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标题: 关于抽象的适配器类 [打印本页]
作者: jing迪    时间: 2014-1-10 14:06
标题: 关于抽象的适配器类
适配器类是抽象类 抽象类不是不能建立对象吗??
但是这句话怎么理解啊
WindowAdapter wa = new WindowAdapter();
上面这句是错误的  提示抽象类不能创建对象这个倒是理解
但是下面这句
WindowAdapter wa = new WindowAdapter(){};
这句话居然没错 这是什么意思???创建WindowAdapter的对象??空参构造??? 对这句话不理解  谁能告诉我??
作者: 猎鹰tianya    时间: 2014-1-10 16:00
这种写是叫匿名内部类。格式：new <类或接口> <类的主体>
new WindowAdapter(){};
这句是的意思说：有一个类（匿名的），实现WindowAdapter这个抽象类，并返回一个这个类对象（不是WindowAdapter对象，抽象类不能new对象，只有实现它的类才能new对象）。

{}里面的内容是这个匿名类的主体，但看到这里空的，我也很纳闷！最起码的你应该把抽象类里的抽象方法都实现一下呀！
于是，把这句代码写到eclipse里面，Ctrl+单击==>打开源码，瞬间懂了，WindowAdapter下面有10个方法，但没有一个是抽象方法，所以这么写是可以的！
WindowAdapter wa=new WindowAdapter(){};这里还有传说中的多态 wa为父类引用
作者: 猎鹰tianya    时间: 2014-1-10 16:11

WindowAdapter源代码贴这里了，来，围观一下！
哎，，，，
说起源代码
心情很是复杂啊
想起了我的英语老师
为什么老师对我那么好
我却还是没把英语学好呢
{:soso_e118:}{:soso_e117:}{:soso_e131:}{:soso_e113:}{:soso_e132:}{:soso_e130:}{:soso_e122:}{:soso_e130:}

  1. package java.awt.event;

  3. /**
  4. * An abstract adapter class for receiving window events.
  5. * The methods in this class are empty. This class exists as
  6. * convenience for creating listener objects.
  7. * <P>
  8. * Extend this class to create a <code>WindowEvent</code> listener
  9. * and override the methods for the events of interest. (If you implement the
  10. * <code>WindowListener</code> interface, you have to define all of
  11. * the methods in it. This abstract class defines null methods for them
  12. * all, so you can only have to define methods for events you care about.)
  13. * <P>
  14. * Create a listener object using the extended class and then register it with
  15. * a Window using the window's <code>addWindowListener</code>
  16. * method. When the window's status changes by virtue of being opened,
  17. * closed, activated or deactivated, iconified or deiconified,
  18. * the relevant method in the listener
  19. * object is invoked, and the <code>WindowEvent</code> is passed to it.
  20. *
  21. * @see WindowEvent
  22. * @see WindowListener
  23. * @see <a >Tutorial: Writing a Window Listener</a>
  24. *
  25. * @author Carl Quinn
  26. * @author Amy Fowler
  27. * @author David Mendenhall
  28. * @since 1.1
  29. */
  30. public abstract class WindowAdapter
  31.     implements WindowListener, WindowStateListener, WindowFocusListener
  32. {
  33.     /**
  34.      * Invoked when a window has been opened.
  35.      */
  36.     public void windowOpened(WindowEvent e) {}

  38.     /**
  39.      * Invoked when a window is in the process of being closed.
  40.      * The close operation can be overridden at this point.
  41.      */
  42.     public void windowClosing(WindowEvent e) {}

  44.     /**
  45.      * Invoked when a window has been closed.
  46.      */
  47.     public void windowClosed(WindowEvent e) {}

  49.     /**
  50.      * Invoked when a window is iconified.
  51.      */
  52.     public void windowIconified(WindowEvent e) {}

  54.     /**
  55.      * Invoked when a window is de-iconified.
  56.      */
  57.     public void windowDeiconified(WindowEvent e) {}

  59.     /**
  60.      * Invoked when a window is activated.
  61.      */
  62.     public void windowActivated(WindowEvent e) {}

  64.     /**
  65.      * Invoked when a window is de-activated.
  66.      */
  67.     public void windowDeactivated(WindowEvent e) {}

  69.     /**
  70.      * Invoked when a window state is changed.
  71.      * @since 1.4
  72.      */
  73.     public void windowStateChanged(WindowEvent e) {}

  75.     /**
  76.      * Invoked when the Window is set to be the focused Window, which means
  77.      * that the Window, or one of its subcomponents, will receive keyboard
  78.      * events.
  79.      *
  80.      * @since 1.4
  81.      */
  82.     public void windowGainedFocus(WindowEvent e) {}

  84.     /**
  85.      * Invoked when the Window is no longer the focused Window, which means
  86.      * that keyboard events will no longer be delivered to the Window or any of
  87.      * its subcomponents.
  88.      *
  89.      * @since 1.4
  90.      */
  91.     public void windowLostFocus(WindowEvent e) {}
  92. }
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