intellij-sdk-code-samples/basics/action_system.md

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Action System

Executing and updating actions

The system of actions allows plugins to add their own items to IDEA menus and toolbars. An action is a class, derived from the AnAction class, whose actionPerformed method is called when the menu item or toolbar button is selected. For example, one of the action classes is responsible for the File | Open File... menu item and for the Open File toolbar button.

Actions are organized into groups, which, in turn, can contain other groups. A group of actions can form a toolbar or a menu. Subgroups of the group can form submenus of the menu.

Every action and action group has an unique identifier. Identifiers of many of the standard IDEA actions are defined in the IdeActions class.

Every action can be included in multiple groups, and thus appear in multiple places within the IDEA user interface. Different places where actions can appear are defined by constants in the ActionPlaces interface. For every place where the action appears, a new Presentation is created. Thus, the same action can have different text or icons when it appears in different places of the user interface. Different presentations for the action are created by copying the presentation returned by the AnAction.getTemplatePresentation() method.

To update the state of the action, the method AnAction.update() is periodically called by IDEA. The AnActionEvent object passed to this method carries the information about the current context for the action, and in particular, the specific presentation which needs to be updated.

To retrieve the information about the current state of the IDE, including the active project, the selected file, the selection in the editor and so on, the method AnActionEvent.getData() can be used. Different data keys that can be passed to that method are defined in the CommonDataKeysclass.

The AnActionEvent instance is also passed to the actionPerformed method.

For a step-by-step walkthrough of defining actions, please check out the action system tutorial.

Registering Actions

There are two main ways to register an action: either by listing it in the <actions> section of the plugin.xml file, or through Java code.

Registering Actions in plugin.xml

Registering actions in plugin.xml is demonstrated in the following example. The example section of plugin.xml demonstrates all elements which can be used in the <actions> section, and describes the meaning of each element.

