eclilpse check 菜单 --Toggle Handler for Eclipse Commands_1

转载：http://eclipsesource.com/blogs/2009/01/15/toggling-a-command-contribution/
package de.ralfebert.rcputil;

import java.util.Map;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.Command;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.commands.State;
import org.eclipse.jface.menus.IMenuStateIds;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.commands.ICommandService;
import org.eclipse.ui.commands.IElementUpdater;
import org.eclipse.ui.menus.UIElement;

/**
* Use this handler for style=”toggle” command contributions. You need to
* declare a state like this to use this:
*
*
*
*
*
*
*
* The id=”STYLE” is chosen because of IMenuStateIds.STYLE – maybe this will
* work without any Handler Foo in later Eclipse versions.
*
* @author Ralf Ebert
*/
public abstract class ToggleHandler extends AbstractHandler implements IElementUpdater {

private String commandId;

public final Object execute(ExecutionEvent event) throws ExecutionException {
ICommandService commandService = (ICommandService) PlatformUI.getWorkbench().getService(ICommandService.class);
this.commandId = event.getCommand().getId();

State state = event.getCommand().getState(IMenuStateIds.STYLE);
if (state == null)
throw new ExecutionException(
“You need to declare a ToggleState with id=STYLE for your command to use ToggleHandler!”);
boolean currentState = (Boolean) state.getValue();
boolean newState = !currentState;
state.setValue(newState);
executeToggle(event, newState);
commandService.refreshElements(event.getCommand().getId(), null);

// return value is reserved for future apis
return null;
}

protected abstract void executeToggle(ExecutionEvent event, boolean newState);

public void updateElement(UIElement element, Map parameters) {
if (this.commandId != null) {
ICommandService commandService = (ICommandService) PlatformUI.getWorkbench().getService(
ICommandService.class);
Command command = commandService.getCommand(commandId);
element.setChecked((Boolean) command.getState(IMenuStateIds.STYLE).getValue());
}
}

}