事件处理【总结】

1. 事件类之间的继承关系？

答：

2. 各个事件及其相关方法？

答：

3. 事件监听器的注册？

答：

1）注册事件监听器

    处理事件的基本方法，是事件监听器的注册，即将组建对象和监听器对象相联系。只需要使用对象的addXXXListener方法，当事件源发生某种类型的事件时，则触发事先已注册过的监听器中相应的处理程序。

2）一个对象注册对个监听器

    事件源可以产生多种不同类型的事件，因而可以注册（触发）多种不同类型的监听器。例如，程序中frame对象注册m1和m2两个监听器，即在一个框架中移动鼠标，或者拖动鼠标并画出痕迹，而且框架下方都显示鼠标的位置：

import java.awt.*;
import java.awt.event.*;

public class TestMultiListener {
	public static void main(String[] args) {
		Frame frame=new Frame("Test");
		TextField msg=new TextField(50);
		Monitor1 m1=new Monitor1(frame);
		Monitor2 m2=new Monitor2(frame, msg);
		frame.addWindowListener(m1);
		frame.addMouseMotionListener(m2);
		frame.add(msg, BorderLayout.SOUTH);
		frame.setSize(200,160);
		frame.setVisible(true);
	}
}
class Monitor1 implements WindowListener{
	private Frame frame;
	public Monitor1(Frame frame) {
		this.frame=frame;
	}
	public void windowClosing(WindowEvent e) {System.exit(0);}
	public void windowOpened(WindowEvent e) {}//windowListener有7个方法，即使不做任何事，也要书写
	public void windowIconified(WindowEvent e) {}
	public void windowDeiconified(WindowEvent e) {}
	public void windowClosed(WindowEvent e) {}
	public void windowActivated(WindowEvent e) {}
	public void windowDeactivated(WindowEvent e) {}
}
class Monitor2 implements MouseMotionListener{
	private Frame frame;
	private TextField msg;
	private boolean bDragged=false;
	public Monitor2(Frame frame,TextField msg) {
		this.frame=frame;
		this.msg=msg;
	}
	public void mouseMoved(MouseEvent e) {
		msg.setText("MouseMoved:"+e.getX()+","+e.getY());
		if(bDragged) {
			msg.setText("MouseMoved:"+e.getX()+","+e.getY());
			bDragged=false;
		}
	}
	public void mouseDragged(MouseEvent e){
		msg.setText("MouseDragged:"+e.getX()+","+e.getY());
		if(!bDragged) {
			frame.setCursor(new Cursor(Cursor.CROSSHAIR_CURSOR));//设置鼠标形态为十字星
			bDragged=true;
		}
		frame.getGraphics().drawLine(e.getX(), e.getY(), e.getX(), e.getY());
	}
}
           

3）多个对象注册到一个监听器

import java.awt.*;
import java.awt.event.*;

public class TestMultiObjectOneListener {
	public static void main(String[] args) {
		Frame frame=new Frame("Test");
		Button b1=new Button("start");
		TextField b2=new TextField("input text:");
		
		Monitor3 m=new Monitor3();
		b1.addActionListener(m);
		b2.addActionListener(m);
		frame.add(b1, "North");
		frame.add(b2,"Center");
		frame.pack();
		frame.setVisible(true);
	}
}
class Monitor3 implements ActionListener{
	public void actionPerformed(ActionEvent e) {
		System.out.println("a button\n"+e.getSource()
		+"\nhas been pressed.\n"+
				"command is: "+e.getActionCommand()
		);
	}
}
           

4. 事件适配器（Adapter）？

答：用实现接口的方法，必须实现接口所规定的的方法，如上面说的windowListener，为简化编程，为一些事件监听器接口定义了相应的实现类——事件适配器类，有七种：

ComponentAdapter，ContainerAdapter，FocusAdapter，KeyAdapter，MouseAdapter，MouseMotionAdapter 和 WindowAdapter。

在定义监听器时就可以继承Adapter类，并只重写所需要的方法。例如，将3.2例中Monitor1改为

class Monitor1 extends WindowAdapter{
	private Frame frame;
	public Monitor1(Frame frame) {
		this.frame=frame;
	}
	public void windowClosing(WindowEvent e) {
		System.exit(0);
	}
}
           

5. 内部类作为事件监听器？

答：例如，

import java.awt.*;
import java.awt.event.*;

public class TestInnerListener {
	Frame frame=new Frame("内部类测试");
	TextField textField=new TextField(30);
	public TestInnerListener() {
		frame.add(new Label("请按下鼠标左键并拖动"),"North");
		frame.add(textField,"South");
		frame.setBackground(new Color(200, 0, 0));//red,green,blue component
		frame.addMouseMotionListener(new InnerMonitor());
		frame.addMouseListener(new InnerMonitor());
		frame.setSize(300, 200);
		frame.setVisible(true);
	}
	public static void main(String[] args) {
		Object t=new TestInnerListener();
	}
	private class InnerMonitor implements MouseMotionListener,
	MouseListener{
		public void mouseDragged(MouseEvent e) {
			String string="鼠标拖动到位置("+e.getX()+","+e.getY()+")";
			textField.setText(string);
		}
		public void mouseEntered(MouseEvent e) {
			String string="鼠标已进入窗体";
			textField.setText(string);
		}
		public void mouseExited(MouseEvent e) {
			String string="鼠标已移出窗体";
			textField.setText(string);
		}
		public void mouseMoved(MouseEvent e) {};//java中一个类只能单继承，所以这里要用实现接口的方法
		public void mousePressed(MouseEvent e) {};
		public void mouseClicked(MouseEvent e) {};
		public void mouseReleased(MouseEvent e) {};
	}
}
           

结果：

6. 匿名类作为事件监听器？

答：例如，

import java.awt.*;
import java.awt.event.*;

public class TestAnonymous {
	Frame frame = new Frame("匿名内部类测试");
	TextField textField = new TextField(30);
	
	public TestAnonymous() {
		frame.add(new Label("请按下鼠标左键并拖动"),"North");
		frame.add(textField, "South");
		
		frame.addMouseMotionListener(new MouseMotionListener() {
			public void mouseMoved(MouseEvent e) {
				String string="鼠标拖动到位置("+e.getX()+","+e.getY()+")";
				textField.setText(string);
			}
			public void mouseDragged(MouseEvent e) {}
		});
		frame.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
		
		frame.setSize(300, 200);
		frame.setVisible(true);
	}
	
	public static void main(String[] args) {
		TestAnonymous t = new TestAnonymous();
	}
}