Overview | Package | Class | Tree | Deprecated | Index | Help
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD

## com.trolltech.qt.gui
Class QDrag

    java.lang.Object
      com.trolltech.qt.QSignalEmitter
          com.trolltech.qt.QtJambiObject
              com.trolltech.qt.core.QObject
                  com.trolltech.qt.gui.QDrag

All Implemented Interfaces:
  QtJambiInterface

    public class QDrag

extends QObject

The `QDrag` class provides support for MIME-based drag and drop data transfer. Drag and drop is an intuitive way for users to copy or move data around in an application, and is used in many desktop environments as a mechanism for copying data between applications. Drag and drop support in Qt is centered around the `QDrag` class that handles most of the details of a drag and drop operation.

The data to be transferred by the drag and drop operation is contained in a `QMimeData` object. This is specified with the `setMimeData()` function in the following way:

                QDrag drag = new QDrag(this);
                QMimeData mimeData = new QMimeData();

                mimeData.setText(commentEdit.toPlainText());
                drag.setMimeData(mimeData);

Note that `setMimeData()` assigns ownership of the `QMimeData` object to the `QDrag` object. The `QDrag` must be constructed on the heap with a parent `QWidget` to ensure that Qt can clean up after the drag and drop operation has been completed.

A pixmap can be used to represent the data while the drag is in progress, and will move with the cursor to the drop target. This pixmap typically shows an icon that represents the MIME type of the data being transferred, but any pixmap can be set with `setPixmap()`. Care must be taken to ensure that the pixmap is not too large. The cursor's hot spot can be given a position relative to the top-left corner of the pixmap with the `setHotSpot()` function. The following code positions the pixmap so that the cursor's hot spot points to the center of its bottom edge:

            drag.setHotSpot(new QPoint(drag.pixmap().width()/2,
                                       drag.pixmap().height()));

Note: On X11, the pixmap may not be able to keep up with the mouse movements if the hot spot causes the pixmap to be displayed directly under the cursor.

The source and target widgets can be found with `source()` and `target()`. These functions are often used to determine whether drag and drop operations started and finished at the same widget, so that special behavior can be implemented.

`QDrag` only deals with the drag and drop operation itself. It is up to the developer to decide when a drag operation begins, and how a `QDrag` object should be constructed and used. For a given widget, it is often necessary to reimplement `mousePressEvent()` to determine whether the user has pressed a mouse button, and reimplement `mouseMoveEvent()` to check whether a `QDrag` is required.

See also:
  Drag and Drop, `QClipboard`, `QMimeData`, QWindowsMime, QMacPasteboardMime, Draggable Icons Example, Draggable Text Example, Drop Site Example, and Fridge Magnets Example.

Nested Class Summary

Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
`QSignalEmitter.Signal0, QSignalEmitter.Signal1, QSignalEmitter.Signal2, QSignalEmitter.Signal3, QSignalEmitter.Signal4, QSignalEmitter.Signal5, QSignalEmitter.Signal6, QSignalEmitter.Signal7, QSignalEmitter.Signal8, QSignalEmitter.Signal9`

Field Summary
`QSignalEmitter.Signal1` | `actionChanged` This signal is emitted when the `action` associated with the drag changes.
`QSignalEmitter.Signal1` | `targetChanged` This signal is emitted when the target of the drag and drop operation changes, with `newTarget` the new target.

Constructor Summary
`QDrag(QWidget dragSource)` Constructs a new drag object for the widget specified by `dragSource`.

Method Summary
`Qt.DropAction` | `exec()` Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed.
`Qt.DropAction` | `exec(Qt.DropAction[] supportedActions)` Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed.
`Qt.DropAction` | `exec(Qt.DropActions supportedActions)` Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed.
`Qt.DropAction` | `exec(Qt.DropActions supportedActions, Qt.DropAction defaultAction)` Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed.
`static QDrag` | `fromNativePointer(QNativePointer nativePointer)` This method returns the QDrag instance pointed to by `nativePointer`.
`QPoint` | `hotSpot()` Returns the position of the hot spot relative to the top-left corner of the cursor.
`QMimeData` | `mimeData()` Returns the MIME data that is encapsulated by the drag object.
`QPixmap` | `pixmap()` Returns the pixmap used to represent the data in a drag and drop operation.
`void` | `setDragCursor(QPixmap cursor, Qt.DropAction action)` Sets the drag `cursor` for the `action`.
`void` | `setHotSpot(QPoint hotspot)` Sets the position of the hot spot relative to the top-left corner of the pixmap used to the point specified by `hotspot`.
`void` | `setMimeData(QMimeData data)` Sets the data to be sent to the given MIME `data`.
`void` | `setPixmap(QPixmap arg__1)` Sets `pixmap` as the pixmap used to represent the data in a drag and drop operation.
`QWidget` | `source()` Returns the source of the drag object.
`QWidget` | `target()` Returns the target of the drag and drop operation.

