* The state of the horizontal and vertical scrollbars is represented
* by two ScrollPaneAdjustable objects (one for each
* dimension) which implement the Adjustable interface.
* The API provides methods to access those objects such that the
* attributes on the Adjustable object (such as unitIncrement, value,
* etc.) can be manipulated.
*
* Certain adjustable properties (minimum, maximum, blockIncrement, * and visibleAmount) are set internally by the scrollpane in accordance * with the geometry of the scrollpane and its child and these should * not be set by programs using the scrollpane. *
* If the scrollbar display policy is defined as "never", then the * scrollpane can still be programmatically scrolled using the * setScrollPosition() method and the scrollpane will move and clip * the child's contents appropriately. This policy is useful if the * program needs to create and manage its own adjustable controls. *
* The placement of the scrollbars is controlled by platform-specific * properties set by the user outside of the program. *
* The initial size of this container is set to 100x100, but can * be reset using setSize(). *
* Scrolling with the wheel on a wheel-equipped mouse is enabled by default.
* This can be disabled using setWheelScrollingEnabled.
* Wheel scrolling can be customized by setting the block and
* unit increment of the horizontal and vertical Adjustables.
* For information on how mouse wheel events are dispatched, see
* the class description for {@link MouseWheelEvent}.
*
* Insets are used to define any space used by scrollbars and any
* borders created by the scroll pane. getInsets() can be used
* to get the current value for the insets. If the value of
* scrollbarsAlwaysVisible is false, then the value of the insets
* will change dynamically depending on whether the scrollbars are
* currently visible or not.
*
* @author Tom Ball
* @author Amy Fowler
* @author Tim Prinzing
*/
public class ScrollPane extends Container implements Accessible {
/**
* Initialize JNI field and method IDs
*/
private static native void initIDs();
static {
/* ensure that the necessary native libraries are loaded */
Toolkit.loadLibraries();
if (!GraphicsEnvironment.isHeadless()) {
initIDs();
}
}
/**
* Specifies that horizontal/vertical scrollbar should be shown
* only when the size of the child exceeds the size of the scrollpane
* in the horizontal/vertical dimension.
*/
public static final int SCROLLBARS_AS_NEEDED = 0;
/**
* Specifies that horizontal/vertical scrollbars should always be
* shown regardless of the respective sizes of the scrollpane and child.
*/
public static final int SCROLLBARS_ALWAYS = 1;
/**
* Specifies that horizontal/vertical scrollbars should never be shown
* regardless of the respective sizes of the scrollpane and child.
*/
public static final int SCROLLBARS_NEVER = 2;
/**
* There are 3 ways in which a scroll bar can be displayed.
* This integer will represent one of these 3 displays -
* (SCROLLBARS_ALWAYS, SCROLLBARS_AS_NEEDED, SCROLLBARS_NEVER)
*
* @serial
* @see #getScrollbarDisplayPolicy
*/
private int scrollbarDisplayPolicy;
/**
* An adjustable vertical scrollbar.
* It is important to note that you must NOT call 3
* Adjustable methods, namely:
* setMinimum(), setMaximum(),
* setVisibleAmount().
*
* @serial
* @see #getVAdjustable
*/
private ScrollPaneAdjustable vAdjustable;
/**
* An adjustable horizontal scrollbar.
* It is important to note that you must NOT call 3
* Adjustable methods, namely:
* setMinimum(), setMaximum(),
* setVisibleAmount().
*
* @serial
* @see #getHAdjustable
*/
private ScrollPaneAdjustable hAdjustable;
private static final String base = "scrollpane";
private static int nameCounter = 0;
private static final boolean defaultWheelScroll = true;
/**
* Indicates whether or not scrolling should take place when a
* MouseWheelEvent is received.
*
* @serial
* @since 1.4
*/
private boolean wheelScrollingEnabled = defaultWheelScroll;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = 7956609840827222915L;
/**
* Create a new scrollpane container with a scrollbar display
* policy of "as needed".
