java.awt
Class Container

java.lang.Object
  java.awt.Component
      java.awt.Container

All Implemented Interfaces:

ImageObserver, MenuContainer, Serializable

Direct Known Subclasses:

BasicSplitPaneDivider, CellRendererPane, DefaultTreeCellEditor.EditorContainer, JComponent, Panel, ScrollPane, Window

public class Container
extends Component

A generic Abstract Window Toolkit(AWT) container object is a component that can contain other AWT components.

Components added to a container are tracked in a list. The order of the list will define the components' front-to-back stacking order within the container. If no index is specified when adding a component to a container, it will be added to the end of the list (and hence to the bottom of the stacking order).

Note: For details on the focus subsystem, see How to Use the Focus Subsystem, a section in The Java Tutorial, and the Focus Specification for more information.

Since:

JDK1.0

See Also:

add(java.awt.Component, int), getComponent(int), LayoutManager, Serialized Form

Nested Class Summary
protected  class	Container.AccessibleAWTContainer           Inner class of Container used to provide default support for accessibility.

 

Nested classes/interfaces inherited from class java.awt.Component
Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy

 

Field Summary

 

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
Container()           Constructs a new Container.

 

Method Summary
Component	add(Component comp)           Appends the specified component to the end of this container.
Component	add(Component comp, int index)           Adds the specified component to this container at the given position.
void	add(Component comp, Object constraints)           Adds the specified component to the end of this container.
void	add(Component comp, Object constraints, int index)           Adds the specified component to this container with the specified constraints at the specified index.
Component	add(String name, Component comp)           Adds the specified component to this container.
void	addContainerListener(ContainerListener l)           Adds the specified container listener to receive container events from this container.
protected  void	addImpl(Component comp, Object constraints, int index)           Adds the specified component to this container at the specified index.
void	addNotify()           Makes this Container displayable by connecting it to a native screen resource.
void	addPropertyChangeListener(PropertyChangeListener listener)           Adds a PropertyChangeListener to the listener list.
void	addPropertyChangeListener(String propertyName, PropertyChangeListener listener)           Adds a PropertyChangeListener to the listener list for a specific property.
void	applyComponentOrientation(ComponentOrientation o)           Sets the ComponentOrientation property of this container and all components contained within it.
boolean	areFocusTraversalKeysSet(int id)           Returns whether the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Container.
int	countComponents()           Deprecated. As of JDK version 1.1, replaced by getComponentCount().
void	deliverEvent(Event e)           Deprecated. As of JDK version 1.1, replaced by dispatchEvent(AWTEvent e)
void	doLayout()           Causes this container to lay out its components.
Component	findComponentAt(int x, int y)           Locates the visible child component that contains the specified position.
Component	findComponentAt(Point p)           Locates the visible child component that contains the specified point.
float	getAlignmentX()           Returns the alignment along the x axis.
float	getAlignmentY()           Returns the alignment along the y axis.
Component	getComponent(int n)           Gets the nth component in this container.
Component	getComponentAt(int x, int y)           Locates the component that contains the x,y position.
Component	getComponentAt(Point p)           Gets the component that contains the specified point.
int	getComponentCount()           Gets the number of components in this panel.
Component[]	getComponents()           Gets all the components in this container.
int	getComponentZOrder(Component comp)           Returns the z-order index of the component inside the container.
ContainerListener[]	getContainerListeners()           Returns an array of all the container listeners registered on this container.
Set<AWTKeyStroke>	getFocusTraversalKeys(int id)           Returns the Set of focus traversal keys for a given traversal operation for this Container.
FocusTraversalPolicy	getFocusTraversalPolicy()           Returns the focus traversal policy that will manage keyboard traversal of this Container's children, or null if this Container is not a focus cycle root.
Insets	getInsets()           Determines the insets of this container, which indicate the size of the container's border.
