Java example source code file (JScrollBar.java)
The JScrollBar.java Java example source code
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package javax.swing;
import java.io.Serializable;
import java.awt.Component;
import java.awt.Adjustable;
import java.awt.Dimension;
import java.awt.event.AdjustmentListener;
import java.awt.event.AdjustmentEvent;
import java.awt.Graphics;
import javax.swing.event.*;
import javax.swing.plaf.*;
import javax.accessibility.*;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;
/**
* 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.
* <p>
* 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.
* <p>
* <strong>Warning: Swing is not thread safe. For more
* information see <a
* href="package-summary.html#threading">Swing's Threading
* Policy</a>.
* <p>
* <strong>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 <code>java.beans package.
* Please see {@link java.beans.XMLEncoder}.
*
* @see JScrollPane
* @beaninfo
* attribute: isContainer false
* description: A component that helps determine the visible content range of an area.
*
* @author David Kloba
*/
public class JScrollBar extends JComponent implements Adjustable, Accessible
{
/**
* @see #getUIClassID
* @see #readObject
*/
private static final String uiClassID = "ScrollBarUI";
/**
* All changes from the model are treated as though the user moved
* the scrollbar knob.
*/
private ChangeListener fwdAdjustmentEvents = new ModelListener();
/**
* The model that represents the scrollbar's minimum, maximum, extent
* (aka "visibleAmount") and current value.
* @see #setModel
*/
protected BoundedRangeModel model;
/**
* @see #setOrientation
*/
protected int orientation;
/**
* @see #setUnitIncrement
*/
protected int unitIncrement;
/**
* @see #setBlockIncrement
*/
protected int blockIncrement;
private void checkOrientation(int orientation) {
switch (orientation) {
case VERTICAL:
case HORIZONTAL:
break;
default:
throw new IllegalArgumentException("orientation must be one of: VERTICAL, HORIZONTAL");
}
}
/**
* 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".
* <p>
* Note: Use <code>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.
*
* @exception IllegalArgumentException if orientation is not one of VERTICAL, HORIZONTAL
*
* @see #setOrientation
* @see #setValue
* @see #setVisibleAmount
* @see #setMinimum
* @see #setMaximum
*/
public JScrollBar(int orientation, int value, int extent, int min, int max)
{
checkOrientation(orientation);
this.unitIncrement = 1;
this.blockIncrement = (extent == 0) ? 1 : extent;
this.orientation = orientation;
this.model = new DefaultBoundedRangeModel(value, extent, min, max);
this.model.addChangeListener(fwdAdjustmentEvents);
setRequestFocusEnabled(false);
updateUI();
}
/**
* Creates a scrollbar with the specified orientation
* and the following initial values:
* <pre>
* minimum = 0
* maximum = 100
* value = 0
* extent = 10
* </pre>
*/
public JScrollBar(int orientation) {
this(orientation, 0, 10, 0, 100);
}
/**
* Creates a vertical scrollbar with the following initial values:
* <pre>
* minimum = 0
* maximum = 100
* value = 0
* extent = 10
* </pre>
*/
public JScrollBar() {
this(VERTICAL);
}
/**
* Sets the {@literal L&F} object that renders this component.
*
* @param ui the <code>ScrollBarUI {@literal L&F} object
* @see UIDefaults#getUI
* @since 1.4
* @beaninfo
* bound: true
* hidden: true
* attribute: visualUpdate true
* description: The UI object that implements the Component's LookAndFeel
*/
public void setUI(ScrollBarUI ui) {
super.setUI(ui);
}
/**
* Returns the delegate that implements the look and feel for
* this component.
*
* @see JComponent#setUI
*/
public ScrollBarUI getUI() {
return (ScrollBarUI)ui;
}
/**
* Overrides <code>JComponent.updateUI.
* @see JComponent#updateUI
*/
public void updateUI() {
setUI((ScrollBarUI)UIManager.getUI(this));
}
/**
* Returns the name of the LookAndFeel class for this component.
*
* @return "ScrollBarUI"
* @see JComponent#getUIClassID
* @see UIDefaults#getUI
*/
public String getUIClassID() {
return uiClassID;
}
/**
* Returns the component's orientation (horizontal or vertical).
