: Class JViewport

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--javax.swing.JComponent
                    |
                    +--javax.swing.JViewport

All Implemented Interfaces:: Accessible, ImageObserver, MenuContainer, Serializable

public class JViewport
extends JComponent
implements Accessible

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:

The view and parent view and checked to see if they are JComponents, if they aren't, stop and repaint the whole viewport.
If the viewport is obscured by an ancestor, stop and repaint the whole viewport.
Compute the region that will become visible, if it is as big as the viewport, stop and repaint the whole view region.
Obtain the ancestor Windows graphics and do a copyArea on the scrolled region.
Message the view to repaint the newly visible region.
The next time paint is invoked on the viewport, if the clip region is smaller than the viewport size a timer is kicked off to repaint the whole region.

In general this approach is much faster. Compared to the backing store approach this avoids the overhead of maintaining an offscreen buffer and having to do two 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.

See Also:: JScrollPane, Serialized Form

Inner Class Summary

protected class JViewport.AccessibleJViewport
JViewport.AccessibleJViewport

This class implements accessibility support for the JViewport class. It provides an implementation of the Java Accessibility API appropriate to viewport user-interface elements.
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.

protected class JViewport.ViewListener
JViewport.ViewListener

A listener for the view.
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.

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
copy-> backingStore

Deprecated. As of Java 2 platform v1.3

True when this viewport is maintaining an offscreen image of its contents, so that some scrolling can take place using fast "bit-blit" operations instead of by accessing the view object to construct the display. The default is false.

See Also:
setScrollMode(int)

static int BACKINGSTORE_SCROLL_MODE
copy-> BACKINGSTORE_SCROLL_MODE

Draws viewport contents into an offscreen image. This was previously the default mode for JTable. This mode may offer advantages over "blit mode" in some cases, but it requires a large chunk of extra RAM.

See Also:
setScrollMode(int)
Since:
1.3

protected Image backingStoreImage
copy-> backingStoreImage

The view image used for a backing store.

static int BLIT_SCROLL_MODE
copy-> BLIT_SCROLL_MODE

Use graphics.copyArea() to implement scrolling. This is the fastest for most applications.

See Also:
setScrollMode(int)
Since:
1.3

protected boolean isViewSizeSet
copy-> isViewSizeSet

True when the viewport dimensions have been determined. The default is false.

protected Point lastPaintPosition
copy-> lastPaintPosition

The last viewPosition that we've painted, so we know how much of the backing store image is valid.

protected boolean scrollUnderway
copy-> scrollUnderway

The 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.

static int SIMPLE_SCROLL_MODE
copy-> SIMPLE_SCROLL_MODE

This mode uses the very simple method of redrawing the entire contents of the scrollpane each time it is scrolled. This was the default behavior in Swing 1.0 and Swing 1.1. Either of the other two options will provide better performance in most cases.

See Also:
setScrollMode(int)
Since:
1.3

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
copy-> new JViewport()
copy-> <JViewport var> = new JViewport();

Creates a JViewport.

Method Summary

void addChangeListener(ChangeListener l)
copy-> .addChangeListener( )
copy-> <JViewport>.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.

Parameters:
l - the ChangeListener to add
See Also:
removeChangeListener(javax.swing.event.ChangeListener), setViewPosition(java.awt.Point), setViewSize(java.awt.Dimension), setExtentSize(java.awt.Dimension)

protected void addImpl(Component child, Object constraints, int index)
copy-> .addImpl(, , )
copy-> <JViewport>.addImpl(<Component child>, <Object constraints>, <int index>);

Sets the 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.)

Overrides:
addImpl in class Container

Parameters:
child - the lightweight child of the viewport
constraints - the constraints to be respected
index - the index
See Also:
setView(java.awt.Component)

protected boolean computeBlit(int dx, int dy, Point blitFrom, Point blitTo, Dimension blitSize, Rectangle blitPaint)
copy-> .computeBlit(, , , , , )
copy-> <boolean var>=<JViewport>.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. The parameters are modified to return the values required for the blit.

Parameters:
dx - the horizontal delta
dy - the vertical delta
blitFrom - the Point we're blitting from
blitTo - the Point we're blitting to
blitSize - the Dimension of the area to blit
blitPaint - the area to blit
Returns:
true if the parameters are modified and we're ready to blit; false otherwise

protected LayoutManager createLayoutManager()
copy-> .createLayoutManager()
copy-> <LayoutManager var>=<JViewport>.createLayoutManager();

Subclassers can override this to install a different layout manager (or null) in the constructor. Returns a new ViewportLayout object.

Returns:
a LayoutManager

protected JViewport.ViewListener createViewListener()
copy-> .createViewListener()
copy-> <JViewport.ViewListener var>=<JViewport>.createViewListener();

Creates a listener for the view.

Returns:
a ViewListener

protected void firePropertyChange(String propertyName, Object oldValue, Object newValue)
copy-> .firePropertyChange(, , )
copy-> <JViewport>.firePropertyChange(<String propertyName>, <Object oldValue>, <Object newValue>);

Notifies listeners of a property change. This is subclassed to update the windowBlit property. (The putClientProperty property is final).

Overrides:
firePropertyChange in class JComponent

Parameters:
propertyName - a string containing the property name
oldValue - the old value of the property
newValue - the new value of the property

protected void fireStateChanged()
copy-> .fireStateChanged()
copy-> <JViewport>.fireStateChanged();

Notifies all ChangeListeners when the views size, position, or the viewports extent size has changed.

See Also:
addChangeListener(javax.swing.event.ChangeListener), removeChangeListener(javax.swing.event.ChangeListener), EventListenerList

AccessibleContext getAccessibleContext()
copy-> .getAccessibleContext()
copy-> <AccessibleContext var>=<JViewport>.getAccessibleContext();

Gets the AccessibleContext associated with this JViewport. For viewports, the AccessibleContext takes the form of an AccessibleJViewport. A new AccessibleJViewport instance is created if necessary.

Specified by:
getAccessibleContext in interface Accessible
Overrides:
getAccessibleContext in class JComponent

Returns:
an AccessibleJViewport that serves as the AccessibleContext of this JViewport

Dimension getExtentSize()
copy-> .getExtentSize()
copy-> <Dimension var>=<JViewport>.getExtentSize();

Returns the size of the visible part of the view in view coordinates.

Returns:
a Dimension object giving the size of the view

Insets getInsets()
copy-> .getInsets()
copy-> <Insets var>=<JViewport>.getInsets();

Returns the insets (border) dimensions as (0,0,0,0), since borders are not supported on a JViewport.

Overrides:
getInsets in class JComponent

Returns:
a Rectange of zero dimension and zero origin
See Also:
setBorder(javax.swing.border.Border)

Insets getInsets(Insets insets)
copy-> .getInsets( )
copy-> <Insets var>=<JViewport>.getInsets(<Insets insets>);

Returns an Insets object containing this JViewports inset values. The passed-in Insets object will be reinitialized, and all existing values within this object are overwritten.

Overrides:
getInsets in class JComponent

Parameters:
insets - the Insets object which can be reused
Returns:
this viewports inset values
See Also:
getInsets()

int getScrollMode()
copy-> .getScrollMode()
copy-> <int var>=<JViewport>.getScrollMode();

Returns the current scrolling mode.

Returns:
the scrollMode property
Since:
1.3

See Also:
setScrollMode(int)

ViewportUI getUI()
copy-> .getUI()
copy-> <ViewportUI var>=<JViewport>.getUI();

Returns the L&F object that renders this component.

Returns:
ViewportUI object

String getUIClassID()
copy-> .getUIClassID()
copy-> <String var>=<JViewport>.getUIClassID();

Returns a string that specifies the name of the L&F class that renders this component.

Overrides:
getUIClassID in class JComponent

Returns:
the string "ViewportUI"
See Also:
JComponent.getUIClassID(), UIDefaults.getUI(javax.swing.JComponent)

Component getView()
copy-> .getView()
copy-> <Component var>=<JViewport>.getView();

Returns the JViewports one child or null.

Returns:
the viewports child, or null if none exists
See Also:
setView(java.awt.Component)

Point getViewPosition()
copy-> .getViewPosition()
copy-> <Point var>=<JViewport>.getViewPosition();

Returns the view coordinates that appear in the upper left hand corner of the viewport, or 0,0 if there's no view.

Returns:
a Point object giving the upper left coordinates

Rectangle getViewRect()
copy-> .getViewRect()
copy-> <Rectangle var>=<JViewport>.getViewRect();

Returns a rectangle whose origin is getViewPosition and size is getExtentSize. This is the visible part of the view, in view coordinates.

Returns:
a Rectangle giving the visible part of the view using view coordinates.

Dimension getViewSize()
copy-> .getViewSize()
copy-> <Dimension var>=<JViewport>.getViewSize();

If the view's size hasn't been explicitly set, return the preferred size, otherwise return the view's current size. If there is no view, return 0,0.

Returns:
a Dimension object specifying the size of the view

boolean isBackingStoreEnabled()
copy-> .isBackingStoreEnabled()
copy-> <boolean var>=<JViewport>.isBackingStoreEnabled();

Deprecated. As of Java 2 platform v1.3, replaced by getScrollMode().

Returns true if this viewport is maintaining an offscreen image of its contents.

Returns:
true if scrollMode is BACKINGSTORE_SCROLL_MODE

boolean isOptimizedDrawingEnabled()
copy-> .isOptimizedDrawingEnabled()
copy-> <boolean var>=<JViewport>.isOptimizedDrawingEnabled();

The 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.

Overrides:
isOptimizedDrawingEnabled in class JComponent

Returns:
false

void paint(Graphics g)
copy-> .paint( )
copy-> <JViewport>.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.
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.)

Overrides:
paint in class JComponent

Parameters:
g - the Graphics context within which to paint

protected String paramString()
copy-> .paramString()
copy-> <String var>=<JViewport>.paramString();

Returns a string representation of this 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.

Overrides:
paramString in class JComponent

Returns:
a string representation of this JViewport

void remove(Component child)
copy-> .remove( )
copy-> <JViewport>.remove(<Component child>);

Removes the Viewports one lightweight child.

Overrides:
remove in class Container

See Also:
setView(java.awt.Component)

void removeChangeListener(ChangeListener l)
copy-> .removeChangeListener( )
copy-> <JViewport>.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.

Parameters:
l - the ChangeListener to remove
See Also:
addChangeListener(javax.swing.event.ChangeListener)

void repaint(long tm, int x, int y, int w, int h)
copy-> .repaint(, , , , )
copy-> <JViewport>.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.

Overrides:
repaint in class JComponent

Parameters:
tm - maximum time in milliseconds before update
x - the x coordinate (pixels over from left)
y - the y coordinate (pixels down from top)
width - the width
height - the height
See Also:
Component.update(java.awt.Graphics)

void reshape(int x, int y, int w, int h)
copy-> .reshape(, , , )
copy-> <JViewport>.reshape(<int x>, <int y>, <int w>, <int h>);

Sets the bounds of this viewport. If the viewports width or height has changed, fire a StateChanged event.

Overrides:
reshape in class JComponent

Parameters:
x - left edge of the origin
y - top edge of the origin
w - width in pixels
h - height in pixels
See Also:
JComponent.reshape(int, int, int, int)

void scrollRectToVisible(Rectangle contentRect)
copy-> .scrollRectToVisible( )
copy-> <JViewport>.scrollRectToVisible(<Rectangle contentRect>);

Overridden to scroll the view so that Rectangle within the view becomes visible.

Overrides:
scrollRectToVisible in class JComponent

Parameters:
contentRect - the Rectangle to display

void setBackingStoreEnabled(boolean enabled)
copy-> .setBackingStoreEnabled( )
copy-> <JViewport>.setBackingStoreEnabled(<boolean enabled>);

Deprecated. As of Java 2 platform v1.3, replaced by setScrollMode().

If true if this viewport will maintain an offscreen image of its contents. The image is used to reduce the cost of small one dimensional changes to the viewPosition. Rather than repainting the entire viewport we use Graphics.copyArea() to effect some of the scroll.

Parameters:
enabled - if true, maintain an offscreen backing store

void setBorder(Border border)
copy-> .setBorder( )
copy-> <JViewport>.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). A non-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.

Overrides:
setBorder in class JComponent

Parameters:
border - the Border to set
Throws:
IllegalArgumentException - this method is not implemented

void setExtentSize(Dimension newExtent)
copy-> .setExtentSize( )
copy-> <JViewport>.setExtentSize(<Dimension newExtent>);

Sets the size of the visible part of the view using view coordinates.

Parameters:
newExtent - a Dimension object specifying the size of the view

void setScrollMode(int mode)
copy-> .setScrollMode( )
copy-> <JViewport>.setScrollMode(<int mode>);

Used to control the method of scrolling the viewport contents. You may want to change this mode to get maximum performance for your use case.

Parameters:
mode - one of the following values:

JViewport.BLIT_SCROLL_MODE
JViewport.BACKINGSTORE_SCROLL_MODE
JViewport.SIMPLE_SCROLL_MODE
Since:
1.3

See Also:
BLIT_SCROLL_MODE, BACKINGSTORE_SCROLL_MODE, SIMPLE_SCROLL_MODE

void setUI(ViewportUI ui)
copy-> .setUI( )
copy-> <JViewport>.setUI(<ViewportUI ui>);

Sets the L&F object that renders this component.

Parameters:
ui - the ViewportUI L&F object
See Also:
UIDefaults.getUI(javax.swing.JComponent)

void setView(Component view)
copy-> .setView( )
copy-> <JViewport>.setView(<Component view>);

Sets the JViewports one lightweight child (view), which can be null.

Parameters:
view - the viewports new lightweight child
See Also:
getView()

void setViewPosition(Point p)
copy-> .setViewPosition( )
copy-> <JViewport>.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.

Parameters:
p - a Point object giving the upper left coordinates

void setViewSize(Dimension newSize)
copy-> .setViewSize( )
copy-> <JViewport>.setViewSize(<Dimension newSize>);

Sets the view coordinates that appear in the upper left hand corner of the viewport, and the size of the view.

Parameters:
newSize - a Dimension object specifying the size and location of the new view coordinates, or null if there is no view

Dimension toViewCoordinates(Dimension size)
copy-> .toViewCoordinates( )
copy-> <Dimension var>=<JViewport>.toViewCoordinates(<Dimension size>);

Converts a size in pixel coordinates to view coordinates. Subclasses of viewport that support "logical coordinates" will override this method.

Parameters:
size - a Dimension object using pixel coordinates
Returns:
a Dimension object converted to view coordinates

Point toViewCoordinates(Point p)
copy-> .toViewCoordinates( )
copy-> <Point var>=<JViewport>.toViewCoordinates(<Point p>);

Converts a point in pixel coordinates to view coordinates. Subclasses of viewport that support "logical coordinates" will override this method.

Parameters:
p - a Point object using pixel coordinates
Returns:
a Point object converted to view coordinates

void updateUI()
copy-> .updateUI()
copy-> <JViewport>.updateUI();

Notification from the UIFactory that the L&F has changed.

