Package org.eclipse.swt.widgets

Class Tracker

java.lang.Object

org.eclipse.swt.widgets.Widget

org.eclipse.swt.widgets.Tracker

public class Tracker
extends Widget

Instances of this class implement rubber banding rectangles that are drawn onto a parent Composite or Display. These rectangles can be specified to respond to mouse and key events by either moving or resizing themselves accordingly. Trackers are typically used to represent window geometries in a lightweight manner.

Styles:

LEFT, RIGHT, UP, DOWN, RESIZE

Events:

Move, Resize

Note: Rectangle move behavior is assumed unless RESIZE is specified.

IMPORTANT: This class is not intended to be subclassed.

See Also:

• Tracker snippets
• Sample code and further information

Restriction:

This class is not intended to be subclassed by clients.

Constructor Summary

Constructors

Constructor	Description
Tracker(Composite parent, int style)	Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.
Tracker(Display display, int style)	Constructs a new instance of this class given the display to create it on and a style value describing its behavior and appearance.

Method Summary

Modifier and Type	Method	Description
void	addControlListener(ControlListener listener)	Adds the listener to the collection of listeners who will be notified when the control is moved or resized, by sending it one of the messages defined in the ControlListener interface.
void	addKeyListener(KeyListener listener)	Adds the listener to the collection of listeners who will be notified when keys are pressed and released on the system keyboard, by sending it one of the messages defined in the KeyListener interface.
void	close()	Stops displaying the tracker rectangles.
Rectangle[]	getRectangles()	Returns the bounds that are being drawn, expressed relative to the parent widget.
boolean	getStippled()	Returns true if the rectangles are drawn with a stippled line, false otherwise.
boolean	open()	Displays the Tracker rectangles for manipulation by the user.
void	removeControlListener(ControlListener listener)	Removes the listener from the collection of listeners who will be notified when the control is moved or resized.
void	removeKeyListener(KeyListener listener)	Removes the listener from the collection of listeners who will be notified when keys are pressed and released on the system keyboard.
void	setCursor(Cursor newCursor)	Sets the Cursor of the Tracker.
void	setRectangles(Rectangle[] rectangles)	Specifies the rectangles that should be drawn, expressed relative to the parent widget.
void	setStippled(boolean stippled)	Changes the appearance of the line used to draw the rectangles.

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

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

Tracker

public Tracker(Composite parent,
 int style)

Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.

The style value is either one of the style constants defined in class SWT which is applicable to instances of this class, or must be built by bitwise OR'ing together (that is, using the int "|" operator) two or more of those SWT style constants. The class description lists the style constants that are applicable to the class. Style bits are also inherited from superclasses.

Parameters:

parent - a widget which will be the parent of the new instance (cannot be null)

style - the style of widget to construct

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the parent is null

SWTException -

• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent
• ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass

See Also:

• SWT.LEFT
• SWT.RIGHT
• SWT.UP
• SWT.DOWN
• SWT.RESIZE
• Widget.checkSubclass()
• Widget.getStyle()

Tracker

public Tracker(Display display,
 int style)

Constructs a new instance of this class given the display to create it on and a style value describing its behavior and appearance.

The style value is either one of the style constants defined in class SWT which is applicable to instances of this class, or must be built by bitwise OR'ing together (that is, using the int "|" operator) two or more of those SWT style constants. The class description lists the style constants that are applicable to the class. Style bits are also inherited from superclasses.

Note: Currently, null can be passed in for the display argument. This has the effect of creating the tracker on the currently active display if there is one. If there is no current display, the tracker is created on a "default" display. Passing in null as the display argument is not considered to be good coding style, and may not be supported in a future release of SWT.

Parameters:

display - the display to create the tracker on

style - the style of control to construct

Throws:

SWTException -

• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent
• ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass

See Also:

• SWT.LEFT
• SWT.RIGHT
• SWT.UP
• SWT.DOWN
• SWT.RESIZE

Method Details

addControlListener

public void addControlListener(ControlListener listener)

Adds the listener to the collection of listeners who will be notified when the control is moved or resized, by sending it one of the messages defined in the ControlListener interface.

Parameters:

listener - the listener which should 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:

• ControlListener
• removeControlListener(org.eclipse.swt.events.ControlListener)

addKeyListener

public void addKeyListener(KeyListener listener)

Adds the listener to the collection of listeners who will be notified when keys are pressed and released on the system keyboard, by sending it one of the messages defined in the KeyListener interface.

Parameters:

listener - the listener which should 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:

• KeyListener
• removeKeyListener(org.eclipse.swt.events.KeyListener)

close

public void close()

Stops displaying the tracker rectangles. Note that this is not considered to be a cancelation by the user.

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

getRectangles

public Rectangle[] getRectangles()

Returns the bounds that are being drawn, expressed relative to the parent widget. If the parent is a Display then these are screen coordinates.

Returns:

the bounds of the Rectangles being drawn

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

getStippled

public boolean getStippled()

Returns true if the rectangles are drawn with a stippled line, false otherwise.

Returns:

the stippled effect of the rectangles

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

open

public boolean open()

Displays the Tracker rectangles for manipulation by the user. Returns when the user has either finished manipulating the rectangles or has cancelled the Tracker.

Returns:

true if the user did not cancel the Tracker, false otherwise

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

removeControlListener

public void removeControlListener(ControlListener listener)

Removes the listener from the collection of listeners who will be notified when the control is moved or resized.

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:

• ControlListener
• addControlListener(org.eclipse.swt.events.ControlListener)

removeKeyListener

public void removeKeyListener(KeyListener listener)

Removes the listener from the collection of listeners who will be notified when keys are pressed and released on the system keyboard.

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:

• KeyListener
• addKeyListener(org.eclipse.swt.events.KeyListener)

setCursor

public void setCursor(Cursor newCursor)

Sets the Cursor of the Tracker. If this cursor is null then the cursor reverts to the default.

Parameters:

newCursor - the new Cursor to display

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

setRectangles

public void setRectangles(Rectangle[] rectangles)

Specifies the rectangles that should be drawn, expressed relative to the parent widget. If the parent is a Display then these are screen coordinates.

Parameters:

rectangles - the bounds of the rectangles to be drawn

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the set of rectangles is null or contains a null rectangle

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setStippled

public void setStippled(boolean stippled)

Changes the appearance of the line used to draw the rectangles.

Parameters:

stippled - true if rectangle should appear stippled

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