org.eclipse.swt.widgets
Class ScrollBar
java.lang.Object
org.eclipse.swt.widgets.Widget
org.eclipse.swt.widgets.ScrollBar
-
public class ScrollBar
- extends
Widget
Instances of this class are selectable user interface
objects that represent a range of positive, numeric values.
At any given moment, a given scroll bar will have a
single 'selection' that is considered to be its
value, which is constrained to be within the range of
values the scroll bar represents (that is, between its
minimum and maximum values).
Typically, scroll bars will be made up of five areas:
- an arrow button for decrementing the value
- a page decrement area for decrementing the value by a larger amount
- a thumb for modifying the value by mouse dragging
- a page increment area for incrementing the value by a larger amount
- an arrow button for incrementing the value
Based on their style, scroll bars are either
HORIZONTAL
(which have a left facing button for decrementing the value and a
right facing button for incrementing it) or
VERTICAL
(which have an upward facing button for decrementing the value
and a downward facing buttons for incrementing it).
On some platforms, the size of the scroll bar's thumb can be
varied relative to the magnitude of the range of values it
represents (that is, relative to the difference between its
maximum and minimum values). Typically, this is used to
indicate some proportional value such as the ratio of the
visible area of a document to the total amount of space that
it would take to display it. SWT supports setting the thumb
size even if the underlying platform does not, but in this
case the appearance of the scroll bar will not change.
Scroll bars are created by specifying either H_SCROLL
,
V_SCROLL
or both when creating a Scrollable
.
They are accessed from the Scrollable
using
getHorizontalBar
and getVerticalBar
.
Note: Scroll bars are not Controls. On some platforms, scroll bars
that appear as part of some standard controls such as a text or list
have no operating system resources and are not children of the control.
For this reason, scroll bars are treated specially. To create a control
that looks like a scroll bar but has operating system resources, use
Slider
.
-
Styles:
- HORIZONTAL, VERTICAL
-
Events:
- Selection
Note: Only one of the styles HORIZONTAL and VERTICAL may be specified.
IMPORTANT: This class is not intended to be subclassed.
-
See Also:
-
Slider
,
Scrollable
,
Scrollable.getHorizontalBar()
,
Scrollable.getVerticalBar()
,
SWT Example: ControlExample,
Sample code and further information
-
Restriction:
- This class is not intended to be subclassed by clients.
Method Summary
|
void
|
addSelectionListener
(
SelectionListener listener)
Adds the listener to the collection of listeners who will
be notified when the user changes the receiver's value, by sending
it one of the messages defined in the SelectionListener
interface. |
boolean
|
getEnabled
()
Returns true if the receiver is enabled, and
false otherwise. |
int
|
getIncrement
()
Returns the amount that the receiver's value will be
modified by when the up/down (or right/left) arrows
are pressed. |
int
|
getMaximum
()
Returns the maximum value which the receiver will allow. |
int
|
getMinimum
()
Returns the minimum value which the receiver will allow. |
int
|
getPageIncrement
()
Returns the amount that the receiver's value will be
modified by when the page increment/decrement areas
are selected. |
Scrollable
|
getParent
()
Returns the receiver's parent, which must be a Scrollable. |
int
|
getSelection
()
Returns the single 'selection' that is the receiver's value. |
Point
|
getSize
()
Returns a point describing the receiver's size. |
int
|
getThumb
()
Returns the size of the receiver's thumb relative to the
difference between its maximum and minimum values. |
boolean
|
getVisible
()
Returns true if the receiver is visible, and
false otherwise. |
boolean
|
isEnabled
()
Returns true if the receiver is enabled and all
of the receiver's ancestors are enabled, and false
otherwise. |
boolean
|
isVisible
()
Returns true if the receiver is visible and all
of the receiver's ancestors are visible and false
otherwise. |
void
|
removeSelectionListener
(
SelectionListener listener)
Removes the listener from the collection of listeners who will
be notified when the user changes the receiver's value. |
void
|
setEnabled
(boolean enabled)
Enables the receiver if the argument is true ,
and disables it otherwise. |
void
|
setIncrement
(int value)
Sets the amount that the receiver's value will be
modified by when the up/down (or right/left) arrows
are pressed to the argument, which must be at least
one. |
void
|
setMaximum
(int value)
Sets the maximum. |
void
|
setMinimum
(int value)
Sets the minimum value. |
void
|
setPageIncrement
(int value)
Sets the amount that the receiver's value will be
modified by when the page increment/decrement areas
are selected to the argument, which must be at least
one. |
void
|
setSelection
(int selection)
Sets the single selection that is the receiver's
value to the argument which must be greater than or equal
to zero. |
void
|
setThumb
(int value)
Sets the size of the receiver's thumb relative to the
difference between its maximum and minimum values. |
void
|
setValues
(int selection,
int minimum,
int maximum,
int thumb,
int increment,
int pageIncrement)
Sets the receiver's selection, minimum value, maximum
value, thumb, increment and page increment all at once. |
void
|
setVisible
(boolean visible)
Marks the receiver as visible if the argument is true ,
and marks it invisible otherwise. |
Methods inherited from class org.eclipse.swt.widgets.
Widget
|
addDisposeListener,
addListener,
checkSubclass,
checkWidget,
dispose,
getData,
getData,
getDisplay,
getListeners,
getStyle,
isDisposed,
isListening,
notifyListeners,
removeDisposeListener,
removeListener,
removeListener,
setData,
setData,
toString
|
addSelectionListener
public void addSelectionListener(
SelectionListener listener)
- Adds the listener to the collection of listeners who will
be notified when the user changes the receiver's value, by sending
it one of the messages defined in the
SelectionListener
interface.
When widgetSelected
is called, the event object detail field contains one of the following values:
SWT.NONE
- for the end of a drag.
SWT.DRAG
.
SWT.HOME
.
SWT.END
.
SWT.ARROW_DOWN
.
SWT.ARROW_UP
.
SWT.PAGE_DOWN
.
SWT.PAGE_UP
.
widgetDefaultSelected
is not called.
-
-
Parameters:
-
listener
- the listener which should be notified when the user changes the receiver's value
-
Throws:
-
IllegalArgumentException
-
- ERROR_NULL_ARGUMENT - if the listener is null
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
-
See Also:
-
SelectionListener
,
removeSelectionListener(org.eclipse.swt.events.SelectionListener)
,
SelectionEvent
getEnabled
public boolean getEnabled()
- Returns
true
if the receiver is enabled, and
false
otherwise. A disabled control is typically
not selectable from the user interface and draws with an
inactive or "grayed" look.
-
-
Returns:
- the receiver's enabled state
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
-
See Also:
-
isEnabled()
getIncrement
public int getIncrement()
- Returns the amount that the receiver's value will be
modified by when the up/down (or right/left) arrows
are pressed.
-
-
Returns:
- the increment
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
getMaximum
public int getMaximum()
- Returns the maximum value which the receiver will allow.
-
-
Returns:
- the maximum
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
getMinimum
public int getMinimum()
- Returns the minimum value which the receiver will allow.
-
-
Returns:
- the minimum
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
getPageIncrement
public int getPageIncrement()
- Returns the amount that the receiver's value will be
modified by when the page increment/decrement areas
are selected.
-
-
Returns:
- the page increment
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
getParent
public
Scrollable getParent()
- Returns the receiver's parent, which must be a Scrollable.
-
-
Returns:
- the receiver's parent
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
getSelection
public int getSelection()
- Returns the single 'selection' that is the receiver's value.
-
-
Returns:
- the selection
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
getSize
public
Point getSize()
- Returns a point describing the receiver's size. The
x coordinate of the result is the width of the receiver.
The y coordinate of the result is the height of the
receiver.
-
-
Returns:
- the receiver's size
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
getThumb
public int getThumb()
- Returns the size of the receiver's thumb relative to the
difference between its maximum and minimum values.
-
-
Returns:
- the thumb value
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
-
See Also:
-
ScrollBar
getVisible
public boolean getVisible()
- Returns
true
if the receiver is visible, and
false
otherwise.
