Java 监听器

监听器监听器的功能是检测到使用者做出的特定的行为从而做出回应实现交互。监听器功能的实现有三个步骤1.确定事件源明确触发交互的组件如登录按钮Button作为监听的目标对象。2.设置监听器根据功能需求选择合适的监听器方法如针对按钮点击动作一般选用动作监听器方法。3.绑定事件处理类创建实现接口的类如ButtonListener重写其中的抽象方法actionPerformed并将该类的对象绑定到监听器方法上。注意接口不能直接创建对象因为调用无方法体的抽象方法无意义必须通过实现类Implements来创建对象。接口接口中定义的方法默认为抽象方法,无意义且需由实现类(implement)重写接口中所有方法。例public class Draw {public void initUI() {JFrame jf new JFrame();jf.setSize(800, 800);jf.setTitle(“画图工具”);jf.setLocationRelativeTo(null);jf.setDefaultCloseOperation(3);JPanel northpanel new JPanel(); northpanel.setBackground(Color.BLACK); northpanel.setPreferredSize(new Dimension(0, 60)); jf.add(northpanel, BorderLayout.NORTH); DrawListener listener new DrawListener(); MPanel drawpanel new MPanel(); drawpanel.setBackground(Color.WHITE); jf.add(drawpanel, BorderLayout.CENTER); drawpanel.addMouseListener(listener);//public class DrawListener implements MouseListener, ActionListener,MouseMotionListener {public void actionPerformed(ActionEvent e) {}public void mouseClicked(MouseEvent e){}public void mousePressed(MouseEvent e){}public void mouseReleased(MouseEvent e){}public void mouseEntered(MouseEvent e){}public void mouseExited(MouseEvent e){}}