JavaTM 2 Platform
Std. Ed. v1.3.1

java.awt
Class Container

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
All Implemented Interfaces:
ImageObserver, MenuContainer, Serializable
Direct Known Subclasses:
BasicSplitPaneDivider, Box, 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).

Since:
JDK1.0
See Also:
add(java.awt.Component, int), getComponent(int), LayoutManager, Serialized Form

Inner Class Summary
protected  class Container.AccessibleAWTContainer
          Inner class of Container used to provide default support for accessibility.
 
Inner classes inherited from class java.awt.Component
Component.AccessibleAWTComponent
 
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)
          Adds 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.
 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.
 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.
 EventListener[] getListeners(Class listenerType)
          Return an array of all the listeners that were added to the Container with addXXXListener(), where XXX is the name of the listenerType argument.
 Dimension getMaximumSize()
          Returns the maximum size of this container.
 Dimension getMinimumSize()
          Returns the minimum size of this container.
 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.
 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 indention, 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 the parameter 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 setFont(Font f)
          Sets the font of this container.
 void setLayout(LayoutManager mgr)
          Sets the layout manager for this container.
 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, addPropertyChangeListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getAccessibleContext, getBackground, getBounds, getBounds, getColorModel, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocation, getLocationOnScreen, getName, getParent, getPeer, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isDisplayable, isDoubleBuffered, isEnabled, isFocusTraversable, isLightweight, isOpaque, 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, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, resize, resize, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus
 
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).
Method Detail

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

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 nth component in this container.
Throws:
ArrayIndexOutOfBoundsException - if the nth 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

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


add

public Component add(Component comp)
Adds the specified component to the end of this container.
Parameters:
comp - the component to be added.
Returns:
the component argument.

add

public Component add(String name,
                     Component comp)
Adds the specified component to this container. It is strongly advised to use the 1.1 method, add(Component, Object), in place of this method.

add

public Component add(Component comp,
                     int index)
Adds the specified component to this container at the given position.
Parameters:
comp - the component to be added.
index - the position at which to insert the component, or -1 to insert the component at the end.
Returns:
the component comp
See Also:
remove(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.
Parameters:
comp - the component to be added
constraints - an object expressing layout contraints for this component
Since:
JDK1.1
See Also:
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.
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
See Also:
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.

This is the method to override if a program needs to track every add request to a container. 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 contraints for this component.
index - the position in the container's list at which to insert the component, where -1 means insert at the end.
Since:
JDK1.1
See Also:
add(java.awt.Component), add(java.awt.Component, int), add(java.awt.Component, java.lang.Object), LayoutManager

remove

public void remove(int index)
Removes the component, specified by index, from this container.
Parameters:
index - the index of the component to be removed.
Since:
JDK1.1
See Also:
add(java.awt.Component)

remove

public void remove(Component comp)
Removes the specified component from this container.
Parameters:
comp - the component to be removed
See Also:
add(java.awt.Component)

removeAll

public void removeAll()
Removes all the components from this container.
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

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.
Overrides:
invalidate in class Component
See Also:
validate(), layout(), LayoutManager

validate

public void validate()
Validates this container and all of its subcomponents.

AWT uses validate to cause a container to lay out its subcomponents again after the components it contains have been added to or modified.

Overrides:
validate in class Component
See Also:
validate(), Component.invalidate()

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.

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.
Overrides:
getPreferredSize in class Component
Returns:
an instance of Dimension that represents the preferred size of this container.
See Also:
getMinimumSize(), getLayout(), LayoutManager.preferredLayoutSize(java.awt.Container), Component.getPreferredSize()

preferredSize

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.
Overrides:
getMinimumSize in class Component
Returns:
an instance of Dimension that represents the minimum size of this container.
Since:
JDK1.1
See Also:
getPreferredSize(), getLayout(), LayoutManager.minimumLayoutSize(java.awt.Container), Component.getMinimumSize()

minimumSize

public Dimension minimumSize()
Deprecated. As of JDK version 1.1, replaced by getMinimumSize().

