Class JScrollBar

java.lang.Object
java.awt.Component
java.awt.Container
javax.swing.JComponent
javax.swing.JScrollBar
All Implemented Interfaces:
Adjustable, ImageObserver, MenuContainer, Serializable, Accessible
Direct Known Subclasses:
JScrollPane.ScrollBar
@JavaBean(defaultProperty="UI", description="A component that helps determine the visible content range of an area.") public class JScrollBar extends JComponent implements Adjustable, Accessible
An implementation of a scrollbar. The user positions the knob in the scrollbar to determine the contents of the viewing area. The program typically adjusts the display so that the end of the scrollbar represents the end of the displayable contents, or 100% of the contents. The start of the scrollbar is the beginning of the displayable contents, or 0%. The position of the knob within those bounds then translates to the corresponding percentage of the displayable contents.

Typically, as the position of the knob in the scrollbar changes a corresponding change is made to the position of the JViewport on the underlying view, changing the contents of the JViewport.

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.

Since:
1.2
See Also:

  • Field Details

    • model

      protected BoundedRangeModel model
      The model that represents the scrollbar's minimum, maximum, extent (aka "visibleAmount") and current value.
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    • orientation

      protected int orientation
      Orientation of this scrollBar.
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    • unitIncrement

      protected int unitIncrement
      Stores the amount by which the value of the scrollbar is changed upon a unit up/down request.
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    • blockIncrement

      protected int blockIncrement
      Stores the amount by which the value of the scrollbar is changed upon a block (usually "page") up/down request.
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  • Constructor Details

    • JScrollBar

      public JScrollBar(int orientation, int value, int extent, int min, int max)
      Creates a scrollbar with the specified orientation, value, extent, minimum, and maximum. The "extent" is the size of the viewable area. It is also known as the "visible amount".

      Note: Use setBlockIncrement to set the block increment to a size slightly smaller than the view's extent. That way, when the user jumps the knob to an adjacent position, one or two lines of the original contents remain in view.

      Parameters:
      orientation - an orientation of the JScrollBar
      value - an int giving the current value
      extent - an int giving the amount by which the value can "jump"
      min - an int giving the minimum value
      max - an int giving the maximum value
      Throws:
      IllegalArgumentException - if orientation is not one of VERTICAL, HORIZONTAL
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    • JScrollBar

      public JScrollBar(int orientation)
      Creates a scrollbar with the specified orientation and the following initial values: 
      minimum = 0
maximum = 100
value = 0
extent = 10
      Parameters:
      orientation - an orientation of the JScrollBar

    • JScrollBar

      public JScrollBar()
      Creates a vertical scrollbar with the following initial values: 
      minimum = 0
maximum = 100
value = 0
extent = 10

  • Method Details

    • setUI

      @BeanProperty(hidden=true, visualUpdate=true, description="The UI object that implements the Component's LookAndFeel") public void setUI(ScrollBarUI ui)
      Sets the L&F object that renders this component.
      Parameters:
      ui - the ScrollBarUI L&F object
      Since:
      1.4
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    • getUI

      public ScrollBarUI getUI()
      Returns the delegate that implements the look and feel for this component.
      Overrides:
      getUI in class JComponent
      Returns:
      the scroll bar's current UI.
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    • updateUI

      public void updateUI()
      Overrides JComponent.updateUI.
      Overrides:
      updateUI in class JComponent
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    • getUIClassID

      @BeanProperty(bound=false) public String getUIClassID()
      Returns the name of the LookAndFeel class for this component.
      Overrides:
      getUIClassID in class JComponent
      Returns:
      the string "ScrollBarUI"
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    • getOrientation

      public int getOrientation()
      Returns the component's orientation (horizontal or vertical).
      Specified by:
      getOrientation in interface Adjustable
      Returns:
      VERTICAL or HORIZONTAL
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    • setOrientation

      @BeanProperty(preferred=true, visualUpdate=true, enumerationValues={"JScrollBar.VERTICAL","JScrollBar.HORIZONTAL"}, description="The scrollbar's orientation.") public void setOrientation(int orientation)
      Set the scrollbar's orientation to either VERTICAL or HORIZONTAL.
      Parameters:
      orientation - an orientation of the JScrollBar
      Throws:
      IllegalArgumentException - if orientation is not one of VERTICAL, HORIZONTAL
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    • getModel

      public BoundedRangeModel getModel()
      Returns data model that handles the scrollbar's four fundamental properties: minimum, maximum, value, extent.
      Returns:
      the data model
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    • setModel

      @BeanProperty(expert=true, description="The scrollbar's BoundedRangeModel.") public void setModel(BoundedRangeModel newModel)
      Sets the model that handles the scrollbar's four fundamental properties: minimum, maximum, value, extent.
      Parameters:
      newModel - a new model
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    • getUnitIncrement

      public int getUnitIncrement(int direction)
      Returns the amount to change the scrollbar's value by, given a unit up/down request. A ScrollBarUI implementation typically calls this method when the user clicks on a scrollbar up/down arrow and uses the result to update the scrollbar's value. Subclasses may override this method to compute a value, e.g. the change required to scroll one (variable height) line of text or one row in a table.