Overrides:
updateUI in class JComponent

See Also:
JComponent.updateUI()

Methods inherited from class javax.swing.JComponent

addAncestorListener, addNotify, addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getGraphics, getHeight, getInputMap, getInputMap, getInputVerifier, getListeners, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getVerifyInputWhenFocusTarget, getWidth, getVisibleRect, getX, getY, grabFocus, hasFocus, hide, isDoubleBuffered, isFocusCycleRoot, isFocusTraversable, isLightweightComponent, isManagingFocus, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPaintingTile, isPreferredSizeSet, isRequestFocusEnabled, isValidateRoot, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processFocusEvent, processKeyBinding, processKeyEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, repaint, requestDefaultFocus, requestFocus, resetKeyboardActions, revalidate, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setDebugGraphicsOptions, setDoubleBuffered, setEnabled, setFont, setForeground, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize,

Inner Class Summary
`protected class`	JViewport.AccessibleJViewport JViewport.AccessibleJViewport This class implements accessibility support for the `JViewport` class. It provides an implementation of the Java Accessibility API appropriate to viewport user-interface elements. 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.
`protected class`	JViewport.ViewListener JViewport.ViewListener A listener for the view. 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.

Field Summary
`protected boolean`	backingStore copy-> `backingStore` Deprecated. As of Java 2 platform v1.3 True when this viewport is maintaining an offscreen image of its contents, so that some scrolling can take place using fast "bit-blit" operations instead of by accessing the view object to construct the display. The default is false. See Also: `setScrollMode(int)`
`static int`	BACKINGSTORE_SCROLL_MODE copy-> `BACKINGSTORE_SCROLL_MODE` Draws viewport contents into an offscreen image. This was previously the default mode for `JTable`. This mode may offer advantages over "blit mode" in some cases, but it requires a large chunk of extra RAM. See Also: `setScrollMode(int)` Since: 1.3
`protected Image`	backingStoreImage copy-> `backingStoreImage` The view image used for a backing store.
`static int`	BLIT_SCROLL_MODE copy-> `BLIT_SCROLL_MODE` Use `graphics.copyArea()` to implement scrolling. This is the fastest for most applications. See Also: `setScrollMode(int)` Since: 1.3
`protected boolean`	isViewSizeSet copy-> `isViewSizeSet` True when the viewport dimensions have been determined. The default is false.
`protected Point`	lastPaintPosition copy-> `lastPaintPosition` The last `viewPosition` that we've painted, so we know how much of the backing store image is valid.
`protected boolean`	scrollUnderway copy-> `scrollUnderway` The `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.
`static int`	SIMPLE_SCROLL_MODE copy-> `SIMPLE_SCROLL_MODE` This mode uses the very simple method of redrawing the entire contents of the scrollpane each time it is scrolled. This was the default behavior in Swing 1.0 and Swing 1.1. Either of the other two options will provide better performance in most cases. See Also: `setScrollMode(int)` Since: 1.3

Constructor Summary
JViewport copy-> `new JViewport()` copy-> `<JViewport var> = new JViewport();` Creates a `JViewport`.

Method Summary
`void`	addChangeListener(ChangeListener l) copy-> `.addChangeListener( )` copy-> `<JViewport>.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. Parameters: `l` - the `ChangeListener` to add See Also: `removeChangeListener(javax.swing.event.ChangeListener)`, `setViewPosition(java.awt.Point)`, `setViewSize(java.awt.Dimension)`, `setExtentSize(java.awt.Dimension)`
`protected void`	addImpl(Component child, Object constraints, int index) copy-> `.addImpl(, , )` copy-> `<JViewport>.addImpl(<Component child>, <Object constraints>, <int index>);` Sets the `JViewport`s 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.) Overrides: `addImpl` in class `Container` Parameters: `child` - the lightweight `child` of the viewport `constraints` - the `constraints` to be respected `index` - the index See Also: `setView(java.awt.Component)`
`protected boolean`	computeBlit(int dx, int dy, Point blitFrom, Point blitTo, Dimension blitSize, Rectangle blitPaint) copy-> `.computeBlit(, , , , , )` copy-> `<boolean var>=<JViewport>.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`. The parameters are modified to return the values required for the blit. Parameters: `dx` - the horizontal delta `dy` - the vertical delta `blitFrom` - the `Point` we're blitting from `blitTo` - the `Point` we're blitting to `blitSize` - the `Dimension` of the area to blit `blitPaint` - the area to blit Returns: true if the parameters are modified and we're ready to blit; false otherwise
`protected LayoutManager`	createLayoutManager() copy-> `.createLayoutManager()` copy-> `<LayoutManager var>=<JViewport>.createLayoutManager();` Subclassers can override this to install a different layout manager (or `null`) in the constructor. Returns a new `ViewportLayout` object. Returns: a `LayoutManager`
`protected JViewport.ViewListener`	createViewListener() copy-> `.createViewListener()` copy-> `<JViewport.ViewListener var>=<JViewport>.createViewListener();` Creates a listener for the view. Returns: a `ViewListener`
`protected void`	firePropertyChange(String propertyName, Object oldValue, Object newValue) copy-> `.firePropertyChange(, , )` copy-> `<JViewport>.firePropertyChange(<String propertyName>, <Object oldValue>, <Object newValue>);` Notifies listeners of a property change. This is subclassed to update the `windowBlit` property. (The `putClientProperty` property is final). Overrides: `firePropertyChange` in class `JComponent` Parameters: `propertyName` - a string containing the property name `oldValue` - the old value of the property `newValue` - the new value of the property
`protected void`	fireStateChanged() copy-> `.fireStateChanged()` copy-> `<JViewport>.fireStateChanged();` Notifies all `ChangeListeners` when the views size, position, or the viewports extent size has changed. See Also: `addChangeListener(javax.swing.event.ChangeListener)`, `removeChangeListener(javax.swing.event.ChangeListener)`, `EventListenerList`
`AccessibleContext`	getAccessibleContext() copy-> `.getAccessibleContext()` copy-> `<AccessibleContext var>=<JViewport>.getAccessibleContext();` Gets the AccessibleContext associated with this JViewport. For viewports, the AccessibleContext takes the form of an AccessibleJViewport. A new AccessibleJViewport instance is created if necessary. Specified by: `getAccessibleContext` in interface `Accessible` Overrides: `getAccessibleContext` in class `JComponent` Returns: an AccessibleJViewport that serves as the AccessibleContext of this JViewport
`Dimension`	getExtentSize() copy-> `.getExtentSize()` copy-> `<Dimension var>=<JViewport>.getExtentSize();` Returns the size of the visible part of the view in view coordinates. Returns: a `Dimension` object giving the size of the view
`Insets`	getInsets() copy-> `.getInsets()` copy-> `<Insets var>=<JViewport>.getInsets();` Returns the insets (border) dimensions as (0,0,0,0), since borders are not supported on a `JViewport`. Overrides: `getInsets` in class `JComponent` Returns: a `Rectange` of zero dimension and zero origin See Also: `setBorder(javax.swing.border.Border)`
`Insets`	getInsets(Insets insets) copy-> `.getInsets( )` copy-> `<Insets var>=<JViewport>.getInsets(<Insets insets>);` Returns an `Insets` object containing this `JViewport`s inset values. The passed-in `Insets` object will be reinitialized, and all existing values within this object are overwritten. Overrides: `getInsets` in class `JComponent` Parameters: `insets` - the `Insets` object which can be reused Returns: this viewports inset values See Also: `getInsets()`
