Graphics class is the abstract base class for
all graphics contexts that allow an application to draw onto
components that are realized on various devices, as well as
onto off-screen images.
A Graphics object encapsulates state information needed
for the basic rendering operations that Java supports. This
state information includes the following properties:
Component object on which to draw.
Coordinates are infinitely thin and lie between the pixels of the output device. Operations that draw the outline of a figure operate by traversing an infinitely thin path between pixels with a pixel-sized pen that hangs down and to the right of the anchor point on the path. Operations that fill a figure operate by filling the interior of that infinitely thin path. Operations that render horizontal text render the ascending portion of character glyphs entirely above the baseline coordinate.
The graphics pen hangs down and to the right from the path it traverses. This has the following implications:
All coordinates that appear as arguments to the methods of this
Graphics object are considered relative to the
translation origin of this Graphics object prior to
the invocation of the method.
All rendering operations modify only pixels which lie within the
area bounded by the current clip, which is specified by a Shape
in user space and is controlled by the program using the
Graphics object. This user clip
is transformed into device space and combined with the
device clip, which is defined by the visibility of windows and
device extents. The combination of the user clip and device clip
defines the composite clip, which determines the final clipping
region. The user clip cannot be modified by the rendering
system to reflect the resulting composite clip. The user clip can only
be changed through the setClip or clipRect
methods.
All drawing or writing is done in the current color,
using the current paint mode, and in the current font.
Beginning with Java 1.1, the background color
of offscreen images may be system dependent. Applications should
use setColor followed by fillRect to
ensure that an offscreen image is cleared to a specific color.
setClip(null),
the specified rectangle becomes the new clip.
This method sets the user clip, which is independent of the
clipping associated with device bounds and window visibility.
This method can only be used to make the current clip smaller.
To set the current clip larger, use any of the setClip methods.
Rendering operations have no effect outside of the clipping area.dx and dy. From the point specified
by x and y, this method
copies downwards and to the right. To copy an area of the
component to the left or upwards, specify a negative value for
dx or dy.
If a portion of the source rectangle lies outside the bounds
of the component, or is obscured by another window or component,
copyArea will be unable to copy the associated
pixels. The area that is omitted can be refreshed by calling
the component's paint method.Graphics object that is
a copy of this Graphics object.Graphics object based on this
Graphics object, but with a new translation and clip area.
The new Graphics object has its origin
translated to the specified point (x, y).
Its clip area is determined by the intersection of the original
clip area with the specified rectangle. The arguments are all
interpreted in the coordinate system of the original
Graphics object. The new graphics context is
identical to the original, except in two respects:
0, 0) in the
new graphics context is the same as (x, y) in
the original graphics context.
0, 0), and its size
is specified by the width and height
arguments.
Graphics object cannot be used after
disposehas been called.
When a Java program runs, a large number of Graphics
objects can be created within a short time frame.
Although the finalization process of the garbage collector
also disposes of the same system resources, it is preferable
to manually free the associated resources by calling this
method rather than to rely on a finalization process which
may not run to completion for a long period of time.
Graphics objects which are provided as arguments to the
paint and update methods
of components are automatically released by the system when
those methods return. For efficiency, programmers should
call dispose when finished using
a Graphics object only if it was created
directly from a component or another Graphics object.
The colors used for the highlighting effect are determined
based on the current color.
The resulting rectangle covers an area that is
width + 1 pixels wide
by height + 1 pixels tall.
The resulting arc begins at startAngle and extends
for arcAngle degrees, using the current color.
Angles are interpreted such that 0 degrees
is at the 3 o'clock position.
A positive value indicates a counter-clockwise rotation
while a negative value indicates a clockwise rotation.
The center of the arc is the center of the rectangle whose origin
is (x, y) and whose size is specified by the
width and height arguments.
The resulting arc covers an area
width + 1 pixels wide
by height + 1 pixels tall.
The angles are specified relative to the non-square extents of the bounding rectangle such that 45 degrees always falls on the line from the center of the ellipse to the upper right corner of the bounding rectangle. As a result, if the bounding rectangle is noticeably longer in one axis than the other, the angles to the start and end of the arc segment will be skewed farther along the longer axis of the bounds.
This operation is equivalent to filling a rectangle of the width and height of the specified image with the given color and then drawing the image on top of it, but possibly more efficient.
This method returns immediately in all cases, even if the complete image has not yet been loaded, and it has not been dithered and converted for the current output device.
If the image has completely loaded and its pixels are
no longer being changed, then
drawImage returns true.
Otherwise, drawImage returns false
and as more of
the image becomes available
or it is time to draw another frame of animation,
the process that loads the image notifies
the specified image observer.
This method returns immediately in all cases, even if the complete image has not yet been loaded, and it has not been dithered and converted for the current output device.
If the image has completely loaded and its pixels are
no longer being changed, then
drawImage returns true.
Otherwise, drawImage returns false
and as more of
the image becomes available
or it is time to draw another frame of animation,
the process that loads the image notifies
the specified image observer.
The image is drawn inside the specified rectangle of this graphics context's coordinate space, and is scaled if necessary. Transparent pixels are drawn in the specified background color. This operation is equivalent to filling a rectangle of the width and height of the specified image with the given color and then drawing the image on top of it, but possibly more efficient.
This method returns immediately in all cases, even if the
entire image has not yet been scaled, dithered, and converted
for the current output device.