* @throws HeadlessException if GraphicsEnvironment.isHeadless()
* returns true
* @see java.awt.GraphicsEnvironment#isHeadless
*/
public ScrollPane() throws HeadlessException {
this(SCROLLBARS_AS_NEEDED);
}
/**
* Create a new scrollpane container.
* @param scrollbarDisplayPolicy policy for when scrollbars should be shown
* @throws IllegalArgumentException if the specified scrollbar
* display policy is invalid
* @throws HeadlessException if GraphicsEnvironment.isHeadless()
* returns true
* @see java.awt.GraphicsEnvironment#isHeadless
*/
@ConstructorProperties({"scrollbarDisplayPolicy"})
public ScrollPane(int scrollbarDisplayPolicy) throws HeadlessException {
GraphicsEnvironment.checkHeadless();
this.layoutMgr = null;
this.width = 100;
this.height = 100;
switch (scrollbarDisplayPolicy) {
case SCROLLBARS_NEVER:
case SCROLLBARS_AS_NEEDED:
case SCROLLBARS_ALWAYS:
this.scrollbarDisplayPolicy = scrollbarDisplayPolicy;
break;
default:
throw new IllegalArgumentException("illegal scrollbar display policy");
}
vAdjustable = new ScrollPaneAdjustable(this, new PeerFixer(this),
Adjustable.VERTICAL);
hAdjustable = new ScrollPaneAdjustable(this, new PeerFixer(this),
Adjustable.HORIZONTAL);
setWheelScrollingEnabled(defaultWheelScroll);
}
/**
* Construct a name for this component. Called by getName() when the
* name is null.
*/
String constructComponentName() {
synchronized (ScrollPane.class) {
return base + nameCounter++;
}
}
// The scrollpane won't work with a windowless child... it assumes
// it is moving a child window around so the windowless child is
// wrapped with a window.
private void addToPanel(Component comp, Object constraints, int index) {
Panel child = new Panel();
child.setLayout(new BorderLayout());
child.add(comp);
super.addImpl(child, constraints, index);
validate();
}
/**
* Adds the specified component to this scroll pane container.
* If the scroll pane has an existing child component, that
* component is removed and the new one is added.
* @param comp the component to be added
* @param constraints not applicable
* @param index position of child component (must be <= 0)
*/
protected final void addImpl(Component comp, Object constraints, int index) {
synchronized (getTreeLock()) {
if (getComponentCount() > 0) {
remove(0);
}
if (index > 0) {
throw new IllegalArgumentException("position greater than 0");
}
if (!SunToolkit.isLightweightOrUnknown(comp)) {
super.addImpl(comp, constraints, index);
} else {
addToPanel(comp, constraints, index);
}
}
}
/**
* Returns the display policy for the scrollbars.
* @return the display policy for the scrollbars
*/
public int getScrollbarDisplayPolicy() {
return scrollbarDisplayPolicy;
}
/**
* Returns the current size of the scroll pane's view port.
* @return the size of the view port in pixels
*/
public Dimension getViewportSize() {
Insets i = getInsets();
return new Dimension(width - i.right - i.left,
height - i.top - i.bottom);
}
/**
* Returns the height that would be occupied by a horizontal
* scrollbar, which is independent of whether it is currently
* displayed by the scroll pane or not.
* @return the height of a horizontal scrollbar in pixels
*/
public int getHScrollbarHeight() {
int h = 0;
if (scrollbarDisplayPolicy != SCROLLBARS_NEVER) {
ScrollPanePeer peer = (ScrollPanePeer)this.peer;
if (peer != null) {
h = peer.getHScrollbarHeight();
}
}
return h;
}
/**
* Returns the width that would be occupied by a vertical
* scrollbar, which is independent of whether it is currently
* displayed by the scroll pane or not.
