How to control the visibility of a popup menu programmatically?

I'm extendi开发者_运维百科ng Eclipse using the Eclipse plugin infrastructure, and I've come into a problem:

I would like to control the visibility of a popup menu depending on the value of an preference variable. So, I must control it programmatically or by adding an parameter in the plugin.xml.

Please help me.

Best regards. Imen.

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If you use org.eclipse.ui.popupMenu, you cannot directly control the state, as Eclipse may show the item as enabled until you try to use it -- only then will your plugin get enabled, and evaluate its visibility. A better way is to use the org.eclipse.ui.menus extension, which has finer control (but also more overhead in terms of what you need to configure):

Contribution visibility

A command's enabled state is controlled by a combination of the command is handled and if so, the handler's enabled state. Menu contributions can use core expressions to control the command's visibility in menus and toolbars.