![\"contextswitchmodel\"](\"http:\/\/www.descher.at\/descher-vu\/wp-content\/uploads\/2014\/07\/contextswitchmodel.png\")
<\/a>1<\/strong> is the global<\/em> definition of our testCommand<\/span>, 2<\/strong> and 3<\/strong> are perspectives in our application where for the given command a separate handler gets activated due to the context switch from perspectiveA<\/span> to perspectiveB<\/span> and vice-versa. 4<\/strong> is the UI contribution of the command visible to the user in the top window trim.<\/p>\nThe resulting application looks like As described in stackoverflow <\/a>and the Eclipse forum<\/a> I did not, at first, find an obvious approach to this (remark in Eclipse 3.x this could be implemented by using an IElementUpdater<\/a>). After some more analysis I found a way to do so. The source for the following example is certainly available<\/a>.<\/p>\n Lets fix the example by having a look at HandlerA<\/span><\/p>\n The @Execute<\/span> method does the simple task of toggling the perspective. The updating itself happens in lines 12-23. This method does listen to property changes of handler::testCommand<\/em> which is the global command (see 1 in the above app model). Each time a context switch happens we get injected the current handler through Object value. So we may act accordingly. Here we act by using the modelService<\/span> to find all contribution elements subsequently setting a new Label and Tooltip.<\/p>\n If more commands and handlers are in your application you should do a more intelligent search and\/or filter on the value to act correct.<\/p>\n This approach, however, is not perfect, as you have to implement this method in both handlers in order to always be able to act upon the change<\/em>. There are other feasible approaches like creating an Addon<\/span> where you put the @Inject part, you would have to do this for each command separately, however.<\/p>\n I would prefer to be able to define a class within the MCommand<\/span> element to put the respective code into which would always be notified in any change that happens related to it. So imagine that a MCommand<\/span> has an option Class Uri<\/span> and the respective referenced class could look like this<\/p>\n Where the injection will happen on change of the activeHandler and I also get the MCommand<\/span> itself injected. This way one could also efficiently store the given UiContribution elements and limit the searches ….<\/p>\n What do you think? Eager to hear your opinion \ud83d\ude42<\/p>\n","protected":false},"excerpt":{"rendered":" During the implementation of a new project, I want to harness the capabilities of the Eclipse application model when it comes to changes in the Eclipse context, or more accurate the de-\/activation of context specific handlers. What does that mean? Lets have a look at the following application model: 1 is the global definition of … e4: Updating UI contributions on context switch<\/span> weiterlesen <\/a>shown on the left hand side. Where the UIContribution 4<\/strong> is marked with a red arrow. Now the task of the handlers is to toggle between the perspectives and update the UI contribution to either show perspectiveA or perspectiveB.<\/p>\n\r\n\r\npublic class HandlerA {\r\n\u00a0\u00a0 \u00a0\r\n\u00a0\u00a0 \u00a0@Execute\r\n\u00a0\u00a0 \u00a0public void execute(EPartService partService,\r\n EModelService modelService, MApplication application) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0MPerspective perspective = (MPerspective) modelService.find(\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0"perspectiveB", application);\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0partService.switchPerspective(perspective);\r\n\u00a0\u00a0 \u00a0}\r\n\r\n\u00a0\u00a0 \u00a0@Inject\r\n\u00a0\u00a0 \u00a0public void bla(\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0@Optional @Active @Named("handler::testCommand") Object value,\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0EModelService modelService, MApplication application) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0if (value == null)\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0return;\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0List<MHandledItem> findElements = modelService.findElements(\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0application, null, MHandledItem.class, null);\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0for (MHandledItem mHandledItem : findElements) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0mHandledItem.setLabel("perspectiveA");\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0mHandledItem.setTooltip("perspectiveA now active");\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0}\r\n\u00a0\u00a0 \u00a0}\r\n}\r\n\r\n<\/pre>\n\r\npublic class TestCommand {\r\n\r\n\u00a0\u00a0 \u00a0@Inject\r\n\u00a0\u00a0 \u00a0EModelService modelService;\r\n\r\n\u00a0\u00a0 \u00a0@Inject\r\n\u00a0\u00a0 \u00a0MApplication application;\r\n\r\n\u00a0\u00a0 \u00a0@Inject\r\n\u00a0\u00a0 \u00a0public void bla(@Optional @Active MHandler activeHandler,\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0@Active MCommand command) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0if (activeHandler == null)\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0return;\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0List<MHandledItem> findElements =\r\n modelService.findElements(\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0application, null, MHandledItem.class, null);\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0for (MHandledItem mHandledItem : findElements) {\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0mHandledItem.setLabel("perspectiveA");\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0mHandledItem.setTooltip("perspectiveA now active");\r\n\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0}\r\n\u00a0\u00a0 \u00a0}\r\n}\r\n<\/pre>\n