* @return the width of a vertical scrollbar in pixels
*/
public int getVScrollbarWidth() {
int w = 0;
if (scrollbarDisplayPolicy != SCROLLBARS_NEVER) {
ScrollPanePeer peer = (ScrollPanePeer)this.peer;
if (peer != null) {
w = peer.getVScrollbarWidth();
}
}
return w;
}
/**
* Returns the ScrollPaneAdjustable object which
* represents the state of the vertical scrollbar.
* The declared return type of this method is
* Adjustable to maintain backward compatibility.
*
* @see java.awt.ScrollPaneAdjustable
* @return the vertical scrollbar state
*/
public Adjustable getVAdjustable() {
return vAdjustable;
}
/**
* Returns the ScrollPaneAdjustable object which
* represents the state of the horizontal scrollbar.
* The declared return type of this method is
* Adjustable to maintain backward compatibility.
*
* @see java.awt.ScrollPaneAdjustable
* @return the horizontal scrollbar state
*/
public Adjustable getHAdjustable() {
return hAdjustable;
}
/**
* Scrolls to the specified position within the child component.
* A call to this method is only valid if the scroll pane contains
* a child. Specifying a position outside of the legal scrolling bounds
* of the child will scroll to the closest legal position.
* Legal bounds are defined to be the rectangle:
* x = 0, y = 0, width = (child width - view port width),
* height = (child height - view port height).
* This is a convenience method which interfaces with the Adjustable
* objects which represent the state of the scrollbars.
* @param x the x position to scroll to
* @param y the y position to scroll to
* @throws NullPointerException if the scrollpane does not contain
* a child
*/
public void setScrollPosition(int x, int y) {
synchronized (getTreeLock()) {
if (getComponentCount()==0) {
throw new NullPointerException("child is null");
}
hAdjustable.setValue(x);
vAdjustable.setValue(y);
}
}
/**
* Scrolls to the specified position within the child component.
* A call to this method is only valid if the scroll pane contains
* a child and the specified position is within legal scrolling bounds
* of the child. Specifying a position outside of the legal scrolling
* bounds of the child will scroll to the closest legal position.
* Legal bounds are defined to be the rectangle:
* x = 0, y = 0, width = (child width - view port width),
* height = (child height - view port height).
* This is a convenience method which interfaces with the Adjustable
* objects which represent the state of the scrollbars.
* @param p the Point representing the position to scroll to
* @throws NullPointerException if {@code p} is {@code null}
*/
public void setScrollPosition(Point p) {
setScrollPosition(p.x, p.y);
}
/**
* Returns the current x,y position within the child which is displayed
* at the 0,0 location of the scrolled panel's view port.
* This is a convenience method which interfaces with the adjustable
* objects which represent the state of the scrollbars.
* @return the coordinate position for the current scroll position
* @throws NullPointerException if the scrollpane does not contain
* a child
*/
@Transient
public Point getScrollPosition() {
synchronized (getTreeLock()) {
if (getComponentCount()==0) {
throw new NullPointerException("child is null");
}
return new Point(hAdjustable.getValue(), vAdjustable.getValue());
}
}
/**
* Sets the layout manager for this container. This method is
* overridden to prevent the layout mgr from being set.
* @param mgr the specified layout manager
*/
public final void setLayout(LayoutManager mgr) {
throw new AWTError("ScrollPane controls layout");
}
/**
* Lays out this container by resizing its child to its preferred size.
* If the new preferred size of the child causes the current scroll
* position to be invalid, the scroll position is set to the closest
* valid position.
*
* @see Component#validate
*/
public void doLayout() {
layout();
}
/**
* Determine the size to allocate the child component.
* If the viewport area is bigger than the preferred size
* of the child then the child is allocated enough
* to fill the viewport, otherwise the child is given
* it's preferred size.
