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Eclipse Platform
Release 3.0

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org.eclipse.jface.viewers
Class Viewer

java.lang.Object
  org.eclipse.jface.viewers.Viewer

All Implemented Interfaces:

IInputProvider, IInputSelectionProvider, ISelectionProvider

Direct Known Subclasses:

ContentViewer, TextViewer

public abstract class Viewer

extends Object

implements IInputSelectionProvider

A viewer is a model-based adapter on a widget.

A viewer can be created as an adapter on a pre-existing control (e.g., creating a ListViewer on an existing List control). All viewers also provide a convenience constructor for creating the control.

Implementing a concrete viewer typically involves the following steps:

• create SWT controls for viewer (in constructor) (optional)
• initialize SWT controls from input (inputChanged)
• define viewer-specific update methods
• support selections (setSelection, getSelection)

Field Summary

protected static String

WIDGET_DATA_KEY Unique key for associating element data with widgets.

Constructor Summary

protected

Viewer() Creates a new viewer.

Method Summary

void	addHelpListener(HelpListener listener) Adds a listener for help requests in this viewer.
void	addSelectionChangedListener(ISelectionChangedListener listener) Adds a listener for selection changes in this selection provider.
protected void	fireHelpRequested(HelpEvent event) Notifies any help listeners that help has been requested.
protected void	fireSelectionChanged(SelectionChangedEvent event) Notifies any selection changed listeners that the viewer's selection has changed.
abstract Control	getControl() Returns the primary control associated with this viewer.
Object	getData(String key) Returns the value of the property with the given name, or null if the property is not found.
abstract Object	getInput() Returns the input.
abstract ISelection	getSelection() Returns the current selection for this provider.
protected void	handleHelpRequest(HelpEvent event) Handles a help request from the underlying SWT control.
protected void	inputChanged(Object input, Object oldInput) Internal hook method called when the input to this viewer is initially set or subsequently changed.
abstract void	refresh() Refreshes this viewer completely with information freshly obtained from this viewer's model.
void	removeHelpListener(HelpListener listener) Removes the given help listener from this viewer.
void	removeSelectionChangedListener(ISelectionChangedListener listener) Removes the given selection change listener from this selection provider.
Item	scrollDown(int x, int y) Scrolls the viewer's control down by one item from the given display-relative coordinates.
Item	scrollUp(int x, int y) Scrolls the viewer's control up by one item from the given display-relative coordinates.
void	setData(String key, Object value) Sets the value of the property with the given name to the given value, or to null if the property is to be removed.
abstract void	setInput(Object input) Sets or clears the input for this viewer.
void	setSelection(ISelection selection) The viewer implementation of this ISelectionProvider method make the new selection for this viewer without making it visible.
abstract void	setSelection(ISelection selection, boolean reveal) Sets a new selection for this viewer and optionally makes it visible.

Methods inherited from class java.lang.Object

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

Field Detail

WIDGET_DATA_KEY

protected static final String WIDGET_DATA_KEY

Unique key for associating element data with widgets.

See Also:

Widget.setData(String, Object), Constant Field Values

Constructor Detail

Viewer

protected Viewer()

Creates a new viewer.

Method Detail

addHelpListener

public void addHelpListener(HelpListener listener)

Adds a listener for help requests in this viewer. Has no effect if an identical listener is already registered.

Parameters:

listener - a help listener

addSelectionChangedListener

public void addSelectionChangedListener(ISelectionChangedListener listener)

Description copied from interface: ISelectionProvider

Adds a listener for selection changes in this selection provider. Has no effect if an identical listener is already registered.

Specified by:

addSelectionChangedListener in interface ISelectionProvider

Parameters:

listener - a selection changed listener

fireHelpRequested

protected void fireHelpRequested(HelpEvent event)

Notifies any help listeners that help has been requested. Only listeners registered at the time this method is called are notified.

Parameters:

event - a help event

See Also:

HelpListener.helpRequested(org.eclipse.swt.events.HelpEvent)

fireSelectionChanged

protected void fireSelectionChanged(SelectionChangedEvent event)

Notifies any selection changed listeners that the viewer's selection has changed. Only listeners registered at the time this method is called are notified.

