软件设计模式复习题(16)

undoC.add (comd); comd.Execute (); redoC.add(comd); comd.Execute();}

public void paintHandler(object sender, PaintEventArgs e) {

Graphics g = e.Graphics ; blueC.draw(g); redC.draw (g); }

[STAThread]

static void Main(){

Application.Run(new Form1());} Command:

public interface Command { void Execute(); void Undo(); void Redo(); bool isUndo(); bool isRedo();}

public class UndoComd:Command { public static ArrayList undolist; public UndoComd(){

undolist = new ArrayList();} public void add(Command comd) { if(! comd.isUndo ()) {

undolist.Add(comd);}} public bool isUndo() { return true;} public void Undo() { } public void Execute() { int unIndex =undolist.Count - 1; if (unIndex >= 0){

Command cmd = (Command)undolist[unIndex]; cmd.Undo();

RedoComd.redolist = new ArrayList(); RedoComd.redolist.Add(cmd); undolist.Remove(unIndex);}}} public class RedoComd:Command { public static ArrayList redolist; public RedoComd(){

redolist = new ArrayList();} public void add(Command comd) { if(! comd.isRedo ()) {

redolist.Add(comd);}} public bool isRedo() {

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