*
* @return VERTICAL or HORIZONTAL
* @see #setOrientation
* @see java.awt.Adjustable#getOrientation
*/
public int getOrientation() {
return orientation;
}
/**
* Set the scrollbar's orientation to either VERTICAL or
* HORIZONTAL.
*
* @exception IllegalArgumentException if orientation is not one of VERTICAL, HORIZONTAL
* @see #getOrientation
* @beaninfo
* preferred: true
* bound: true
* attribute: visualUpdate true
* description: The scrollbar's orientation.
* enum: VERTICAL JScrollBar.VERTICAL
* HORIZONTAL JScrollBar.HORIZONTAL
*/
public void setOrientation(int orientation)
{
checkOrientation(orientation);
int oldValue = this.orientation;
this.orientation = orientation;
firePropertyChange("orientation", oldValue, orientation);
if ((oldValue != orientation) && (accessibleContext != null)) {
accessibleContext.firePropertyChange(
AccessibleContext.ACCESSIBLE_STATE_PROPERTY,
((oldValue == VERTICAL)
? AccessibleState.VERTICAL : AccessibleState.HORIZONTAL),
((orientation == VERTICAL)
? AccessibleState.VERTICAL : AccessibleState.HORIZONTAL));
}
if (orientation != oldValue) {
revalidate();
}
}
/**
* Returns data model that handles the scrollbar's four
* fundamental properties: minimum, maximum, value, extent.
*
* @see #setModel
*/
public BoundedRangeModel getModel() {
return model;
}
/**
* Sets the model that handles the scrollbar's four
* fundamental properties: minimum, maximum, value, extent.
*
* @see #getModel
* @beaninfo
* bound: true
* expert: true
* description: The scrollbar's BoundedRangeModel.
*/
public void setModel(BoundedRangeModel newModel) {
Integer oldValue = null;
BoundedRangeModel oldModel = model;
if (model != null) {
model.removeChangeListener(fwdAdjustmentEvents);
oldValue = Integer.valueOf(model.getValue());
}
model = newModel;
if (model != null) {
model.addChangeListener(fwdAdjustmentEvents);
}
firePropertyChange("model", oldModel, model);
if (accessibleContext != null) {
accessibleContext.firePropertyChange(
AccessibleContext.ACCESSIBLE_VALUE_PROPERTY,
oldValue, new Integer(model.getValue()));
}
}
/**
* 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 my override this method to compute
* a value, e.g. the change required to scroll up or down one
* (variable height) line text or one row in a table.
* <p>
* 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.
* <p>
* Some look and feels implement custom scrolling behavior
* and ignore this property.
*
* @param direction is -1 or 1 for up/down respectively
* @return the value of the unitIncrement property
* @see #setUnitIncrement
* @see #setValue
* @see Scrollable#getScrollableUnitIncrement
*/
public int getUnitIncrement(int direction) {
return unitIncrement;
}
/**
* Sets the unitIncrement property.
* <p>
* Note, that if the argument is equal to the value of Integer.MIN_VALUE,
* the most look and feels will not provide the scrolling to the right/down.
* <p>
* Some look and feels implement custom scrolling behavior
* and ignore this property.
*
* @see #getUnitIncrement
* @beaninfo
* preferred: true
* bound: true
* description: The scrollbar's unit increment.
*/
public void setUnitIncrement(int unitIncrement) {
int oldValue = this.unitIncrement;
this.unitIncrement = unitIncrement;
firePropertyChange("unitIncrement", oldValue, unitIncrement);
}
/**
* 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
* above or below the scrollbar "knob" to change the value
* up or down by large amount. Subclasses my override this
* method to compute a value, e.g. the change required to scroll
* up or down one paragraph in a text document.
* <p>
* 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.
* <p>
* Some look and feels implement custom scrolling behavior
* and ignore this property.
*
* @param direction is -1 or 1 for up/down respectively
* @return the value of the blockIncrement property
* @see #setBlockIncrement
* @see #setValue
* @see Scrollable#getScrollableBlockIncrement
*/
public int getBlockIncrement(int direction) {
return blockIncrement;
}
/**
* Sets the blockIncrement property.
