FocusListener焦点监听器

【FocusListener焦点监听器】

public class Demo extends JFrame {
    public Demo(){
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setBounds(100,100,200,120);

        Container c=getContentPane();
        c.setLayout(new FlowLayout());
        JTextField sk1=new JTextField(); 
        JTextField sk2=new JTextField();
        JTextField sk3=new JTextField();
        sk1.setColumns(15); 
        sk2.setColumns(15); 
        sk3.setColumns(15); 
        c.add(sk1); 
        c.add(sk2); 
        c.add(sk3); 
        sk1.addFocusListener(new myFocusListenera() );//调用自定义焦点监听方法类 
        sk2.addFocusListener(new myFocusListener());
        sk3.addFocusListener(new myFocusListener());

         setVisible(true);
     }
//在myFocusListener 上 ，按Alt+Ins导入Java类快捷键 implements FocusListener
      class  myFocusListener implements FocusListener{//实现焦点监听 有光标点击为绿色，无光标点击为红色。
     @Override
        public void focusGained(FocusEvent e) {
          JTextField sk=(JTextField) e.getSource();//获取触发焦点事件的控件，强制转换为文本
           sk.setBorder(BorderFactory.createLineBorder(Color.green));
        }

        @Override
        public void focusLost(FocusEvent e) {
          JTextField sk=(JTextField) e.getSource();//获取焦点事件触发的控件。强制转换为文本
            sk.setBorder(BorderFactory.createLineBorder(Color.RED));
        }
    }
    public static void main(String[] args) {
        new Demo();
    }
}