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| Commands |
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| <h3>Commands</h3> |
| |
| |
| <p>A <b>command</b> is the declaration of a behaviour by <b>id</b>. |
| Commands are used to declare semantic behaviour so that action implementations defined |
| elsewhere by handlers, or linked to the action extension points (see |
| <a href="workbench_basicext.htm" |
| class="XRef">Basic workbench extension points using actions</a>) |
| can associate themselves with a particular semantic |
| command. The separation of the command from the action |
| implementation allows multiple plug-ins to define actions that implement the |
| same semantic command. The command is what gets associated with a |
| particular key binding.</p> |
| |
| |
| <p>The workbench defines many common commands in its <b>plugin.xml</b> |
| file, and plug-ins are encouraged to associate their own actions with these |
| commands where it makes sense. In this way, semantically similar |
| actions implemented in different plug-ins may share the same key binding.</p> |
| |
| |
| <h4>Defining a command</h4> |
| |
| |
| <p>Commands are defined using the <b><a href="../reference/extension-points/org_eclipse_ui_commands.html">org.eclipse.ui.commands</a></b> |
| extension point. The following comes from the Info example markup:</p> |
| |
| |
| <pre> |
| <extension |
| point="org.eclipse.ui.commands"> |
| ... |
| <command |
| categoryId="org.eclipse.ui.examples.contributions.commands.category" |
| id="org.eclipse.ui.examples.contributions.view.count" |
| description="%contributions.view.count.desc" |
| name="%contributions.view.count.name"> |
| </command> |
| ... |
| </pre> |
| |
| |
| <p>The command definition specifies a <b>name</b>, <b>description</b>, and <b>id</b> for |
| the action. It also specifies the id of a category for the command, which is |
| used to group commands in the preferences dialog. The categories are also |
| defined in the <b><a href="../reference/extension-points/org_eclipse_ui_commands.html">org.eclipse.ui.commands</a> |
| </b> |
| extension point:</p> |
| <pre> |
| ... |
| <category |
| name="%contributions.commands.category.name" |
| description="%contributions.commands.category.desc" |
| id="org.eclipse.ui.examples.contributions.commands.category"> |
| </category> |
| ... |
| </pre> |
| |
| <p>Note that there is no implementation specified for a |
| command. A command only becomes concrete when a plug-in |
| associates its handler or action with the command id. We'll |
| talk about the different ways to associate handler implementations |
| with commands in the |
| <a href="workbench_cmd_handlers.htm" |
| class="XRef">org.eclipse.ui.handlers</a> section. We'll talk about |
| binding key sequences to commands in the <a href="workbench_cmd_bindings.htm" |
| class="XRef">org.eclipse.ui.bindings</a> section. |
| </p> |
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