Module java.desktop
Package 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:
1.0
See Also:
add(java.awt.Component, int), getComponent(int), LayoutManager, Serialized Form

  • Constructor Details

    • 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 Details

    • getComponentCount

      public int getComponentCount()
      Gets the number of components in this panel.

      Note: This method should be called under AWT tree lock.

      Returns:
      the number of components in this panel.
      Since:
      1.1
      See Also:
      getComponent(int), Component.getTreeLock()

    • countComponents

      @Deprecated public int countComponents()
      Deprecated.
      As of JDK version 1.1, replaced by getComponentCount().
      Returns the number of components in this container.
      Returns:
      the number of components in this container

    • getComponent

      public Component getComponent​(int n)
      Gets the nth component in this container.

      Note: This method should be called under AWT tree lock.

      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.
      See Also:
      Component.getTreeLock()

    • getComponents

      public Component[] getComponents()
      Gets all the components in this container.

      Note: This method should be called under AWT tree lock.

      Returns:
      an array of all the components in this container.
      See Also:
      Component.getTreeLock()

    • 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:
      1.1
      See Also:
      Insets, LayoutManager

    • insets

      @Deprecated public Insets insets()
      Deprecated.
      As of JDK version 1.1, replaced by getInsets().
      Returns the insets for this container.
      Returns:
      the insets for this container

    • 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).

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to display the added component.

      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), invalidate(), 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.

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to display the added component.

      Parameters:
      name - the name of the component to be added
      comp - the component to be added
      Returns:
      the component added
      Throws:
      NullPointerException - if comp is null
      See Also:
      add(Component, Object), invalidate()

    • 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).

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to display the added component.

      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), invalidate(), 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.

      This method changes layout-related information, and therefore, invalidates the component hierarchy.

      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), invalidate()

    • 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).

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to display the added component.

      Parameters:
      comp - the component to be added
      constraints - an object expressing layout constraints for this component
      Throws:
      NullPointerException - if comp is null
      Since:
      1.1
      See Also:
      addImpl(java.awt.Component, java.lang.Object, int), invalidate(), 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).

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to display the added component.

      Parameters:
      comp - the component to be added
      constraints - an object expressing layout constraints 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), invalidate(), 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)

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to display the added component.

      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:
      1.1
      See Also:
      add(Component), add(Component, int), add(Component, java.lang.Object), invalidate(), 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.

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to reflect the changes.

      Parameters:
      index - the index of the component to be removed
      Throws:
      ArrayIndexOutOfBoundsException - if index is not in range [0, getComponentCount()-1]
      Since:
      1.1
      See Also:
      add(java.awt.Component), invalidate(), 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.

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to reflect the changes.

      Parameters:
      comp - the component to be removed
      Throws:
      NullPointerException - if comp is null
      See Also:
      add(java.awt.Component), invalidate(), 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.

      This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to reflect the changes.

      See Also:
      add(java.awt.Component), remove(int), invalidate()

    • getLayout

      public LayoutManager getLayout()
      Gets the layout manager for this container.
      Returns:
      the current 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.

      This method changes layout-related information, and therefore, invalidates the component hierarchy.

      Parameters:
      mgr - the specified layout manager
      See Also:
      doLayout(), getLayout(), invalidate()

    • 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:
      1.1
      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

    • isValidateRoot

      public boolean isValidateRoot()
      Indicates if this container is a validate root.

      Layout-related changes, such as bounds of the validate root descendants, do not affect the layout of the validate root parent. This peculiarity enables the invalidate() method to stop invalidating the component hierarchy when the method encounters a validate root. However, to preserve backward compatibility this new optimized behavior is enabled only when the java.awt.smartInvalidate system property value is set to true.

      If a component hierarchy contains validate roots and the new optimized invalidate() behavior is enabled, the validate() method must be invoked on the validate root of a previously invalidated component to restore the validity of the hierarchy later. Otherwise, calling the validate() method on the top-level container (such as a Frame object) should be used to restore the validity of the component hierarchy.

      The Window class and the Applet class are the validate roots in AWT. Swing introduces more validate roots.

      Returns:
      whether this container is a validate root
      Since:
      1.7
      See Also:
      invalidate(), Component.invalidate(), JComponent.isValidateRoot(), JComponent.revalidate()

    • invalidate

      public void invalidate()
      Invalidates the container.