*/
Dimension calculateChildSize() {
//
// calculate the view size, accounting for border but not scrollbars
// - don't use right/bottom insets since they vary depending
// on whether or not scrollbars were displayed on last resize
//
Dimension size = getSize();
Insets insets = getInsets();
int viewWidth = size.width - insets.left*2;
int viewHeight = size.height - insets.top*2;
//
// determine whether or not horz or vert scrollbars will be displayed
//
boolean vbarOn;
boolean hbarOn;
Component child = getComponent(0);
Dimension childSize = new Dimension(child.getPreferredSize());
if (scrollbarDisplayPolicy == SCROLLBARS_AS_NEEDED) {
vbarOn = childSize.height > viewHeight;
hbarOn = childSize.width > viewWidth;
} else if (scrollbarDisplayPolicy == SCROLLBARS_ALWAYS) {
vbarOn = hbarOn = true;
} else { // SCROLLBARS_NEVER
vbarOn = hbarOn = false;
}
//
// adjust predicted view size to account for scrollbars
//
int vbarWidth = getVScrollbarWidth();
int hbarHeight = getHScrollbarHeight();
if (vbarOn) {
viewWidth -= vbarWidth;
}
if(hbarOn) {
viewHeight -= hbarHeight;
}
//
// if child is smaller than view, size it up
//
if (childSize.width < viewWidth) {
childSize.width = viewWidth;
}
if (childSize.height < viewHeight) {
childSize.height = viewHeight;
}
return childSize;
}
/**
* @deprecated As of JDK version 1.1,
* replaced by doLayout().
*/
@Deprecated
public void layout() {
if (getComponentCount()==0) {
return;
}
Component c = getComponent(0);
Point p = getScrollPosition();
Dimension cs = calculateChildSize();
Dimension vs = getViewportSize();
Insets i = getInsets();
c.reshape(i.left - p.x, i.top - p.y, cs.width, cs.height);
ScrollPanePeer peer = (ScrollPanePeer)this.peer;
if (peer != null) {
peer.childResized(cs.width, cs.height);
}
// update adjustables... the viewport size may have changed
// with the scrollbars coming or going so the viewport size
// is updated before the adjustables.
vs = getViewportSize();
hAdjustable.setSpan(0, cs.width, vs.width);
vAdjustable.setSpan(0, cs.height, vs.height);
}
/**
* Prints the component in this scroll pane.
* @param g the specified Graphics window
* @see Component#print
* @see Component#printAll
*/
public void printComponents(Graphics g) {
if (getComponentCount()==0) {
return;
}
Component c = getComponent(0);
Point p = c.getLocation();
Dimension vs = getViewportSize();
Insets i = getInsets();
Graphics cg = g.create();
try {
cg.clipRect(i.left, i.top, vs.width, vs.height);
cg.translate(p.x, p.y);
c.printAll(cg);
} finally {
cg.dispose();
}
}
/**
* Creates the scroll pane's peer.
*/
public void addNotify() {
synchronized (getTreeLock()) {
int vAdjustableValue = 0;
int hAdjustableValue = 0;
// Bug 4124460. Save the current adjustable values,
// so they can be restored after addnotify. Set the
// adjustables to 0, to prevent crashes for possible
// negative values.
if (getComponentCount() > 0) {
vAdjustableValue = vAdjustable.getValue();
hAdjustableValue = hAdjustable.getValue();
vAdjustable.setValue(0);
hAdjustable.setValue(0);
}
if (peer == null)
peer = getToolkit().createScrollPane(this);
super.addNotify();
// Bug 4124460. Restore the adjustable values.
if (getComponentCount() > 0) {
vAdjustable.setValue(vAdjustableValue);
hAdjustable.setValue(hAdjustableValue);
}
}
}
/**
* Returns a string representing the state of this
* ScrollPane. 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.
