JApplet (Java Platform SE 8 )
Keywords: javax.swing.JApplet class
Date: 2018-07-01

javax.swing

## Class JApplet

- java.lang.Object
- - java.awt.Component
  - - java.awt.Container
    - - java.awt.Panel
      - - java.applet.Applet
        - - javax.swing.JApplet

- All Implemented Interfaces:
    ImageObserver, MenuContainer, Serializable, Accessible, RootPaneContainer

      public class JApplet
      extends Applet
      implements Accessible, RootPaneContainer

  An extended version of `java.applet.Applet` that adds support for the JFC/Swing component architecture. You can find task-oriented documentation about using `JApplet` in The Java Tutorial, in the section How to Make Applets.

  The `JApplet` class is slightly incompatible with `java.applet.Applet`. `JApplet` contains a `JRootPane` as its only child. The `contentPane` should be the parent of any children of the `JApplet`. As a convenience, the `add`, `remove`, and `setLayout` methods of this class are overridden, so that they delegate calls to the corresponding methods of the `ContentPane`. For example, you can add a child component to an applet as follows:

             applet.add(child);

  And the child will be added to the `contentPane`. The `contentPane` will always be non-`null`. Attempting to set it to `null` will cause the `JApplet` to throw an exception. The default `contentPane` will have a `BorderLayout` manager set on it. Refer to `RootPaneContainer` for details on adding, removing and setting the `LayoutManager` of a `JApplet`.

  Please see the `JRootPane` documentation for a complete description of the `contentPane`, `glassPane`, and `layeredPane` properties.

  Warning: Swing is not thread safe. For more information see Swing's Threading Policy.

  Warning: Serialized objects of this 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 the `java.beans` package. Please see `XMLEncoder`.

  See Also:
    `RootPaneContainer`

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `protected class` | `JApplet.AccessibleJApplet` This class implements accessibility support for the `JApplet` class.

    - ### Nested classes/interfaces inherited from class java.applet.Applet

      `Applet.AccessibleApplet`

    - ### Nested classes/interfaces inherited from class java.awt.Panel

      `Panel.AccessibleAWTPanel`

    - ### Nested classes/interfaces inherited from class java.awt.Container

      `Container.AccessibleAWTContainer`

    - ### Nested classes/interfaces inherited from class java.awt.Component

      `Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected AccessibleContext` | `accessibleContext`
    `protected JRootPane` | `rootPane`
    `protected boolean` | `rootPaneCheckingEnabled` If true then calls to `add` and `setLayout` will be forwarded to the `contentPane`.

    - ### Fields inherited from class java.awt.Component

      `BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT`

    - ### Fields inherited from interface java.awt.image.ImageObserver

      `ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `JApplet()` Creates a swing applet instance.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `addImpl(Component comp, Object constraints, int index)` Adds the specified child `Component`.
    `protected JRootPane` | `createRootPane()` Called by the constructor methods to create the default rootPane.
    `AccessibleContext` | `getAccessibleContext()` Gets the AccessibleContext associated with this JApplet.
    `Container` | `getContentPane()` Returns the contentPane object for this applet.
    `Component` | `getGlassPane()` Returns the glassPane object for this applet.
    `Graphics` | `getGraphics()` Creates a graphics context for this component.
    `JMenuBar` | `getJMenuBar()` Returns the menubar set on this applet.
    `JLayeredPane` | `getLayeredPane()` Returns the layeredPane object for this applet.
    `JRootPane` | `getRootPane()` Returns the rootPane object for this applet.
    `TransferHandler` | `getTransferHandler()` Gets the `transferHandler` property.
    `protected boolean` | `isRootPaneCheckingEnabled()` Returns whether calls to `add` and `setLayout` are forwarded to the `contentPane`.
    `protected String` | `paramString()` Returns a string representation of this JApplet.
    `void` | `remove(Component comp)` Removes the specified component from the container.
    `void` | `repaint(long time, int x, int y, int width, int height)` Repaints the specified rectangle of this component within `time` milliseconds.
    `void` | `setContentPane(Container contentPane)` Sets the contentPane property.
    `void` | `setGlassPane(Component glassPane)` Sets the glassPane property.
    `void` | `setJMenuBar(JMenuBar menuBar)` Sets the menubar for this applet.
    `void` | `setLayeredPane(JLayeredPane layeredPane)` Sets the layeredPane property.
    `void` | `setLayout(LayoutManager manager)` Sets the `LayoutManager`.
    `protected void` | `setRootPane(JRootPane root)` Sets the rootPane property.
    `protected void` | `setRootPaneCheckingEnabled(boolean enabled)` Sets whether calls to `add` and `setLayout` are forwarded to the `contentPane`.
    `void` | `setTransferHandler(TransferHandler newHandler)` Sets the `transferHandler` property, which is a mechanism to support transfer of data into this component.
    `void` | `update(Graphics g)` Just calls `paint(g)`.

