The state of the horizontal and vertical scrollbars is represented
by two ScrollPaneAdjustable objects (one for each
dimension) which implement the Adjustable interface.
The API provides methods to access those objects such that the
attributes on the Adjustable object (such as unitIncrement, value,
etc.) can be manipulated.
Certain adjustable properties (minimum, maximum, blockIncrement, and visibleAmount) are set internally by the scrollpane in accordance with the geometry of the scrollpane and its child and these should not be set by programs using the scrollpane.
If the scrollbar display policy is defined as "never", then the scrollpane can still be programmatically scrolled using the setScrollPosition() method and the scrollpane will move and clip the child's contents appropriately. This policy is useful if the program needs to create and manage its own adjustable controls.
The placement of the scrollbars is controlled by platform-specific properties set by the user outside of the program.
The initial size of this container is set to 100x100, but can be reset using setSize().
Scrolling with the wheel on a wheel-equipped mouse is enabled by default.
This can be disabled using setWheelScrollingEnabled.
Wheel scrolling can be customized by setting the block and
unit increment of the horizontal and vertical Adjustables.
For information on how mouse wheel events are dispatched, see
the class description for MouseWheelEvent
.
Insets are used to define any space used by scrollbars and any borders created by the scroll pane. getInsets() can be used to get the current value for the insets. If the value of scrollbarsAlwaysVisible is false, then the value of the insets will change dynamically depending on whether the scrollbars are currently visible or not.
getAlignmentY.
Specifies an alignment to the bottom of the component.getAlignmentY and
getAlignmentX. Specifies an alignment to
the center of the componentgetAlignmentX.
Specifies an alignment to the left side of the component.getAlignmentX.
Specifies an alignment to the right side of the component.getAlignmentY().
Specifies an alignment to the top of the component.
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.
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.
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.
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.
This method is obsolete as of 1.1. Please use the
method add(Component, Object) instead.
l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.getInputMethodRequests to return an
InputMethodRequests instance.
If listener l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.For information on how mouse wheel events are dispatched, see the class description for MouseWheelEvent .
If l is null, no exception is thrown and no
action is performed.
If listener is null, no exception is thrown and no action is performed.
If listener is null, no exception is thrown and no action is performed.
ComponentOrientation property of this container
and all components contained within it.false, this Container is inheriting the
Set from an ancestor, or from the current KeyboardFocusManager.
This method does not cause the image to begin loading. An
application must use the prepareImage method
to force the loading of an image.
Information on the flags returned by this method can be found
with the discussion of the ImageObserver interface.
This method does not cause the image to begin loading. An
application must use the prepareImage method
to force the loading of an image.
The checkImage method of Component
calls its peer's checkImage method to calculate
the flags. If this component does not yet have a peer, the
component's toolkit's checkImage method is called
instead.
Information on the flags returned by this method can be found
with the discussion of the ImageObserver interface.
x and y are defined to be
relative to the coordinate system of this component.VolatileImage interface.processEvent before returning for 1.1-style
events which have been enabled for the Component.
The equals method implements an equivalence relation
on non-null object references:
x, x.equals(x) should return
true.
x and y, x.equals(y)
should return true if and only if
y.equals(x) returns true.
x, y, and z, if
x.equals(y) returns true and
y.equals(z) returns true, then
x.equals(z) should return true.
x and y, multiple invocations of
x.equals(y) consistently return true
or consistently return false, provided no
information used in equals comparisons on the
objects is modified.
x,
x.equals(null) should return false.
The equals method for class Object implements
the most discriminating possible equivalence relation on objects;
that is, for any non-null reference values x and
y, this method returns true if and only
if x and y refer to the same object
(x == y has the value true).
Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.
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.
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.
Rectangle object. The bounds specify this
component's width, height, and location relative to
its parent.null a new
Rectangle is allocated.
This version of getBounds is useful if the caller
wants to avoid allocating a new Rectangle object
on the heap.ColorModel used to display
the component on the output device.LayoutManager
and Component
subclasses that wish to respect orientation should call this method to
get the component's orientation before performing layout or drawing.Cursor.DEFAULT_CURSOR is returned.DropTarget associated with this
Component.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.
null if this component is currently not
displayable.GraphicsConfiguration associated with this
Component.