      The JScrollPane component creates scrollbars (by default) that override this method and delegate to the viewports Scrollable view, if it has one. The Scrollable interface provides a more specialized version of this method.

      Some look and feel implementations that provide custom scrolling behavior ignore this property.

      Parameters:
      direction - is -1 or 1 for up/down respectively
      Returns:
      the value of the unitIncrement property
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    • setUnitIncrement

      @BeanProperty(preferred=true, description="The scrollbar's unit increment.") public void setUnitIncrement(int unitIncrement)
      Sets the unitIncrement property.

      Note, that if the argument is equal to the value of Integer.MIN_VALUE, then most look and feel implementations will not provide scrolling to the right/down.

      Some look and feel implementations that provide custom scrolling behavior ignore this property.

      Specified by:
      setUnitIncrement in interface Adjustable
      Parameters:
      unitIncrement - the unit increment
      See Also:

    • getBlockIncrement

      public int getBlockIncrement(int direction)
      Returns the amount to change the scrollbar's value by, given a block (usually "page") up/down request. A ScrollBarUI implementation typically calls this method when the user clicks outside the scrollbar "knob" to scroll up or down by a large amount. Subclasses may override this method to compute a value, e.g. the change required to scroll one paragraph in a text document.

      The JScrollPane component creates scrollbars (by default) that override this method and delegate to the viewports Scrollable view, if it has one. The Scrollable interface provides a more specialized version of this method.

      Some look and feel implementations that provide custom scrolling behavior ignore this property.

      Parameters:
      direction - is -1 or 1 for up/down respectively
      Returns:
      the value of the blockIncrement property
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    • setBlockIncrement

      @BeanProperty(preferred=true, description="The scrollbar's block increment.") public void setBlockIncrement(int blockIncrement)
      Sets the blockIncrement property.

      Note, that if the argument is equal to the value of Integer.MIN_VALUE, then most look and feel implementations will not provide scrolling to the right/down.

      Some look and feel implementations that provide custom scrolling behavior ignore this property.

      Specified by:
      setBlockIncrement in interface Adjustable
      Parameters:
      blockIncrement - the block increment
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    • getUnitIncrement

      public int getUnitIncrement()
      For backwards compatibility with java.awt.Scrollbar.
      Specified by:
      getUnitIncrement in interface Adjustable
      Returns:
      the unit value increment for the adjustable object
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    • getBlockIncrement

      public int getBlockIncrement()
      For backwards compatibility with java.awt.Scrollbar.
      Specified by:
      getBlockIncrement in interface Adjustable
      Returns:
      the block value increment for the adjustable object
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    • getValue

      public int getValue()
      Returns the scrollbar's value.
      Specified by:
      getValue in interface Adjustable
      Returns:
      the model's value property
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    • setValue

      @BeanProperty(bound=false, preferred=true, description="The scrollbar's current value.") public void setValue(int value)
      Sets the scrollbar's value. This method just forwards the value to the model.
      Specified by:
      setValue in interface Adjustable
      Parameters:
      value - the current value, between minimum and maximum - visibleAmount
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    • getVisibleAmount

      public int getVisibleAmount()
      Returns the scrollbar's extent, aka its "visibleAmount". In many scrollbar look and feel implementations the size of the scrollbar "knob" or "thumb" is proportional to the extent.
      Specified by:
      getVisibleAmount in interface Adjustable
      Returns:
      the value of the model's extent property
      See Also:

    • setVisibleAmount

      @BeanProperty(bound=false, preferred=true, description="The amount of the view that is currently visible.") public void setVisibleAmount(int extent)
      Set the model's extent property.
      Specified by:
      setVisibleAmount in interface Adjustable
      Parameters:
      extent - the length of the indicator
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    • getMinimum

      public int getMinimum()
      Returns the minimum value supported by the scrollbar (usually zero).
      Specified by:
      getMinimum in interface Adjustable
      Returns:
      the value of the model's minimum property
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    • setMinimum

      @BeanProperty(bound=false, preferred=true, description="The scrollbar's minimum value.") public void setMinimum(int minimum)
      Sets the model's minimum property.
      Specified by:
      setMinimum in interface Adjustable
      Parameters:
      minimum - the minimum value
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    • getMaximum

      public int getMaximum()
      The maximum value of the scrollbar is maximum - extent.
      Specified by:
      getMaximum in interface Adjustable
      Returns:
      the value of the model's maximum property
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    • setMaximum

      @BeanProperty(bound=false, preferred=true, description="The scrollbar's maximum value.") public void setMaximum(int maximum)
      Sets the model's maximum property. Note that the scrollbar's value can only be set to maximum - extent.
      Specified by:
      setMaximum in interface Adjustable
      Parameters:
      maximum - the maximum value
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    • getValueIsAdjusting

      public boolean getValueIsAdjusting()
      True if the scrollbar knob is being dragged.
      Returns:
      the value of the model's valueIsAdjusting property
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    • setValueIsAdjusting

