Package org.eclipse.jface.viewers

Class 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)

    • 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

      • 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

      • 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.
        Parameters:
        event - the event

      • 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 effect if an identical listener is not registered.
        Parameters:
        listener - a help 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
        Returns:
        the item scrolled down to

      • 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
        Returns:
        the item scrolled up to

      • 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).

        Note that some implementations may not be able to set the selection without also revealing it, for example (as of 3.3) TreeViewer.

        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