If the Component has not been assigned a specific
GraphicsConfiguration,
the GraphicsConfiguration of the
Component object's top-level container is
returned.
If the Component has been created, but not yet added
to a Container, this method returns null.ScrollPaneAdjustable object which
represents the state of the horizontal scrollbar.
The declared return type of this method is
Adjustable to maintain backward compatibility.component.getBounds().heightcomponent.getSize().height because it
doesn't cause any heap allocations.InputMethodRequests instance.
At the same time, it also has to handle input method events.
A Frame object, for example, has a top inset that
corresponds to the height of the frame's title bar.
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.
Due to the asynchronous nature of native event handling, this
method can return outdated values (for instance, after several calls
of setLocation() in rapid succession). For this
reason, the recommended method of obtaining a component's position is
within java.awt.event.ComponentListener.componentMoved(),
which is called after the operating system has finished moving the
component.
null a new
Point is allocated.
This version of getLocation is useful if the
caller wants to avoid allocating a new Point
object on the heap.Component's
coordinate space if the Component is directly under the mouse
pointer, otherwise returns null.
If the Component is not showing on the screen, this method
returns null even if the mouse pointer is above the area
where the Component would be displayed.
If the Component is partially or fully obscured by other
Components or native windows, this method returns a non-null
value only if the mouse pointer is located above the unobscured part of the
Component.
For Containers it returns a non-null value if the mouse is
above the Container itself or above any of its descendants.
Use
if you need to exclude children.
Sometimes the exact mouse coordinates are not important, and the only thing
that matters is whether a specific Component is under the mouse
pointer. If the return value of this method is null, mouse
pointer is not directly above the Component.
Container's
coordinate space if the Container is under the mouse pointer,
otherwise returns null.
This method is similar to
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.Dimension object. The height
field of the Dimension object contains
this component's height, and the width
field of the Dimension object contains
this component's width.null a new
Dimension object is allocated. This version of
getSize is useful if the caller wants to avoid
allocating a new Dimension object on the heap.ScrollPaneAdjustable object which
represents the state of the vertical scrollbar.
The declared return type of this method is
Adjustable to maintain backward compatibility.component.getBounds().width,
or component.getSize().width because it
doesn't cause any heap allocations.component.getBounds().x,
or component.getLocation().x because it doesn't
cause any heap allocations.component.getBounds().y,
or component.getLocation().y because it
doesn't cause any heap allocations.true if this Component is the
focus owner. This method is obsolete, and has been replaced by
isFocusOwner().java.util.Hashtable.
The general contract of hashCode is:
hashCode method on each of
the two objects must produce the same integer result.
As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM programming language.)
imageUpdate method of an ImageObserver
is called when more information about an
image which had been previously requested using an asynchronous
routine such as the drawImage method of
Graphics becomes available.
See the definition of imageUpdate for
more information on this method and its arguments.
The imageUpdate method of Component
incrementally draws an image on the component as more of the bits
of the image are available.
If the system property awt.image.incrementaldraw
is missing or has the value true, the image is
incrementally drawn. If the system property has any other value,
then the image is not drawn until it has been completely loaded.
Also, if incremental drawing is in effect, the value of the
system property awt.image.redrawrate is interpreted
as an integer to give the maximum redraw rate, in milliseconds. If
the system property is missing or cannot be interpreted as an
integer, the redraw rate is once every 100ms.
The interpretation of the x, y,
width, and height arguments depends on
the value of the infoflags argument.
false, this Component is
inheriting its background color from an ancestor.false, this Component is inheriting
its cursor from an ancestor.A component is made displayable either when it is added to a displayable containment hierarchy or when its containment hierarchy is made displayable. A containment hierarchy is made displayable when its ancestor window is either packed or made visible.