LayoutManager	getLayout()           Gets the layout manager for this container.
<T extends EventListener> T[]	getListeners(Class<T> listenerType)           Returns an array of all the objects currently registered as FooListeners upon this Container.
Dimension	getMaximumSize()           Returns the maximum size of this container.
Dimension	getMinimumSize()           Returns the minimum size of this container.
Point	getMousePosition(boolean allowChildren)           Returns the position of the mouse pointer in this Container's coordinate space if the Container is under the mouse pointer, otherwise returns null.
Dimension	getPreferredSize()           Returns the preferred size of this container.
Insets	insets()           Deprecated. As of JDK version 1.1, replaced by getInsets().
void	invalidate()           Invalidates the container.
boolean	isAncestorOf(Component c)           Checks if the component is contained in the component hierarchy of this container.
boolean	isFocusCycleRoot()           Returns whether this Container is the root of a focus traversal cycle.
boolean	isFocusCycleRoot(Container container)           Returns whether the specified Container is the focus cycle root of this Container's focus traversal cycle.
boolean	isFocusTraversalPolicyProvider()           Returns whether this container provides focus traversal policy.
boolean	isFocusTraversalPolicySet()           Returns whether the focus traversal policy has been explicitly set for this Container.
void	layout()           Deprecated. As of JDK version 1.1, replaced by doLayout().
void	list(PrintStream out, int indent)           Prints a listing of this container to the specified output stream.
void	list(PrintWriter out, int indent)           Prints out a list, starting at the specified indentation, to the specified print writer.
Component	locate(int x, int y)           Deprecated. As of JDK version 1.1, replaced by getComponentAt(int, int).
Dimension	minimumSize()           Deprecated. As of JDK version 1.1, replaced by getMinimumSize().
void	paint(Graphics g)           Paints the container.
void	paintComponents(Graphics g)           Paints each of the components in this container.
protected  String	paramString()           Returns a string representing the state of this Container.
Dimension	preferredSize()           Deprecated. As of JDK version 1.1, replaced by getPreferredSize().
void	print(Graphics g)           Prints the container.
void	printComponents(Graphics g)           Prints each of the components in this container.
protected  void	processContainerEvent(ContainerEvent e)           Processes container events occurring on this container by dispatching them to any registered ContainerListener objects.
protected  void	processEvent(AWTEvent e)           Processes events on this container.
void	remove(Component comp)           Removes the specified component from this container.
void	remove(int index)           Removes the component, specified by index, from this container.
void	removeAll()           Removes all the components from this container.
void	removeContainerListener(ContainerListener l)           Removes the specified container listener so it no longer receives container events from this container.
void	removeNotify()           Makes this Container undisplayable by removing its connection to its native screen resource.
void	setComponentZOrder(Component comp, int index)           Moves the specified component to the specified z-order index in the container.
void	setFocusCycleRoot(boolean focusCycleRoot)           Sets whether this Container is the root of a focus traversal cycle.
void	setFocusTraversalKeys(int id, Set<? extends AWTKeyStroke> keystrokes)           Sets the focus traversal keys for a given traversal operation for this Container.
void	setFocusTraversalPolicy(FocusTraversalPolicy policy)           Sets the focus traversal policy that will manage keyboard traversal of this Container's children, if this Container is a focus cycle root.
void	setFocusTraversalPolicyProvider(boolean provider)           Sets whether this container will be used to provide focus traversal policy.
void	setFont(Font f)           Sets the font of this container.
void	setLayout(LayoutManager mgr)           Sets the layout manager for this container.
void	transferFocusBackward()           Transfers the focus to the previous component, as though this Component were the focus owner.
void	transferFocusDownCycle()           Transfers the focus down one focus traversal cycle.
void	update(Graphics g)           Updates the container.
void	validate()           Validates this container and all of its subcomponents.
protected  void	validateTree()           Recursively descends the container tree and recomputes the layout for any subtrees marked as needing it (those marked as invalid).

