undomanager.java

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package net.sf.component.simplenote;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.commands.operations.AbstractOperation;
import org.eclipse.core.commands.operations.IOperationHistory;
import org.eclipse.core.commands.operations.IUndoContext;
import org.eclipse.core.commands.operations.ObjectUndoContext;
import org.eclipse.core.commands.operations.OperationHistoryFactory;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.swt.custom.ExtendedModifyEvent;
import org.eclipse.swt.custom.ExtendedModifyListener;
import org.eclipse.swt.custom.StyledText;
/**
 * 为simplenote增加undo功能
 * @since 2008-2-9 下午12:07:35
 * @see http://www.blogjava.net/qujinlong123/archive/2007/06/07/122520.html
 */
public class UndoManager {
		//动作常数
		public static final int UNDO = Integer.MAX_VALUE-888;
		public static final int REDO = UNDO - 1;

	   /*
	    * 用于存储历史Undo操作，每改变一次文本内容，就将构造一个Undo操作存入OperationHistory中。
	    */
	   private final IOperationHistory opHistory;
	 
	   /*
	    * Undo操作上下文，一般用于在OperationHistory中查找当前文本框的Undo操作。
	    */
	   private IUndoContext undoContext = null;
	 
	   /*
	    * 所要监听的需要实现Undo操作的文本框。
	    */
	   private StyledText styledText = null;
	 
	   private int undoLevel = 0;
	 
	   public UndoManager(int undoLevel)
	   {
	     opHistory = OperationHistoryFactory.getOperationHistory();
	 
	     setMaxUndoLevel(undoLevel);
	   }
	 
	   public void setMaxUndoLevel(int undoLevel)
	   {
	     this.undoLevel = Math.max(0, undoLevel);
	 
	     if (isConnected())
	       opHistory.setLimit(undoContext, this.undoLevel);
	   }
	 
	   public boolean isConnected()
	   {
	     return styledText != null;
	   }
	 
	   /*
	    * 将Undo管理器与指定的StyledText文本框相关联。
	    */
	   public void connect(StyledText styledText)
	   {
	     if (! isConnected() && styledText != null)
	     {
	       this.styledText = styledText;
	 
	       if (undoContext == null)
	         undoContext = new ObjectUndoContext(this);
	 
	       opHistory.setLimit(undoContext, undoLevel);
	       opHistory.dispose(undoContext, true, true, false);
	 
	       addListeners();
	     }
	   }
	 
	   public void disconnect()
	   {
	     if (isConnected())
	     {
	       removeListeners();
	 
	       styledText = null;
	 
	       opHistory.dispose(undoContext, true, true, true);
	 
	       undoContext = null;
	     }
	   }
	 
	   private ExtendedModifyListener extendedModifyListener = null;
	 
	   private boolean isUndoing = false;
	 
	   /*
	    * 向Styled中注册监听文本改变的监听器。
	    * 
	    * 如果文本改变，就构造一个Undo操作压入Undo操作栈中。
	    */
	   private void addListeners()
	   {
	     if (styledText != null)
	     {
	       extendedModifyListener = new ExtendedModifyListener() {
	         public void modifyText(ExtendedModifyEvent event)
	         {
	           if (isUndoing)
	             return;
	 
	           String newText = styledText.getText().substring(event.start,
	               event.start + event.length);
	 
	           UndoableOperation operation = new UndoableOperation(undoContext);
	 
	           operation.set(event.start, newText, event.replacedText);
	 
	           opHistory.add(operation);
	         }
	       };
	 
	       styledText.addExtendedModifyListener(extendedModifyListener);
	     }
	   }
	 
	   private void removeListeners()
	   {
	     if (styledText != null)
	     {
	       if (extendedModifyListener != null)
	       {
	         styledText.removeExtendedModifyListener(extendedModifyListener);
	 
	         extendedModifyListener = null;
	       }
	     }
	   }
	 
	   public void redo()
	   {
	     if (isConnected())
	     {
	       try
	       {
	         opHistory.redo(undoContext, null, null);
	       }
	       catch (ExecutionException ex)
	       {
	       }
	     }
	   }
	 
	   public void undo()
	   {
	     if (isConnected())
	     {
	       try
	       {
	         opHistory.undo(undoContext, null, null);
	       }
	       catch (ExecutionException ex)
	       {
	       }
	     }
	   }
	 
	   /*
	    * Undo操作用于记录StyledText的文本被改变时的相关数据。
	    * 
	    * 比如文本框中本来的文本为111222333，如果此时选中222替换为444（用复制粘帖的方法），
	    * 
	    * 则Undo操作中记录的相关数据为： startIndex = 3; newText = 444; replacedText = 222;
	    */
	   private class UndoableOperation extends AbstractOperation
	   {
	     // 记录Undo操作时,被替换文本的开始索引
	     protected int startIndex = - 1;
	 
	     // 新输入的文本
	     protected String newText = null;
	 
	     // 被替换掉的文本
	     protected String replacedText = null;
	 
	     public UndoableOperation(IUndoContext context)
	     {
	       super("Undo-Redo");
	 
	       addContext(context);
	     }
	 
	     /*
	      * 设置Undo操作中要存储的相关数据。
	      */
	     public void set(int startIndex, String newText, String replacedText)
	     {
	       this.startIndex = startIndex;
	 
	       this.newText = newText;
	       this.replacedText = replacedText;
	     }
	 
	     /*
	      * (non-Javadoc)
	      * 
	      * @see org.eclipse.core.commands.operations.AbstractOperation#undo(org.eclipse.core.runtime.IProgressMonitor,
	      *      org.eclipse.core.runtime.IAdaptable)
	      */
	     public IStatus undo(IProgressMonitor monitor, IAdaptable info)
	         throws ExecutionException
	     {
	       isUndoing = true;
	       styledText.replaceTextRange(startIndex, newText.length(), replacedText);
	       isUndoing = false;
	 
	       return Status.OK_STATUS;
	     }
	 
	     /*
	      * (non-Javadoc)
	      * 
	      * @see org.eclipse.core.commands.operations.AbstractOperation#redo(org.eclipse.core.runtime.IProgressMonitor,
	      *      org.eclipse.core.runtime.IAdaptable)
	      */
	     public IStatus redo(IProgressMonitor monitor, IAdaptable info)
	         throws ExecutionException
	     {
	       isUndoing = true;
	       styledText.replaceTextRange(startIndex, replacedText.length(), newText);
	       isUndoing = false;
	 
	       return Status.OK_STATUS;
	     }
	 
	     /*
	      * (non-Javadoc)
	      * 
	      * @see org.eclipse.core.commands.operations.AbstractOperation#execute(org.eclipse.core.runtime.IProgressMonitor,
	      *      org.eclipse.core.runtime.IAdaptable)
	      */
	     public IStatus execute(IProgressMonitor monitor, IAdaptable info)
	         throws ExecutionException
	     {
	       return Status.OK_STATUS;
	     }
	   }
}