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 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

### actionChanged

    public final QSignalEmitter.Signal1 actionChanged

  This signal is emitted when the `action` associated with the drag changes.

See also:
  `targetChanged()` .

### targetChanged

    public final QSignalEmitter.Signal1 targetChanged

  This signal is emitted when the target of the drag and drop operation changes, with `newTarget` the new target.

See also:
  `target()`, and `actionChanged()` .

Constructor Detail

### QDrag

    public QDrag(QWidget dragSource)

  Constructs a new drag object for the widget specified by `dragSource`.

Method Detail

### exec

    public final Qt.DropAction exec(Qt.DropAction[] supportedActions)

  Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed. The drop actions that the user can choose from are specified in `supportedActions`. The default proposed action will be selected among the allowed actions in the following order: Move, Copy and Link.

  Note: On Linux and Mac OS X, the drag and drop operation can take some time, but this function does not block the event loop. Other events are still delivered to the application while the operation is performed. On Windows, the Qt event loop is blocked while during the operation.

### exec

    public final Qt.DropAction exec()

  Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed. The drop actions that the user can choose from are specified in `supportedActions`. The default proposed action will be selected among the allowed actions in the following order: Move, Copy and Link.

  Note: On Linux and Mac OS X, the drag and drop operation can take some time, but this function does not block the event loop. Other events are still delivered to the application while the operation is performed. On Windows, the Qt event loop is blocked while during the operation.

### exec

    public final Qt.DropAction exec(Qt.DropActions supportedActions)

  Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed. The drop actions that the user can choose from are specified in `supportedActions`. The default proposed action will be selected among the allowed actions in the following order: Move, Copy and Link.

  Note: On Linux and Mac OS X, the drag and drop operation can take some time, but this function does not block the event loop. Other events are still delivered to the application while the operation is performed. On Windows, the Qt event loop is blocked while during the operation.

### exec

    public final Qt.DropAction exec(Qt.DropActions supportedActions,
                                    Qt.DropAction defaultAction)

  Starts the drag and drop operation and returns a value indicating the requested drop action when it is completed. The drop actions that the user can choose from are specified in `supportedActions`.

  The `defaultDropAction` determines which action will be proposed when the user performs a drag without using modifier keys.

  Note: Although the drag and drop operation is blocking, the function does not block the event loop. Other events are still delivered to the application while the operation is performed.

### hotSpot

    public final QPoint hotSpot()

  Returns the position of the hot spot relative to the top-left corner of the cursor.

See also:
  `setHotSpot()`.

### mimeData

    public final QMimeData mimeData()

  Returns the MIME data that is encapsulated by the drag object.

See also:
  `setMimeData()`.

### pixmap

    public final QPixmap pixmap()

  Returns the pixmap used to represent the data in a drag and drop operation.

See also:
  `setPixmap()`.

### setDragCursor

    public final void setDragCursor(QPixmap cursor,
                                    Qt.DropAction action)

  Sets the drag `cursor` for the `action`. This allows you to override the default native cursors. To revert to using the native cursor for `action` pass in a null `QPixmap` as `cursor`.

  The `action` can only be `CopyAction`, `MoveAction` or `LinkAction`. All other values of `DropAction` are ignored.

### setHotSpot

    public final void setHotSpot(QPoint hotspot)

  Sets the position of the hot spot relative to the top-left corner of the pixmap used to the point specified by `hotspot`.

  Note: on X11, the pixmap may not be able to keep up with the mouse movements if the hot spot causes the pixmap to be displayed directly under the cursor.

See also:
  `hotSpot()`.

### setMimeData

    public final void setMimeData(QMimeData data)

  Sets the data to be sent to the given MIME `data`. Ownership of the data is transferred to the `QDrag` object.

See also:
  `mimeData()`.

### setPixmap

    public final void setPixmap(QPixmap arg__1)

  Sets `pixmap` as the pixmap used to represent the data in a drag and drop operation. You can only set a pixmap before the drag is started.

See also:
  `pixmap()`.

### source

    public final QWidget source()

  Returns the source of the drag object. This is the widget where the drag and drop operation originated.

### target

    public final QWidget target()

  Returns the target of the drag and drop operation. This is the widget where the drag object was dropped.

### fromNativePointer

    public static QDrag fromNativePointer(QNativePointer nativePointer)

  This method returns the QDrag instance pointed to by `nativePointer`.

Overview | Package | Class | Tree | Deprecated | Index | Help
PREV CLASS NEXT CLASS | FRAMES NO FRAMES
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD