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JavaTM 2 Platform Std. Ed. v1.3 |
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java.lang.Object
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+--java.awt.Component
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+--java.awt.Container
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+--javax.swing.JComponent
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+--javax.swing.JViewport
The "viewport" or "porthole" through which you see the underlying information. When you scroll, what moves is the viewport. It is like peering through a camera's viewfinder. Moving the viewfinder upwards brings new things into view at the top of the picture and loses things that were at the bottom.
By default, JViewport is opaque. To change this, use the
setOpaque method.
NOTE:We have implemented a faster scrolling algorithm that does not require a buffer to draw in. The algorithm works as follows:
JComponents,
if they aren't, stop and repaint the whole viewport.
copyArea
on the scrolled region.
copyAreas.
Compared to the non backing store case this
approach will greatly reduce the painted region.
This approach can cause slower times than the backing store approach when the viewport is obscured by another window, or partially offscreen. When another window obscures the viewport the copyArea will copy garbage and a paint event will be generated by the system to inform us we need to paint the newly exposed region. The only way to handle this is to repaint the whole viewport, which can cause slower performance than the backing store case. In most applications very rarely will the user be scrolling while the viewport is obscured by another window or offscreen, so this optimization is usually worth the performance hit when obscured. Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. A future release of Swing will provide support for long term persistence.
JScrollPane, Serialized Form| Inner Class Summary | |
protected class |
JViewport.AccessibleJViewport
This class implements accessibility support for the JViewport class. |
protected class |
JViewport.ViewListener
A listener for the view. |
| Inner classes inherited from class javax.swing.JComponent |
JComponent.AccessibleJComponent |
| Inner classes inherited from class java.awt.Container |
Container.AccessibleAWTContainer |
| Inner classes inherited from class java.awt.Component |
Component.AccessibleAWTComponent |
| Field Summary | |
protected boolean |
backingStore
Deprecated. As of Java 2 platform v1.3 |
static int |
BACKINGSTORE_SCROLL_MODE
Draws viewport contents into an offscreen image. |
protected Image |
backingStoreImage
The view image used for a backing store. |
static int |
BLIT_SCROLL_MODE
Use graphics.copyArea() to implement scrolling. |
protected boolean |
isViewSizeSet
True when the viewport dimensions have been determined. |
protected Point |
lastPaintPosition
The last viewPosition that we've painted, so we know how
much of the backing store image is valid. |
protected boolean |
scrollUnderway
The scrollUnderway flag is used for components like
JList. |
static int |
SIMPLE_SCROLL_MODE
This mode uses the very simple method of redrawing the entire contents of the scrollpane each time it is scrolled. |
| Fields inherited from class javax.swing.JComponent |
accessibleContext, listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW |
| Fields inherited from class java.awt.Component |
BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT |
| Fields inherited from interface java.awt.image.ImageObserver |
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH |
| Constructor Summary | |
JViewport()
Creates a JViewport. |
|
| Method Summary | |
void |
addChangeListener(ChangeListener l)
Adds a ChangeListener to the list that is
notified each time the view's
size, position, or the viewport's extent size has changed. |
protected void |
addImpl(Component child,
Object constraints,
int index)
Sets the JViewports one lightweight child,
which can be null. |
protected boolean |
computeBlit(int dx,
int dy,
Point blitFrom,
Point blitTo,
Dimension blitSize,
Rectangle blitPaint)
Computes the parameters for a blit where the backing store image currently contains oldLoc in the upper left hand corner
and we're scrolling to newLoc. |
protected LayoutManager |
createLayoutManager()
Subclassers can override this to install a different layout manager (or null) in the constructor. |
protected JViewport.ViewListener |
createViewListener()
Creates a listener for the view. |
protected void |
firePropertyChange(String propertyName,
Object oldValue,
Object newValue)
Notifies listeners of a property change. |
protected void |
fireStateChanged()
Notifies all ChangeListeners when the views
size, position, or the viewports extent size has changed. |
AccessibleContext |
getAccessibleContext()
Gets the AccessibleContext associated with this JViewport. |
Dimension |
getExtentSize()
Returns the size of the visible part of the view in view coordinates. |
Insets |
getInsets()
Returns the insets (border) dimensions as (0,0,0,0), since borders are not supported on a JViewport. |
Insets |
getInsets(Insets insets)
Returns an Insets object containing this
JViewports inset values. |
int |
getScrollMode()
Returns the current scrolling mode. |
ViewportUI |
getUI()
Returns the L&F object that renders this component. |
String |
getUIClassID()
Returns a string that specifies the name of the L&F class that renders this component. |
Component |
getView()
Returns the JViewports one child or null. |
Point |
getViewPosition()
Returns the view coordinates that appear in the upper left hand corner of the viewport, or 0,0 if there's no view. |
Rectangle |
getViewRect()
Returns a rectangle whose origin is getViewPosition
and size is getExtentSize. |
Dimension |
getViewSize()
If the view's size hasn't been explicitly set, return the preferred size, otherwise return the view's current size. |
boolean |
isBackingStoreEnabled()
Deprecated. As of Java 2 platform v1.3, replaced by getScrollMode(). |
boolean |
isOptimizedDrawingEnabled()
The JViewport overrides the default implementation of
this method (in JComponent) to return false. |
void |
paint(Graphics g)
Depending on whether the backingStore is enabled,
either paint the image through the backing store or paint
just the recently exposed part, using the backing store
to "blit" the remainder. |
protected String |
paramString()
Returns a string representation of this JViewport. |
void |
remove(Component child)
Removes the Viewports one lightweight child. |
void |
removeChangeListener(ChangeListener l)
Removes a ChangeListener from the list that's notified each
time the views size, position, or the viewports extent size
has changed. |
void |
repaint(long tm,
int x,
int y,
int w,
int h)
Always repaint in the parents coordinate system to make sure only one paint is performed by the RepaintManager. |
void |
reshape(int x,
int y,
int w,
int h)
Sets the bounds of this viewport. |
void |
scrollRectToVisible(Rectangle contentRect)
Overridden to scroll the view so that Rectangle
within the view becomes visible. |
void |
setBackingStoreEnabled(boolean enabled)
Deprecated. As of Java 2 platform v1.3, replaced by setScrollMode(). |
void |
setBorder(Border border)
The viewport "scrolls" it's child (called the "view") by the normal parent/child clipping (typically the view is moved in the opposite direction of the scroll). |
void |
setExtentSize(Dimension newExtent)
Sets the size of the visible part of the view using view coordinates. |
void |
setScrollMode(int mode)
Used to control the method of scrolling the viewport contents. |
void |
setUI(ViewportUI ui)
Sets the L&F object that renders this component. |
void |
setView(Component view)
Sets the JViewports one lightweight child
(view), which can be null. |
void |
setViewPosition(Point p)
Sets the view coordinates that appear in the upper left hand corner of the viewport, does nothing if there's no view. |
void |
setViewSize(Dimension newSize)
Sets the view coordinates that appear in the upper left hand corner of the viewport, and the size of the view. |
Dimension |
toViewCoordinates(Dimension size)
Converts a size in pixel coordinates to view coordinates. |
Point |
toViewCoordinates(Point p)
Converts a point in pixel coordinates to view coordinates. |
void |
updateUI()
Notification from the UIFactory that the L&F
has changed. |
| Methods inherited from class java.awt.Container |
add, add, add, add, add, addContainerListener, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getLayout, insets, invalidate, isAncestorOf, layout, list, list, locate, minimumSize, paintComponents, preferredSize, printComponents, processContainerEvent, processEvent, remove, removeAll, removeContainerListener, setLayout, validate, validateTree |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Field Detail |
protected boolean isViewSizeSet
protected Point lastPaintPosition
viewPosition that we've painted, so we know how
much of the backing store image is valid.protected boolean backingStore
setScrollMode(int)protected transient Image backingStoreImage
protected boolean scrollUnderway
scrollUnderway flag is used for components like
JList. When the downarrow key is pressed on a
JList and the selected
cell is the last in the list, the scrollpane autoscrolls.
