Undo/Redo

 

步骤１

首先识别出你希望哪些操作能支持Undo/Redo。然后，识别出你将在哪个容器下支持Undo/Redo以及你希望哪些对象支持Undo/Redo。

步骤２

为了进一步处理每个Undo/Redo操作，识别出需要被保存的属性。

步骤３

然后创建一个类（ChangeRepresentationObject），它包含支持全部操作Undo/Redo的所有属性。同样，准备一个动作类型enum，它将代表全部操作。这个动作类型enum是ChangeRepresentationObject类的一部分。

步骤４

然后创建一个名为UndoRedo的类，它包含两个类型的ChangeRepresentationObject栈。一个用于撤销操作，一个用于重做操作。

 

步骤５

然后实现具体方法：Undo、 Redo、InsertObjectforUndoRedo。
在每个Undo操作中：

•首先检查Undo栈是否为空。
•如果不是，则弹出一个ChangeRepresentationObject并将其压入重做栈。
•检查动作类型。
•然后基于动作类型，利用ChangeRepresentationObject的属性完成撤销操作。
在每个Redo操作中，你几乎做与Undo同样的事。
•首先检查Redo栈是否为空。
•如果不是，弹出一个ChangeRepresentationObject，然后将其压入撤销栈。
•检查动作类型。
•然后基于动作的类型，利用ChangeRepresentationObject属性完成重做操作。
在InsertObjectforUndoRedo操作中，你只要把数据对象插入Undo栈并清空Redo栈中。

步骤６

然后，在完成每次操作前，调用InsertObjectforUndoRedo方法以对所有操作提供Undo/Redo支持。在用户界面上点击Undo时，只需调用UndoRedo类的Undo方法，而在用户界面上点击Redo时，只需调用UndoRedo类的redo方法。

public enum ActionType
     {
         Delete = 0,
         Move = 1,
         Resize = 2,
         Insert = 3
     } 
    public class ChangeRepresentationObject
     {
        public ActionType Action;
        public Point Margin;
        public double Width;
        public double height;
        public FrameworkElement UiElement;
     }

interface IUndoRedo
     {
        void Undo(int level);
        void Redo(int level);
        void InsertObjectforUndoRedo(ChangeRepresentationObject dataobject);
     }
public partial class UnDoRedo : IUndoRedo
     {
        private Stack<ChangeRepresentationObject> _UndoActionsCollection =
     new Stack<ChangeRepresentationObject>();
        private Stack<ChangeRepresentationObject> _RedoActionsCollection =
     new Stack<ChangeRepresentationObject>();
        
        #region IUndoRedo Members

        public void Undo(int level)
         {
            for (int i = 1; i <= level; i++)
             {
                if (_UndoActionsCollection.Count == 0) return;

                 ChangeRepresentationObject Undostruct = _UndoActionsCollection.Pop();
                if (Undostruct.Action == ActionType.Delete)
                 {
                     Container.Children.Add(Undostruct.UiElement);
                    this.RedoPushInUnDoForDelete(Undostruct.UiElement);
                 }
                else if (Undostruct.Action == ActionType.Insert)
                 {
                     Container.Children.Remove(Undostruct.UiElement);
                    this.RedoPushInUnDoForInsert(Undostruct.UiElement);
                 }
                else if (Undostruct.Action == ActionType.Resize)
                 {
                    if (_UndoActionsCollection.Count != 0)
                     {
                         Point previousMarginOfSelectedObject = new Point
   (((FrameworkElement)Undostruct.UiElement).Margin.Left,
                             ((FrameworkElement)Undostruct.UiElement).Margin.Top);
                        this.RedoPushInUnDoForResize(previousMarginOfSelectedObject,
   Undostruct.UiElement.Width,
                             Undostruct.UiElement.Height, Undostruct.UiElement);
                         Undostruct.UiElement.Margin = new Thickness
   (Undostruct.Margin.X, Undostruct.Margin.Y, 0, 0);
                         Undostruct.UiElement.Height = Undostruct.height;
                         Undostruct.UiElement.Width = Undostruct.Width;
                     }
                 }
                else if (Undostruct.Action == ActionType.Move)
                 {
                     Point previousMarginOfSelectedObject = new Point
   (((FrameworkElement)Undostruct.UiElement).Margin.Left,
                         ((FrameworkElement)Undostruct.UiElement).Margin.Top);
                    this.RedoPushInUnDoForMove(previousMarginOfSelectedObject,
       Undostruct.UiElement);
                     Undostruct.UiElement.Margin = new Thickness
   (Undostruct.Margin.X, Undostruct.Margin.Y, 0, 0);
                 }
             }
         }

        public void Redo(int level)
         {
            for (int i = 1; i <= level; i++)
             {
                if (_RedoActionsCollection.Count == 0) return;

                 ChangeRepresentationObject Undostruct = _RedoActionsCollection.Pop();
                if (Undostruct.Action == ActionType.Delete)
                 {
                     Container.Children.Remove(Undostruct.UiElement);
                    this.PushInUnDoForDelete(Undostruct.UiElement);
                 }
                else if (Undostruct.Action == ActionType.Insert)
                 {
                     Container.Children.Add(Undostruct.UiElement);
                    this.PushInUnDoForInsert(Undostruct.UiElement);
                 }
                else if (Undostruct.Action == ActionType.Resize)
                 {
                     Point previousMarginOfSelectedObject = new Point
   (((FrameworkElement)Undostruct.UiElement).Margin.Left,
                         ((FrameworkElement)Undostruct.UiElement).Margin.Top);
                    this.PushInUnDoForResize(previousMarginOfSelectedObject,
       Undostruct.UiElement.Width,
                         Undostruct.UiElement.Height, Undostruct.UiElement);
                     Undostruct.UiElement.Margin = new Thickness
   (Undostruct.Margin.X, Undostruct.Margin.Y, 0, 0);
                     Undostruct.UiElement.Height = Undostruct.height;
                     Undostruct.UiElement.Width = Undostruct.Width;
                 }
                else if (Undostruct.Action == ActionType.Move)
                 {
                     Point previousMarginOfSelectedObject = new Point
   (((FrameworkElement)Undostruct.UiElement).Margin.Left,
                         ((FrameworkElement)Undostruct.UiElement).Margin.Top);
                    this.PushInUnDoForMove(previousMarginOfSelectedObject,
       Undostruct.UiElement);
                     Undostruct.UiElement.Margin = new Thickness
     (Undostruct.Margin.X, Undostruct.Margin.Y, 0, 0);
                 }
             }
         }
        public void InsertObjectforUndoRedo(ChangeRepresentationObject dataobject)
         {
             _UndoActionsCollection.Push(dataobject);_RedoActionsCollection.Clear();
         }
       #endregion

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