| org.netbeans.actions.api.ContextProvider
All known Subclasses: org.netbeans.actions.spi.ContextProviderSupport, org.netbeans.actions.examples.MiniEdit, org.netbeans.actions.spi.ProxyContextProvider,
| ContextProvider | | public interface ContextProvider (Code) | | A ContextProvider is supplied to the engine. When the engine needs
to produce or update presenters, it will request the context from the
current contextProvider. This context will be passed in calls to
the system ActionProvider when fetching the enablement & visibility
of actions. The Map's contents is a private contract defined by
an implementation of the actions framework.
author:
Tim Boudreau |
| Field Summary | |
| static String | IDENTITY
Key for an object which can be fetched from the context map,
representing the identity of the context in some unique way.
If non null, the Engine will compare the result of this with
the previous result to determine if it needs to do any work
at all, or if nothing has changed, and any previous state it
set on presenters is still valid. |
| Method Summary | |
| public Map | getContext()
Get a map representing the current application context. |
| IDENTITY | | static String IDENTITY(Code) | | Key for an object which can be fetched from the context map,
representing the identity of the context in some unique way.
If non null, the Engine will compare the result of this with
the previous result to determine if it needs to do any work
at all, or if nothing has changed, and any previous state it
set on presenters is still valid.
getContext().get(IDENTITY).equals(previousContext.get(IDENTITY)) if
the keysets of the last-fetched map and the current map contain the
same elements (which must be strings). This makes it possible to
avoid updating actions if a context change has not made any change
that would affect the enablement of actions - i.e. selecting one
text file, then selecting another should cause the engine to be advised
that it may need to update actions, but in fact, no change in state
is needed. So the engine will first test if the last identity equals
the current identity, and if so, never iterate the visible presenters
and try to change their state to the state they're already in.
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| getContext | | public Map getContext()(Code) | | Get a map representing the current application context. All the keys
in this map must be Strings. The values are up to the application. In
determining if an action should be enabled, only the presence of a key
is used as the test. Objects needed for the invocation of actions
should be put into the map as values, with a well-defined key to test
against for whether the action should be enabled. The invoker can
then retrieve the object whose method should be called and invoke
the method.
Implementations should preferably return a meaningful value from
getContext(IDENTITY) which will be the same if the key set is the
same.
Note that the actions framework reserves the string "identity"
(ContextProvider.IDENTITY) as a map key - implementations of ContextProvider
should not use it as a map key or unpredictable things may happen.
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