public class JScrollPane extends JComponent implements ScrollPaneConstants, Accessible
Provides a scrollable view of a lightweight component. A JScrollPane manages a viewport, optional vertical and horizontal scroll bars, and optional row and column heading viewports. You can find task-oriented documentation of JScrollPane in How to Use Scroll Panes, a section in The Java Tutorial. Note that JScrollPane does not support heavyweight components.
JViewport provides a window, or "viewport" onto a data source -- for example, a text file. That data source is the "scrollable client" (aka data model) displayed by the JViewport view. A JScrollPane basically consists of JScrollBars, a JViewport, and the wiring between them, as shown in the diagram at right.
In addition to the scroll bars and viewport, a JScrollPane can have a column header and a row header. Each of these is a JViewport object that you specify with setRowHeaderView, and setColumnHeaderView. The column header viewport automatically scrolls left and right, tracking the left-right scrolling of the main viewport. (It never scrolls vertically, however.) The row header acts in a similar fashion.
Where two scroll bars meet, the row header meets the column header, or a scroll bar meets one of the headers, both components stop short of the corner, leaving a rectangular space which is, by default, empty. These spaces can potentially exist in any number of the four corners. In the previous diagram, the top right space is present and identified by the label "corner component".
Any number of these empty spaces can be replaced by using the setCorner method to add a component to a particular corner. (Note: The same component cannot be added to multiple corners.) This is useful if there's some extra decoration or function you'd like to add to the scroll pane. The size of each corner component is entirely determined by the size of the headers and/or scroll bars that surround it.
A corner component will only be visible if there is an empty space in that corner for it to exist in. For example, consider a component set into the top right corner of a scroll pane with a column header. If the scroll pane's vertical scrollbar is not present, perhaps because the view component hasn't grown large enough to require it, then the corner component will not be shown (since there is no empty space in that corner created by the meeting of the header and vertical scroll bar). Forcing the scroll bar to always be shown, using setVerticalScrollBarPolicy(VERTICAL_SCROLLBAR_ALWAYS), will ensure that the space for the corner component always exists.
To add a border around the main viewport, you can use setViewportBorder. (Of course, you can also add a border around the whole scroll pane using setBorder.)
A common operation to want to do is to set the background color that will be used if the main viewport view is smaller than the viewport, or is not opaque. This can be accomplished by setting the background color of the viewport, via scrollPane.getViewport().setBackground(). The reason for setting the color of the viewport and not the scrollpane is that by default JViewport is opaque which, among other things, means it will completely fill in its background using its background color. Therefore when JScrollPane draws its background the viewport will usually draw over it.
By default JScrollPane uses ScrollPaneLayout to handle the layout of its child Components. ScrollPaneLayout determines the size to make the viewport view in one of two ways:
Scrollable a combination of getPreferredScrollableViewportSize, getScrollableTracksViewportWidth and getScrollableTracksViewportHeightis used, otherwise getPreferredSize is used. Warning: Swing is not thread safe. For more information see Swing's Threading Policy.
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. As of 1.4, support for long term storage of all JavaBeans™ has been added to the java.beans package. Please see XMLEncoder.
JScrollBar, JViewport, ScrollPaneLayout, Scrollable, Component.getPreferredSize(), setViewportView(java.awt.Component), setRowHeaderView(java.awt.Component), setColumnHeaderView(java.awt.Component), setCorner(java.lang.String, java.awt.Component), setViewportBorder(javax.swing.border.Border)
| Modifier and Type | Class and Description |
|---|---|
protected class |
JScrollPane.AccessibleJScrollPane This class implements accessibility support for the |
protected class |
JScrollPane.ScrollBar By default |
JComponent.AccessibleJComponent Container.AccessibleAWTContainer Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy protected int verticalScrollBarPolicy
The display policy for the vertical scrollbar. The default is ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED.
setVerticalScrollBarPolicy(int)protected int horizontalScrollBarPolicy
The display policy for the horizontal scrollbar. The default is ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED.
setHorizontalScrollBarPolicy(int)protected JViewport viewport
The scrollpane's viewport child. Default is an empty JViewport.