Overrides:
minimumSize in class Component

getMaximumSize

public Dimension getMaximumSize()
Returns the maximum size of this container.
Overrides:
getMaximumSize in class Component
See Also:
getPreferredSize()

getAlignmentX

public float getAlignmentX()
Returns the alignment along the x axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.
Overrides:
getAlignmentX in class Component

getAlignmentY

public float getAlignmentY()
Returns the alignment along the y axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.
Overrides:
getAlignmentY in class Component

paint

public void paint(Graphics g)
Paints the container. This forwards the paint to any lightweight components that are children of this container. If this method is reimplemented, super.paint(g) should be called so that lightweight components are properly rendered. If a child component is entirely clipped by the current clipping setting in g, paint() will not be forwarded to that child.
Overrides:
paint in class Component
Parameters:
g - the specified Graphics window
See Also:
Component.update(java.awt.Graphics)

update

public void update(Graphics g)
Updates the container. This forwards the update to any lightweight components that are children of this container. If this method is reimplemented, super.update(g) should be called so that lightweight components are properly rendered. If a child component is entirely clipped by the current clipping setting in g, update() will not be forwarded to that child.
Overrides:
update in class Component
Parameters:
g - the specified Graphics window
See Also:
Component.update(java.awt.Graphics)

print

public void print(Graphics g)
Prints the container. This forwards the print to any lightweight components that are children of this container. If this method is reimplemented, super.print(g) should be called so that lightweight components are properly rendered. If a child component is entirely clipped by the current clipping setting in g, print() will not be forwarded to that child.
Overrides:
print in class Component
Parameters:
g - the specified Graphics window
See Also:
Component.update(java.awt.Graphics)

paintComponents

public void paintComponents(Graphics g)
Paints each of the components in this container.
Parameters:
g - the graphics context.
See Also:
Component.paint(java.awt.Graphics), Component.paintAll(java.awt.Graphics)

printComponents

public void printComponents(Graphics g)
Prints each of the components in this container.
Parameters:
g - the graphics context.
See Also:
Component.print(java.awt.Graphics), Component.printAll(java.awt.Graphics)

addContainerListener

public void addContainerListener(ContainerListener l)
Adds the specified container listener to receive container events from this container. If l is null, no exception is thrown and no action is performed.
Parameters:
l - the container listener

removeContainerListener

public void removeContainerListener(ContainerListener l)
Removes the specified container listener so it no longer receives container events from this container. If l is null, no exception is thrown and no action is performed.
Parameters:
l - the container listener

getListeners

public EventListener[] getListeners(Class listenerType)
Return an array of all the listeners that were added to the Container with addXXXListener(), where XXX is the name of the listenerType argument. For example, to get all of the ContainerListener(s) for the given Container c, one would write:
 ContainerListener[] cls = (ContainerListener[])(c.getListeners(ContainerListener.class))
 
If no such listener list exists, then an empty array is returned.
Overrides:
getListeners in class Component
Parameters:
listenerType - Type of listeners requested
Returns:
all of the listeners of the specified type supported by this container
Since:
1.3

processEvent

protected void processEvent(AWTEvent e)
Processes events on this container. If the event is a ContainerEvent, it invokes the processContainerEvent method, else it invokes its superclass's processEvent.
Overrides:
processEvent in class Component
Parameters:
e - the event

processContainerEvent

protected void processContainerEvent(ContainerEvent e)
Processes container events occurring on this container by dispatching them to any registered ContainerListener objects. NOTE: This method will not be called unless container events are enabled for this component; this happens when one of the following occurs: a) A ContainerListener object is registered via addContainerListener() b) Container events are enabled via enableEvents()
Parameters:
e - the container event
See Also:
Component.enableEvents(long)

deliverEvent

public void deliverEvent(Event e)
Deprecated. As of JDK version 1.1, replaced by dispatchEvent(AWTEvent e)