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

      Afterwards this method marks this container invalid, and invalidates its ancestors. See the Component.invalidate() method for more details.

      Overrides:
      invalidate in class Component
      See Also:
      validate(), layout(), LayoutManager2

    • validate

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

      Validating a container means laying out its subcomponents. Layout-related changes, such as setting the bounds of a component, or adding a component to the container, invalidate the container automatically. Note that the ancestors of the container may be invalidated also (see Component.invalidate() for details.) Therefore, to restore the validity of the hierarchy, the validate() method should be invoked on the top-most invalid container of the hierarchy.

      Validating the container may be a quite time-consuming operation. For performance reasons a developer may postpone the validation of the hierarchy till a set of layout-related operations completes, e.g. after adding all the children to the container.

      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), invalidate(), isValidateRoot(), 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.

      This method changes layout-related information, and therefore, invalidates the component hierarchy.

      Overrides:
      setFont in class Component
      Parameters:
      f - The font to become this container's font.
      Since:
      1.0
      See Also:
      Component.getFont(), invalidate()

    • 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().
      Description copied from class: Component
      Returns the component's preferred size.
      Overrides:
      preferredSize in class Component
      Returns:
      the component's preferred size

    • 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:
      getMinimumSize in class Component
      Returns:
      an instance of Dimension that represents the minimum size of this container.
      Since:
      1.1
      See Also:
      getPreferredSize(), getMaximumSize(), getLayout(), LayoutManager.minimumLayoutSize(Container), Component.getMinimumSize()

    • minimumSize

      @Deprecated public Dimension minimumSize()
      Deprecated.
      As of JDK version 1.1, replaced by getMinimumSize().
      Description copied from class: Component
      Returns the minimum size of this component.
      Overrides:
      minimumSize in class Component
      Returns:
      the minimum size of this component

    • getMaximumSize

      public Dimension getMaximumSize()
      Returns the maximum size of this container. If the maximum size has not been set explicitly by Component.setMaximumSize(Dimension) and the LayoutManager installed on this Container is an instance of LayoutManager2, then LayoutManager2.maximumLayoutSize(Container) is used to calculate the maximum size.

      Note: some implementations may cache the value returned from the LayoutManager2. Implementations that cache need not invoke maximumLayoutSize on the LayoutManager2 every time this method is invoked, rather the LayoutManager2 will only be queried after the Container becomes invalid.

      Overrides:
      getMaximumSize in class Component
      Returns:
      an instance of Dimension that represents the maximum size of this container.
      See Also:
      getPreferredSize(), getMinimumSize(), getLayout(), LayoutManager2.maximumLayoutSize(Container), Component.getMaximumSize()

    • 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
      Returns:
      the horizontal alignment of this 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
      Returns:
      the vertical alignment of this 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(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(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(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.

      Refer to AWT Threading Issues for details on AWT's threading model.

      Parameters:
      l - the container listener
      See Also:
      removeContainerListener(java.awt.event.ContainerListener), getContainerListeners()

    • 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.

      Refer to AWT Threading Issues for details on AWT's threading model.

      Parameters:
      l - the container listener
      See Also:
      addContainerListener(java.awt.event.ContainerListener), getContainerListeners()

    • getContainerListeners

      public ContainerListener[] getContainerListeners()
      Returns an array of all the container listeners registered on this container.
      Returns:
      all of this container's ContainerListeners or an empty array if no container listeners are currently registered
      Since:
      1.4
      See Also:
      addContainerListener(java.awt.event.ContainerListener), removeContainerListener(java.awt.event.ContainerListener)

    • getListeners

      public <T extends EventListener> T[] getListeners​(Class<T> listenerType)
      Returns an array of all the objects currently registered as FooListeners upon this Container. FooListeners are registered using the addFooListener method.

      You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a Container c for its container listeners with the following code: 

      ContainerListener[] cls = (ContainerListener[])(c.getListeners(ContainerListener.class));
      If no such listeners exist, this method returns an empty array.
      Overrides:
      getListeners in class Component
      Type Parameters:
      T - the type of the listeners
      Parameters:
      listenerType - the type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener
      Returns:
      an array of all objects registered as FooListeners on this container, or an empty array if no such listeners have been added
      Throws:
      ClassCastException - if listenerType doesn't specify a class or interface that implements java.util.EventListener
      NullPointerException - if listenerType is null
      Since:
      1.3
      See Also:
      getContainerListeners()

    • 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.