 

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, getAccessibleContext, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, 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, 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, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, reshape, resize, resize, 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, transferFocusUpCycle

 

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

 

Constructor Detail

Container

public Container()

Constructs a new Container. Containers can be extended directly, but are lightweight in this case and must be contained by a parent somewhere higher up in the component tree that is native. (such as Frame for example).

getComponentCount

public int getComponentCount()

Gets the number of components in this panel.

Returns:

the number of components in this panel.

Since:

JDK1.1

See Also:

getComponent(int)

countComponents

@Deprecated
public int countComponents()

Deprecated. As of JDK version 1.1, replaced by getComponentCount().

getComponent

public Component getComponent(int n)

Gets the nth component in this container.

Parameters:

n - the index of the component to get.

Returns:

the n^th component in this container.

Throws:

ArrayIndexOutOfBoundsException - if the n^th value does not exist.

getComponents

public Component[] getComponents()

Gets all the components in this container.

Returns:

an array of all the components in this container.

getInsets

public Insets getInsets()

Determines the insets of this container, which indicate the size of the container's border.

A Frame object, for example, has a top inset that corresponds to the height of the frame's title bar.

Returns:

the insets of this container.

Since:

JDK1.1

See Also:

Insets, LayoutManager

insets

@Deprecated
public Insets insets()

Deprecated. As of JDK version 1.1, replaced by getInsets().

add

public Component add(Component comp)

Appends the specified component to the end of this container. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.

Parameters:

comp - the component to be added

Returns:

the component argument

Throws:

NullPointerException - if comp is null

See Also:

addImpl(java.awt.Component, java.lang.Object, int), validate(), JComponent.revalidate()

add

public Component add(String name,
                     Component comp)

Adds the specified component to this container. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

This method is obsolete as of 1.1. Please use the method add(Component, Object) instead.

Throws:

NullPointerException - if comp is null

See Also:

add(Component, Object)

add

public Component add(Component comp,
                     int index)

Adds the specified component to this container at the given position. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.

Parameters:

comp - the component to be added

index - the position at which to insert the component, or -1 to append the component to the end

Returns:

the component comp

Throws:

NullPointerException - if comp is null

IllegalArgumentException - if index is invalid (see addImpl(java.awt.Component, java.lang.Object, int) for details)

See Also:

addImpl(java.awt.Component, java.lang.Object, int), remove(int), validate(), JComponent.revalidate()

setComponentZOrder

public void setComponentZOrder(Component comp,
                               int index)

Moves the specified component to the specified z-order index in the container. The z-order determines the order that components are painted; the component with the highest z-order paints first and the component with the lowest z-order paints last. Where components overlap, the component with the lower z-order paints over the component with the higher z-order.

If the component is a child of some other container, it is removed from that container before being added to this container. The important difference between this method and java.awt.Container.add(Component, int) is that this method doesn't call removeNotify on the component while removing it from its previous container unless necessary and when allowed by the underlying native windowing system. This way, if the component has the keyboard focus, it maintains the focus when moved to the new position.

This property is guaranteed to apply only to lightweight non-Container components.

Note: Not all platforms support changing the z-order of heavyweight components from one container into another without the call to removeNotify. There is no way to detect whether a platform supports this, so developers shouldn't make any assumptions.

Parameters:

comp - the component to be moved

index - the position in the container's list to insert the component, where getComponentCount() appends to the end

Throws:

NullPointerException - if comp is null

IllegalArgumentException - if comp is one of the container's parents

IllegalArgumentException - if index is not in the range [0, getComponentCount()] for moving between containers, or not in the range [0, getComponentCount()-1] for moving inside a container

IllegalArgumentException - if adding a container to itself

IllegalArgumentException - if adding a Window to a container

Since:

1.5

See Also:

getComponentZOrder(java.awt.Component)

getComponentZOrder

public int getComponentZOrder(Component comp)

Returns the z-order index of the component inside the container. The higher a component is in the z-order hierarchy, the lower its index. The component with the lowest z-order index is painted last, above all other child components.

