命令模式和OnPaint事件发布
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我正在尝试使命令模式适应具有撤消功能的简单绘画应用程序。而且我在撤销操作上一直坚持
OnPaint
interface ICommand {
void Execute();
void UnExecute();
}
class DrawLineCommand : ICommand {
private SimpleImage simpleImage;
private Image prevImage;
public DrawLineCommand(SimpleImage simpleImage) {
this.simpleImage = simpleImage;
this.prevImage = simpleImage.Image;
}
public void Execute() {
simpleImage.DrawLine();
}
public void UnExecute() {
simpleImage.Image = prevImage;
}
}
class CommandManager {
private Stack undoStack = new Stack();
public void ExecuteCommand(ICommand command) {
command.Execute();
undoStack.Push(command);
}
public void UnExecuteCommand() {
if (undoStack.Count > 0) {
ICommand command = (ICommand)undoStack.Pop();
command.UnExecute();
}
}
}
class SimpleImage {
private Point startPoint;
private Point endPoint;
private PictureBox pictureBox;
public SimpleImage(PictureBox pictureBox) {
this.pictureBox = pictureBox;
pictureBox.Paint += new PaintEventHandler(pictureBox_Paint);
}
void pictureBox_Paint(object sender, PaintEventArgs e) {
// this code shows the line during drawing
// this code is under \"if operation == drawLine\" block
Graphics graphics = e.Graphics;
graphics.DrawLine(Pens.Red, startPoint, endPoint);
// how can i refresh picturebox after undo operation?
// \"if operation == undo\" then ??
}
public void DrawLine() {
// this code actually saves finally drawn line
Image img = Image;
Graphics graphics = Graphics.FromImage(img);
graphics.DrawLine(Pens.Red, startPoint, endPoint);
Image = img;
}
public void Invalidate() {
pictureBox.Invalidate();
}
public Image Image {
get { return pictureBox.Image; }
set { pictureBox.Image = value; }
}
public Point StartPoint {
get { return startPoint; }
set { startPoint = value; }
}
public Point EndPoint {
get { return endPoint; }
set { endPoint = value; }
}
}
public partial class FormMain : Form {
private PictureBox pictureBox;
private SimpleImage simpleImage;
private CommandManager commandManager;
public FormMain() {
InitializeComponent();
simpleImage = new SimpleImage(this.pictureBox);
commandManager = new CommandManager();
}
void pictureBox_MouseDown(object sender, MouseEventArgs e) {
if (e.Button != MouseButtons.Left)
return;
simpleImage.StartPoint = e.Location;
}
void pictureBox_MouseMove(object sender, MouseEventArgs e) {
if (e.Button != MouseButtons.Left)
return;
simpleImage.EndPoint = e.Location;
simpleImage.Invalidate();
}
void pictureBox_MouseUp(object sender, MouseEventArgs e) {
simpleImage.Invalidate();
commandManager.ExecuteCommand(new DrawLineCommand(simpleImage));
}
}
this.prevImage = simpleImage.Image;
没有找到相关结果
已邀请:
2 个回复
荤碗
现在，您具有对同一对象的两个引用。绘制线操作发生在您对同一图像进行操作时：上面的内容使ѭ9成为不必要的Image引用。但是，您的命令中仍然还有对Image的引用。垃圾收集器运行之后，您将回到对同一图像对象的引用。然后，撤消执行以下操作：在这里，您没有更改Image，仅使ѭ11引用了一直引用的同一对象。 尽管我非常同意m0sa，但在这种情况下，解决的方法是在创建命令时将作为原始图像的副本。对于以下内容，我假设实现了Image.Clone（），尽管我自己从未尝试过：注意：如果使用此方法，您可能会很快耗尽大图像或许多命令的内存。莽缓逢
interface IPaintable // intarface for Lines, Text, Circles, ... { void OnPaint(Image i); // does the painting } interface IPaintableCommand // interface for commands { void Do(ICollection<IPaintable> painting); // adds line/text/circle to painting void Undo(ICollection<IPaintable> painting); // removes line/text/circle from painting }