Here, the old selected cell needs repainting and so we need
a flag to make the viewport do the optimized painting
only when there is an explicit call to
setViewPosition(Point).
When setBounds is called through other routes,
the flag is off and the view repaints normally. Another approach
would be to remove this from the JViewport
class and have the JList manage this case by using
setBackingStoreEnabled. The default is false.public static final int BLIT_SCROLL_MODE
graphics.copyArea() to implement scrolling.
This is the fastest for most applications.setScrollMode(int)public static final int BACKINGSTORE_SCROLL_MODE
JTable.
This mode may offer advantages over "blit mode"
in some cases, but it requires a large chunk of extra RAM.setScrollMode(int)public static final int SIMPLE_SCROLL_MODE
setScrollMode(int)| Constructor Detail |
public JViewport()
JViewport.| Method Detail |
public ViewportUI getUI()
public void setUI(ViewportUI ui)
ui - the ViewportUI L&F objectUIDefaults.getUI(javax.swing.JComponent)public void updateUI()
UIFactory that the L&F
has changed.updateUI in class JComponentJComponent.updateUI()public String getUIClassID()
getUIClassID in class JComponentJComponent.getUIClassID(),
UIDefaults.getUI(javax.swing.JComponent)
protected void addImpl(Component child,
Object constraints,
int index)
JViewports one lightweight child,
which can be null.
(Since there is only one child which occupies the entire viewport,
the constraints and index arguments are ignored.)addImpl in class Containerchild - the lightweight child of the viewportconstraints - the constraints to be respectedindex - the indexsetView(java.awt.Component)public void remove(Component child)
Viewports one lightweight child.remove in class ContainersetView(java.awt.Component)public void scrollRectToVisible(Rectangle contentRect)
Rectangle
within the view becomes visible.scrollRectToVisible in class JComponentcontentRect - the Rectangle to displaypublic final void setBorder(Border border)
null border,
or non-zero insets, isn't supported, to prevent the geometry
of this component from becoming complex enough to inhibit
subclassing. To create a JViewport with a border,
add it to a JPanel that has a border.
Note: If border is non-null, this
method will throw an exception as borders are not supported on
a JViewPort.
setBorder in class JComponentborder - the Border to setIllegalArgumentException - this method is not implementedpublic final Insets getInsets()
JViewport.getInsets in class JComponentRectange of zero dimension and zero originsetBorder(javax.swing.border.Border)public final Insets getInsets(Insets insets)
Insets object containing this
JViewports inset values. The passed-in
Insets object will be reinitialized, and
all existing values within this object are overwritten.getInsets in class JComponentinsets - the Insets object which can be reusedgetInsets()public boolean isOptimizedDrawingEnabled()
JViewport overrides the default implementation of
this method (in JComponent) to return false.
This ensures
that the drawing machinery will call the Viewports
paint
implementation rather than messaging the JViewports
children directly.isOptimizedDrawingEnabled in class JComponentpublic void paint(Graphics g)
backingStore is enabled,
either paint the image through the backing store or paint
just the recently exposed part, using the backing store
to "blit" the remainder.
The term "blit" is the pronounced version of the PDP-10 BLT (BLock Transfer) instruction, which copied a block of bits. (In case you were curious.)
paint in class JComponentg - the Graphics context within which to paint
public void reshape(int x,
int y,
int w,
int h)
StateChanged event.reshape in class JComponentx - left edge of the originy - top edge of the originw - width in pixelsh - height in pixelsJComponent.reshape(int, int, int, int)public void setScrollMode(int mode)
mode - one of the following values:
BLIT_SCROLL_MODE,
BACKINGSTORE_SCROLL_MODE,
SIMPLE_SCROLL_MODEpublic int getScrollMode()
scrollMode propertysetScrollMode(int)public boolean isBackingStoreEnabled()
getScrollMode().
scrollMode is BACKINGSTORE_SCROLL_MODEpublic void setBackingStoreEnabled(boolean enabled)
setScrollMode().
viewPosition.
