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## com.trolltech.qt.core
Class QObject

    java.lang.Object
      com.trolltech.qt.internal.QSignalEmitterInternal
          com.trolltech.qt.QSignalEmitter
              com.trolltech.qt.QtJambiObject
                  com.trolltech.qt.core.QObject

All Implemented Interfaces:
  QtJambiInterface

Direct Known Subclasses:
  AbstractAudioOutput, Effect, MediaController, MediaObject, QAbstractEventDispatcher, QAbstractItemDelegate, QAbstractItemModel, QAbstractMessageHandler, QAbstractTextDocumentLayout, QAbstractUriResolver, QAccessiblePlugin, QAction, QActionGroup, QButtonGroup, QClipboard, QCompleter, QCoreApplication, QDataWidgetMapper, QDrag, QEventLoop, QFileSystemWatcher, QFtp, QFutureWatcherBase, QGraphicsItemAnimation, QGraphicsScene, QGraphicsSvgItem, QGraphicsTextItem, QGraphicsWidget, QHttp, QIconEnginePluginV2, QImageIOPlugin, QInputContext, QInputContextPlugin, QIODevice, QItemSelectionModel, QLayout, QLocalServer, QMimeData, QMovie, QNetworkAccessManager, QNetworkCookieJar, QPictureFormatPlugin, QSessionManager, QSettings, QShortcut, QSignalMapper, QSocketNotifier, QSound, QSqlDriver, QStyle, QStylePlugin, QSvgRenderer, QSyntaxHighlighter, QSystemTrayIcon, QTcpServer, QTextCodecPlugin, QTextDocument, QTextObject, QThreadPool, QTimeLine, QTimer, QTranslator, QUndoGroup, QUndoStack, QValidator, QWebFrame, QWebHistoryInterface, QWebPage, QWidget

    public class QObject

extends QtJambiObject

The QObject class is the base class of all Qt objects. QObject is the heart of the Qt object model. The central feature in this model is a very powerful mechanism for seamless object communication called signals and slots. You can connect a signal to a slot with connect() and destroy the connection with disconnect(). To avoid never ending notification loops you can temporarily block signals with blockSignals(). The protected functions connectNotify() and disconnectNotify() make it possible to track connections.

QObjects organize themselves in object trees. When you create a QObject with another object as parent, the object will automatically add itself to the parent's `children()` list. The parent takes ownership of the object i.e. it will automatically delete its children in its destructor. You can look for an object by name and optionally type using `findChild()` or `findChildren()`.

Every object has an `objectName()` and its class name can be found via the corresponding metaObject() (see QMetaObject::className()). You can determine whether the object's class inherits another class in the QObject inheritance hierarchy by using the inherits() function.

When an object is deleted, it emits a destroyed() signal. You can catch this signal to avoid dangling references to QObjects.

QObjects can receive events through `event()` and filter the events of other objects. See `installEventFilter()` and `eventFilter()` for details. A convenience handler, `childEvent()`, can be reimplemented to catch child events.

Events are delivered in the thread in which the object was created; see Thread Support in Qt and thread() for details. Note that event processing is not done at all for QObjects with no thread affinity (thread() returns zero). Use the `moveToThread()` function to change the thread affinity for an object and its children (the object cannot be moved if it has a parent).

Last but not least, QObject provides the basic timer support in Qt; see `QTimer` for high-level support for timers.

Notice that the Q_OBJECT macro is mandatory for any object that implements signals, slots or properties. You also need to run the Meta Object Compiler on the source file. We strongly recommend the use of this macro in all subclasses of QObject regardless of whether or not they actually use signals, slots and properties, since failure to do so may lead certain functions to exhibit strange behavior.

All Qt widgets inherit QObject. The convenience function `isWidgetType()` returns whether an object is actually a widget. It is much faster than qobject_cast<`QWidget` *>(obj) or obj->inherits("`QWidget`").

Some QObject functions, e.g. `children()`, return a QObjectList. QObjectList is a typedef for QList<QObject *>.