Parameters:

comp - the component being queried

Returns:

the z-order index of the component; otherwise returns -1 if the component is null or doesn't belong to the container

Since:

1.5

See Also:

setComponentZOrder(java.awt.Component, int)

add

public void add(Component comp,
                Object constraints)

Adds the specified component to the end of this container. Also notifies the layout manager to add the component to this container's layout using the specified constraints object. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.

Parameters:

comp - the component to be added

constraints - an object expressing layout contraints for this component

Throws:

NullPointerException - if comp is null

Since:

JDK1.1

See Also:

addImpl(java.awt.Component, java.lang.Object, int), validate(), JComponent.revalidate(), LayoutManager

add

public void add(Component comp,
                Object constraints,
                int index)

Adds the specified component to this container with the specified constraints at the specified index. Also notifies the layout manager to add the component to the this container's layout using the specified constraints object. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.

Parameters:

comp - the component to be added

constraints - an object expressing layout contraints for this

index - the position in the container's list at which to insert the component; -1 means insert at the end component

Throws:

NullPointerException - if comp is null

IllegalArgumentException - if index is invalid (see addImpl(java.awt.Component, java.lang.Object, int) for details)

See Also:

addImpl(java.awt.Component, java.lang.Object, int), validate(), JComponent.revalidate(), remove(int), LayoutManager

addImpl

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

Adds the specified component to this container at the specified index. This method also notifies the layout manager to add the component to this container's layout using the specified constraints object via the addLayoutComponent method.

The constraints are defined by the particular layout manager being used. For example, the BorderLayout class defines five constraints: BorderLayout.NORTH, BorderLayout.SOUTH, BorderLayout.EAST, BorderLayout.WEST, and BorderLayout.CENTER.

The GridBagLayout class requires a GridBagConstraints object. Failure to pass the correct type of constraints object results in an IllegalArgumentException.

If the current layout manager implements LayoutManager2, then LayoutManager2.addLayoutComponent(Component,Object) is invoked on it. If the current layout manager does not implement LayoutManager2, and constraints is a String, then LayoutManager.addLayoutComponent(String,Component) is invoked on it.

If the component is not an ancestor of this container and has a non-null parent, it is removed from its current parent before it is added to this container.

This is the method to override if a program needs to track every add request to a container as all other add methods defer to this one. An overriding method should usually include a call to the superclass's version of the method:

super.addImpl(comp, constraints, index)

Parameters:

comp - the component to be added

constraints - an object expressing layout constraints for this component

index - the position in the container's list at which to insert the component, where -1 means append to the end

Throws:

IllegalArgumentException - if index is invalid; if comp is a child of this container, the valid range is [-1, getComponentCount()-1]; if component is not a child of this container, the valid range is [-1, getComponentCount()]

IllegalArgumentException - if comp is an ancestor of this container

IllegalArgumentException - if adding a window to a container

NullPointerException - if comp is null

Since:

JDK1.1

See Also:

add(Component), add(Component, int), add(Component, java.lang.Object), LayoutManager, LayoutManager2

remove

public void remove(int index)

Removes the component, specified by index, from this container. This method also notifies the layout manager to remove the component from this container's layout via the removeLayoutComponent method.

Note: If a component has been removed from a container that had been displayed, validate() must be called on that container to reflect changes. If multiple components are being removed, you can improve efficiency by calling validate() only once, after all the components have been removed.

Parameters:

index - the index of the component to be removed

Throws:

ArrayIndexOutOfBoundsException - if index is not in range [0, getComponentCount()-1]

Since:

JDK1.1

See Also:

add(java.awt.Component), validate(), getComponentCount()

remove

public void remove(Component comp)

Removes the specified component from this container. This method also notifies the layout manager to remove the component from this container's layout via the removeLayoutComponent method.

Note: If a component has been removed from a container that had been displayed, validate() must be called on that container to reflect changes. If multiple components are being removed, you can improve efficiency by calling validate() only once, after all the components have been removed.

