事件处理【总结】

素颜马尾好姑娘i 2022-05-31 13:09 263阅读 0赞

**1. 事件类之间的继承关系？**

答：

![20180225222206579][]

**2. 各个事件及其相关方法？**

答：

![20180225225940354][]

**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。

![20180227141848559][]

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());
    	}
    }

![20180227153845759][] ![20180227153903721][]

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()
    		);
    	}
    }

![20180227160018509][]

**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：

![20180228144631344][]

**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();
    	}
    }

[20180225222206579]: /images/20220531/dd0b3ddabb8941199097bd5479617c71.png
[20180225225940354]: /images/20220531/82ac9cd05d164b68bd03faa42e49a1aa.png
[20180227141848559]: /images/20220531/f30bb3c3c21648d8a2d3ccc28a0cafb2.png
[20180227153845759]: https://img-blog.csdn.net/20180227153845759
[20180227153903721]: /images/20220531/83abc88beca24bb8b22af2cf56d1478c.png
[20180227160018509]: /images/20220531/8d71f55fc3134f88a90774598efd6996.png
[20180228144631344]: /images/20220531/59a8790bde8547ada2fbc4e9685136d6.png