setViewport(javax.swing.JViewport)protected JScrollBar verticalScrollBar
The scrollpane's vertical scrollbar child. Default is a JScrollBar.
protected JScrollBar horizontalScrollBar
The scrollpane's horizontal scrollbar child. Default is a JScrollBar.
protected JViewport rowHeader
The row header child. Default is null.
setRowHeader(javax.swing.JViewport)protected JViewport columnHeader
The column header child. Default is null.
setColumnHeader(javax.swing.JViewport)protected Component lowerLeft
The component to display in the lower left corner. Default is null.
protected Component lowerRight
The component to display in the lower right corner. Default is null.
protected Component upperLeft
The component to display in the upper left corner. Default is null.
protected Component upperRight
The component to display in the upper right corner. Default is null.
public JScrollPane(Component view,
int vsbPolicy,
int hsbPolicy) Creates a JScrollPane that displays the view component in a viewport whose view position can be controlled with a pair of scrollbars. The scrollbar policies specify when the scrollbars are displayed, For example, if vsbPolicy is VERTICAL_SCROLLBAR_AS_NEEDED then the vertical scrollbar only appears if the view doesn't fit vertically. The available policy settings are listed at setVerticalScrollBarPolicy(int) and setHorizontalScrollBarPolicy(int).
view - the component to display in the scrollpanes viewportvsbPolicy - an integer that specifies the vertical scrollbar policyhsbPolicy - an integer that specifies the horizontal scrollbar policysetViewportView(java.awt.Component)public JScrollPane(Component view)
Creates a JScrollPane that displays the contents of the specified component, where both horizontal and vertical scrollbars appear whenever the component's contents are larger than the view.
view - the component to display in the scrollpane's viewportsetViewportView(java.awt.Component)public JScrollPane(int vsbPolicy,
int hsbPolicy) Creates an empty (no viewport view) JScrollPane with specified scrollbar policies. The available policy settings are listed at setVerticalScrollBarPolicy(int) and setHorizontalScrollBarPolicy(int).
vsbPolicy - an integer that specifies the vertical scrollbar policyhsbPolicy - an integer that specifies the horizontal scrollbar policysetViewportView(java.awt.Component)public JScrollPane()
Creates an empty (no viewport view) JScrollPane where both horizontal and vertical scrollbars appear when needed.
public ScrollPaneUI getUI()
Returns the look and feel (L&F) object that renders this component.
ScrollPaneUI object that renders this componentsetUI(javax.swing.plaf.ScrollPaneUI)public void setUI(ScrollPaneUI ui)
Sets the ScrollPaneUI object that provides the look and feel (L&F) for this component.
ui - the ScrollPaneUI L&F objectgetUI()public void updateUI()
Replaces the current ScrollPaneUI object with a version from the current default look and feel. To be called when the default look and feel changes.
updateUI in class JComponent
JComponent.updateUI(), UIManager.getUI(javax.swing.JComponent)
public String getUIClassID()
Returns the suffix used to construct the name of the L&F class used to render this component.
getUIClassID in class JComponent
JComponent.getUIClassID(), UIDefaults.getUI(javax.swing.JComponent)
public void setLayout(LayoutManager layout)
Sets the layout manager for this JScrollPane. This method overrides setLayout in java.awt.Container to ensure that only LayoutManagers which are subclasses of ScrollPaneLayout can be used in a JScrollPane. If layout is non-null, this will invoke syncWithScrollPane on it.
setLayout in class Container
layout - the specified layout managerClassCastException - if layout is not a ScrollPaneLayout
Container.getLayout(), Container.setLayout(java.awt.LayoutManager)
public boolean isValidateRoot()
Overridden to return true so that any calls to revalidate on any descendants of this JScrollPane will cause the entire tree beginning with this JScrollPane to be validated.
isValidateRoot in class JComponent
Container.validate(), JComponent.revalidate(), JComponent.isValidateRoot(), Container.isValidateRoot()
public int getVerticalScrollBarPolicy()
Returns the vertical scroll bar policy value.
verticalScrollBarPolicy propertysetVerticalScrollBarPolicy(int)public void setVerticalScrollBarPolicy(int policy)
Determines when the vertical scrollbar appears in the scrollpane. Legal values are:
ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED ScrollPaneConstants.VERTICAL_SCROLLBAR_NEVER ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS policy - one of the three values listed aboveIllegalArgumentException - if policy is not one of the legal values shown abovegetVerticalScrollBarPolicy()public int getHorizontalScrollBarPolicy()
Returns the horizontal scroll bar policy value.
horizontalScrollBarPolicy propertysetHorizontalScrollBarPolicy(int)public void setHorizontalScrollBarPolicy(int policy)
Determines when the horizontal scrollbar appears in the scrollpane. The options are:
ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS policy - one of the three values listed aboveIllegalArgumentException - if policy is not one of the legal values shown abovegetHorizontalScrollBarPolicy()public Border getViewportBorder()
Returns the Border object that surrounds the viewport.
viewportBorder propertysetViewportBorder(javax.swing.border.Border)public void setViewportBorder(Border viewportBorder)
Adds a border around the viewport. Note that the border isn't set on the viewport directly, JViewport doesn't support the JComponent border property. Similarly setting the JScrollPanes viewport doesn't affect the viewportBorder property.
The default value of this property is computed by the look and feel implementation.
viewportBorder - the border to be addedgetViewportBorder(), setViewport(javax.swing.JViewport)
public Rectangle getViewportBorderBounds()
Returns the bounds of the viewport's border.
Rectangle object specifying the viewport borderpublic JScrollBar createHorizontalScrollBar()
Returns a JScrollPane.ScrollBar by default. Subclasses may override this method to force ScrollPaneUI implementations to use a JScrollBar subclass. Used by ScrollPaneUI implementations to create the horizontal scrollbar.
JScrollBar with a horizontal orientationJScrollBarpublic JScrollBar getHorizontalScrollBar()
Returns the horizontal scroll bar that controls the viewport's horizontal view position.
horizontalScrollBar propertysetHorizontalScrollBar(javax.swing.JScrollBar)public void setHorizontalScrollBar(JScrollBar horizontalScrollBar)
Adds the scrollbar that controls the viewport's horizontal view position to the scrollpane. This is usually unnecessary, as JScrollPane creates horizontal and vertical scrollbars by default.
horizontalScrollBar - the horizontal scrollbar to be addedcreateHorizontalScrollBar(), getHorizontalScrollBar()
public JScrollBar createVerticalScrollBar()
Returns a JScrollPane.ScrollBar by default. Subclasses may override this method to force ScrollPaneUI implementations to use a JScrollBar subclass. Used by ScrollPaneUI implementations to create the vertical scrollbar.
JScrollBar with a vertical orientationJScrollBarpublic JScrollBar getVerticalScrollBar()
Returns the vertical scroll bar that controls the viewports vertical view position.
verticalScrollBar propertysetVerticalScrollBar(javax.swing.JScrollBar)public void setVerticalScrollBar(JScrollBar verticalScrollBar)
Adds the scrollbar that controls the viewports vertical view position to the scrollpane. This is usually unnecessary, as JScrollPane creates vertical and horizontal scrollbars by default.
verticalScrollBar - the new vertical scrollbar to be addedcreateVerticalScrollBar(), getVerticalScrollBar()
protected JViewport createViewport()
Returns a new JViewport by default. Used to create the viewport (as needed) in setViewportView, setRowHeaderView, and setColumnHeaderView. Subclasses may override this method to return a subclass of JViewport.
JViewport
public JViewport getViewport()
Returns the current JViewport.
viewport propertysetViewport(javax.swing.JViewport)public void setViewport(JViewport viewport)
Removes the old viewport (if there is one); forces the viewPosition of the new viewport to be in the +x,+y quadrant; syncs up the row and column headers (if there are any) with the new viewport; and finally syncs the scrollbars and headers with the new viewport.
Most applications will find it more convenient to use setViewportView to add a viewport and a view to the scrollpane.
viewport - the new viewport to be used; if viewport is null, the old viewport is still removed and the new viewport is set to null
createViewport(), getViewport(), setViewportView(java.awt.Component)
public void setViewportView(Component view)
Creates a viewport if necessary and then sets its view. Applications that don't provide the view directly to the JScrollPane constructor should use this method to specify the scrollable child that's going to be displayed in the scrollpane. For example:
JScrollPane scrollpane = new JScrollPane(); scrollpane.setViewportView(myBigComponentToScroll);Applications should not add children directly to the scrollpane.
view - the component to add to the viewportsetViewport(javax.swing.JViewport), JViewport.setView(java.awt.Component)
public JViewport getRowHeader()
Returns the row header.
rowHeader propertysetRowHeader(javax.swing.JViewport)public void setRowHeader(JViewport rowHeader)
Removes the old rowHeader, if it exists; if the new rowHeader isn't null, syncs the y coordinate of its viewPosition with the viewport (if there is one) and then adds it to the scroll pane.
Most applications will find it more convenient to use setRowHeaderView to add a row header component and its viewport to the scroll pane.
rowHeader - the new row header to be used; if null the old row header is still removed and the new rowHeader is set to null
getRowHeader(), setRowHeaderView(java.awt.Component)
public void setRowHeaderView(Component view)
Creates a row-header viewport if necessary, sets its view and then adds the row-header viewport to the scrollpane. For example:
JScrollPane scrollpane = new JScrollPane(); scrollpane.setViewportView(myBigComponentToScroll); scrollpane.setRowHeaderView(myBigComponentsRowHeader);
view - the component to display as the row headersetRowHeader(javax.swing.JViewport), JViewport.setView(java.awt.Component)
public JViewport getColumnHeader()
Returns the column header.
columnHeader propertysetColumnHeader(javax.swing.JViewport)public void setColumnHeader(JViewport columnHeader)
Removes the old columnHeader, if it exists; if the new columnHeader isn't null, syncs the x coordinate of its viewPosition with the viewport (if there is one) and then adds it to the scroll pane.
Most applications will find it more convenient to use setColumnHeaderView to add a column header component and its viewport to the scroll pane.
public void setColumnHeaderView(Component view)
Creates a column-header viewport if necessary, sets its view, and then adds the column-header viewport to the scrollpane. For example:
JScrollPane scrollpane = new JScrollPane(); scrollpane.setViewportView(myBigComponentToScroll); scrollpane.setColumnHeaderView(myBigComponentsColumnHeader);
view - the component to display as the column headersetColumnHeader(javax.swing.JViewport), JViewport.setView(java.awt.Component)
public Component getCorner(String key)
Returns the component at the specified corner. The key value specifying the corner is one of:
key - one of the values as shown abovenull) identified by the given key, or null if the key is invalidsetCorner(java.lang.String, java.awt.Component)public void setCorner(String key,
Component corner) Adds a child that will appear in one of the scroll panes corners, if there's room. For example with both scrollbars showing (on the right and bottom edges of the scrollpane) the lower left corner component will be shown in the space between ends of the two scrollbars. Legal values for the key are:
Although "corner" doesn't match any beans property signature, PropertyChange events are generated with the property name set to the corner key.
key - identifies which corner the component will appear incorner - one of the following components: IllegalArgumentException - if corner key is invalidpublic void setComponentOrientation(ComponentOrientation co)
Sets the orientation for the vertical and horizontal scrollbars as determined by the ComponentOrientation argument.
setComponentOrientation in class Component
co - one of the following values: ComponentOrientationpublic boolean isWheelScrollingEnabled()
Indicates whether or not scrolling will take place in response to the mouse wheel. Wheel scrolling is enabled by default.
setWheelScrollingEnabled(boolean)public void setWheelScrollingEnabled(boolean handleWheel)
Enables/disables scrolling in response to movement of the mouse wheel. Wheel scrolling is enabled by default.
handleWheel - true if scrolling should be done automatically for a MouseWheelEvent, false otherwise.isWheelScrollingEnabled(), MouseWheelEvent, MouseWheelListener
protected String paramString()
Returns a string representation of this JScrollPane. 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 JComponent
JScrollPane.public AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this JScrollPane. For scroll panes, the AccessibleContext takes the form of an AccessibleJScrollPane. A new AccessibleJScrollPane instance is created if necessary.
getAccessibleContext in interface Accessible
getAccessibleContext in class Component
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