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[md] action.update rewritten

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Anna Bulenkova 2015-01-21 11:21:02 +01:00
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tutorials/action_system/action_system.md
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@ -105,43 +105,51 @@ After performing the steps described above we need to compile and run the plugin
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#How to make an action available and visible?
##Setting up action's visibility and availability.
You need to override
AnAction.update
To manipulate with action's visibility and availability we need to override it's ```public void update(@NotNull AnActionEvent e);```
Default implementation of this method does nothing.
Override this method to provide the ability to dynamically change action's
state and(or) presentation depending on the context (For example
when your action state depends on the selection you can check for
selection and change the state accordingly).
This method can be called frequently, for instance, if an action is added to a toolbar, it will be updated twice a second.
This means that this method is supposed to work really fast,
no real work should be done at this phase.
For example, checking selection in a tree or a list,
is considered valid, but working with a file system is not.
If you cannot understand the state of
the action fast you should do it in the [AnActionEvent] (https://github.com/JetBrains/intellij-community/blob/ff16ce78a1e0ddb6e67fd1dbc6e6a597e20d483a/platform/editor-ui-api/src/com/intellij/openapi/actionSystem/AnActionEvent.java)
method and notify
the user that action cannot be executed if it's the case.
Parameter e carries information on the invocation place and data available
state and(or) presentation depending on the context.
public class SimpleAction extends AnAction {
@Override
public void actionPerformed(@NotNull AnActionEvent anActionEvent) {
public void actionPerformed(AnActionEvent anActionEvent) {
}
@Override
public void update(@NotNull AnActionEvent e) {
//Make action visible and available only when project is defined
final Project project = e.getProject();
boolean isAvailable = project != null;
e.getPresentation().setVisible(isAvailable);
e.getPresentation().setEnabled(isAvailable);
public void update(AnActionEvent anActionEvent) {
}
}
[Link to source code] (https://github.com/JetBrains/intellij-sdk/blob/master/code_samples/plugin_sample/src/org/jetbrains/plugins/sample/SimpleAction.java)
The following code sample illustrates how to make the action visible and available only when the following conditions are met:
there's a project available and there's an item you can navigate to selected in the project view pane:
public class SimpleAction extends AnAction {
@Override
public void actionPerformed(AnActionEvent anActionEvent) {
}
@Override
public void update(AnActionEvent anActionEvent) {
final Project project = anActionEvent.getData(CommonDataKeys.PROJECT);
if (project == null)
return;
Object navigatable = anActionEvent.getData(CommonDataKeys.NAVIGATABLE);
anActionEvent.getPresentation().setEnabledAndVisible(navigatable != null);
}
}
Parameter anActionEvent carries information on the invocation place and data available.
**Note** This method can be called frequently, for instance, if an action is added to a toolbar, it will be updated twice a second.
This means that this method is supposed to work really fast, no real work should be done at this phase.
For example, checking selection in a tree or a list, is considered valid, but working with a file system is not.
If you cannot understand the state of the action fast you should do it in the
[AnActionEvent] (https://github.com/JetBrains/intellij-community/blob/ff16ce78a1e0ddb6e67fd1dbc6e6a597e20d483a/platform/editor-ui-api/src/com/intellij/openapi/actionSystem/AnActionEvent.java)
method and notify the user that action cannot be executed if it's the case.
-------------