Eclipse RCP SelectionListener 执行两次

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Eclipse RCP SelectionListener 执行两次5

大伙们，小弟最近有一个问题关于Eclipse RCP的，就是为什么在两个视图间进行消息传递，监听的视图执行了两次？
我的代码如下：

事件提供者：

package myproject;

import org.eclipse.jface.viewers.IStructuredContentProvider;
import org.eclipse.jface.viewers.ITableLabelProvider;
import org.eclipse.jface.viewers.LabelProvider;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.ui.ISharedImages;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.part.ViewPart;

public class View extends ViewPart {
	public static final String ID = "myproject.view";

	private TableViewer viewer;

	/**
	 * The content provider class is responsible for providing objects to the
	 * view. It can wrap existing objects in adapters or simply return objects
	 * as-is. These objects may be sensitive to the current input of the view,
	 * or ignore it and always show the same content (like Task List, for
	 * example).
	 */
	class ViewContentProvider implements IStructuredContentProvider {
		public void inputChanged(Viewer v, Object oldInput, Object newInput) {
		}

		public void dispose() {
		}

		public Object[] getElements(Object parent) {
			if (parent instanceof Object[]) {
				return (Object[]) parent;
			}
	        return new Object[0];
		}
	}

	class ViewLabelProvider extends LabelProvider implements
			ITableLabelProvider {
		public String getColumnText(Object obj, int index) {
			return getText(obj);
		}

		public Image getColumnImage(Object obj, int index) {
			return getImage(obj);
		}

		public Image getImage(Object obj) {
			return PlatformUI.getWorkbench().getSharedImages().getImage(
					ISharedImages.IMG_OBJ_ELEMENT);
		}
	}

	/**
	 * This is a callback that will allow us to create the viewer and initialize
	 * it.
	 */
	public void createPartControl(Composite parent) {
		viewer = new TableViewer(parent, SWT.MULTI | SWT.H_SCROLL
				| SWT.V_SCROLL);
		viewer.setContentProvider(new ViewContentProvider());
		viewer.setLabelProvider(new ViewLabelProvider());
		// Provide the input to the ContentProvider
		viewer.setInput(new String[] {"One", "Two", "Three"});
		this.getSite().setSelectionProvider(viewer);
	}

	/**
	 * Passing the focus request to the viewer's control.
	 */
	public void setFocus() {
		viewer.getControl().setFocus();
	}
}

事件监听者：

package myproject;

import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Text;
import org.eclipse.ui.ISelectionListener;
import org.eclipse.ui.IWorkbenchPart;
import org.eclipse.ui.part.ViewPart;

public class Detail extends ViewPart implements ISelectionListener {

	public static final String ID = "myproject.detail";
	
	private Text text;
	
	public Detail() {
		// TODO Auto-generated constructor stub
	}

	@Override
	public void selectionChanged(IWorkbenchPart part, ISelection selection) {
		IStructuredSelection structuredSelection = (IStructuredSelection) selection;
		Object obj = structuredSelection.getFirstElement();
		if(obj != null) { //这里执行了两次！
			System.out.println(obj);
		}
	}

	@Override
	public void createPartControl(Composite parent) {
		text = new Text(parent, SWT.NONE);
		text.setBounds(20, 20, 100, 15);
		this.getSite().getPage().addSelectionListener(View.ID, this);
	}

	@Override
	public void setFocus() {
		// TODO Auto-generated method stub

	}

}

即selectionChanged这个方法执行了两次，太不解了！
望大家能帮手看看为什么，谢谢了。