      @BeanProperty(bound=false, expert=true, description="True if the scrollbar thumb is being dragged.") public void setValueIsAdjusting(boolean b)
      Sets the model's valueIsAdjusting property. Scrollbar look and feel implementations should set this property to true when a knob drag begins, and to false when the drag ends. The scrollbar model will not generate ChangeEvents while valueIsAdjusting is true.
      Parameters:
      b - true if the upcoming changes to the value property are part of a series
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    • setValues

      public void setValues(int newValue, int newExtent, int newMin, int newMax)
      Sets the four BoundedRangeModel properties after forcing the arguments to obey the usual constraints: 
      minimum ≤ value ≤ value+extent ≤ maximum
      Parameters:
      newValue - an int giving the current value
      newExtent - an int giving the amount by which the value can "jump"
      newMin - an int giving the minimum value
      newMax - an int giving the maximum value
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    • addAdjustmentListener

      public void addAdjustmentListener(AdjustmentListener l)
      Adds an AdjustmentListener. Adjustment listeners are notified each time the scrollbar's model changes. Adjustment events are provided for backwards compatibility with java.awt.Scrollbar.

      Note that the AdjustmentEvents type property will always have a placeholder value of AdjustmentEvent.TRACK because all changes to a BoundedRangeModels value are considered equivalent. To change the value of a BoundedRangeModel one just sets its value property, i.e. model.setValue(123). No information about the origin of the change, e.g. it's a block decrement, is provided. We don't try to fabricate the origin of the change here.

      Specified by:
      addAdjustmentListener in interface Adjustable
      Parameters:
      l - the AdjustmentLister to add
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    • removeAdjustmentListener

      public void removeAdjustmentListener(AdjustmentListener l)
      Removes an AdjustmentEvent listener.
      Specified by:
      removeAdjustmentListener in interface Adjustable
      Parameters:
      l - the AdjustmentLister to remove
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    • getAdjustmentListeners

      @BeanProperty(bound=false) public AdjustmentListener[] getAdjustmentListeners()
      Returns an array of all the AdjustmentListeners added to this JScrollBar with addAdjustmentListener().
      Returns:
      all of the AdjustmentListeners added or an empty array if no listeners have been added
      Since:
      1.4

    • fireAdjustmentValueChanged

      protected void fireAdjustmentValueChanged(int id, int type, int value)
      Notify listeners that the scrollbar's model has changed.
      Parameters:
      id - an integer indicating the type of event.
      type - an integer indicating the adjustment type.
      value - the current value of the adjustment
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    • setMinimumSize

      public void setMinimumSize(Dimension minimumSize)
      Unlike most components, JScrollBar derives the minimum size from the preferred size in one axis and a fixed minimum size in the other. Thus, it overrides JComponent.setMinimumSize contract that subsequent calls to getMinimumSize will return the same value as set in JComponent.setMinimumSize.
      Overrides:
      setMinimumSize in class JComponent
      Parameters:
      minimumSize - the new minimum size of this component
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    • setMaximumSize

      public void setMaximumSize(Dimension maximumSize)
      Unlike most components, JScrollBar derives the maximum size from the preferred size in one axis and a fixed maximum size in the other. Thus, it overrides JComponent.setMaximumSize contract that subsequent calls to getMaximumSize will return the same value as set in JComponent.setMaximumSize.
      Overrides:
      setMaximumSize in class JComponent
      Parameters:
      maximumSize - the desired maximum allowable size
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    • getMinimumSize

      public Dimension getMinimumSize()
      Returns the minimum size for the JScrollBar. The scrollbar is flexible along its scrolling axis and rigid along the other axis. As specified in setMinimumSize JScrollBar will derive the minimum size from the preferred size in one axis and a fixed minimum size in the other.
      Overrides:
      getMinimumSize in class JComponent
      Returns:
      the minimum size as specified above
      See Also:

    • getMaximumSize

      public Dimension getMaximumSize()
      Returns the maximum size for the JScrollBar. The scrollbar is flexible along its scrolling axis and rigid along the other axis. As specified in setMaximumSize JScrollBar will derive the maximum size from the preferred size in one axis and a fixed maximum size in the other.
      Overrides:
      getMaximumSize in class JComponent
      Returns:
      the maximum size as specified above
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    • setEnabled

      public void setEnabled(boolean x)
      Enables the component so that the knob position can be changed. When the disabled, the knob position cannot be changed.
      Overrides:
      setEnabled in class JComponent
      Parameters:
      x - a boolean value, where true enables the component and false disables it
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    • paramString

      protected String paramString()
      Returns a string representation of this JScrollBar. 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 JScrollBar.

    • getAccessibleContext

      @BeanProperty(bound=false) public AccessibleContext getAccessibleContext()
      Gets the AccessibleContext associated with this JScrollBar. For JScrollBar, the AccessibleContext takes the form of an AccessibleJScrollBar. A new AccessibleJScrollBar instance is created if necessary.
      Specified by:
      getAccessibleContext in interface Accessible
      Overrides:
      getAccessibleContext in class Component
      Returns:
      an AccessibleJScrollBar that serves as the AccessibleContext of this JScrollBar