`int`	getScrollMode() copy-> `.getScrollMode()` copy-> `<int var>=<JViewport>.getScrollMode();` Returns the current scrolling mode. Returns: the `scrollMode` property Since: 1.3 See Also: `setScrollMode(int)`
`ViewportUI`	getUI() copy-> `.getUI()` copy-> `<ViewportUI var>=<JViewport>.getUI();` Returns the L&F object that renders this component. Returns: ViewportUI object
`String`	getUIClassID() copy-> `.getUIClassID()` copy-> `<String var>=<JViewport>.getUIClassID();` Returns a string that specifies the name of the L&F class that renders this component. Overrides: `getUIClassID` in class `JComponent` Returns: the string "ViewportUI" See Also: `JComponent.getUIClassID()`, `UIDefaults.getUI(javax.swing.JComponent)`
`Component`	getView() copy-> `.getView()` copy-> `<Component var>=<JViewport>.getView();` Returns the `JViewport`s one child or `null`. Returns: the viewports child, or `null` if none exists See Also: `setView(java.awt.Component)`
`Point`	getViewPosition() copy-> `.getViewPosition()` copy-> `<Point var>=<JViewport>.getViewPosition();` Returns the view coordinates that appear in the upper left hand corner of the viewport, or 0,0 if there's no view. Returns: a `Point` object giving the upper left coordinates
`Rectangle`	getViewRect() copy-> `.getViewRect()` copy-> `<Rectangle var>=<JViewport>.getViewRect();` Returns a rectangle whose origin is `getViewPosition` and size is `getExtentSize`. This is the visible part of the view, in view coordinates. Returns: a `Rectangle` giving the visible part of the view using view coordinates.
`Dimension`	getViewSize() copy-> `.getViewSize()` copy-> `<Dimension var>=<JViewport>.getViewSize();` If the view's size hasn't been explicitly set, return the preferred size, otherwise return the view's current size. If there is no view, return 0,0. Returns: a `Dimension` object specifying the size of the view
`boolean`	isBackingStoreEnabled() copy-> `.isBackingStoreEnabled()` copy-> `<boolean var>=<JViewport>.isBackingStoreEnabled();` Deprecated. As of Java 2 platform v1.3, replaced by `getScrollMode()`. Returns true if this viewport is maintaining an offscreen image of its contents. Returns: true if `scrollMode` is BACKINGSTORE_SCROLL_MODE
`boolean`	isOptimizedDrawingEnabled() copy-> `.isOptimizedDrawingEnabled()` copy-> `<boolean var>=<JViewport>.isOptimizedDrawingEnabled();` The `JViewport` overrides the default implementation of this method (in `JComponent`) to return false. This ensures that the drawing machinery will call the `Viewport`s `paint` implementation rather than messaging the `JViewport`s children directly. Overrides: `isOptimizedDrawingEnabled` in class `JComponent` Returns: false
`void`	paint(Graphics g) copy-> `.paint( )` copy-> `<JViewport>.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. 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.) Overrides: `paint` in class `JComponent` Parameters: `g` - the `Graphics` context within which to paint
`protected String`	paramString() copy-> `.paramString()` copy-> `<String var>=<JViewport>.paramString();` Returns a string representation of this `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`. Overrides: `paramString` in class `JComponent` Returns: a string representation of this `JViewport`
`void`	remove(Component child) copy-> `.remove( )` copy-> `<JViewport>.remove(<Component child>);` Removes the `Viewport`s one lightweight child. Overrides: `remove` in class `Container` See Also: `setView(java.awt.Component)`
`void`	removeChangeListener(ChangeListener l) copy-> `.removeChangeListener( )` copy-> `<JViewport>.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. Parameters: `l` - the `ChangeListener` to remove See Also: `addChangeListener(javax.swing.event.ChangeListener)`
`void`	repaint(long tm, int x, int y, int w, int h) copy-> `.repaint(, , , , )` copy-> `<JViewport>.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`. Overrides: `repaint` in class `JComponent` Parameters: `tm` - maximum time in milliseconds before update `x` - the `x` coordinate (pixels over from left) `y` - the `y` coordinate (pixels down from top) `width` - the width `height` - the height See Also: `Component.update(java.awt.Graphics)`
