Class Panel

java.lang.Object

vaadinx.awt.Component

vaadinx.awt.Container

vaadinx.awt.Panel

All Implemented Interfaces:

ImageObserver, MenuContainer, Serializable, Accessible

public class Panel
extends Container
implements Accessible

Emulator for Panel — AWT's generic on-screen container, not JPanel. Peers over a plain Vaadin <div> (inherited from Container), which is what every built-in LayoutManager needs: the CSS emitters refuse to write to a non-<div> host.

Panel form = new Panel(new BorderLayout(8, 4));
form.add(new Label("Name"), BorderLayout.NORTH);
form.add(field, BorderLayout.CENTER);
outer.add(form);                 // FlowLayout by default on `outer`

Everything a migrator calls on a Panel is inherited Container: add and its four overloads, remove / removeAll, setLayout / getLayout, getComponent(int) / getComponents() / getComponentCount(), getInsets, validate / doLayout / invalidate, isAncestorOf, Z-order, and ContainerListener — which this layer fires for real, unlike a pure-surrogate container (SD_listeners_without_analog).

There is deliberately no SPanel surrogate: subtract SJPanel's Swing half (border, opaque, client properties, L&F) and nothing is left for one to hold — the child list belongs to Vaadin's HasComponents, the layout manager to LayoutStore. Per SD_no_spanel this is CLAUDE.md's group-2 shape (a structural shell on a bare Vaadin element), the carve-out against D_surrogate_first's surrogate-first default.

Leaf peer is locked down per R_leaf_peer_lockdown. java.applet.Applet is java.awt.Panel's only JDK subclass, and applets are permanently out of scope (R_match_swing_errors sub-bucket (b)) — the JDK classes are removed in Java 26 per JEP 504, so unlike javax.swing.plaf this subclass cannot come back as future non-leaf pressure. Both ctors funnel through super(), so every instance — including a user-code subclass — peers over a Div and no ctor offers a peer seam.

A layout installed after the Panel is on screen does not take effect until validate() / revalidate(), matching AWT — setLayout only invalidates. The outgoing manager's CSS *is* dropped at setLayout, so the un-revalidated interval renders as plain block flow rather than the old layout's; see Container#setLayout.

See Also:

• Serialized Form

Field Summary

Fields inherited from class Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, FILL_CHROME, FILL_DEFAULT, LEFT_ALIGNMENT, listenerList, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface ImageObserver

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

Constructor Summary

Constructors

Constructor	Description
Panel()	JDK chains this to this(new FlowLayout()) — centered, 5px gaps.
Panel(LayoutManager layout)

Method Summary

Modifier and Type	Method	Description
void	addNotify()
AccessibleContext	getAccessibleContext()

Methods inherited from class Container

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

Methods inherited from class Component

action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, applyBackgroundToPeer, applyVisibleToPeer, awtListeners, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, defaultFillCssClass, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, fireComponentEvent, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBaseline, getBounds, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getListeners, getLocale, 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, isThemeDefault, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, peerIs, 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, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, reshape, resize, resize, revalidate, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeysEnabled, setFont, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setMixingCutoutShape, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, suppressMouseBridge, toString, transferFocus, transferFocusBackward, transferFocusUpCycle, withPeer, withPeerOnLiveUI

Methods inherited from class Object

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

Constructor Details

Panel

public Panel()

JDK chains this to this(new FlowLayout()) — centered, 5px gaps.

Panel

public Panel(LayoutManager layout)

Parameters:

layout - null is legal and installs no manager, exactly as in AWT — children then render in the peer <div>'s default block flow and getLayout() returns null. Do not substitute a FlowLayout here.

Method Details

addNotify

public void addNotify()

Overrides:

addNotify in class Container

getAccessibleContext

public AccessibleContext getAccessibleContext()

Specified by:

getAccessibleContext in interface Accessible

Overrides:

getAccessibleContext in class Component

Returns:

always null — accessibility contexts are permanently out of scope (R_match_swing_errors sub-bucket (b)), as on Button / Label / JPanel