com.trolltech.qt.gui
Class QAbstractItemDelegate

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
All Implemented Interfaces:
QtJambiInterface
Direct Known Subclasses:
QItemDelegate, QStyledItemDelegate

public abstract class QAbstractItemDelegate
extends QObject

The QAbstractItemDelegate class is used to display and edit data items from a model. A QAbstractItemDelegate provides the interface and common functionality for delegates in the model/view architecture. Delegates display individual items in views, and handle the editing of model data.

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

To render an item in a custom way, you must implement paint() and sizeHint(). The QItemDelegate class provides default implementations for these functions; if you do not need custom rendering, subclass that class instead.

We give an example of drawing a progress bar in items; in our case for a package management program.


We create the WidgetDelegate class, which inherits from QStyledItemDelegate. We do the drawing in the paint() function:

The following code example is written in c++.
void WidgetDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option,
                           const QModelIndex &index) const
{
    if (index.column() == 1) {
        int progress = index.data().toInt();

        QStyleOptionProgressBar progressBarOption;
        progressBarOption.rect = option.rect;
        progressBarOption.minimum = 0;
        progressBarOption.maximum = 100;
        progressBarOption.progress = progress;
        progressBarOption.text = QString::number(progress) + "%";
        progressBarOption.textVisible = true;

        QApplication::style()->drawControl(QStyle::CE_ProgressBar,
                                           &progressBarOption, painter);
    } else
        QStyledItemDelegate::paint(painter, option, index);

Notice that we use a QStyleOptionProgressBar and initialize its members. We can then use the current QStyle to draw it.

To provide custom editing, there are two approaches that can be used. The first approach is to create an editor widget and display it directly on top of the item. To do this you must reimplement createEditor() to provide an editor widget, setEditorData() to populate the editor with the data from the model, and setModelData() so that the delegate can update the model with data from the editor.

The second approach is to handle user events directly by reimplementing editorEvent().

See also:
Model/View Programming, QItemDelegate, Pixelator Example, QStyledItemDelegate, and QStyle.


Nested Class Summary
static class QAbstractItemDelegate.EndEditHint
          This enum describes the different hints that the delegate can give to the model and view components to make editing data in a model a comfortable experience for the user.
 
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
 QSignalEmitter.Signal2 closeEditor
          This signal takes 2 generic argument(s).
 QSignalEmitter.Signal1 commitData
          This signal takes 1 generic argument(s).
 QSignalEmitter.Signal1 sizeHintChanged
          This signal takes 1 generic argument(s).
 
Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal
currentSender
 
Constructor Summary
QAbstractItemDelegate()
          Creates a new abstract item delegate with the given parent.
QAbstractItemDelegate(QObject parent)
          Creates a new abstract item delegate with the given parent.
 
Method Summary
 QWidget createEditor(QWidget parent, QStyleOptionViewItem option, com.trolltech.qt.core.QModelIndex index)
          Returns the editor to be used for editing the data item with the given index.
 boolean editorEvent(QEvent event, QAbstractItemModel model, QStyleOptionViewItem option, com.trolltech.qt.core.QModelIndex index)
          Whenever an event occurs, this function is called with the eventmodeloption and the index that corresponds to the item being edited.
 boolean helpEvent(QHelpEvent event, QAbstractItemView view, QStyleOptionViewItem option, com.trolltech.qt.core.QModelIndex index)
          Whenever a help event occurs, this function is called with the eventviewoption and the index that corresponds to the item where the event occurs.
abstract  void paint(QPainter painter, QStyleOptionViewItem option, com.trolltech.qt.core.QModelIndex index)
          This pure abstract function must be reimplemented if you want to provide custom rendering.
 void setEditorData(QWidget editor, com.trolltech.qt.core.QModelIndex index)
          Sets the contents of the given editor to the data for the item at the given index.
 void setModelData(QWidget editor, QAbstractItemModel model, com.trolltech.qt.core.QModelIndex index)
          Sets the data for the item at the given index in the model to the contents of the given editor.
abstract  QSize sizeHint(QStyleOptionViewItem option, com.trolltech.qt.core.QModelIndex index)
          This pure abstract function must be reimplemented if you want to provide custom rendering.
 void updateEditorGeometry(QWidget editor, QStyleOptionViewItem option, com.trolltech.qt.core.QModelIndex index)
          Updates the geometry of the editor for the item with the given index, according to the rectangle specified in the option.
 