Parameters:

event - a selection changed event

See Also:

ISelectionChangedListener.selectionChanged(org.eclipse.jface.viewers.SelectionChangedEvent)

getControl

public abstract Control getControl()

Returns the primary control associated with this viewer.

Returns:

the SWT control which displays this viewer's content

getData

public Object getData(String key)

Returns the value of the property with the given name, or null if the property is not found.

The default implementation performs a (linear) search of an internal table. Overriding this method is generally not required if the number of different keys is small. If a more efficient representation of a viewer's properties is required, override both getData and setData.

Parameters:

key - the property name

Returns:

the property value, or null if the property is not found

getInput

public abstract Object getInput()

Description copied from interface: IInputProvider

Returns the input.

Specified by:

getInput in interface IInputProvider

Returns:

the input object

getSelection

public abstract ISelection getSelection()

Description copied from interface: ISelectionProvider

Returns the current selection for this provider.

Specified by:

getSelection in interface ISelectionProvider

Returns:

the current selection

handleHelpRequest

protected void handleHelpRequest(HelpEvent event)

Handles a help request from the underlying SWT control. The default behavior is to fire a help request, with the event's data modified to hold this viewer.

inputChanged

protected void inputChanged(Object input,
                            Object oldInput)

Internal hook method called when the input to this viewer is initially set or subsequently changed.

The default implementation does nothing. Subclassers may override this method to do something when a viewer's input is set. A typical use is populate the viewer.

Parameters:

input - the new input of this viewer, or null if none

oldInput - the old input element or null if there was previously no input

refresh

public abstract void refresh()

Refreshes this viewer completely with information freshly obtained from this viewer's model.

removeHelpListener

public void removeHelpListener(HelpListener listener)

Removes the given help listener from this viewer. Has no affect if an identical listener is not registered.

Parameters:

listener - a help listener

removeSelectionChangedListener

public void removeSelectionChangedListener(ISelectionChangedListener listener)

Description copied from interface: ISelectionProvider

Removes the given selection change listener from this selection provider. Has no affect if an identical listener is not registered.

Specified by:

removeSelectionChangedListener in interface ISelectionProvider

Parameters:

listener - a selection changed listener

scrollDown

public Item scrollDown(int x,
                       int y)

Scrolls the viewer's control down by one item from the given display-relative coordinates. Returns the newly revealed Item, or null if no scrolling occurred or if the viewer doesn't represent an item-based widget.

Parameters:

x - horizontal coordinate

y - vertical coordinate

scrollUp

public Item scrollUp(int x,
                     int y)

Scrolls the viewer's control up by one item from the given display-relative coordinates. Returns the newly revealed Item, or null if no scrolling occurred or if the viewer doesn't represent an item-based widget.

Parameters:

x - horizontal coordinate

y - vertical coordinate

setData

public void setData(String key,
                    Object value)

Sets the value of the property with the given name to the given value, or to null if the property is to be removed. If this viewer has such a property, its value is replaced; otherwise a new property is added.

The default implementation records properties in an internal table which is searched linearly. Overriding this method is generally not required if the number of different keys is small. If a more efficient representation of a viewer's properties is required, override both getData and setData.

Parameters:

key - the property name

value - the property value, or null if the property is not found

setInput

public abstract void setInput(Object input)

Sets or clears the input for this viewer.

Parameters:

input - the input of this viewer, or null if none

setSelection

public void setSelection(ISelection selection)

The viewer implementation of this ISelectionProvider method make the new selection for this viewer without making it visible.

This method is equivalent to setSelection(selection,false).

Specified by:

setSelection in interface ISelectionProvider

Parameters:

selection - the new selection

setSelection

public abstract void setSelection(ISelection selection,
                                  boolean reveal)

Sets a new selection for this viewer and optionally makes it visible.

Subclasses must implement this method.

Parameters:

selection - the new selection

reveal - true if the selection is to be made visible, and false otherwise