A component is made undisplayable either when it is removed from a displayable containment hierarchy or when its containment hierarchy is made undisplayable. A containment hierarchy is made undisplayable when its ancestor window is disposed.
setEnabled method.true for both such
Containers in this case.true if this Component is the
focus owner.Component can become the focus
owner.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.false, this
Container will inherit its focus traversal policy from an ancestor.false, this Component is inheriting its
font from an ancestor.false, this Component is
inheriting its foreground color from an ancestor.Component and Container,
other than the ones defined in this package like Button
or Scrollbar, are lightweight.
All of the Swing components are lightweights.
This method will always return false if this component
is not displayable because it is impossible to determine the
weight of an undisplayable component.
null
value otherwise returns false.setMinimumSize has been
invoked with a non-null value.An opaque component paints every pixel within its rectangular region. A non-opaque component paints only some of its pixels, allowing the pixels underneath it to "show through". A component that does not fully paint its pixels therefore provides a degree of transparency. Only lightweight components can be transparent.
Subclasses that guarantee to always completely paint their contents should override this method and return true. All of the "heavyweight" AWT components are opaque.
null value otherwise returns false.Frame objects.System.out.
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.
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.
wait methods.
The awakened thread will not be able to proceed until the current thread relinquishes the lock on this object. The awakened thread will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened thread enjoys no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner of this object's monitor. A thread becomes the owner of the object's monitor in one of three ways:
synchronized statement
that synchronizes on the object.
Class, by executing a
synchronized static method of that class.
Only one thread at a time can own an object's monitor.
wait methods.
The awakened threads will not be able to proceed until the current thread relinquishes the lock on this object. The awakened threads will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened threads enjoy no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.
The origin of the graphics context, its
(0, 0) coordinate point, is the
top-left corner of this component. The clipping region of the
graphics context is the bounding rectangle of this component.
ScrollPane. 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.The image data is downloaded asynchronously in another thread, and an appropriately scaled screen representation of the image is generated.
The origin of the graphics context, its
(0, 0) coordinate point, is the
top-left corner of this component. The clipping region of the
graphics context is the bounding rectangle of this component.
removeLayoutComponent method.index,
from this container.
This method also notifies the layout manager to remove the
component from this container's layout via the
removeLayoutComponent method.removeLayoutComponent method.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.l is null,
no exception is thrown and no action is performed.If listener is null, no exception is thrown and no action is performed.
PropertyChangeListener from the listener
list for a specific property. This method should be used to remove
PropertyChangeListeners
that were registered for a specific bound property.
If propertyName or listener is null,
no exception is thrown and no action is taken.
If this component is a lightweight component, this method
causes a call to this component's paint
method as soon as possible. Otherwise, this method causes
a call to this component's update method as soon
as possible.
Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.
If this component is a lightweight component, this method
causes a call to this component's paint method
as soon as possible. Otherwise, this method causes a call to
this component's update method as soon as possible.
Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.
paint
within tm milliseconds.
Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.
tm milliseconds.
If this component is a lightweight component, this method causes
a call to this component's paint method.
Otherwise, this method causes a call to this component's
update method.
Note: For more information on the paint mechanisms utilitized by AWT and Swing, including information on how to write the most efficient painting code, see Painting in AWT and Swing.
This method cannot be used to set the focus owner to no Component at
all. Use KeyboardFocusManager.clearGlobalFocusOwner()
instead.
Because the focus behavior of this method is platform-dependent,
developers are strongly encouraged to use
requestFocusInWindow when possible.
This method returns a boolean value. If false is returned,
the request is guaranteed to fail. If true is
returned, the request will succeed unless it is vetoed, or an
extraordinary event, such as disposal of the Component's peer, occurs
before the request can be granted by the native windowing system. Again,
while a return value of true indicates that the request is
likely to succeed, developers must never assume that this Component is
the focus owner until this Component receives a FOCUS_GAINED event.
This method cannot be used to set the focus owner to no Component at
all. Use KeyboardFocusManager.clearGlobalFocusOwner()
instead.
The focus behavior of this method can be implemented uniformly across
platforms, and thus developers are strongly encouraged to use this
method over requestFocus when possible. Code which relies
on requestFocus may exhibit different focus behavior on
different platforms.