If the current output representation is not yet complete then
drawImage returns false. As more of
the image becomes available, the process that loads the image notifies
the specified image observer.
A scaled version of an image will not necessarily be available immediately just because an unscaled version of the image has been constructed for this output device. Each size of the image may be cached separately and generated from the original data in a separate image production sequence.
The image is drawn inside the specified rectangle of this graphics context's coordinate space, and is scaled if necessary. Transparent pixels do not affect whatever pixels are already there.
This method returns immediately in all cases, even if the
entire image has not yet been scaled, dithered, and converted
for the current output device.
If the current output representation is not yet complete, then
drawImage returns false. As more of
the image becomes available, the process that loads the image notifies
the image observer by calling its imageUpdate method.
A scaled version of an image will not necessarily be available immediately just because an unscaled version of the image has been constructed for this output device. Each size of the image may be cached separately and generated from the original data in a separate image production sequence.
Transparent pixels are drawn in the specified background color. This operation is equivalent to filling a rectangle of the width and height of the specified image with the given color and then drawing the image on top of it, but possibly more efficient.
This method returns immediately in all cases, even if the
image area to be drawn has not yet been scaled, dithered, and converted
for the current output device.
If the current output representation is not yet complete then
drawImage returns false. As more of
the image becomes available, the process that loads the image notifies
the specified image observer.
This method always uses the unscaled version of the image to render the scaled rectangle and performs the required scaling on the fly. It does not use a cached, scaled version of the image for this operation. Scaling of the image from source to destination is performed such that the first coordinate of the source rectangle is mapped to the first coordinate of the destination rectangle, and the second source coordinate is mapped to the second destination coordinate. The subimage is scaled and flipped as needed to preserve those mappings.
This method returns immediately in all cases, even if the
image area to be drawn has not yet been scaled, dithered, and converted
for the current output device.
If the current output representation is not yet complete then
drawImage returns false. As more of
the image becomes available, the process that loads the image notifies
the specified image observer.
This method always uses the unscaled version of the image to render the scaled rectangle and performs the required scaling on the fly. It does not use a cached, scaled version of the image for this operation. Scaling of the image from source to destination is performed such that the first coordinate of the source rectangle is mapped to the first coordinate of the destination rectangle, and the second source coordinate is mapped to the second destination coordinate. The subimage is scaled and flipped as needed to preserve those mappings.
(x1, y1) and (x2, y2)
in this graphics context's coordinate system.x, y,
width, and height arguments.
The oval covers an area that is
width + 1 pixels wide
and height + 1 pixels tall.
This method draws the polygon defined by nPoint line
segments, where the first nPoint - 1
line segments are line segments from
(xPoints[i - 1], yPoints[i - 1])
to (xPoints[i], yPoints[i]), for
1 ≤ i ≤ nPoints.
The figure is automatically closed by drawing a line connecting
the final point to the first point, if those points are different.
Polygon object.x and x + width.
The top and bottom edges are at
y and y + height.
The rectangle is drawn using the graphics context's current color.x and x + width,
respectively. The top and bottom edges of the rectangle are at
y and y + height.
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 resulting arc begins at startAngle and extends
for arcAngle degrees.
Angles are interpreted such that 0 degrees
is at the 3 o'clock position.
A positive value indicates a counter-clockwise rotation
while a negative value indicates a clockwise rotation.
The center of the arc is the center of the rectangle whose origin
is (x, y) and whose size is specified by the
width and height arguments.
The resulting arc covers an area
width + 1 pixels wide
by height + 1 pixels tall.
The angles are specified relative to the non-square extents of the bounding rectangle such that 45 degrees always falls on the line from the center of the ellipse to the upper right corner of the bounding rectangle. As a result, if the bounding rectangle is noticeably longer in one axis than the other, the angles to the start and end of the arc segment will be skewed farther along the longer axis of the bounds.
This method draws the polygon defined by nPoint line
segments, where the first nPoint - 1
line segments are line segments from
(xPoints[i - 1], yPoints[i - 1])
to (xPoints[i], yPoints[i]), for
1 ≤ i ≤ nPoints.
The figure is automatically closed by drawing a line connecting
the final point to the first point, if those points are different.
The area inside the polygon is defined using an even-odd fill rule, also known as the alternating rule.
The area inside the polygon is defined using an even-odd fill rule, also known as the alternating rule.
x and x + width - 1.
The top and bottom edges are at
y and y + height - 1.
The resulting rectangle covers an area
width pixels wide by
height pixels tall.
The rectangle is filled using the graphics context's current color.x and x + width - 1,
respectively. The top and bottom edges of the rectangle are at
y and y + height - 1.setClip(null), this method returns
null.setClip(null), this method returns
null.
The coordinates in the rectangle are relative to the coordinate
system origin of this graphics context.setClip(null), this method returns the
specified Rectangle.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.)
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.
Shape
interface can be used to set the clip. The only
Shape objects that are guaranteed to be
supported are Shape objects that are
obtained via the getClip method and via
Rectangle objects. This method sets the
user clip, which is independent of the clipping associated
with device bounds and window visibility.When drawing operations are performed, pixels which are the current color are changed to the specified color, and vice versa.
Pixels that are of colors other than those two colors are changed in an unpredictable but reversible manner; if the same figure is drawn twice, then all pixels are restored to their original values.
String object representing this
Graphics object's value.
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.