【求助】有关事件模型的问题

/*
2008年11月1日15:01:44
功能：生成一个"退出"按钮，一点击它，就关闭整个窗口!
*/import java.awt.*;
import java.awt.event.*;public class TestFrame implements ActionListener
{
Frame f = new Frame("嘿嘿"); public static void main(String[] args)
{
TestFrame tf = new TestFrame(); Button bt = new Button("退出!");
tf.f.add(bt);
tf.f.pack();
tf.f.setVisible(true);

bt.addActionListener(new TestFrame());
} public void actionPerformed(ActionEvent e)
{
//Frame f = (Frame)e.getSource(); //为什么这行代码一旦生效，运行时点击"退出"按钮，就无法关闭窗口了! f.setVisible(false);
f.dispose();
System.exit(0);
}
}

解决方案 »

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我搞了半天基本搞懂了
贴出来和大家一起分享import java.awt.*;
import java.awt.event.*;class TestFrame2 extends Frame
{
public static void main(String[] args)
{
new TestFrame2().launchFrame();
} public void launchFrame()
{
Button bt = new Button("退出");
add(bt);
pack();
setVisible(true);

bt.addActionListener(new MyActionListener());
}
}class MyActionListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
System.out.println("我行，我行，我很行!");
Frame f = (Frame)e.getSource(); //27行
}
}/*
在JDK 1.6中的运行结果是：一旦点击"退出"按钮，则立即输出：
---------------------------------------
我行，我行，我很行!
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.awt.Bu
tton cannot be cast to java.awt.Frame
        at MyActionListener.actionPerformed(TestFrame2.java:27)
        at java.awt.Button.processActionEvent(Button.java:392)
        at java.awt.Button.processEvent(Button.java:360)
        at java.awt.Component.dispatchEventImpl(Component.java:4501)
        at java.awt.Component.dispatchEvent(Component.java:4331)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)---------------------------------------
总结： 27行语句编译时无错误，但运行时会出错的!*/
再贴一个import java.awt.*;
import java.awt.event.*;class TestFrame2 extends Frame
{
public static void main(String[] args)
{
new TestFrame2().launchFrame();
} public void launchFrame()
{
Button bt = new Button("退出");
add(bt);
pack();
setVisible(true);

bt.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
System.out.println("匿名类被执行了!");
Frame f = (Frame)e.getSource(); //30行
}
}
);
}
}
/*
在JDK 1.6中的运行结果是：一旦点击"退出"按钮，则立即输出：
---------------------------------------
匿名类被执行了!
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.awt.Bu
tton cannot be cast to java.awt.Frame
        at TestFrame2$1.actionPerformed(TestFrame2.java:30)
        at java.awt.Button.processActionEvent(Button.java:392)
        at java.awt.Button.processEvent(Button.java:360)
        at java.awt.Component.dispatchEventImpl(Component.java:4501)
        at java.awt.Component.dispatchEvent(Component.java:4331)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)---------------------------------------
总结： 30行语句编译时无错误，但运行时会出错的!*/
//Frame f = (Frame)e.getSource(); //为什么这行代码一旦生效，运行时点击"退出"按钮，就无法关闭窗口了!因为e.getSource()是一个Button对象，而不是一个Frame对象。另外这个变量的名字f和类成员名冲突，会覆盖类成员f的。你可以将其换为：Button bt = (Button)e.getSource();
我想通过ActionEvent对象获得window信息，看来这是不可能的，因为按钮事件只能获得按钮的相关信息，没法获得按钮所在的整个屏幕的信息，我总结心得如下：写的不太好，　我今天发现把自己的心得录成视频要比写成文件要好的多，当我们想通过ActionEvent事件关闭整个窗口时，写如下代码
Frame f = (Frame)e.getSource();
得到Frame对象f，然后再通过执行f中的setVisible和dispose来关闭整个窗口
想法是好的，但问题是
Frame f = (Frame)e.getSource();
这行代码就是错的，编译时没错误，但运行时会出错！换句话说：
如果e是ActionEvent类型，则
Frame f = (Frame)e.getSource(); //error