* <p>
* Note, that if the argument is equal to the value of Integer.MIN_VALUE,
* the most look and feels will not provide the scrolling to the right/down.
* <p>
* Some look and feels implement custom scrolling behavior
* and ignore this property.
*
* @see #getBlockIncrement()
* @beaninfo
* preferred: true
* bound: true
* description: The scrollbar's block increment.
*/
public void setBlockIncrement(int blockIncrement) {
int oldValue = this.blockIncrement;
this.blockIncrement = blockIncrement;
firePropertyChange("blockIncrement", oldValue, blockIncrement);
}
/**
* For backwards compatibility with java.awt.Scrollbar.
* @see Adjustable#getUnitIncrement
* @see #getUnitIncrement(int)
*/
public int getUnitIncrement() {
return unitIncrement;
}
/**
* For backwards compatibility with java.awt.Scrollbar.
* @see Adjustable#getBlockIncrement
* @see #getBlockIncrement(int)
*/
public int getBlockIncrement() {
return blockIncrement;
}
/**
* Returns the scrollbar's value.
* @return the model's value property
* @see #setValue
*/
public int getValue() {
return getModel().getValue();
}
/**
* Sets the scrollbar's value. This method just forwards the value
* to the model.
*
* @see #getValue
* @see BoundedRangeModel#setValue
* @beaninfo
* preferred: true
* description: The scrollbar's current value.
*/
public void setValue(int value) {
BoundedRangeModel m = getModel();
int oldValue = m.getValue();
m.setValue(value);
if (accessibleContext != null) {
accessibleContext.firePropertyChange(
AccessibleContext.ACCESSIBLE_VALUE_PROPERTY,
Integer.valueOf(oldValue),
Integer.valueOf(m.getValue()));
}
}
/**
* 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.
*
* @return the value of the model's extent property
* @see #setVisibleAmount
*/
public int getVisibleAmount() {
return getModel().getExtent();
}
/**
* Set the model's extent property.
*
* @see #getVisibleAmount
* @see BoundedRangeModel#setExtent
* @beaninfo
* preferred: true
* description: The amount of the view that is currently visible.
*/
public void setVisibleAmount(int extent) {
getModel().setExtent(extent);
}
/**
* Returns the minimum value supported by the scrollbar
* (usually zero).
*
* @return the value of the model's minimum property
* @see #setMinimum
*/
public int getMinimum() {
return getModel().getMinimum();
}
/**
* Sets the model's minimum property.
*
* @see #getMinimum
* @see BoundedRangeModel#setMinimum
* @beaninfo
* preferred: true
* description: The scrollbar's minimum value.
*/
public void setMinimum(int minimum) {
getModel().setMinimum(minimum);
}
/**
* The maximum value of the scrollbar is maximum - extent.
*
* @return the value of the model's maximum property
* @see #setMaximum
*/
public int getMaximum() {
return getModel().getMaximum();
}
/**
* Sets the model's maximum property. Note that the scrollbar's value
* can only be set to maximum - extent.
*
* @see #getMaximum
* @see BoundedRangeModel#setMaximum
* @beaninfo
* preferred: true
* description: The scrollbar's maximum value.
*/
public void setMaximum(int maximum) {
getModel().setMaximum(maximum);
}
/**
* True if the scrollbar knob is being dragged.
*
* @return the value of the model's valueIsAdjusting property
* @see #setValueIsAdjusting
*/
public boolean getValueIsAdjusting() {
return getModel().getValueIsAdjusting();
}
/**
* 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.
*
* @see #getValueIsAdjusting
* @see BoundedRangeModel#setValueIsAdjusting
* @beaninfo
* expert: true
* description: True if the scrollbar thumb is being dragged.
