WebCast听课录(7)

课程名：Windows应用程序开发入门到精通四：Windows窗体开发中的面向对象概念

1,自定义控件的开发。

最简单的控件自定义是重写公共控件的方法。例如，可以重写 TextBox 控件的 OnKeyPress 继承方法，提供将输入限制为数字字符的代码。

public class NumricTextBox : System.Windows.Forms.TextBox
    {
        bool allowSpace = false; //不允许出现空格

        protected override void OnKeyPress(KeyPressEventArgs e)
        {    // 限制输入字符为数字，小数点，负号，Backspace键    
            base.OnKeyPress(e);

            NumberFormatInfo numberFormatInfo = System.Globalization.CultureInfo.CurrentCulture.NumberFormat;
            string decimalSeparator = numberFormatInfo.NumberDecimalSeparator;
            string groupSeparator = numberFormatInfo.NumberGroupSeparator;
            string negativeSign = numberFormatInfo.NegativeSign;

            string keyInput = e.KeyChar.ToString();

            if (Char.IsDigit(e.KeyChar))
            {
                //输入为数字
            }
            else if (keyInput.Equals(decimalSeparator) || keyInput.Equals(groupSeparator) ||
                keyInput.Equals(negativeSign))
            {
                // 输入小数分隔符号
            }
            else if (e.KeyChar == '\b')
            {
                // Backspace键    
            }
            else if (this.allowSpace && e.KeyChar == ' ')
            {

            }
            else
            {
                e.Handled = true; //通知父类事件已经处理过了，父类不必再响应
            }
        }

        public int IntValue
        {
            get
            {
                return Int32.Parse(this.Text);
            }
        }

        public decimal DecimalValue
        {
            get
            {
                return Decimal.Parse(this.Text);
            }
        }

        public bool AllowSpace
        {
            set
            {
                this.allowSpace = value;
            }

            get
            {
                return this.allowSpace;
            }
        }

    }

2, “组合”和“聚合”的区别到底是什么呢？用接口来代替继承更易于应对变化？

3，Observer模式实例

public interface ISubject
    {
    }

    public interface IObserver
    {
        ISubject Subject
        {
            set;
        }
    }

    public class MainSubject : ISubject
    {
        public event EventHandler SelectedChanged;
        private int m_selected;

        public int Selected
        {
            get
            {
                return m_selected;
            }
            set
            {
                m_selected = value;
                if (SelectedChanged != null)
                {
                    SelectedChanged(this, EventArgs.Empty);
                }
            }
        }

        public MainSubject()
        {
        }
    }

    public class Buttons : System.Windows.Forms.UserControl, IObserver
    {
        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.Button button2;
        private System.Windows.Forms.Button button3;

        private MainSubject m_subject;

        private void button1_Click(object sender, System.EventArgs e)
        {
            this.m_subject.Selected = 1;
        }

        private void button2_Click(object sender, System.EventArgs e)
        {
            this.m_subject.Selected = 2;
        }

        private void button3_Click(object sender, System.EventArgs e)
        {
            this.m_subject.Selected = 3;
        }
        IObserver Members#region IObserver Members

        public ISubject Subject
        {
            set
            {
                m_subject = (MainSubject)value;
            }
        }

        #endregion
    }

    public class Views : System.Windows.Forms.UserControl, IObserver
    {
        private System.Windows.Forms.TextBox textBox1;
        private MainSubject m_subject;

        IObserver Members#region IObserver Members

        public ISubject Subject
        {
            set
            {
                m_subject = (MainSubject)value;
                m_subject.SelectedChanged += new EventHandler(m_subject_SelectedChanged);
            }
        }

        #endregion

        private void m_subject_SelectedChanged(object sender, EventArgs e)
        {
            this.textBox1.Text = m_subject.Selected.ToString();
        }
    }

    public class Form1 : System.Windows.Forms.Form
    {
        private ObserverPattern.Buttons buttons1;
        private ObserverPattern.Views views1;
        private MainSubject m_subject;

        private System.ComponentModel.Container components = null;

        public Form1()
        {
            InitializeComponent();
            m_subject = new MainSubject();
            this.buttons1.Subject = m_subject;
            this.views1.Subject = m_subject;
        }
}