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| <title>Implementing multiplexing components</title> |
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| <H2>Implementing multiplexing components</H2> |
| In order to be used in a Multiplexer, site interfaces need to register an alternative |
| default implementation with the <span |
| style="font-style: italic;">org.eclipse.ui.part.SiteMultiplexerInitializer</span> |
| scope. Since this extends the site scope, the more specific multiplexer version |
| will take priority over the default version when used in a Multiplexer. <br> |
| <br> |
| A multiplexed component will almost always use the following pattern: |
| <ol> |
| <li>Implement the INestedComponent lifecycle interface;</li> |
| <li>Take an IMultiplexer in their constructor and use it to access the shared |
| version of their interface; </li> |
| <li>Store the part's state;</li> |
| <li>Listen to state changes in the child and update the stored state appropriately;</li> |
| <li>Each time the component is activated, it should forward the stored state |
| to the shared interface in the multiplexer; </li> |
| <li>While the component is active, it should forward state changes directly |
| to the shared interface.</li> |
| </ol> |
| The following example demonstrates the code used by the workbench to multiplex |
| the ISelectionHandler interface with ChildSelectionHandler. |
| <pre> |
| /** |
| * Multiplexed version of the ISelectionHandler interface |
| * |
| * @since 3.1 |
| */ |
| public class ChildSelectionHandler implements ISelectionHandler, INestedComponent { |
| |
| private ISelectionHandler parent; |
| private ISelection selection; |
| private boolean isActive = false; |
| private IMultiplexer multiplexer; |
| |
| public ChildSelectionHandler(IMultiplexer mplex) throws DependencyException { |
| this.multiplexer = mplex; |
| // Get access to the shared ISelectionHandler being multiplexed (we should |
| // only modify it when we're the active child) |
| this.parent = (ISelectionHandler) |
| mplex.getSharedComponents().getComponent(ISelectionHandler.class); |
| |
| // Set the initial state (the part's initial selection will be null |
| // until it explicitly sets it). |
| } |
| |
| public IMultiplexer getMultiplexer() { |
| // Return the multiplexer we were created with |
| return multiplexer; |
| } |
| |
| public void activate() { |
| // Forward our stored selection to the shared interface |
| parent.setSelection(selection); |
| isActive = true; |
| } |
| |
| public void deactivate() { |
| isActive = false; |
| } |
| |
| public void setSelection(ISelection newSelection) { |
| // Remember the child's new selection |
| selection = newSelection; |
| if (isActive) { |
| // If we're active, forward the selection directly to the |
| // shared interface |
| parent.setSelection(newSelection); |
| } |
| } |
| } |
| </pre> |
| Here is the associated extension point markup for ChildSelectionHandler. |
| <pre> |
| <extension point="org.eclipse.core.component.types"> |
| <component |
| implementation="org.eclipse.ui.internal.part.services.ChildSelectionHandler" |
| interface="org.eclipse.ui.part.services.ISelectionHandler" |
| singleton="false" |
| initializer="org.eclipse.ui.part.SiteMultiplexerInitializer"/> |
| </extension> |
| </pre> |
| <div style="margin-left: 40px;"><img src="images/composite_view.PNG" alt="Screenshot of TestCompositeView"><br> |
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