*/
public void setValueIsAdjusting(boolean b) {
BoundedRangeModel m = getModel();
boolean oldValue = m.getValueIsAdjusting();
m.setValueIsAdjusting(b);
if ((oldValue != b) && (accessibleContext != null)) {
accessibleContext.firePropertyChange(
AccessibleContext.ACCESSIBLE_STATE_PROPERTY,
((oldValue) ? AccessibleState.BUSY : null),
((b) ? AccessibleState.BUSY : null));
}
}
/**
* Sets the four BoundedRangeModel properties after forcing
* the arguments to obey the usual constraints:
* <pre>
* minimum ≤ value ≤ value+extent ≤ maximum
* </pre>
*
*
* @see BoundedRangeModel#setRangeProperties
* @see #setValue
* @see #setVisibleAmount
* @see #setMinimum
* @see #setMaximum
*/
public void setValues(int newValue, int newExtent, int newMin, int newMax)
{
BoundedRangeModel m = getModel();
int oldValue = m.getValue();
m.setRangeProperties(newValue, newExtent, newMin, newMax, m.getValueIsAdjusting());
if (accessibleContext != null) {
accessibleContext.firePropertyChange(
AccessibleContext.ACCESSIBLE_VALUE_PROPERTY,
Integer.valueOf(oldValue),
Integer.valueOf(m.getValue()));
}
}
/**
* 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.
* <p>
* 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
* fabricate the origin of the change here.
*
* @param l the AdjustmentLister to add
* @see #removeAdjustmentListener
* @see BoundedRangeModel#addChangeListener
*/
public void addAdjustmentListener(AdjustmentListener l) {
listenerList.add(AdjustmentListener.class, l);
}
/**
* Removes an AdjustmentEvent listener.
*
* @param l the AdjustmentLister to remove
* @see #addAdjustmentListener
*/
public void removeAdjustmentListener(AdjustmentListener l) {
listenerList.remove(AdjustmentListener.class, l);
}
/**
* Returns an array of all the <code>AdjustmentListeners added
* to this JScrollBar with addAdjustmentListener().
*
* @return all of the <code>AdjustmentListeners added or an empty
* array if no listeners have been added
* @since 1.4
*/
public AdjustmentListener[] getAdjustmentListeners() {
return listenerList.getListeners(AdjustmentListener.class);
}
/**
* Notify listeners that the scrollbar's model has changed.
*
* @see #addAdjustmentListener
* @see EventListenerList
*/
protected void fireAdjustmentValueChanged(int id, int type, int value) {
fireAdjustmentValueChanged(id, type, value, getValueIsAdjusting());
}
/**
* Notify listeners that the scrollbar's model has changed.
*
* @see #addAdjustmentListener
* @see EventListenerList
*/
private void fireAdjustmentValueChanged(int id, int type, int value,
boolean isAdjusting) {
Object[] listeners = listenerList.getListenerList();
AdjustmentEvent e = null;
for (int i = listeners.length - 2; i >= 0; i -= 2) {
if (listeners[i]==AdjustmentListener.class) {
if (e == null) {
e = new AdjustmentEvent(this, id, type, value, isAdjusting);
}
((AdjustmentListener)listeners[i+1]).adjustmentValueChanged(e);
}
}
}
/**
* This class listens to ChangeEvents on the model and forwards
* AdjustmentEvents for the sake of backwards compatibility.
* Unfortunately there's no way to determine the proper
* type of the AdjustmentEvent as all updates to the model's
* value are considered equivalent.
*/
private class ModelListener implements ChangeListener, Serializable {
public void stateChanged(ChangeEvent e) {
Object obj = e.getSource();
if (obj instanceof BoundedRangeModel) {
int id = AdjustmentEvent.ADJUSTMENT_VALUE_CHANGED;
int type = AdjustmentEvent.TRACK;
BoundedRangeModel model = (BoundedRangeModel)obj;
int value = model.getValue();
boolean isAdjusting = model.getValueIsAdjusting();
fireAdjustmentValueChanged(id, type, value, isAdjusting);
}
}
}
// PENDING(hmuller) - the next three methods should be removed
/**
* The scrollbar is flexible along it's scrolling axis and
* rigid along the other axis.
*/
public Dimension getMinimumSize() {
Dimension pref = getPreferredSize();
if (orientation == VERTICAL) {
return new Dimension(pref.width, 5);
} else {
return new Dimension(5, pref.height);
}
}
/**
* The scrollbar is flexible along it's scrolling axis and
* rigid along the other axis.
