEditorFactory().


setClipping

public final void setClipping(boolean clip)
This property holds if the delegate should clip the paint events. This property will set the paint clip to the size of the item. The default value is on. It is useful for cases such as when images are larger than the size of the item.


setItemEditorFactory

public final void setItemEditorFactory(QItemEditorFactory factory)
Sets the editor factory to be used by the item delegate to be the factory specified. If no editor factory is set, the item delegate will use the default editor factory.

See also:
itemEditorFactory().


drawCheck

protected void drawCheck(QPainter painter,
                         QStyleOptionViewItem option,
                         QRect rect,
                         Qt.CheckState state)
Renders a check indicator within the rectangle specified by rect, using the given painter and style option, using the given state.


drawDecoration

protected void drawDecoration(QPainter painter,
                              QStyleOptionViewItem option,
                              QRect rect,
                              QPixmap pixmap)
Renders the decoration pixmap within the rectangle specified by rect using the given painter and style option.


drawDisplay

protected void drawDisplay(QPainter painter,
                           QStyleOptionViewItem option,
                           QRect rect,
                           java.lang.String text)
Renders the item view text within the rectangle specified by rect using the given painter and style option.


drawFocus

protected void drawFocus(QPainter painter,
                         QStyleOptionViewItem option,
                         QRect rect)
Renders the region within the rectangle specified by rect, indicating that it has the focus, using the given painter and style option.