Overrides:
deliverEvent in class Component

getComponentAt

public Component getComponentAt(int x,
                                int y)
Locates the component that contains the x,y position. The top-most child component is returned in the case where there is overlap in the components. This is determined by finding the component closest to the index 0 that claims to contain the given point via Component.contains(), except that Components which have native peers take precedence over those which do not (i.e., lightweight Components).
Overrides:
getComponentAt in class Component
Parameters:
x - the x coordinate
y - the y coordinate
Returns:
null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of the container the container itself is returned; otherwise the top-most child is returned.
Since:
JDK1.1
See Also:
Component.contains(int, int)

locate

public Component locate(int x,
                        int y)
Deprecated. As of JDK version 1.1, replaced by getComponentAt(int, int).

Overrides:
locate in class Component

getComponentAt

public Component getComponentAt(Point p)
Gets the component that contains the specified point.
Overrides:
getComponentAt in class Component
Parameters:
p - the point.
Returns:
returns the component that contains the point, or null if the component does not contain the point.
Since:
JDK1.1
See Also:
Component.contains(int, int)

findComponentAt

public Component findComponentAt(int x,
                                 int y)
Locates the visible child component that contains the specified position. The top-most child component is returned in the case where there is overlap in the components. If the containing child component is a Container, this method will continue searching for the deepest nested child component. Components which are not visible are ignored during the search.

The findComponentAt method is different from getComponentAt in that getComponentAt only searches the Container's immediate children; if the containing component is a Container, findComponentAt will search that child to find a nested component.

Parameters:
x - the x coordinate
y - the y coordinate
Returns:
null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of the container the container itself is returned.
Since:
1.2
See Also:
Component.contains(int, int), getComponentAt

findComponentAt

public Component findComponentAt(Point p)
Locates the visible child component that contains the specified point. The top-most child component is returned in the case where there is overlap in the components. If the containing child component is a Container, this method will continue searching for the deepest nested child component. Components which are not visible are ignored during the search.

The findComponentAt method is different from getComponentAt in that getComponentAt only searches the Container's immediate children; if the containing component is a Container, findComponentAt will search that child to find a nested component.

Parameters:
p - the point.
Returns:
null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of the container the container itself is returned.
Since:
1.2
See Also:
Component.contains(int, int), getComponentAt

addNotify

public void addNotify()
Makes this Container displayable by connecting it to a native screen resource. Making a container displayable will cause any of its children to be made displayable. This method is called internally by the toolkit and should not be called directly by programs.
Overrides:
addNotify in class Component
See Also:
Component.isDisplayable(), removeNotify()

removeNotify

public void removeNotify()
Makes this Container undisplayable by removing its connection to its native screen resource. Make a container undisplayable will cause any of its children to be made undisplayable. This method is called by the toolkit internally and should not be called directly by programs.
Overrides:
removeNotify in class Component
See Also:
Component.isDisplayable(), addNotify()

isAncestorOf

public boolean isAncestorOf(Component c)
Checks if the component is contained in the component hierarchy of this container.
Parameters:
c - the component
Returns:
true if it is an ancestor; false otherwise.
Since:
JDK1.1

paramString

protected String paramString()
Returns the parameter string representing the state of this container. This string is useful for debugging.
Overrides:
paramString in class Component
Returns:
the parameter string of this container.

list

public void list(PrintStream out,
                 int indent)
Prints a listing of this container to the specified output stream. The listing starts at the specified indentation.
Overrides:
list in class Component
Parameters:
out - a print stream.
indent - the number of spaces to indent.
Since:
JDK
See Also:
Component.list(java.io.PrintStream, int)

list

public void list(PrintWriter out,
                 int indent)
Prints out a list, starting at the specified indention, to the specified print writer.
Overrides:
list in class Component
Following copied from class: java.awt.Component
Parameters:
out - The print writer to print to.
indent - The number of spaces to indent.
See Also:
PrintStream.println(java.lang.Object)

JavaTM 2 Platform
Std. Ed. v1.3.1

Submit a bug or feature
For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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