如果e是WindowEvent类型，则
Frame f = (Frame)e.getSource(); //OK参见下面三个程序
---------------------------------------------------------------
/*
2008年11月1日15:46:49
功能：点"退出"按钮和左上角的叉子都可以关闭窗口不过本程序是有问题的，点"退出"按钮是不起作用的
*/import java.awt.*;
import java.awt.event.*;class TestFrame2
{
public static void main(String[] args)
{
Frame f = new Frame("哈哈");
Button bt = new Button("退出");
f.add(bt);
f.setSize(300, 300);
f.setVisible(true);

bt.addActionListener(new MyActionListener());
f.addWindowListener(new MyWindowListener());
}
}class MyActionListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
Frame f = (Frame)e.getSource(); // 因为本行编译无错误，但运行时会出错，所以一点击"退出"按钮，立马出错
f.setVisible(false);
System.exit(0);
}
}//Frame是Window的一个子类，
class MyWindowListener extends  WindowAdapter
{
public void windowClosing(WindowEvent e)
{
Frame f = (Frame)e.getSource(); //本行正确，所以点击右上角的×
f.setVisible(false); //改成e.setVisible(false); 编译时会报错，因为e是WindowEvent类对象，而WindowEvent中是没有setVisible 和 dispose()方法的
System.exit(0);
}
}
/*
本程序点退出按钮时，提示出错，但按右上角的×按钮时，窗口正常关闭!
actionPerformed() 和 windowClosing()中的代码是一样的，但前者运行
出错，后者运行时可以关闭整个窗口
*/
--------------------------------------------------------------------------------------------------------------------------------
import java.awt.*;
import java.awt.event.*;class TestFrame2 extends Frame
{
public static void main(String[] args)
{
new TestFrame2().launchFrame();
} public void launchFrame()
{
Button bt = new Button("退出");
add(bt);
pack();
setVisible(true);

bt.addActionListener(new MyActionListener());
}
}class MyActionListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
System.out.println("我行，我行，我很行!");
Frame f = (Frame)e.getSource(); //27行
}
}/*
在JDK 1.6中的运行结果是：一旦点击"退出"按钮，则立即输出：
---------------------------------------
我行，我行，我很行!
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.awt.Bu
tton cannot be cast to java.awt.Frame
        at MyActionListener.actionPerformed(TestFrame2.java:27)
        at java.awt.Button.processActionEvent(Button.java:392)
        at java.awt.Button.processEvent(Button.java:360)
        at java.awt.Component.dispatchEventImpl(Component.java:4501)
        at java.awt.Component.dispatchEvent(Component.java:4331)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)---------------------------------------
总结： 27行语句编译时无错误，但运行时会出错的!*/-----------------------------------------------------------------
import java.awt.*;
import java.awt.event.*;class TestFrame2 extends Frame
{
public static void main(String[] args)
{
new TestFrame2().launchFrame();
} public void launchFrame()
{
Button bt = new Button("退出");
add(bt);
pack();
setVisible(true);

bt.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
System.out.println("匿名类被执行了!");
Frame f = (Frame)e.getSource(); //30行
}
}
);
}
}
/*
在JDK 1.6中的运行结果是：一旦点击"退出"按钮，则立即输出：
---------------------------------------
匿名类被执行了!
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.awt.Bu
tton cannot be cast to java.awt.Frame
        at TestFrame2$1.actionPerformed(TestFrame2.java:30)
        at java.awt.Button.processActionEvent(Button.java:392)
        at java.awt.Button.processEvent(Button.java:360)
        at java.awt.Component.dispatchEventImpl(Component.java:4501)
        at java.awt.Component.dispatchEvent(Component.java:4331)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)---------------------------------------
总结： 30行语句编译时无错误，但运行时会出错的!*/
-----------------------------------------------------------------
谢谢huoyin
结贴去

【求助】 有关事件模型的问题

解决方案 »

【求助】有关事件模型的问题