<!-- Actions -->
<actions>
  <!-- The <action> element defines an action to register.
       The mandatory "id" attribute specifies an unique 
       identifier for the action.
       The mandatory "class" attribute specifies the
       full-qualified name of the class implementing the action.
       The mandatory "text" attribute specifies the text of the
       action (tooltip for toolbar button or text for menu item).
       The optional "use-shortcut-of" attribute specifies the ID
       of the action whose keyboard shortcut this action will use.
       The optional "description" attribute specifies the text
       which is displayed in the status bar when the action is focused.
       The optional "icon" attribute specifies the icon which is
       displayed on the toolbar button or next to the menu item. -->
  <action id="VssIntegration.GarbageCollection" class="com.foo.impl.CollectGarbage" text="Collect _Garbage" description="Run garbage collector" icon="icons/garbage.png">
    <!-- The <add-to-group> node specifies that the action should be added
         to an existing group. An action can be added to several groups.
         The mandatory "group-id" attribute specifies the ID of the group
         to which the action is added.
         The group must be implemented by an instance of the DefaultActionGroup class.
         The mandatory "anchor" attribute specifies the position of the
         action in the group relative to other actions. It can have the values
         "first", "last", "before" and "after".
         The "relative-to-action" attribute is mandatory if the anchor
         is set to "before" and "after", and specifies the action before or after which
         the current action is inserted. -->
    <add-to-group group-id="ToolsMenu" relative-to-action="GenerateJavadoc" anchor="after"/>
      <!-- The <keyboard-shortcut> node specifies the keyboard shortcut
           for the action. An action can have several keyboard shortcuts.
           The mandatory "first-keystroke" attribute specifies the first
           keystroke of the action. The key strokes are specified according
           to the regular Swing rules.
           The optional "second-keystroke" attribute specifies the second
           keystroke of the action.
           The mandatory "keymap" attribute specifies the keymap for which
           the action is active. IDs of the standard keymaps are defined as
           constants in the com.intellij.openapi.keymap.KeymapManager class. 
           The optional "remove" attribute in the second <keyboard-shortcut>
           element below means the specified shortcut should be removed from 
           the specified action.
           The optional "replace-all" attribute in the third <keyboard-shortcut>
           element below means remove all keyboard and mouse shortcuts from the specified 
           action before adding the specified shortcut.  -->
    <!-- Add the first and second keystrokes to all keymaps  -->
    <keyboard-shortcut keymap="$default" first-keystroke="control alt G" second-keystroke="C"/>
    <!-- Except to the "Mac OS X" keymap and its children -->
    <keyboard-shortcut keymap="Mac OS X" first-keystroke="control alt G" second-keystroke="C" remove="true"/>
    <!-- The "Mac OS X 10.5+" keymap and its children will have only this keyboard shortcut for this action.  -->
    <keyboard-shortcut keymap="Mac OS X 10.5+" first-keystroke="control alt G" second-keystroke="C" replace-all="true"/>
    <!-- The <mouse-shortcut> node specifies the mouse shortcut for the
           action. An action can have several mouse shortcuts.
           The mandatory "keystroke" attribute specifies the clicks and
           modifiers for the action. It is defined as a sequence of words
           separated by spaces: 
           "button1", "button2", "button3" for the mouse buttons;
           "shift", "control", "meta", "alt", "altGraph" for the modifier keys;
           "doubleClick" if the action is activated by a double-click of the button.
           The mandatory "keymap" attribute specifies the keymap for which
           the action is active. IDs of the standard keymaps are defined as
           constants in the com.intellij.openapi.keymap.KeymapManager class.
           The "remove" and "replace-all" attributes can also be used in
           a <mouse-shortcut> element. See <keyboard-shortcut> for documentation.  -->
    <mouse-shortcut keymap="$default" keystroke="control button3 doubleClick"/>
  </action>
  <!-- The <group> element defines an action group. <action>, <group> and 
       <separator> elements defined within it are automatically included in the group.
       The mandatory "id" attribute specifies an unique identifier for the action.
       The optional "class" attribute specifies the full-qualified name of
       the class implementing the group. If not specified,
       com.intellij.openapi.actionSystem.DefaultActionGroup is used.
       The optional "text" attribute specifies the text of the group (text
       for the menu item showing the submenu).
       The optional "description" attribute specifies the text which is displayed
       in the status bar when the group is focused.
       The optional "icon" attribute specifies the icon which is displayed on
       the toolbar button or next to the group.
       The optional "popup" attribute specifies how the group is presented in
       the menu. If a group has popup="true", actions in it are placed in a
       submenu; for popup="false", actions are displayed as a section of the
       same menu delimited by separators. -->
  <group class="com.foo.impl.MyActionGroup" id="TestActionGroup" text="Test Group" description="Group with test actions" icon="icons/testgroup.png" popup="true">
    <action id="VssIntegration.TestAction" class="com.foo.impl.TestAction" text="My Test Action" description="My test action"/>
    <!-- The <separator> element defines a separator between actions.
         It can also have an <add-to-group> child element. -->
    <separator/>
    <group id="TestActionSubGroup"/>
    <!-- The <reference> element allows to add an existing action to the group.
         The mandatory "ref" attribute specifies the ID of the action to add. -->
    <reference ref="EditorCopy"/>
    <add-to-group group-id="MainMenu" relative-to-action="HelpMenu" anchor="before"/>
  </group>
</actions>

Registering Actions from Code

To register an action from code, two steps are required.

• First, an instance of the class derived from AnAction must be passed to the registerAction method of the ActionManager class, to associate the action with an ID.
• Second, the action needs to be added to one or more groups. To get an instance of an action group by ID, it is necessary to call ActionManager.getAction() and cast the returned value to the DefaultActionGroup class.

Building UI from Actions

If a plugin needs to include a toolbar or popup menu built from a group of actions in its own user interface, that can be accomplished through the ActionPopupMenu and ActionToolbar classes. These objects can be created through calls to ActionManager.createActionPopupMenu and ActionManager.createActionToolbar. To get a Swing component from such an object, simply call the getComponent() method.

If your action toolbar is attached to a specific component (for example, a panel in a tool window), you usually need to call ActionToolbar.setTargetComponent() and pass the instance of the related component as a parameter. This ensures that the state of the toolbar buttons depends on the state of the related component, and not on the current focus location within the IDE frame.