## No copy constructor or assignment operator

QObject has neither a copy constructor nor an assignment operator. This is by design. Actually, they are declared, but in a `private` section with the macro Q_DISABLE_COPY(). In fact, all Qt classes derived from QObject (direct or indirect) use this macro to declare their copy constructor and assignment operator to be private. The reasoning is found in the discussion on Identity vs Value on the Qt Object Model page.

The main consequence is that you should use pointers to QObject (or to your QObject subclass) where you might otherwise be tempted to use your QObject subclass as a value. For example, without a copy constructor, you can't use a subclass of QObject as the value to be stored in one of the container classes. You must store pointers.

### Auto-Connection

Qt's meta-object system provides a mechanism to automatically connect signals and slots between QObject subclasses and their children. As long as objects are defined with suitable object names, and slots follow a simple naming convention, this connection can be performed at run-time by the QMetaObject::connectSlotsByName() function.

uic generates code that invokes this function to enable auto-connection to be performed between widgets on forms created with Qt Designer. More information about using auto-connection with Qt Designer is given in the Using a Component in Your Application section of the Qt Designer manual.

### Dynamic Properties

From Qt 4.2, dynamic properties can be added to and removed from QObject instances at run-time. Dynamic properties do not need to be declared at compile-time, yet they provide the same advantages as static properties and are manipulated using the same API - using `property()` to read them and `setProperty()` to write them.

From Qt 4.3, dynamic properties are supported by Qt Designer, and both standard Qt widgets and user-created forms can be given dynamic properties.

{Object Trees and Object Ownership}

See also:
  QMetaObject, QPointer, QObjectCleanupHandler, and Q_DISABLE_COPY().

Nested Class Summary

Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
`QSignalEmitter.AbstractSignal, 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.internal.QSignalEmitterInternal
`currentSender`

Constructor Summary
`QObject()`
`QObject(QObject parent)`

Method Summary
`protected void` | `childEvent(QChildEvent arg__1)`
`java.util.List` | `children()`
`void` | `connectSlotsByName()` Searches recursively for all child objects of the given object, and connects matching signals from them to slots of object that follow the following form.
`protected void` | `customEvent(QEvent arg__1)`
`void` | `disposeLater()`
`void` | `dumpObjectInfo()`
`void` | `dumpObjectTree()`
`java.util.List` | `dynamicPropertyNames()`
`boolean` | `event(QEvent arg__1)`
`boolean` | `eventFilter(QObject arg__1, QEvent arg__2)`
`QObject` | `findChild()` Returns a child of this object, or 0 if there is no such object.
`QObject` | `findChild(java.lang.Class cl)` This functions searches for descendant(s) of this QObject.
`QObject` | `findChild(java.lang.Class cl, java.lang.String name)` This functions searches for descendant(s) of this QObject.
`java.util.List` | `findChildren()` Returns all children of this QObject, or an empty list if it has no children.
`java.util.List` | `findChildren(java.lang.Class cl)` This functions searches for descendant(s) of this QObject.
`java.util.List` | `findChildren(java.lang.Class cl, QRegExp name)` This functions searches for descendant(s) of this QObject.
`java.util.List` | `findChildren(java.lang.Class cl, java.lang.String name)` This functions searches for descendant(s) of this QObject.
`int` | `indexOfProperty(java.lang.String name)` Finds property `name` and returns its index; otherwise returns -1.
`void` | `installEventFilter(QObject arg__1)`
`boolean` | `isWidgetType()`
`void` | `killTimer(int id)`
`void` | `moveToThread(java.lang.Thread thread)`
`java.lang.String` | `objectName()`
`QObject` | `parent()`
`java.util.List` | `properties()` This functions searches for descendant(s) of this QObject.
`java.lang.Object` | `property(java.lang.String name)` Returns the value of the object's `name` property.
`void` | `removeEventFilter(QObject arg__1)`
`void` | `setObjectName(java.lang.String name)`
`void` | `setParent(QObject arg__1)`
`void` | `setProperty(java.lang.String name, java.lang.Object value)` Sets the value of the object's `name` property to `value`.
`int` | `startTimer(int interval)`
`protected void` | `timerEvent(QTimerEvent arg__1)`
`java.lang.String` | `toString()` Returns a string representation of the `this QObject`.
`QtProperty` | `userProperty()` Returns the property that has the `USER` flag set to true.

