eclipse中对redo与undo的支持

大家在使用eclipse时，一定对ctrl+z和ctrl+r使用起来感觉比较爽。这个功能的基础是
Org.eclipse.core.commands.operations包的IUndoableOperation可撤销的操作，OperationHistory操作历史记录，IUndoContext撤销上下文目录，OperationHistory负责执行并记录Operation。IUndoContext作为检索operation的key，OperationHistory根据IUndoContext是否匹配来判断该操作是否要执行撤销。通过IUndoContext可以将操作局限到某一层次上进行撤销，例如一个操作仅在一个view/editor内可以撤销，或者一个操作可以在多个view内撤销（jdt的重构功能），或者一个操作可以在所有的范围（workbanch）内撤销。获得可以在所有范围内撤销的IUndoContext：

IOperationHistory operationHistory = workbench.getOperationSupport().getOperationHistory();
	IUndoContext undoContext = workbench.getOperationSupport().getUndoContext();

也可以根据view/editor的含义，实现IUndoContext接口，定义一个有含义的IUndoContext。
对eclipse工作空间（workspace）的操作，eclipse建议使用

IUndoContext workspaceContext = (IUndoContext)ResourcesPlugin.getWorkspace().getAdapter(IUndoContext.class);

获得上下文这样可以协同eclipse提供的插件一起工作(package explorer等等)。

做一个例子。

package org.rufus.operation.sample.views;

import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.commands.operations.AbstractOperation;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;

public class MYOperation extends AbstractOperation {

	private SampleView part;

	public MYOperation(SampleView part) {
		super("MYOperation");
		this.part = part;
	}

	@Override
	public IStatus execute(IProgressMonitor monitor, IAdaptable info)
			throws ExecutionException {
		part.setDifInput();
		return Status.OK_STATUS;
	}

	@Override
	public IStatus redo(IProgressMonitor monitor, IAdaptable info)
			throws ExecutionException {
		execute(null, null);
		return Status.OK_STATUS;
	}

	@Override
	public IStatus undo(IProgressMonitor monitor, IAdaptable info)
			throws ExecutionException {
		part.setDefaultInput();
		return Status.OK_STATUS;
	}
}

package org.rufus.operation.sample.views;
import org.eclipse.core.commands.operations.IUndoContext;
public class MyUndoContext implements IUndoContext {
	public String getLabel() {
		return "my context";
	}
	public boolean matches(IUndoContext context) {
		//过滤重做操作，只有在SampleView中才可以重做
		return context instanceof MyUndoContext;
	}
}

package org.rufus.operation.sample.views;

import java.util.ArrayList;

import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.commands.operations.IOperationHistory;
import org.eclipse.core.commands.operations.IUndoableOperation;
import org.eclipse.core.commands.operations.OperationHistoryFactory;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.jface.action.Action;
import org.eclipse.jface.viewers.IStructuredContentProvider;
import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.LabelProvider;
import org.eclipse.jface.viewers.TreeViewer;
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.IActionBars;
import org.eclipse.ui.ISharedImages;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.operations.UndoRedoActionGroup;
import org.eclipse.ui.part.DrillDownAdapter;
import org.eclipse.ui.part.ViewPart;


public class SampleView extends ViewPart {
	private TreeViewer viewer;
	private DrillDownAdapter drillDownAdapter;
	class TreeObject implements IAdaptable {
		private String name;
		private TreeParent parent;

		public TreeObject(String name) {
			this.name = name;
		}

		public String getName() {
			return name;
		}

		public void setParent(TreeParent parent) {
			this.parent = parent;
		}

		public TreeParent getParent() {
			return parent;
		}

		public String toString() {
			return getName();
		}

		public Object getAdapter(Class key) {
			return null;
		}
	}

	class TreeParent extends TreeObject {
		private ArrayList children;

		public TreeParent(String name) {
			super(name);
			children = new ArrayList();
		}

		public void addChild(TreeObject child) {
			children.add(child);
			child.setParent(this);
		}

		public void removeChild(TreeObject child) {
			children.remove(child);
			child.setParent(null);
		}

		public TreeObject[] getChildren() {
			return (TreeObject[]) children.toArray(new TreeObject[children
					.size()]);
		}

		public boolean hasChildren() {
			return children.size() > 0;
		}
	}

	private TreeParent invisibleRoot;
	private Action undoable;

	class ViewContentProvider implements IStructuredContentProvider,
			ITreeContentProvider {

		public void inputChanged(Viewer v, Object oldInput, Object newInput) {
		}

		public void dispose() {
		}

		public Object[] getElements(Object parent) {
			if (parent.equals(getViewSite())) {
				if (invisibleRoot == null)
					initialize();
				return getChildren(invisibleRoot);
			}
			return getChildren(parent);
		}

		public Object getParent(Object child) {
			if (child instanceof TreeObject) {
				return ((TreeObject) child).getParent();
			}
			return null;
		}

		public Object[] getChildren(Object parent) {
			if (parent instanceof TreeParent) {
				return ((TreeParent) parent).getChildren();
			}
			return new Object[0];
		}

		public boolean hasChildren(Object parent) {
			if (parent instanceof TreeParent)
				return ((TreeParent) parent).hasChildren();
			return false;
		}		
		private void initialize() {
			TreeParent root = createDefaultInput();
			createTreeRoot(root);
		}
	}

	private void createTreeRoot(TreeParent root) {
		invisibleRoot = new TreeParent("");
		invisibleRoot.addChild(root);
	}

	private TreeParent createDefaultInput() {
		TreeObject to1 = new TreeObject("Leaf 1");
		TreeObject to2 = new TreeObject("Leaf 2");
		TreeObject to3 = new TreeObject("Leaf 3");
		TreeParent p1 = new TreeParent("Parent 1");
		p1.addChild(to1);
		p1.addChild(to2);
		p1.addChild(to3);

		TreeObject to4 = new TreeObject("Leaf 4");
		TreeParent p2 = new TreeParent("Parent 2");
		p2.addChild(to4);

		TreeParent root = new TreeParent("Root");
		root.addChild(p1);
		root.addChild(p2);
		return root;
	}

	private TreeParent createDifInput() {
		TreeObject to1 = new TreeObject("File");
		TreeObject to2 = new TreeObject("File");
		TreeObject to3 = new TreeObject("File");
		TreeParent p1 = new TreeParent("Folder");
		p1.addChild(to1);
		p1.addChild(to2);
		p1.addChild(to3);

		TreeObject to4 = new TreeObject("File");
		TreeParent p2 = new TreeParent("Folder");
		p2.addChild(to4);

		TreeParent root = new TreeParent("Folder");
		root.addChild(p1);
		root.addChild(p2);
		return root;
	}

	class ViewLabelProvider extends LabelProvider {

		public String getText(Object obj) {
			return obj.toString();
		}

		public Image getImage(Object obj) {
			String imageKey = ISharedImages.IMG_OBJ_ELEMENT;
			if (obj instanceof TreeParent)
				imageKey = ISharedImages.IMG_OBJ_FOLDER;
			return PlatformUI.getWorkbench().getSharedImages().getImage(
					imageKey);
		}
	}

	public void setDifInput() {
		this.createTreeRoot(this.createDifInput());
		viewer.setInput(getViewSite());
	}

	public void setDefaultInput() {
		this.createTreeRoot(this.createDefaultInput());
		viewer.setInput(getViewSite());
	}

	/**
	 * The constructor.
	 */
	public SampleView() {
	}

	/**
	 * This is a callback that will allow us to create the viewer and initialize
	 * it.
	 */
	public void createPartControl(Composite parent) {
		viewer = new TreeViewer(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
		drillDownAdapter = new DrillDownAdapter(viewer);
		viewer.setContentProvider(new ViewContentProvider());
		viewer.setLabelProvider(new ViewLabelProvider());
		viewer.setInput(getViewSite());
		makeActions();
		contributeToActionBars();
	}

	private void contributeToActionBars() {
		IActionBars bars = getViewSite().getActionBars();
		bars.getToolBarManager().add(undoable);
		//在sampleview的site下，创建redoundoaction支持MyUndoContext，
// fillActionBars是将redo，undoaction注册为全局action。当part切换时，
//retargetaction会重新设置相应的全局action handler
		new UndoRedoActionGroup(getSite(), new MyUndoContext(), true)
				.fillActionBars(bars);

	}

	private void makeActions() {
		undoable = new Action() {
			public void run() {
				//创建重做Operation
				IUndoableOperation operation = new MYOperation(SampleView.this);
				IOperationHistory operationHistory = OperationHistoryFactory
						.getOperationHistory();
				//设置特定的UndoContext
				operation.addContext(new MyUndoContext());
				try {
					//运行Operation
					operationHistory.execute(operation, null, null);
				} catch (ExecutionException e) {
					e.printStackTrace();
				}
			}
		};
		undoable.setText("Undoable");
		undoable.setToolTipText("Undoable Action  tooltip");
		undoable.setImageDescriptor(PlatformUI.getWorkbench().getSharedImages()
				.getImageDescriptor(ISharedImages.IMG_OBJS_INFO_TSK));

	}

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

点击I后，使用ctrl+z，ctrl+y进行撤销，恢复操作。