QAbstractItemDelegate

The QAbstractItemDelegate class is used to display and edit data items from a model. More

Inheritance diagram of PySide2.QtWidgets.QAbstractItemDelegate

Inherited by: QItemDelegate, QStyledItemDelegate

Synopsis

Virtual functions

Signals

Static functions

Detailed Description

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 QStyledItemDelegate 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.

../../_images/widgetdelegate.png

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

class WidgetDelegate (QStyledItemDelegate):
    # ...

    def paint(painter, option, index):
        if index.column() == 1:
            progress = index.data().toInt()

            progressBarOption = QStyleOptionProgressBar()
            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(self, 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() .

class QAbstractItemDelegate([parent=None])
param parent

QObject

Creates a new abstract item delegate with the given parent .

PySide2.QtWidgets.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.

Constant

Description

QAbstractItemDelegate.NoHint

There is no recommended action to be performed.

These hints let the delegate influence the behavior of the view:

Constant

Description

QAbstractItemDelegate.EditNextItem

The view should use the delegate to open an editor on the next item in the view.

QAbstractItemDelegate.EditPreviousItem

The view should use the delegate to open an editor on the previous item in the view.

Note that custom views may interpret the concepts of next and previous differently.

The following hints are most useful when models are used that cache data, such as those that manipulate data locally in order to increase performance or conserve network bandwidth.

Constant

Description

QAbstractItemDelegate.SubmitModelCache

If the model caches data, it should write out cached data to the underlying data store.

QAbstractItemDelegate.RevertModelCache

If the model caches data, it should discard cached data and replace it with data from the underlying data store.

Although models and views should respond to these hints in appropriate ways, custom components may ignore any or all of them if they are not relevant.

PySide2.QtWidgets.QAbstractItemDelegate.closeEditor(editor[, hint=NoHint])
Parameters
PySide2.QtWidgets.QAbstractItemDelegate.commitData(editor)
Parameters

editorQWidget

PySide2.QtWidgets.QAbstractItemDelegate.createEditor(parent, option, index)
Parameters
Return type

QWidget

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 None . If you want custom editing you will need to reimplement this function.

The returned editor widget should have StrongFocus ; otherwise, QMouseEvent s 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() ).

PySide2.QtWidgets.QAbstractItemDelegate.destroyEditor(editor, index)
Parameters
  • editorQWidget

  • indexQModelIndex

Called when the editor is no longer needed for editing the data item with the given index and should be destroyed. The default behavior is a call to deleteLater on the editor. It is possible e.g. to avoid this delete by reimplementing this function.

See also

createEditor()

PySide2.QtWidgets.QAbstractItemDelegate.editorEvent(event, model, option, index)
Parameters
  • eventQEvent

  • modelQAbstractItemModel

  • optionQStyleOptionViewItem

  • indexQModelIndex

Return type

bool

When editing of an item starts, this function is called with the event that triggered the editing, the model , the index of the item, and the option used for rendering the item.

Mouse events are sent to even if they don’t start editing of the item. This can, for instance, be useful if you wish to open a context menu when the right mouse button is pressed on an item.

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

static PySide2.QtWidgets.QAbstractItemDelegate.elidedText(fontMetrics, width, mode, text)
Parameters
  • fontMetricsQFontMetrics

  • widthint

  • modeTextElideMode

  • text – unicode

Return type

unicode

Note

This function is deprecated.

Use elidedText() instead.

For example, if you have code like

you can rewrite it as

PySide2.QtWidgets.QAbstractItemDelegate.helpEvent(event, view, option, index)
Parameters
Return type

bool

Whenever a help event occurs, this function is called with the event view option 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 ToolTip and WhatsThis events that were handled successfully, the relevant popup may be shown depending on the user’s system configuration.

See also

QHelpEvent

PySide2.QtWidgets.QAbstractItemDelegate.paint(painter, option, index)
Parameters

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() .

PySide2.QtWidgets.QAbstractItemDelegate.paintingRoles()
Return type

This virtual method is reserved and will be used in Qt 5.1.

PySide2.QtWidgets.QAbstractItemDelegate.setEditorData(editor, index)
Parameters
  • editorQWidget

  • indexQModelIndex

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()

PySide2.QtWidgets.QAbstractItemDelegate.setModelData(editor, model, index)
Parameters
  • editorQWidget

  • modelQAbstractItemModel

  • indexQModelIndex

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()

PySide2.QtWidgets.QAbstractItemDelegate.sizeHint(option, index)
Parameters
Return type

QSize

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() .

PySide2.QtWidgets.QAbstractItemDelegate.sizeHintChanged(arg__1)
Parameters

arg__1QModelIndex

PySide2.QtWidgets.QAbstractItemDelegate.updateEditorGeometry(editor, option, index)
Parameters

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.