      Note that if the event parameter is null the behavior is unspecified and may result in an exception.

      Overrides:
      processEvent in class Component
      Parameters:
      e - the event
      See Also:
      Component.processComponentEvent(java.awt.event.ComponentEvent), Component.processFocusEvent(java.awt.event.FocusEvent), Component.processKeyEvent(java.awt.event.KeyEvent), Component.processMouseEvent(java.awt.event.MouseEvent), Component.processMouseMotionEvent(java.awt.event.MouseEvent), Component.processInputMethodEvent(java.awt.event.InputMethodEvent), Component.processHierarchyEvent(java.awt.event.HierarchyEvent), Component.processMouseWheelEvent(java.awt.event.MouseWheelEvent)

    • 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 ContainerListener object is registered via addContainerListener
      • Container events are enabled via enableEvents

      Note that if the event parameter is null the behavior is unspecified and may result in an exception.

      Parameters:
      e - the container event
      See Also:
      Component.enableEvents(long)

    • deliverEvent

      @Deprecated public void deliverEvent​(Event e)
      Deprecated.
      As of JDK version 1.1, replaced by dispatchEvent(AWTEvent e)
      Overrides:
      deliverEvent in class Component
      Parameters:
      e - the event to deliver

    • 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:
      1.1
      See Also:
      Component.contains(int, int)

    • locate

      @Deprecated public Component locate​(int x, int y)
      Deprecated.
      As of JDK version 1.1, replaced by getComponentAt(int, int).
      Description copied from class: Component
      Returns the component occupying the position specified (this component, or immediate child component, or null if neither of the first two occupies the location).
      Overrides:
      locate in class Component
      Parameters:
      x - the x coordinate to search for components at
      y - the y coordinate to search for components at
      Returns:
      the component at the specified location or null

    • 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:
      1.1
      See Also:
      Component.contains(int, int)

    • getMousePosition

      public Point getMousePosition​(boolean allowChildren) throws HeadlessException
      Returns the position of the mouse pointer in this Container's coordinate space if the Container is under the mouse pointer, otherwise returns null. This method is similar to Component.getMousePosition() with the exception that it can take the Container's children into account. If allowChildren is false, this method will return a non-null value only if the mouse pointer is above the Container directly, not above the part obscured by children. If allowChildren is true, this method returns a non-null value if the mouse pointer is above Container or any of its descendants.
      Parameters:
      allowChildren - true if children should be taken into account
      Returns:
      mouse coordinates relative to this Component, or null
      Throws:
      HeadlessException - if GraphicsEnvironment.isHeadless() returns true
      Since:
      1.5
      See Also:
      Component.getMousePosition()

    • 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(int, int)

    • 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.
      Throws:
      NullPointerException - if p is null
      Since:
      1.2
      See Also:
      Component.contains(int, int), getComponentAt(int, int)

    • addNotify

      public void addNotify()
      Makes this Container displayable by connecting it to a native screen resource. Making a container displayable will cause all 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. Making a container undisplayable will cause all 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:
      1.1

    • paramString

      protected String paramString()
      Returns a string representing the state of this Container. 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 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.

      The immediate children of the container are printed with an indentation of indent+1. The children of those children are printed at indent+2 and so on.

      Overrides:
      list in class Component
      Parameters:
      out - a print stream
      indent - the number of spaces to indent
      Throws:
      NullPointerException - if out is null
      Since:
      1.0
      See Also:
      Component.list(java.io.PrintStream, int)

    • list

      public void list​(PrintWriter out, int indent)
      Prints out a list, starting at the specified indentation, to the specified print writer.

      The immediate children of the container are printed with an indentation of indent+1. The children of those children are printed at indent+2 and so on.

      Overrides:
      list in class Component
      Parameters:
      out - a print writer
      indent - the number of spaces to indent
      Throws:
      NullPointerException - if out is null
      Since:
      1.1
      See Also:
      Component.list(java.io.PrintWriter, int)

    • setFocusTraversalKeys

      public void setFocusTraversalKeys​(int id, Set<? extends AWTKeyStroke> keystrokes)
      Sets the focus traversal keys for a given traversal operation for this Container.

