Class ScrollBar
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:
- Restriction:
- This class is not intended to be subclassed by clients.
-
Field Summary
Fields inherited from class org.eclipse.swt.widgets.Widget
nativeZoom
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Method Summary
Modifier and TypeMethodDescriptionvoid
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 theSelectionListener
interface.boolean
Returnstrue
if the receiver is enabled, andfalse
otherwise.int
Returns the amount that the receiver's value will be modified by when the up/down (or right/left) arrows are pressed.int
Returns the maximum value which the receiver will allow.int
Returns the minimum value which the receiver will allow.int
Returns the amount that the receiver's value will be modified by when the page increment/decrement areas are selected.Returns the receiver's parent, which must be a Scrollable.int
Returns the single 'selection' that is the receiver's value.getSize()
Returns a point describing the receiver's size.int
getThumb()
Returns the receiver's thumb value.Returns a rectangle describing the size and location of the receiver's thumb relative to its parent.Returns a rectangle describing the size and location of the receiver's thumb track relative to its parent.boolean
Returnstrue
if the receiver is visible, andfalse
otherwise.boolean
Returnstrue
if the receiver is enabled and all of the receiver's ancestors are enabled, andfalse
otherwise.boolean
Returnstrue
if the receiver is visible and all of the receiver's ancestors are visible andfalse
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 istrue
, 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 thumb value.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 istrue
, and marks it invisible otherwise.Methods inherited from class org.eclipse.swt.widgets.Widget
addDisposeListener, addListener, addTypedListener, checkSubclass, checkWidget, dispose, getData, getData, getDisplay, getListeners, getStyle, getTypedListeners, isAutoDirection, isDisposed, isListening, notifyListeners, removeDisposeListener, removeListener, removeListener, removeTypedListener, reskin, setData, setData, toString
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Method Details
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addSelectionListener
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 theSelectionListener
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:
-
getEnabled
public boolean getEnabled()Returnstrue
if the receiver is enabled, andfalse
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:
-
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
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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
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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
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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
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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
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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
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getThumb
public int getThumb()Returns the receiver's thumb value.- 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:
-
getThumbBounds
Returns a rectangle describing the size and location of the receiver's thumb relative to its parent.- Returns:
- the thumb bounds, relative to the
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
- Since:
- 3.6
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getThumbTrackBounds
Returns a rectangle describing the size and location of the receiver's thumb track relative to its parent. This rectangle comprises the areas 2, 3, and 4 as described inScrollBar
.- Returns:
- the thumb track bounds, relative to the
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
- Since:
- 3.6
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getVisible
public boolean getVisible()Returnstrue
if the receiver is visible, andfalse
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
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isEnabled
public boolean isEnabled()Returnstrue
if the receiver is enabled and all of the receiver's ancestors are enabled, andfalse
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:
-
isVisible
public boolean isVisible()Returnstrue
if the receiver is visible and all of the receiver's ancestors are visible andfalse
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:
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removeSelectionListener
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:
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setEnabled
public void setEnabled(boolean enabled) Enables the receiver if the argument istrue
, 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
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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
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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
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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
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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
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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
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setThumb
public void setThumb(int value) Sets the thumb value. The thumb value should be used to represent the size of the visual portion of the current range. This value is usually the same as the page increment value.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
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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 valueminimum
- the new minimum valuemaximum
- the new maximum valuethumb
- the new thumb valueincrement
- the new increment valuepageIncrement
- 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
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setVisible
public void setVisible(boolean visible) Marks the receiver as visible if the argument istrue
, 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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