    - ### Methods inherited from class java.applet.Applet

      `destroy, getAppletContext, getAppletInfo, getAudioClip, getAudioClip, getCodeBase, getDocumentBase, getImage, getImage, getLocale, getParameter, getParameterInfo, init, isActive, isValidateRoot, newAudioClip, play, play, resize, resize, setStub, showStatus, start, stop`

    - ### Methods inherited from class java.awt.Panel

      `addNotify`

    - ### Methods inherited from class java.awt.Container

      `add, add, add, add, add, addContainerListener, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getComponentZOrder, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getInsets, getLayout, getListeners, getMaximumSize, getMinimumSize, getMousePosition, getPreferredSize, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicyProvider, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paint, paintComponents, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, removeAll, removeContainerListener, removeNotify, setComponentZOrder, setFocusCycleRoot, setFocusTraversalKeys, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, setFont, transferFocusDownCycle, validate, validateTree`

    - ### Methods inherited from class java.awt.Component

      `action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocation, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPeer, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, reshape, revalidate, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeysEnabled, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- - ### Field Detail

    - #### rootPane

          protected JRootPane rootPane

      See Also:
        `getRootPane()`, `setRootPane(javax.swing.JRootPane)`

    - #### rootPaneCheckingEnabled

          protected boolean rootPaneCheckingEnabled

      If true then calls to `add` and `setLayout` will be forwarded to the `contentPane`. This is initially false, but is set to true when the `JApplet` is constructed.
      See Also:
        `isRootPaneCheckingEnabled()`, `setRootPaneCheckingEnabled(boolean)`, `RootPaneContainer`

    - #### accessibleContext

          protected AccessibleContext accessibleContext

  - ### Constructor Detail

    - #### JApplet

          public JApplet()
                  throws HeadlessException

      Creates a swing applet instance.

      This constructor sets the component's locale property to the value returned by `JComponent.getDefaultLocale`.

      Throws:
        `HeadlessException` - if GraphicsEnvironment.isHeadless() returns true.
      See Also:
        `GraphicsEnvironment.isHeadless()`, `JComponent.getDefaultLocale()`

  - ### Method Detail

    - #### createRootPane

          protected JRootPane createRootPane()

      Called by the constructor methods to create the default rootPane.

    - #### setTransferHandler

          public void setTransferHandler(TransferHandler newHandler)

      Sets the `transferHandler` property, which is a mechanism to support transfer of data into this component. Use `null` if the component does not support data transfer operations.

      If the system property `suppressSwingDropSupport` is `false` (the default) and the current drop target on this component is either `null` or not a user-set drop target, this method will change the drop target as follows: If `newHandler` is `null` it will clear the drop target. If not `null` it will install a new `DropTarget`.

      Note: When used with `JApplet`, `TransferHandler` only provides data import capability, as the data export related methods are currently typed to `JComponent`.

      Please see How to Use Drag and Drop and Data Transfer, a section in The Java Tutorial, for more information.