      The default values for a Container's focus traversal keys are implementation-dependent. Sun recommends that all implementations for a particular native platform use the same default values. The recommendations for Windows and Unix are listed below. These recommendations are used in the Sun AWT implementations.

      Recommended default values for a Container's focus traversal keys
      Identifier Meaning Default
      KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS Normal forward keyboard traversal TAB on KEY_PRESSED, CTRL-TAB on KEY_PRESSED
      KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS Normal reverse keyboard traversal SHIFT-TAB on KEY_PRESSED, CTRL-SHIFT-TAB on KEY_PRESSED
      KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS Go up one focus traversal cycle none
      KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS Go down one focus traversal cycle none
      To disable a traversal key, use an empty Set; Collections.EMPTY_SET is recommended.

      Using the AWTKeyStroke API, client code can specify on which of two specific KeyEvents, KEY_PRESSED or KEY_RELEASED, the focus traversal operation will occur. Regardless of which KeyEvent is specified, however, all KeyEvents related to the focus traversal key, including the associated KEY_TYPED event, will be consumed, and will not be dispatched to any Container. It is a runtime error to specify a KEY_TYPED event as mapping to a focus traversal operation, or to map the same event to multiple default focus traversal operations.

      If a value of null is specified for the Set, this Container inherits the Set from its parent. If all ancestors of this Container have null specified for the Set, then the current KeyboardFocusManager's default Set is used.

      This method may throw a ClassCastException if any Object in keystrokes is not an AWTKeyStroke.

      Overrides:
      setFocusTraversalKeys in class Component
      Parameters:
      id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS
      keystrokes - the Set of AWTKeyStroke for the specified operation
      Throws:
      IllegalArgumentException - if id is not one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS, or if keystrokes contains null, or if any keystroke represents a KEY_TYPED event, or if any keystroke already maps to another focus traversal operation for this Container
      Since:
      1.4
      See Also:
      getFocusTraversalKeys(int), KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

    • getFocusTraversalKeys

      public Set<AWTKeyStroke> getFocusTraversalKeys​(int id)
      Returns the Set of focus traversal keys for a given traversal operation for this Container. (See setFocusTraversalKeys for a full description of each key.)

      If a Set of traversal keys has not been explicitly defined for this Container, then this Container's parent's Set is returned. If no Set has been explicitly defined for any of this Container's ancestors, then the current KeyboardFocusManager's default Set is returned.

      Overrides:
      getFocusTraversalKeys in class Component
      Parameters:
      id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS
      Returns:
      the Set of AWTKeyStrokes for the specified operation. The Set will be unmodifiable, and may be empty. null will never be returned.
      Throws:
      IllegalArgumentException - if id is not one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS
      Since:
      1.4
      See Also:
      setFocusTraversalKeys(int, java.util.Set<? extends java.awt.AWTKeyStroke>), KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

    • areFocusTraversalKeysSet

      public 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. If this method returns false, this Container is inheriting the Set from an ancestor, or from the current KeyboardFocusManager.
      Overrides:
      areFocusTraversalKeysSet in class Component
      Parameters:
      id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS
      Returns:
      true if the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Component; false otherwise.
      Throws:
      IllegalArgumentException - if id is not one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS
      Since:
      1.4

    • isFocusCycleRoot

      public boolean isFocusCycleRoot​(Container container)
      Returns whether the specified Container is the focus cycle root of this Container's focus traversal cycle. Each focus traversal cycle has only a single focus cycle root and each Container which is not a focus cycle root belongs to only a single focus traversal cycle. Containers which are focus cycle roots belong to two cycles: one rooted at the Container itself, and one rooted at the Container's nearest focus-cycle-root ancestor. This method will return true for both such Containers in this case.
      Overrides:
      isFocusCycleRoot in class Component
      Parameters:
      container - the Container to be tested
      Returns:
      true if the specified Container is a focus-cycle- root of this Container; false otherwise
      Since:
      1.4
      See Also:
      isFocusCycleRoot()

    • setFocusTraversalPolicy

      public 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. If the argument is null, this Container inherits its policy from its focus- cycle-root ancestor. If the argument is non-null, this policy will be inherited by all focus-cycle-root children that have no keyboard- traversal policy of their own (as will, recursively, their focus-cycle- root children).