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

### QObject

    public QObject()

### QObject

    public QObject(QObject parent)

Method Detail

### children

    public final java.util.List children()

### disposeLater

    public final void disposeLater()

### dumpObjectInfo

    public final void dumpObjectInfo()

### dumpObjectTree

    public final void dumpObjectTree()

### dynamicPropertyNames

    public final java.util.List dynamicPropertyNames()

### installEventFilter

    public final void installEventFilter(QObject arg__1)

### isWidgetType

    public final boolean isWidgetType()

### killTimer

    public final void killTimer(int id)

### moveToThread

    public final void moveToThread(java.lang.Thread thread)

### objectName

    public final java.lang.String objectName()

### parent

    public final QObject parent()

### removeEventFilter

    public final void removeEventFilter(QObject arg__1)

### setObjectName

    public final void setObjectName(java.lang.String name)

### setParent

    public final void setParent(QObject arg__1)

### startTimer

    public final int startTimer(int interval)

### childEvent

    protected void childEvent(QChildEvent arg__1)

### customEvent

    protected void customEvent(QEvent arg__1)

### event

    public boolean event(QEvent arg__1)

### eventFilter

    public boolean eventFilter(QObject arg__1,
                               QEvent arg__2)

### timerEvent

    protected void timerEvent(QTimerEvent arg__1)

### findChildren

    public final java.util.List findChildren()

  Returns all children of this QObject, or an empty list if it has no children.

### findChildren

    public final java.util.List findChildren(java.lang.Class cl)

  This functions searches for descendant(s) of this QObject.

### findChildren

    public final java.util.List findChildren(java.lang.Class cl,
                                             java.lang.String name)

  This functions searches for descendant(s) of this QObject.

### findChildren

    public final java.util.List findChildren(java.lang.Class cl,
                                             QRegExp name)

  This functions searches for descendant(s) of this QObject.

### findChild

    public final QObject findChild()

  Returns a child of this object, or 0 if there is no such object. The search is performed recursively.

  If there is more than one child matching the search, the most direct ancestor is returned. If there are several direct ancestors, it is undefined which one will be returned. In that case, findChildren() should be used.

### findChild

    public final QObject findChild(java.lang.Class cl)

  This functions searches for descendant(s) of this QObject.

### findChild

    public final QObject findChild(java.lang.Class cl,
                                   java.lang.String name)

  This functions searches for descendant(s) of this QObject.

### setProperty

    public final void setProperty(java.lang.String name,
                                  java.lang.Object value)

  Sets the value of the object's `name` property to `value`.

  If the property is defined in the class using Q_PROPERTY then true is returned on success and false otherwise. If the property is not defined using Q_PROPERTY, and therefore not listed in the meta-object, it is added as a dynamic property and false is returned.

  Information about all available properties is provided through the metaObject() and dynamicPropertyNames().

  Dynamic properties can be queried again using property() and can be removed by setting the property value to an invalid QVariant. Changing the value of a dynamic property causes a QDynamicPropertyChangeEvent to be sent to the object.

  Note: Dynamic properties starting with "_q_" are reserved for internal purposes.

### property

    public final java.lang.Object property(java.lang.String name)

  Returns the value of the object's `name` property.

  If no such property exists, the returned object is invalid.

  Information about all available properties is provided through the metaObject() and dynamicPropertyNames().

### userProperty

    public final QtProperty userProperty()

  Returns the property that has the `USER` flag set to true.

See also:
  QMetaProperty::isUser().

### properties

    public final java.util.List properties()

  This functions searches for descendant(s) of this QObject.

### indexOfProperty

    public final int indexOfProperty(java.lang.String name)

  Finds property `name` and returns its index; otherwise returns -1.

### connectSlotsByName

    public final void connectSlotsByName()

  Searches recursively for all child objects of the given object, and connects matching signals from them to slots of object that follow the following form.

  `void on__();`

  Let's assume our object has a child object of type QPushButton with the object name button1. The slot to catch the button's `clicked` signal would be:

  `void on_button1_clicked()`

### toString

    public java.lang.String toString()

  Returns a string representation of the `this QObject`.

  Overrides:
    `toString` in class `java.lang.Object`

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