      Parameters:
        `newHandler` - the new `TransferHandler`
      Since:
        1.6
      See Also:
        `TransferHandler`, `getTransferHandler()`, `Component.setDropTarget(java.awt.dnd.DropTarget)`

    - #### getTransferHandler

          public TransferHandler getTransferHandler()

      Gets the `transferHandler` property.
      Returns:
        the value of the `transferHandler` property
      Since:
        1.6
      See Also:
        `TransferHandler`, `setTransferHandler(javax.swing.TransferHandler)`

    - #### update

          public void update(Graphics g)

      Just calls `paint(g)`. This method was overridden to prevent an unnecessary call to clear the background.
      Overrides:
        `update` in class `Container`
      Parameters:
        `g` - the specified Graphics window
      See Also:
        `Component.update(Graphics)`

    - #### setJMenuBar

          public void setJMenuBar(JMenuBar menuBar)

      Sets the menubar for this applet.
      Parameters:
        `menuBar` - the menubar being placed in the applet
      See Also:
        `getJMenuBar()`

    - #### getJMenuBar

          public JMenuBar getJMenuBar()

      Returns the menubar set on this applet.
      See Also:
        `setJMenuBar(javax.swing.JMenuBar)`

    - #### isRootPaneCheckingEnabled

          protected boolean isRootPaneCheckingEnabled()

      Returns whether calls to `add` and `setLayout` are forwarded to the `contentPane`.
      Returns:
        true if `add` and `setLayout` are forwarded; false otherwise
      See Also:
        `addImpl(java.awt.Component, java.lang.Object, int)`, `setLayout(java.awt.LayoutManager)`, `setRootPaneCheckingEnabled(boolean)`, `RootPaneContainer`

    - #### setRootPaneCheckingEnabled

          protected void setRootPaneCheckingEnabled(boolean enabled)

      Sets whether calls to `add` and `setLayout` are forwarded to the `contentPane`.
      Parameters:
        `enabled` - true if `add` and `setLayout` are forwarded, false if they should operate directly on the `JApplet`.
      See Also:
        `addImpl(java.awt.Component, java.lang.Object, int)`, `setLayout(java.awt.LayoutManager)`, `isRootPaneCheckingEnabled()`, `RootPaneContainer`

    - #### addImpl

          protected void addImpl(Component comp,
                                 Object constraints,
                                 int index)

      Adds the specified child `Component`. This method is overridden to conditionally forward calls to the `contentPane`. By default, children are added to the `contentPane` instead of the frame, refer to `RootPaneContainer` for details.
      Overrides:
        `addImpl` in class `Container`
      Parameters:
        `comp` - the component to be enhanced
        `constraints` - the constraints to be respected
        `index` - the index
      Throws:
        `IllegalArgumentException` - if `index` is invalid
        `IllegalArgumentException` - if adding the container's parent to itself
        `IllegalArgumentException` - if adding a window to a container
      See Also:
        `setRootPaneCheckingEnabled(boolean)`, `RootPaneContainer`

    - #### remove

          public void remove(Component comp)

      Removes the specified component from the container. If `comp` is not the `rootPane`, this will forward the call to the `contentPane`. This will do nothing if `comp` is not a child of the `JFrame` or `contentPane`.
      Overrides:
        `remove` in class `Container`
      Parameters:
        `comp` - the component to be removed
      Throws:
        `NullPointerException` - if `comp` is null
      See Also:
        `Container.add(java.awt.Component)`, `RootPaneContainer`

    - #### setLayout

          public void setLayout(LayoutManager manager)

      Sets the `LayoutManager`. Overridden to conditionally forward the call to the `contentPane`. Refer to `RootPaneContainer` for more information.
      Overrides:
        `setLayout` in class `Container`
      Parameters:
        `manager` - the `LayoutManager`
      See Also:
        `setRootPaneCheckingEnabled(boolean)`, `RootPaneContainer`

    - #### getRootPane

          public JRootPane getRootPane()

      Returns the rootPane object for this applet.
      Specified by:
        `getRootPane` in interface `RootPaneContainer`
      Returns:
        this components single JRootPane child.
      See Also:
        `setRootPane(javax.swing.JRootPane)`, `RootPaneContainer.getRootPane()`

    - #### setRootPane

          protected void setRootPane(JRootPane root)