The background color affects each component differently and the parts of the component that are affected by the background color may differ between operating systems.
x and y, and the
new size is specified by width and height.r. This component's new
position is specified by r.x and r.y,
and its new size is specified by r.width and
r.heightLayoutManager and Component
subclasses will use this property to
determine how to lay out and draw components.
At construction time, a component's orientation is set to
ComponentOrientation.UNKNOWN,
indicating that it has not been specified
explicitly. The UNKNOWN orientation behaves the same as
ComponentOrientation.LEFT_TO_RIGHT.
To set the orientation of a single component, use this method. To set the orientation of an entire component hierarchy, use applyComponentOrientation .
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.
contains method for
this component returns true for the current cursor location, and
this Component is visible, displayable, and enabled. Setting the
cursor of a Container causes that cursor to be displayed
within all of the container's subcomponents, except for those
that have a non-null cursor.DropTarget with this component.
The Component will receive drops only if it
is enabled.b. An enabled component can respond to user
input and generate events. Components are enabled initially by default.
Note: Disabling a lightweight component does not prevent it from receiving MouseEvents.
The alternative way to specify the traversal order of this Container's children is to make this Container a focus traversal policy provider.
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.
| 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 |
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.
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.
true will be used to acquire focus traversal policy
instead of closest focus cycle root ancestor.This is useful, for example, if running under full-screen mode and better performance is desired, or if page-flipping is used as the buffer strategy.
x and y
parameters in the coordinate space of this component's parent.p. Point
p is given in the parent's coordinate space.getMaximumSize will always
return this value. Setting the maximum size to null
restores the default behavior.getMinimumSize will always
return this value. Setting the minimum size to null
restores the default behavior.getPreferredSize will always
return this value. Setting the preferred size to null
restores the default behavior.d.width
and height d.height.width
and height height.b.
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.
The current thread must own this object's monitor. The thread
releases ownership of this monitor and waits until another thread
notifies threads waiting on this object's monitor to wake up
either through a call to the notify method or the
notifyAll method. The thread then waits until it can
re-obtain ownership of the monitor and resumes execution.
As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:
synchronized (obj) {
while (<condition does not hold>)
obj.wait();
... // Perform action appropriate to condition
}
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.The current thread must own this object's monitor.
This method causes the current thread (call it T) to place itself in the wait set for this object and then to relinquish any and all synchronization claims on this object. Thread T becomes disabled for thread scheduling purposes and lies dormant until one of four things happens:
A thread can also wake up without being notified, interrupted, or timing out, a so-called spurious wakeup. While this will rarely occur in practice, applications must guard against it by testing for the condition that should have caused the thread to be awakened, and continuing to wait if the condition is not satisfied. In other words, waits should always occur in loops, like this one:
synchronized (obj) {
while (<condition does not hold>)
obj.wait(timeout);
... // Perform action appropriate to condition
}
(For more information on this topic, see Section 3.2.3 in Doug Lea's
"Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
2000), or Item 50 in Joshua Bloch's "Effective Java Programming
Language Guide" (Addison-Wesley, 2001).
If the current thread is interrupted by another thread while it is waiting, then an InterruptedException is thrown. This exception is not thrown until the lock status of this object has been restored as described above.
Note that the wait method, as it places the current thread into the wait set for this object, unlocks only this object; any other objects on which the current thread may be synchronized remain locked while the thread waits.
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.
This method is similar to the wait method of one
argument, but it allows finer control over the amount of time to
wait for a notification before giving up. The amount of real time,
measured in nanoseconds, is given by:
1000000*timeout+nanos
In all other respects, this method does the same thing as the method of one argument. In particular, wait(0, 0) means the same thing as wait(0).
The current thread must own this object's monitor. The thread releases ownership of this monitor and waits until either of the following two conditions has occurred:
notify method
or the notifyAll method.
timeout
milliseconds plus nanos nanoseconds arguments, has
elapsed.
The thread then waits until it can re-obtain ownership of the monitor and resumes execution.
As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:
synchronized (obj) {
while (<condition does not hold>)
obj.wait(timeout, nanos);
... // Perform action appropriate to condition
}
This method should only be called by a thread that is the owner
of this object's monitor. See the notify method for a
description of the ways in which a thread can become the owner of
a monitor.