*
* @return the parameter string of this scroll pane
*/
public String paramString() {
String sdpStr;
switch (scrollbarDisplayPolicy) {
case SCROLLBARS_AS_NEEDED:
sdpStr = "as-needed";
break;
case SCROLLBARS_ALWAYS:
sdpStr = "always";
break;
case SCROLLBARS_NEVER:
sdpStr = "never";
break;
default:
sdpStr = "invalid display policy";
}
Point p = (getComponentCount()>0)? getScrollPosition() : new Point(0,0);
Insets i = getInsets();
return super.paramString()+",ScrollPosition=("+p.x+","+p.y+")"+
",Insets=("+i.top+","+i.left+","+i.bottom+","+i.right+")"+
",ScrollbarDisplayPolicy="+sdpStr+
",wheelScrollingEnabled="+isWheelScrollingEnabled();
}
void autoProcessMouseWheel(MouseWheelEvent e) {
processMouseWheelEvent(e);
}
/**
* Process mouse wheel events that are delivered to this
* ScrollPane by scrolling an appropriate amount.
*
Note that if the event parameter is null
* the behavior is unspecified and may result in an
* exception.
*
* @param e the mouse wheel event
* @since 1.4
*/
protected void processMouseWheelEvent(MouseWheelEvent e) {
if (isWheelScrollingEnabled()) {
ScrollPaneWheelScroller.handleWheelScrolling(this, e);
e.consume();
}
super.processMouseWheelEvent(e);
}
/**
* If wheel scrolling is enabled, we return true for MouseWheelEvents
* @since 1.4
*/
protected boolean eventTypeEnabled(int type) {
if (type == MouseEvent.MOUSE_WHEEL && isWheelScrollingEnabled()) {
return true;
}
else {
return super.eventTypeEnabled(type);
}
}
/**
* Enables/disables scrolling in response to movement of the mouse wheel.
* Wheel scrolling is enabled by default.
*
* @param handleWheel true if scrolling should be done
* automatically for a MouseWheelEvent,
* false otherwise.
* @see #isWheelScrollingEnabled
* @see java.awt.event.MouseWheelEvent
* @see java.awt.event.MouseWheelListener
* @since 1.4
*/
public void setWheelScrollingEnabled(boolean handleWheel) {
wheelScrollingEnabled = handleWheel;
}
/**
* Indicates whether or not scrolling will take place in response to
* the mouse wheel. Wheel scrolling is enabled by default.
*
* @return {@code true} if the wheel scrolling enabled;
* otherwise {@code false}
*
* @see #setWheelScrollingEnabled(boolean)
* @since 1.4
*/
public boolean isWheelScrollingEnabled() {
return wheelScrollingEnabled;
}
/**
* Writes default serializable fields to stream.
*/
private void writeObject(ObjectOutputStream s) throws IOException {
// 4352819: We only need this degenerate writeObject to make
// it safe for future versions of this class to write optional
// data to the stream.
s.defaultWriteObject();
}
/**
* Reads default serializable fields to stream.
* @exception HeadlessException if
* GraphicsEnvironment.isHeadless() returns
* true
* @see java.awt.GraphicsEnvironment#isHeadless
*/
private void readObject(ObjectInputStream s)
throws ClassNotFoundException, IOException, HeadlessException
{
GraphicsEnvironment.checkHeadless();
// 4352819: Gotcha! Cannot use s.defaultReadObject here and
// then continue with reading optional data. Use GetField instead.
ObjectInputStream.GetField f = s.readFields();
// Old fields
scrollbarDisplayPolicy = f.get("scrollbarDisplayPolicy",
SCROLLBARS_AS_NEEDED);
hAdjustable = (ScrollPaneAdjustable)f.get("hAdjustable", null);
vAdjustable = (ScrollPaneAdjustable)f.get("vAdjustable", null);
// Since 1.4
wheelScrollingEnabled = f.get("wheelScrollingEnabled",
defaultWheelScroll);
// // Note to future maintainers
// if (f.defaulted("wheelScrollingEnabled")) {
// // We are reading pre-1.4 stream that doesn't have
// // optional data, not even the TC_ENDBLOCKDATA marker.
// // Reading anything after this point is unsafe as we will
// // read unrelated objects further down the stream (4352819).