If one of the receiver's ancestors is not visible or some
other condition makes the receiver not visible, this method
may still indicate that it is considered visible even though
it may not actually be showing.
-
-
Returns:
- the receiver's visibility state
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
isEnabled
public boolean isEnabled()
- Returns
true
if the receiver is enabled and all
of the receiver's ancestors are enabled, and false
otherwise. A disabled control is typically not selectable from the
user interface and draws with an inactive or "grayed" look.
-
-
Returns:
- the receiver's enabled state
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
-
See Also:
-
getEnabled()
isVisible
public boolean isVisible()
- Returns
true
if the receiver is visible and all
of the receiver's ancestors are visible and false
otherwise.
-
-
Returns:
- the receiver's visibility state
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
-
See Also:
-
getVisible()
removeSelectionListener
public void removeSelectionListener(
SelectionListener listener)
- Removes the listener from the collection of listeners who will
be notified when the user changes the receiver's value.
-
-
Parameters:
-
listener
- the listener which should no longer be notified
-
Throws:
-
IllegalArgumentException
-
- ERROR_NULL_ARGUMENT - if the listener is null
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
-
See Also:
-
SelectionListener
,
addSelectionListener(org.eclipse.swt.events.SelectionListener)
setEnabled
public void setEnabled(boolean enabled)
- Enables the receiver if the argument is
true
,
and disables it otherwise. A disabled control is typically
not selectable from the user interface and draws with an
inactive or "grayed" look.
-
-
Parameters:
-
enabled
- the new enabled state
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
setIncrement
public void setIncrement(int value)
- Sets the amount that the receiver's value will be
modified by when the up/down (or right/left) arrows
are pressed to the argument, which must be at least
one.
-
-
Parameters:
-
value
- the new increment (must be greater than zero)
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
setMaximum
public void setMaximum(int value)
- Sets the maximum. If this value is negative or less than or
equal to the minimum, the value is ignored. If necessary, first
the thumb and then the selection are adjusted to fit within the
new range.
-
-
Parameters:
-
value
- the new maximum
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
setMinimum
public void setMinimum(int value)
- Sets the minimum value. If this value is negative or greater
than or equal to the maximum, the value is ignored. If necessary,
first the thumb and then the selection are adjusted to fit within
the new range.
-
-
Parameters:
-
value
- the new minimum
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
setPageIncrement
public void setPageIncrement(int value)
- Sets the amount that the receiver's value will be
modified by when the page increment/decrement areas
are selected to the argument, which must be at least
one.
-
-
Parameters:
-
value
- the page increment (must be greater than zero)
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
setSelection
public void setSelection(int selection)
- Sets the single selection that is the receiver's
value to the argument which must be greater than or equal
to zero.
-
-
Parameters:
-
selection
- the new selection (must be zero or greater)
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
setThumb
public void setThumb(int value)
- Sets the size of the receiver's thumb relative to the
difference between its maximum and minimum values. This new
value will be ignored if it is less than one, and will be
clamped if it exceeds the receiver's current range.
-
-
Parameters:
-
value
- the new thumb value, which must be at least one and not
larger than the size of the current range
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
setValues
public void setValues(int selection,
int minimum,
int maximum,
int thumb,
int increment,
int pageIncrement)
- Sets the receiver's selection, minimum value, maximum
value, thumb, increment and page increment all at once.
Note: This is similar to setting the values individually
using the appropriate methods, but may be implemented in a
more efficient fashion on some platforms.
-
-
Parameters:
-
selection
- the new selection value -
minimum
- the new minimum value -
maximum
- the new maximum value -
thumb
- the new thumb value -
increment
- the new increment value -
pageIncrement
- the new pageIncrement value
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
setVisible
public void setVisible(boolean visible)
- Marks the receiver as visible if the argument is
true
,
and marks it invisible otherwise.
If one of the receiver's ancestors is not visible or some
other condition makes the receiver not visible, marking
it visible may not actually cause it to be displayed.
-
-
Parameters:
-
visible
- the new visibility state
-
Throws:
-
SWTException
-
- ERROR_WIDGET_DISPOSED - if the receiver has been disposed
- ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
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