      Sets the rootPane property. This method is called by the constructor.
      Parameters:
        `root` - the rootPane object for this applet
      See Also:
        `getRootPane()`

    - #### getContentPane

          public Container getContentPane()

      Returns the contentPane object for this applet.
      Specified by:
        `getContentPane` in interface `RootPaneContainer`
      Returns:
        the value of the contentPane property.
      See Also:
        `setContentPane(java.awt.Container)`, `RootPaneContainer.getContentPane()`

    - #### setContentPane

          public void setContentPane(Container contentPane)

      Sets the contentPane property. This method is called by the constructor.
      Specified by:
        `setContentPane` in interface `RootPaneContainer`
      Parameters:
        `contentPane` - the contentPane object for this applet
      Throws:
        `IllegalComponentStateException` - (a runtime exception) if the content pane parameter is null
      See Also:
        `getContentPane()`, `RootPaneContainer.setContentPane(java.awt.Container)`

    - #### getLayeredPane

          public JLayeredPane getLayeredPane()

      Returns the layeredPane object for this applet.
      Specified by:
        `getLayeredPane` in interface `RootPaneContainer`
      Returns:
        the value of the layeredPane property.
      Throws:
        `IllegalComponentStateException` - (a runtime exception) if the layered pane parameter is null
      See Also:
        `setLayeredPane(javax.swing.JLayeredPane)`, `RootPaneContainer.getLayeredPane()`

    - #### setLayeredPane

          public void setLayeredPane(JLayeredPane layeredPane)

      Sets the layeredPane property. This method is called by the constructor.
      Specified by:
        `setLayeredPane` in interface `RootPaneContainer`
      Parameters:
        `layeredPane` - the layeredPane object for this applet
      See Also:
        `getLayeredPane()`, `RootPaneContainer.setLayeredPane(javax.swing.JLayeredPane)`

    - #### getGlassPane

          public Component getGlassPane()

      Returns the glassPane object for this applet.
      Specified by:
        `getGlassPane` in interface `RootPaneContainer`
      Returns:
        the value of the glassPane property.
      See Also:
        `setGlassPane(java.awt.Component)`, `RootPaneContainer.getGlassPane()`

    - #### setGlassPane

          public void setGlassPane(Component glassPane)

      Sets the glassPane property. This method is called by the constructor.
      Specified by:
        `setGlassPane` in interface `RootPaneContainer`
      Parameters:
        `glassPane` - the glassPane object for this applet
      See Also:
        `getGlassPane()`, `RootPaneContainer.setGlassPane(java.awt.Component)`

    - #### getGraphics

          public Graphics getGraphics()

      Creates a graphics context for this component. This method will return `null` if this component is currently not displayable.
      Overrides:
        `getGraphics` in class `Component`
      Returns:
        a graphics context for this component, or `null` if it has none
      Since:
        1.6
      See Also:
        `Component.paint(java.awt.Graphics)`

    - #### repaint

          public void repaint(long time,
                              int x,
                              int y,
                              int width,
                              int height)

      Repaints the specified rectangle of this component within `time` milliseconds. Refer to `RepaintManager` for details on how the repaint is handled.
      Overrides:
        `repaint` in class `Component`
      Parameters:
        `time` - maximum time in milliseconds before update
        `x` - the x coordinate
        `y` - the y coordinate
        `width` - the width
        `height` - the height
      Since:
        1.6
      See Also:
        `RepaintManager`

    - #### paramString

          protected String paramString()

      Returns a string representation of this JApplet. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be `null`.
      Overrides:
        `paramString` in class `Container`
      Returns:
        a string representation of this JApplet.

    - #### getAccessibleContext

          public AccessibleContext getAccessibleContext()

      Gets the AccessibleContext associated with this JApplet. For JApplets, the AccessibleContext takes the form of an AccessibleJApplet. A new AccessibleJApplet instance is created if necessary.
      Specified by:
        `getAccessibleContext` in interface `Accessible`
      Overrides:
        `getAccessibleContext` in class `Applet`
      Returns:
        an AccessibleJApplet that serves as the AccessibleContext of this JApplet

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