Rather than repainting the entire viewport we use
Graphics.copyArea() to effect some of the scroll.enabled - if true, maintain an offscreen backing storepublic Component getView()
JViewports one child or null.null if none existssetView(java.awt.Component)public void setView(Component view)
JViewports one lightweight child
(view), which can be null.view - the viewports new lightweight childgetView()public Dimension getViewSize()
Dimension object specifying the size of the viewpublic void setViewSize(Dimension newSize)
newSize - a Dimension object specifying the size and
location of the new view coordinates,
or null if there
is no viewpublic Point getViewPosition()
Point object giving the upper left coordinatespublic void setViewPosition(Point p)
p - a Point object giving the upper left coordinatespublic Rectangle getViewRect()
getViewPosition
and size is getExtentSize.
This is the visible part of the view, in view coordinates.Rectangle giving the visible part of
the view using view coordinates.
protected boolean computeBlit(int dx,
int dy,
Point blitFrom,
Point blitTo,
Dimension blitSize,
Rectangle blitPaint)
oldLoc in the upper left hand corner
and we're scrolling to newLoc.
The parameters are modified
to return the values required for the blit.dx - the horizontal deltady - the vertical deltablitFrom - the Point we're blitting fromblitTo - the Point we're blitting toblitSize - the Dimension of the area to blitblitPaint - the area to blitpublic Dimension getExtentSize()
Dimension object giving the size of the viewpublic Dimension toViewCoordinates(Dimension size)
size - a Dimension object using pixel coordinatesDimension object converted to view coordinatespublic Point toViewCoordinates(Point p)
p - a Point object using pixel coordinatesPoint object converted to view coordinatespublic void setExtentSize(Dimension newExtent)
newExtent - a Dimension object specifying
the size of the viewprotected JViewport.ViewListener createViewListener()
ViewListenerprotected LayoutManager createLayoutManager()
null) in the constructor. Returns
a new ViewportLayout object.LayoutManagerpublic void addChangeListener(ChangeListener l)
ChangeListener to the list that is
notified each time the view's
size, position, or the viewport's extent size has changed.l - the ChangeListener to addremoveChangeListener(javax.swing.event.ChangeListener),
setViewPosition(java.awt.Point),
setViewSize(java.awt.Dimension),
setExtentSize(java.awt.Dimension)public void removeChangeListener(ChangeListener l)
ChangeListener from the list that's notified each
time the views size, position, or the viewports extent size
has changed.l - the ChangeListener to removeaddChangeListener(javax.swing.event.ChangeListener)protected void fireStateChanged()
ChangeListeners when the views
size, position, or the viewports extent size has changed.addChangeListener(javax.swing.event.ChangeListener),
removeChangeListener(javax.swing.event.ChangeListener),
EventListenerList
public void repaint(long tm,
int x,
int y,
int w,
int h)
RepaintManager.repaint in class JComponenttm - maximum time in milliseconds before updatex - the x coordinate (pixels over from left)y - the y coordinate (pixels down from top)width - the widthheight - the heightComponent.update(java.awt.Graphics)protected String paramString()
JViewport.
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.paramString in class JComponentJViewport
protected void firePropertyChange(String propertyName,
Object oldValue,
Object newValue)
windowBlit property.
(The putClientProperty property is final).firePropertyChange in class JComponentpropertyName - a string containing the property nameoldValue - the old value of the propertynewValue - the new value of the propertypublic AccessibleContext getAccessibleContext()
getAccessibleContext in interface AccessiblegetAccessibleContext in class JComponent
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JavaTM 2 Platform Std. Ed. v1.3 |
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