Package javax.swing
Swing's Threading Policy
In general Swing is not thread safe. All Swing components and related classes, unless otherwise documented, must be accessed on the event dispatching thread.
Typical Swing applications do processing in response to an event generated
from a user gesture. For example, clicking on a JButton notifies all
ActionListeners added to the JButton. As all events generated
from a user gesture are dispatched on the event dispatching thread, most
developers are not impacted by the restriction.
Where the impact lies, however, is in constructing and showing a Swing
application. Calls to an application's main method, or methods in
Applet, are not invoked on the event dispatching thread. As such,
care must be taken to transfer control to the event dispatching thread when
constructing and showing an application or applet. The preferred way to
transfer control and begin working with Swing is to use invokeLater.
The invokeLater method schedules a Runnable to be processed
on the event dispatching thread. The following two examples work equally well
for transferring control and starting up a Swing application:
import javax.swing.SwingUtilities;
public class MyApp implements Runnable {
public void run() {
// Invoked on the event dispatching thread.
// Construct and show GUI.
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new MyApp());
}
}
Or:
import javax.swing.SwingUtilities;
public class MyApp {
MyApp(String[] args) {
// Invoked on the event dispatching thread.
// Do any initialization here.
}
public void show() {
// Show the UI.
}
public static void main(final String[] args) {
// Schedule a job for the event-dispatching thread:
// creating and showing this application's GUI.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new MyApp(args).show();
}
});
}
}
This restriction also applies to models attached to Swing components. For
example, if a TableModel is attached to a JTable, the
TableModel should only be modified on the event dispatching thread.
If you modify the model on a separate thread you run the risk of exceptions
and possible display corruption.
Although it is generally safe to make updates to the UI immediately,
when executing on the event dispatch thread, there is an exception :
if a model listener tries to further change the UI before the UI has been
updated to reflect a pending change then the UI may render incorrectly.
This can happen if an application installed listener needs to update the UI
in response to an event which will cause a change in the model structure.
It is important to first allow component installed listeners to process this
change, since there is no guarantee of the order in which listeners may be
called.
The solution is for the application listener to make the change using
SwingUtilities.invokeLater(Runnable) so that any changes
to UI rendering will be done post processing all the model listeners
installed by the component.
As all events are delivered on the event dispatching thread, care must be
taken in event processing. In particular, a long running task, such as
network io or computational intensive processing, executed on the event
dispatching thread blocks the event dispatching thread from dispatching any
other events. While the event dispatching thread is blocked the application
is completely unresponsive to user input. Refer to
SwingWorker for the preferred way to do such processing
when working with Swing.
More information on this topic can be found in the Swing tutorial, in particular the section on Concurrency in Swing.
Swing's Serialization policy
Warning: Serialized objects of any Swing class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans has been added to thejava.beans package.
Related Documentation
For overviews, tutorials, examples, guides, and other documentation, please see:- Since:
- 1.2
-
ClassDescriptionThis class provides default implementations for the JFC
Actioninterface.Defines common behaviors for buttons and menu items.A base class forCellEditors, providing default implementations for the methods in theCellEditorinterface exceptgetCellEditorValue().The abstract definition for the data model that provides aListwith its contents.This class provides the ChangeListener part of the SpinnerModel interface that should be suitable for most concrete SpinnerModel implementations.TheActioninterface provides a useful extension to theActionListenerinterface in cases where the same functionality may be accessed by several controls.ActionMapprovides mappings fromObjects (called keys orActionnames) toActions.Factory class for vending standardBorderobjects.Defines the data model used by components likeSliders andProgressBars.A lightweight container that uses a BoxLayout object as its layout manager.An implementation of a lightweight component that participates in layout but has no view.A layout manager that allows multiple components to be laid out either vertically or horizontally.This class is used to create a multiple-exclusion scope for a set of buttons.State model for buttons.This interface defines the methods any general editor should be able to implement.This class is inserted in between cell renderers and the components that use them.The editor component used for JComboBox components.A data model for a combo box.AComponentInputMapis anInputMapassociated with a particularJComponent.Graphics subclass supporting graphics debugging.A generic implementation of BoundedRangeModel.The default implementation of aButtoncomponent's data model.The default editor for table and tree cells.The default model for combo boxes.This is an implementation of theDesktopManager.This class has been obsoleted by the 1.4 focus APIs.Renders an item in a list.A subclass of DefaultListCellRenderer that implements UIResource.This class loosely implements thejava.util.VectorAPI, in that it implements the 1.1.x version ofjava.util.Vector, has no collection class support, and notifies theListDataListeners when changes occur.Default data model for list selections.DefaultRowSorter<M,I> An implementation ofRowSorterthat provides sorting and filtering around a grid-based data model.DefaultRowSorter.ModelWrapperis responsible for providing the data that gets sorted byDefaultRowSorter.A generic implementation of SingleSelectionModel.DesktopManager objects are owned by a JDesktopPane object.Drop modes, used to determine the method by which a component tracks and indicates a drop location during drag and drop.This class has been obsoleted by the 1.4 focus APIs.An image filter that "disables" an image by turning it into a grayscale image, and brightening the pixels in the image.GroupLayoutis aLayoutManagerthat hierarchically groups components in order to position them in aContainer.Enumeration of the possible waysParallelGroupcan align its children.A small fixed size picture, typically used to decorate components.An implementation of the Icon interface that paints Icons from Images.InputMapprovides a binding between an input event (currently onlyKeyStrokes are used) and anObject.This class provides the validation mechanism for Swing components.A FocusTraversalPolicy which can optionally provide an algorithm for determining a JInternalFrame's initial Component.Deprecated, for removal: This API element is subject to removal in a future version.The Applet API is deprecated, no replacement.An implementation of a "push" button.An implementation of a check box -- an item that can be selected or deselected, and which displays its state to the user.A menu item that can be selected or deselected.JColorChooserprovides a pane of controls designed to allow a user to manipulate and select a color.JComboBox<E>A component that combines a button or editable field and a drop-down list.The interface that defines aKeySelectionManager.The base class for all Swing components except top-level containers.A container used to create a multiple-document interface or a virtual desktop.The main class for creating a dialog window.A text component to edit various kinds of content.JFileChooserprovides a simple mechanism for the user to choose a file.JFormattedTextFieldextendsJTextFieldadding support for formatting arbitrary values, as well as retrieving a particular object once the user has edited the text.Instances ofAbstractFormatterare used byJFormattedTextFieldto handle the conversion both from an Object to a String, and back from a String to an Object.Instances ofAbstractFormatterFactoryare used byJFormattedTextFieldto obtain instances ofAbstractFormatterwhich in turn are used to format values.An extended version ofjava.awt.Framethat adds support for the JFC/Swing component architecture.A lightweight object that provides many of the features of a native frame, including dragging, closing, becoming an icon, resizing, title display, and support for a menu bar.This component represents an iconified version of aJInternalFrame.A display area for a short text string or an image, or both.JLayeris a universal decorator for Swing components which enables you to implement various advanced painting effects as well as receive notifications of allAWTEvents generated within its borders.JLayeredPaneadds depth to a JFC/Swing container, allowing components to overlap each other when needed.JList<E>A component that displays a list of objects and allows the user to select one or more items.A subclass ofTransferHandler.DropLocationrepresenting a drop location for aJList.An implementation of a menu -- a popup window containingJMenuItems that is displayed when the user selects an item on theJMenuBar.An implementation of a menu bar.An implementation of an item in a menu.JOptionPanemakes it easy to pop up a standard dialog box that prompts users for a value or informs them of something.