步骤４＆５
然后我们将包含两个ChangeRepresentationObject类型的栈的类命名为UndoRedo。一个栈用于撤销操作而另一个用于重做操作。类的代码如下：
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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
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
步骤６
在完成每个操作前，调用InsertObjectforUndoRedo方法。当用户界面上Undo被点击，我们调用UndoRedo类的Undo方法，而当用户界面上Redo被点击，我们调用UndoRedo类的redo方法。
这里，我们没有明确设置Undo栈和Redo栈的大小，因此，应用程序能具有的状态数目取决于系统的内存。
使用单个对象表示变化的方法时的变更管理
如果你想要用单个对象表示变化的方法来为新的操作支持Undo/Redo时，你不得不作一些改变。你不得不修改表示变化的对象，动作类型Enum并改变Undo/Redo方法的代码。所以，它的可维护性很低。
使用单个对象表示变化的方法的优缺点
它的优点是实现简单，而不需要知道任何的设计模式，你就可以实现Undo/Redo。
可维护性很低。代表该方法的对象包含很多额外信息，因为这里，单个对象用来容纳所有动作类型的数据。例如，对移动而言，我们只需保存移动相关的数据，而对调整尺寸，我们应该仅保存该操作相关的数据。所以，我们在保存冗余的数据。随着操作数目的增加，冗余也在增加。这并不是好的面向对象的设计。