`void`	reshape(int x, int y, int w, int h) copy-> `.reshape(, , , )` copy-> `<JViewport>.reshape(<int x>, <int y>, <int w>, <int h>);` Sets the bounds of this viewport. If the viewports width or height has changed, fire a `StateChanged` event. Overrides: `reshape` in class `JComponent` Parameters: `x` - left edge of the origin `y` - top edge of the origin `w` - width in pixels `h` - height in pixels See Also: `JComponent.reshape(int, int, int, int)`
`void`	scrollRectToVisible(Rectangle contentRect) copy-> `.scrollRectToVisible( )` copy-> `<JViewport>.scrollRectToVisible(<Rectangle contentRect>);` Overridden to scroll the view so that `Rectangle` within the view becomes visible. Overrides: `scrollRectToVisible` in class `JComponent` Parameters: `contentRect` - the `Rectangle` to display
`void`	setBackingStoreEnabled(boolean enabled) copy-> `.setBackingStoreEnabled( )` copy-> `<JViewport>.setBackingStoreEnabled(<boolean enabled>);` Deprecated. As of Java 2 platform v1.3, replaced by `setScrollMode()`. If true if this viewport will maintain an offscreen image of its contents. The image is used to reduce the cost of small one dimensional changes to the `viewPosition`. Rather than repainting the entire viewport we use `Graphics.copyArea()` to effect some of the scroll. Parameters: `enabled` - if true, maintain an offscreen backing store
`void`	setBorder(Border border) copy-> `.setBorder( )` copy-> `<JViewport>.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). A non-`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`. Overrides: `setBorder` in class `JComponent` Parameters: `border` - the `Border` to set Throws: `IllegalArgumentException` - this method is not implemented
`void`	setExtentSize(Dimension newExtent) copy-> `.setExtentSize( )` copy-> `<JViewport>.setExtentSize(<Dimension newExtent>);` Sets the size of the visible part of the view using view coordinates. Parameters: `newExtent` - a `Dimension` object specifying the size of the view
`void`	setScrollMode(int mode) copy-> `.setScrollMode( )` copy-> `<JViewport>.setScrollMode(<int mode>);` Used to control the method of scrolling the viewport contents. You may want to change this mode to get maximum performance for your use case. Parameters: `mode` - one of the following values: JViewport.BLIT_SCROLL_MODE JViewport.BACKINGSTORE_SCROLL_MODE JViewport.SIMPLE_SCROLL_MODE Since: 1.3 See Also: `BLIT_SCROLL_MODE`, `BACKINGSTORE_SCROLL_MODE`, `SIMPLE_SCROLL_MODE`
`void`	setUI(ViewportUI ui) copy-> `.setUI( )` copy-> `<JViewport>.setUI(<ViewportUI ui>);` Sets the L&F object that renders this component. Parameters: `ui` - the `ViewportUI` L&F object See Also: `UIDefaults.getUI(javax.swing.JComponent)`
`void`	setView(Component view) copy-> `.setView( )` copy-> `<JViewport>.setView(<Component view>);` Sets the `JViewport`s one lightweight child (`view`), which can be `null`. Parameters: `view` - the viewports new lightweight child See Also: `getView()`
`void`	setViewPosition(Point p) copy-> `.setViewPosition( )` copy-> `<JViewport>.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. Parameters: `p` - a `Point` object giving the upper left coordinates
`void`	setViewSize(Dimension newSize) copy-> `.setViewSize( )` copy-> `<JViewport>.setViewSize(<Dimension newSize>);` Sets the view coordinates that appear in the upper left hand corner of the viewport, and the size of the view. Parameters: `newSize` - a `Dimension` object specifying the size and location of the new view coordinates, or `null` if there is no view
`Dimension`	toViewCoordinates(Dimension size) copy-> `.toViewCoordinates( )` copy-> `<Dimension var>=<JViewport>.toViewCoordinates(<Dimension size>);` Converts a size in pixel coordinates to view coordinates. Subclasses of viewport that support "logical coordinates" will override this method. Parameters: `size` - a `Dimension` object using pixel coordinates Returns: a `Dimension` object converted to view coordinates
`Point`	toViewCoordinates(Point p) copy-> `.toViewCoordinates( )` copy-> `<Point var>=<JViewport>.toViewCoordinates(<Point p>);` Converts a point in pixel coordinates to view coordinates. Subclasses of viewport that support "logical coordinates" will override this method. Parameters: `p` - a `Point` object using pixel coordinates Returns: a `Point` object converted to view coordinates
`void`	updateUI() copy-> `.updateUI()` copy-> `<JViewport>.updateUI();` Notification from the `UIFactory` that the L&F has changed. Overrides: `updateUI` in class `JComponent` See Also: `JComponent.updateUI()`

javax.swing Class JViewport

javax.swing
Class JViewport