      If this Container is not a focus cycle root, the policy will be remembered, but will not be used or inherited by this or any other Containers until this Container is made a focus cycle root.

      Parameters:
      policy - the new focus traversal policy for this Container
      Since:
      1.4
      See Also:
      getFocusTraversalPolicy(), setFocusCycleRoot(boolean), isFocusCycleRoot(java.awt.Container)

    • getFocusTraversalPolicy

      public 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. If no traversal policy has been explicitly set for this Container, then this Container's focus-cycle-root ancestor's policy is returned.
      Returns:
      this Container's focus traversal policy, or null if this Container is not a focus cycle root.
      Since:
      1.4
      See Also:
      setFocusTraversalPolicy(java.awt.FocusTraversalPolicy), setFocusCycleRoot(boolean), isFocusCycleRoot(java.awt.Container)

    • isFocusTraversalPolicySet

      public boolean isFocusTraversalPolicySet()
      Returns whether the focus traversal policy has been explicitly set for this Container. If this method returns false, this Container will inherit its focus traversal policy from an ancestor.
      Returns:
      true if the focus traversal policy has been explicitly set for this Container; false otherwise.
      Since:
      1.4

    • setFocusCycleRoot

      public void setFocusCycleRoot​(boolean focusCycleRoot)
      Sets whether this Container is the root of a focus traversal cycle. Once focus enters a traversal cycle, typically it cannot leave it via focus traversal unless one of the up- or down-cycle keys is pressed. Normal traversal is limited to this Container, and all of this Container's descendants that are not descendants of inferior focus cycle roots. Note that a FocusTraversalPolicy may bend these restrictions, however. For example, ContainerOrderFocusTraversalPolicy supports implicit down-cycle traversal.

      The alternative way to specify the traversal order of this Container's children is to make this Container a focus traversal policy provider.

      Parameters:
      focusCycleRoot - indicates whether this Container is the root of a focus traversal cycle
      Since:
      1.4
      See Also:
      isFocusCycleRoot(), setFocusTraversalPolicy(java.awt.FocusTraversalPolicy), getFocusTraversalPolicy(), ContainerOrderFocusTraversalPolicy, setFocusTraversalPolicyProvider(boolean)

    • isFocusCycleRoot

      public boolean isFocusCycleRoot()
      Returns whether this Container is the root of a focus traversal cycle. Once focus enters a traversal cycle, typically it cannot leave it via focus traversal unless one of the up- or down-cycle keys is pressed. Normal traversal is limited to this Container, and all of this Container's descendants that are not descendants of inferior focus cycle roots. Note that a FocusTraversalPolicy may bend these restrictions, however. For example, ContainerOrderFocusTraversalPolicy supports implicit down-cycle traversal.
      Returns:
      whether this Container is the root of a focus traversal cycle
      Since:
      1.4
      See Also:
      setFocusCycleRoot(boolean), setFocusTraversalPolicy(java.awt.FocusTraversalPolicy), getFocusTraversalPolicy(), ContainerOrderFocusTraversalPolicy

    • setFocusTraversalPolicyProvider

      public final void setFocusTraversalPolicyProvider​(boolean provider)
      Sets whether this container will be used to provide focus traversal policy. Container with this property as true will be used to acquire focus traversal policy instead of closest focus cycle root ancestor.
      Parameters:
      provider - indicates whether this container will be used to provide focus traversal policy
      Since:
      1.5
      See Also:
      setFocusTraversalPolicy(java.awt.FocusTraversalPolicy), getFocusTraversalPolicy(), isFocusTraversalPolicyProvider()

    • isFocusTraversalPolicyProvider

      public final boolean isFocusTraversalPolicyProvider()
      Returns whether this container provides focus traversal policy. If this property is set to true then when keyboard focus manager searches container hierarchy for focus traversal policy and encounters this container before any other container with this property as true or focus cycle roots then its focus traversal policy will be used instead of focus cycle root's policy.
      Returns:
      true if this container provides focus traversal policy, false otherwise
      Since:
      1.5
      See Also:
      setFocusTraversalPolicy(java.awt.FocusTraversalPolicy), getFocusTraversalPolicy(), setFocusCycleRoot(boolean), setFocusTraversalPolicyProvider(boolean)

    • transferFocusDownCycle

      public void transferFocusDownCycle()
      Transfers the focus down one focus traversal cycle. If this Container is a focus cycle root, then the focus owner is set to this Container's default Component to focus, and the current focus cycle root is set to this Container. If this Container is not a focus cycle root, then no focus traversal operation occurs.
      Since:
      1.4
      See Also:
      Component.requestFocus(), isFocusCycleRoot(java.awt.Container), setFocusCycleRoot(boolean)

    • applyComponentOrientation

      public void applyComponentOrientation​(ComponentOrientation o)
      Sets the ComponentOrientation property of this container and all components contained within it.