*/
public Dimension getMaximumSize() {
Dimension pref = getPreferredSize();
if (getOrientation() == VERTICAL) {
return new Dimension(pref.width, Short.MAX_VALUE);
} else {
return new Dimension(Short.MAX_VALUE, pref.height);
}
}
/**
* Enables the component so that the knob position can be changed.
* When the disabled, the knob position cannot be changed.
*
* @param x a boolean value, where true enables the component and
* false disables it
*/
public void setEnabled(boolean x) {
super.setEnabled(x);
Component[] children = getComponents();
for (Component child : children) {
child.setEnabled(x);
}
}
/**
* See readObject() and writeObject() in JComponent for more
* information about serialization in Swing.
*/
private void writeObject(ObjectOutputStream s) throws IOException {
s.defaultWriteObject();
if (getUIClassID().equals(uiClassID)) {
byte count = JComponent.getWriteObjCounter(this);
JComponent.setWriteObjCounter(this, --count);
if (count == 0 && ui != null) {
ui.installUI(this);
}
}
}
/**
* 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 <code>null.
*
* @return a string representation of this JScrollBar.
*/
protected String paramString() {
String orientationString = (orientation == HORIZONTAL ?
"HORIZONTAL" : "VERTICAL");
return super.paramString() +
",blockIncrement=" + blockIncrement +
",orientation=" + orientationString +
",unitIncrement=" + unitIncrement;
}
/////////////////
// Accessibility support
////////////////
/**
* 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.
*
* @return an AccessibleJScrollBar that serves as the
* AccessibleContext of this JScrollBar
*/
public AccessibleContext getAccessibleContext() {
if (accessibleContext == null) {
accessibleContext = new AccessibleJScrollBar();
}
return accessibleContext;
}
/**
* This class implements accessibility support for the
* <code>JScrollBar class. It provides an implementation of the
* Java Accessibility API appropriate to scroll bar user-interface
* elements.
* <p>
* <strong>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 <code>java.beans package.
* Please see {@link java.beans.XMLEncoder}.
*/
protected class AccessibleJScrollBar extends AccessibleJComponent
implements AccessibleValue {
/**
* Get the state set of this object.
*
* @return an instance of AccessibleState containing the current state
* of the object
* @see AccessibleState
*/
public AccessibleStateSet getAccessibleStateSet() {
AccessibleStateSet states = super.getAccessibleStateSet();
if (getValueIsAdjusting()) {
states.add(AccessibleState.BUSY);
}
if (getOrientation() == VERTICAL) {
states.add(AccessibleState.VERTICAL);
} else {
states.add(AccessibleState.HORIZONTAL);
}
return states;
}
/**
* Get the role of this object.
*
* @return an instance of AccessibleRole describing the role of the
* object
*/
public AccessibleRole getAccessibleRole() {
return AccessibleRole.SCROLL_BAR;
}
/**
* Get the AccessibleValue associated with this object. In the
* implementation of the Java Accessibility API for this class,
* return this object, which is responsible for implementing the
* AccessibleValue interface on behalf of itself.
*
* @return this object
*/
public AccessibleValue getAccessibleValue() {
return this;
}
/**
* Get the accessible value of this object.
*
* @return The current value of this object.
*/
public Number getCurrentAccessibleValue() {
return Integer.valueOf(getValue());
}
/**
* Set the value of this object as a Number.
*
* @return True if the value was set.
*/
public boolean setCurrentAccessibleValue(Number n) {
// TIGER - 4422535
if (n == null) {
return false;
}
setValue(n.intValue());
return true;
}
/**
* Get the minimum accessible value of this object.
*
* @return The minimum value of this object.
*/
public Number getMinimumAccessibleValue() {
return Integer.valueOf(getMinimum());
}
/**
* Get the maximum accessible value of this object.
*
* @return The maximum value of this object.
*/
public Number getMaximumAccessibleValue() {
// TIGER - 4422362
return new Integer(model.getMaximum() - model.getExtent());
}
} // AccessibleJScrollBar
}
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