Parameters:

comp - the component to be removed

See Also:

add(java.awt.Component), validate(), remove(int)

removeAll

public void removeAll()

Removes all the components from this container. This method also notifies the layout manager to remove the components from this container's layout via the removeLayoutComponent method.

See Also:

add(java.awt.Component), remove(int)

getLayout

public LayoutManager getLayout()

Gets the layout manager for this container.

See Also:

doLayout(), setLayout(java.awt.LayoutManager)

setLayout

public void setLayout(LayoutManager mgr)

Sets the layout manager for this container.

Parameters:

mgr - the specified layout manager

See Also:

doLayout(), getLayout()

doLayout

public void doLayout()

Causes this container to lay out its components. Most programs should not call this method directly, but should invoke the validate method instead.

Overrides:

doLayout in class Component

Since:

JDK1.1

See Also:

LayoutManager.layoutContainer(java.awt.Container), setLayout(java.awt.LayoutManager), validate()

layout

@Deprecated
public void layout()

Deprecated. As of JDK version 1.1, replaced by doLayout().

Overrides:

layout in class Component

invalidate

public void invalidate()

Invalidates the container. The container and all parents above it are marked as needing to be laid out. This method can be called often, so it needs to execute quickly.

If the LayoutManager installed on this container is an instance of LayoutManager2, then LayoutManager2.invalidateLayout(Container) is invoked on it supplying this Container as the argument.

Overrides:

invalidate in class Component

See Also:

validate(), layout(), LayoutManager, LayoutManager2.invalidateLayout(Container)

validate

public void validate()

Validates this container and all of its subcomponents.

The validate method is used to cause a container to lay out its subcomponents again. It should be invoked when this container's subcomponents are modified (added to or removed from the container, or layout-related information changed) after the container has been displayed.

If this Container is not valid, this method invokes the validateTree method and marks this Container as valid. Otherwise, no action is performed.

Overrides:

validate in class Component

See Also:

add(java.awt.Component), Component.invalidate(), JComponent.revalidate(), validateTree()

validateTree

protected void validateTree()

Recursively descends the container tree and recomputes the layout for any subtrees marked as needing it (those marked as invalid). Synchronization should be provided by the method that calls this one: validate.

See Also:

doLayout(), validate()

setFont

public void setFont(Font f)

Sets the font of this container.

Overrides:

setFont in class Component

Parameters:

f - The font to become this container's font.

Since:

JDK1.0

See Also:

Component.getFont()

getPreferredSize

public Dimension getPreferredSize()

Returns the preferred size of this container. If the preferred size has not been set explicitly by Component.setPreferredSize(Dimension) and this Container has a non-null LayoutManager, then LayoutManager.preferredLayoutSize(Container) is used to calculate the preferred size.

Note: some implementations may cache the value returned from the LayoutManager. Implementations that cache need not invoke preferredLayoutSize on the LayoutManager every time this method is invoked, rather the LayoutManager will only be queried after the Container becomes invalid.

Overrides:

getPreferredSize in class Component

Returns:

an instance of Dimension that represents the preferred size of this container.

See Also:

getMinimumSize(), getMaximumSize(), getLayout(), LayoutManager.preferredLayoutSize(Container), Component.getPreferredSize()

preferredSize

@Deprecated
public Dimension preferredSize()

Deprecated. As of JDK version 1.1, replaced by getPreferredSize().

Overrides:

preferredSize in class Component

getMinimumSize

public Dimension getMinimumSize()

Returns the minimum size of this container. If the minimum size has not been set explicitly by Component.setMinimumSize(Dimension) and this Container has a non-null LayoutManager, then LayoutManager.minimumLayoutSize(Container) is used to calculate the minimum size.

Note: some implementations may cache the value returned from the LayoutManager. Implementations that cache need not invoke minimumLayoutSize on the LayoutManager every time this method is invoked, rather the LayoutManager will only be queried after the Container becomes invalid.

Overrides: