.NET圖像界面按鈕的clicked事件淺談

更新時(shí)間：2013年04月17日 10:54:40 投稿：shangke

在.NET圖像界面開發(fā)中最常見的一個(gè)事件大概就是按鈕的clicked事件了，當(dāng)點(diǎn)擊圖形界面的按鈕時(shí)，就會(huì)調(diào)用一個(gè)與這個(gè)事件相關(guān)的方法對這個(gè)事件進(jìn)行響應(yīng)，做一些相關(guān)操作。

發(fā)送方的對象為了給事件接收對象傳遞一些額外信息，就需要寫一個(gè)派生于System.EventArgs的類，封裝一些數(shù)據(jù)。

復(fù)制代碼代碼如下:

    public class DrawEventArgs:EventArgs
    {
        privatedouble m_Size;
        public DrawEventArgs(doublesize)
        {
            m_Size = size;
        }
        public double Size
        {
            get
            {
                returnm_Size;
            }
        }
    }

    public class DrawManager
    {
        public event ShapeSizeChangedSizeChanged;
        protectedvoid OnSizeChanged(DrawEventArgse)
        {
            ShapeSizeChangedtemp = SizeChanged;

if(temp != null)
            {
                temp(this,e);
            }
        }
        public void SizeChange(doublesize)
        {
            DrawEventArgse = new DrawEventArgs(size);
            OnSizeChanged(e);
        }
    }

復(fù)制代碼代碼如下:

    public class Square
    {
        publicSquare(DrawManager drawManager)
        {
            //drawManager.SizeChanged+= DrawSquare;
            drawManager.SizeChanged += new ShapeSizeChanged(DrawSquare);
        }
        public void DrawSquare(objectsender, DrawEventArgs e)
        {
            Console.WriteLine(string.Format("TheSquare'Length = {0}", e.Size));
        }
        public void Detach(DrawManagerdrawManager)
        {
            //drawManager.SizeChanged-= DrawSquare;
            drawManager.SizeChanged -= new ShapeSizeChanged(DrawSquare);
        }
    }
    public class Rectangle
    {
        publicRectangle(DrawManager drawManager)
        {
            drawManager.SizeChanged +=DrawRectangle;
        }
        public void DrawRectangle(objectsender, DrawEventArgs e)
        {
            Console.WriteLine(string.Format("TheRectangle'length={0} and width={1}.",e.Size*2,e.Size));
        }
        public void Detach(DrawManagerdrawManager)
        {
            drawManager.SizeChanged -=DrawRectangle;
        }
    }

測試代碼，

復(fù)制代碼代碼如下:

    class Program
    {
        static void Main(string[]args)
        {
            DrawManagerdrawManager = new DrawManager();
            Rectanglerect = new Rectangle(drawManager);
            Squaresquare = new Square(drawManager);
            //引發(fā)事件
            drawManager.SizeChange(5);
    
            square.Detach(drawManager);
            drawManager.SizeChange(10);
            Console.ReadLine();
        }
    }
/*運(yùn)行結(jié)果
  The Rectangle'length=10 and width=5.
  The Square'Length = 5
  The Rectangle'length=20 and width=10.
 */

.NET中的事件模式和觀察者模式非常相似，也可謂是觀察者模式在.NET下的進(jìn)化版吧，下面用觀察者模式實(shí)現(xiàn)上面功能以做對比，首先定義兩個(gè)接口，IObserver和IObservable，如下

復(fù)制代碼代碼如下:

public interface IObserver
    {
        voidNotify(DrawEventArgs e);
    }
    public interface IObservable
    {
        voidRegister(IObserver observer);
        voidUnRegister(IObserver observer);
    }

下面是改寫后的兩個(gè)觀察者類，

復(fù)制代碼代碼如下:

    public class NewRectangle:IObserver
    {
        privateObserverManager m;
        publicNewRectangle(ObserverManager oManager)
        {
            m=oManager;
            oManager.Register(this);
        }
        public void Notify(DrawEventArgse)
        {
            Console.WriteLine(string.Format("TheRectangle'length={0} and width={1}.", e.Size * 2, e.Size));
        }
        public void Detach()
        {
            m.UnRegister(this);
        }
    }
    public class NewSquare:IObserver
    {
        privateObserverManager m;
 
        publicNewSquare(ObserverManager oManager)
        {
            m=oManager;
            oManager.Register(this);
        }
        public void Notify(DrawEventArgse)
        {
            Console.WriteLine(string.Format("TheSquare'Length = {0}.", e.Size));
        }
        public void Detach()
        {
            m.UnRegister(this);
        }
    }

下面是負(fù)責(zé)通知觀察者的類型，

復(fù)制代碼代碼如下:

    public class ObserverManager:IObservable
    {
        protectedArrayList arrList;
        publicObserverManager()
        {
            arrList = newArrayList();
        }
        public void Register(IObserverobserver)
        {
            arrList.Add(observer);
        }
        public void UnRegister(IObserverobserver)
        {
            if(arrList.Contains(observer))
            {
                arrList.Remove(observer);
            }
        }
        public void NotifyObservers(doublesize)
        {
            DrawEventArgse = new DrawEventArgs(size);
            foreach(IObserver observer inarrList)
            {
                observer.Notify(e);
            }
        }
        public void SizeChanged(doublesize)
        {
            NotifyObservers(size);
        }
    }

下面是調(diào)用代碼，

復(fù)制代碼代碼如下:

        static void Main(string[]args)
        {
            ObserverManageroManager = new ObserverManager();
            NewRectanglerect = new NewRectangle(oManager);
            NewSquaresquare = new NewSquare(oManager);
            oManager.SizeChanged(5);
            square.Detach();
            oManager.SizeChanged(10);
     Console.ReadLine();
        }

最好運(yùn)行下代碼，這樣可以更easy的理解這兩種模式微妙的差別了。
對事件來說，還可以顯式的用add和remove編寫事件訪問器，事件訪問器通常有編譯器生成，所以可以顯式的用事件訪問器修改DrawManager類型，

復(fù)制代碼代碼如下:

    public class DrawManager
    {
        privateevent ShapeSizeChangedm_SizeChanged;
        privatereadonly objectm_lock = new object();
        public event ShapeSizeChangedSizeChanged
        {
            add
            {
                lock(m_lock)
                {
                    m_SizeChanged += value;
                }
            }
            remove
            {
                lock(m_lock)
                {
                    m_SizeChanged -= value;
                }
            }
        }
        protectedvoid OnSizeChanged(DrawEventArgse)
        {
            ShapeSizeChangedtemp = m_SizeChanged;