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
 

Field Detail

closeEditor

public final QSignalEmitter.Signal2 closeEditor

This signal takes 2 generic argument(s). We list their type and the name they go by in the description of this signal. <com.trolltech.qt.gui.QWidget(named: editor), com.trolltech.qt.gui.QAbstractItemDelegate$EndEditHint(named: hint)>:

This signal is emitted when the user has finished editing an item using the specified editor.

The hint provides a way for the delegate to influence how the model and view behave after editing is completed. It indicates to these components what action should be performed next to provide a comfortable editing experience for the user. For example, if EditNextItem is specified, the view should use a delegate to open an editor on the next item in the model.

See also:
EndEditHint .


commitData

public final QSignalEmitter.Signal1 commitData

This signal takes 1 generic argument(s). We list their type and the name they go by in the description of this signal. <com.trolltech.qt.gui.QWidget(named: editor)>:

This signal must be emitted when the editor widget has completed editing the data, and wants to write it back into the model.


sizeHintChanged

public final QSignalEmitter.Signal1 sizeHintChanged

This signal takes 1 generic argument(s). We list their type and the name they go by in the description of this signal. <com.trolltech.qt.core.QModelIndex(named: index)>:

This signal must be emitted when the sizeHint() of index changed.

Views automatically connect to this signal and relayout items as necessary.

Constructor Detail

QAbstractItemDelegate

public QAbstractItemDelegate()
Creates a new abstract item delegate with the given parent.


QAbstractItemDelegate

public QAbstractItemDelegate(QObject parent)
Creates a new abstract item delegate with the given parent.

Method Detail

helpEvent

public final boolean helpEvent(QHelpEvent event,
                               QAbstractItemView view,
                               QStyleOptionViewItem option,
                               com.trolltech.qt.core.QModelIndex index)
Whenever a help event occurs, this function is called with the eventviewoption and the index that corresponds to the item where the event occurs.

Returns true if the delegate can handle the event; otherwise returns false. A return value of true indicates that the data obtained using the index had the required role.

For QEvent::ToolTip and QEvent::WhatsThis events that were handled successfully, the relevant popup may be shown depending on the user's system configuration.

See also:
QHelpEvent.


createEditor

public QWidget createEditor(QWidget parent,
                            QStyleOptionViewItem option,
                            com.trolltech.qt.core.QModelIndex index)
Returns the editor to be used for editing the data item with the given index. Note that the index contains information about the model being used. The editor's parent widget is specified by parent, and the item options by option.

The base implementation returns 0. If you want custom editing you will need to reimplement this function.

The returned editor widget should have Qt::StrongFocus ; otherwise, QMouseEvents received by the widget will propagate to the view. The view's background will shine through unless the editor paints its own background (e.g., with setAutoFillBackground()).

See also:
setModelData(), and setEditorData().


editorEvent

public boolean editorEvent(QEvent event,
                           QAbstractItemModel model,
                           QStyleOptionViewItem option,
                           com.trolltech.qt.core.QModelIndex index)
Whenever an event occurs, this function is called with the eventmodeloption and the index that corresponds to the item being edited.

The base implementation returns false (indicating that it has not handled the event).


paint

public abstract void paint(QPainter painter,
                           QStyleOptionViewItem option,
                           com.trolltech.qt.core.QModelIndex index)
This pure abstract function must be reimplemented if you want to provide custom rendering. Use the painter and style option to render the item specified by the item index.

If you reimplement this you must also reimplement sizeHint().


setEditorData

public void setEditorData(QWidget editor,
                          com.trolltech.qt.core.QModelIndex index)
Sets the contents of the given editor to the data for the item at the given index. Note that the index contains information about the model being used.

The base implementation does nothing. If you want custom editing you will need to reimplement this function.

See also:
setModelData().


setModelData

public void setModelData(QWidget editor,
                         QAbstractItemModel model,
                         com.trolltech.qt.core.QModelIndex index)
Sets the data for the item at the given index in the model to the contents of the given editor.

The base implementation does nothing. If you want custom editing you will need to reimplement this function.

See also:
setEditorData().


sizeHint

public abstract QSize sizeHint(QStyleOptionViewItem option,
                               com.trolltech.qt.core.QModelIndex index)
This pure abstract function must be reimplemented if you want to provide custom rendering. The options are specified by option and the model item by index.

If you reimplement this you must also reimplement paint().


updateEditorGeometry

public void updateEditorGeometry(QWidget editor,
                                 QStyleOptionViewItem option,
                                 com.trolltech.qt.core.QModelIndex index)
Updates the geometry of the editor for the item with the given index, according to the rectangle specified in the option. If the item has an internal layout, the editor will be laid out accordingly. Note that the index contains information about the model being used.

The base implementation does nothing. If you want custom editing you must reimplement this function.