// }
// else {
// // Reading data from 1.4 or later, it's ok to try to read
// // optional data as OptionalDataException with eof == true
// // will be correctly reported
// }
}
class PeerFixer implements AdjustmentListener, java.io.Serializable
{
private static final long serialVersionUID = 1043664721353696630L;
PeerFixer(ScrollPane scroller) {
this.scroller = scroller;
}
/**
* Invoked when the value of the adjustable has changed.
*/
@SuppressWarnings("deprecation")
public void adjustmentValueChanged(AdjustmentEvent e) {
Adjustable adj = e.getAdjustable();
int value = e.getValue();
ScrollPanePeer peer = (ScrollPanePeer) scroller.peer;
if (peer != null) {
peer.setValue(adj, value);
}
Component c = scroller.getComponent(0);
switch(adj.getOrientation()) {
case Adjustable.VERTICAL:
c.move(c.getLocation().x, -(value));
break;
case Adjustable.HORIZONTAL:
c.move(-(value), c.getLocation().y);
break;
default:
throw new IllegalArgumentException("Illegal adjustable orientation");
}
}
private ScrollPane scroller;
}
/////////////////
// Accessibility support
////////////////
/**
* Gets the AccessibleContext associated with this ScrollPane.
* For scroll panes, the AccessibleContext takes the form of an
* AccessibleAWTScrollPane.
* A new AccessibleAWTScrollPane instance is created if necessary.
*
* @return an AccessibleAWTScrollPane that serves as the
* AccessibleContext of this ScrollPane
* @since 1.3
*/
public AccessibleContext getAccessibleContext() {
if (accessibleContext == null) {
accessibleContext = new AccessibleAWTScrollPane();
}
return accessibleContext;
}
/**
* This class implements accessibility support for the
* ScrollPane class. It provides an implementation of the
* Java Accessibility API appropriate to scroll pane user-interface
* elements.
* @since 1.3
*/
protected class AccessibleAWTScrollPane extends AccessibleAWTContainer
{
/*
* JDK 1.3 serialVersionUID
*/
private static final long serialVersionUID = 6100703663886637L;
/**
* Get the role of this object.
*
* @return an instance of AccessibleRole describing the role of the
* object
* @see AccessibleRole
*/
public AccessibleRole getAccessibleRole() {
return AccessibleRole.SCROLL_PANE;
}
} // class AccessibleAWTScrollPane
}
/*
* In JDK 1.1.1, the pkg private class java.awt.PeerFixer was moved to
* become an inner class of ScrollPane, which broke serialization
* for ScrollPane objects using JDK 1.1.
* Instead of moving it back out here, which would break all JDK 1.1.x
* releases, we keep PeerFixer in both places. Because of the scoping rules,
* the PeerFixer that is used in ScrollPane will be the one that is the
* inner class. This pkg private PeerFixer class below will only be used
* if the Java 2 platform is used to deserialize ScrollPane objects that were serialized
* using JDK1.1
*/
class PeerFixer implements AdjustmentListener, java.io.Serializable {
/*
* serialVersionUID
*/
private static final long serialVersionUID = 7051237413532574756L;
PeerFixer(ScrollPane scroller) {
this.scroller = scroller;
}
/**
* Invoked when the value of the adjustable has changed.
*/
@SuppressWarnings("deprecation")
public void adjustmentValueChanged(AdjustmentEvent e) {
Adjustable adj = e.getAdjustable();
int value = e.getValue();
ScrollPanePeer peer = (ScrollPanePeer) scroller.peer;
if (peer != null) {
peer.setValue(adj, value);
}
Component c = scroller.getComponent(0);
switch(adj.getOrientation()) {
case Adjustable.VERTICAL:
c.move(c.getLocation().x, -(value));
break;
case Adjustable.HORIZONTAL:
c.move(-(value), c.getLocation().y);
break;
default:
throw new IllegalArgumentException("Illegal adjustable orientation");
}
}
private ScrollPane scroller;
}