      This method changes layout-related information, and therefore, invalidates the component hierarchy.

      Overrides:
      applyComponentOrientation in class Component
      Parameters:
      o - the new component orientation of this container and the components contained within it.
      Throws:
      NullPointerException - if orientation is null.
      Since:
      1.4
      See Also:
      Component.setComponentOrientation(java.awt.ComponentOrientation), Component.getComponentOrientation(), invalidate()

    • addPropertyChangeListener

      public void addPropertyChangeListener​(PropertyChangeListener listener)
      Adds a PropertyChangeListener to the listener list. The listener is registered for all bound properties of this class, including the following:
      • this Container's font ("font")
      • this Container's background color ("background")
      • this Container's foreground color ("foreground")
      • this Container's focusability ("focusable")
      • this Container's focus traversal keys enabled state ("focusTraversalKeysEnabled")
      • this Container's Set of FORWARD_TRAVERSAL_KEYS ("forwardFocusTraversalKeys")
      • this Container's Set of BACKWARD_TRAVERSAL_KEYS ("backwardFocusTraversalKeys")
      • this Container's Set of UP_CYCLE_TRAVERSAL_KEYS ("upCycleFocusTraversalKeys")
      • this Container's Set of DOWN_CYCLE_TRAVERSAL_KEYS ("downCycleFocusTraversalKeys")
      • this Container's focus traversal policy ("focusTraversalPolicy")
      • this Container's focus-cycle-root state ("focusCycleRoot")
      Note that if this Container is inheriting a bound property, then no event will be fired in response to a change in the inherited property.

      If listener is null, no exception is thrown and no action is performed.

      Overrides:
      addPropertyChangeListener in class Component
      Parameters:
      listener - the PropertyChangeListener to be added
      See Also:
      Component.removePropertyChangeListener(java.beans.PropertyChangeListener), addPropertyChangeListener(java.lang.String,java.beans.PropertyChangeListener)

    • addPropertyChangeListener

      public void addPropertyChangeListener​(String propertyName, PropertyChangeListener listener)
      Adds a PropertyChangeListener to the listener list for a specific property. The specified property may be user-defined, or one of the following defaults:
      • this Container's font ("font")
      • this Container's background color ("background")
      • this Container's foreground color ("foreground")
      • this Container's focusability ("focusable")
      • this Container's focus traversal keys enabled state ("focusTraversalKeysEnabled")
      • this Container's Set of FORWARD_TRAVERSAL_KEYS ("forwardFocusTraversalKeys")
      • this Container's Set of BACKWARD_TRAVERSAL_KEYS ("backwardFocusTraversalKeys")
      • this Container's Set of UP_CYCLE_TRAVERSAL_KEYS ("upCycleFocusTraversalKeys")
      • this Container's Set of DOWN_CYCLE_TRAVERSAL_KEYS ("downCycleFocusTraversalKeys")
      • this Container's focus traversal policy ("focusTraversalPolicy")
      • this Container's focus-cycle-root state ("focusCycleRoot")
      • this Container's focus-traversal-policy-provider state("focusTraversalPolicyProvider")
      • this Container's focus-traversal-policy-provider state("focusTraversalPolicyProvider")
      Note that if this Container is inheriting a bound property, then no event will be fired in response to a change in the inherited property.

      If listener is null, no exception is thrown and no action is performed.

      Overrides:
      addPropertyChangeListener in class Component
      Parameters:
      propertyName - one of the property names listed above
      listener - the PropertyChangeListener to be added
      See Also:
      addPropertyChangeListener(java.beans.PropertyChangeListener), Component.removePropertyChangeListener(java.beans.PropertyChangeListener)