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  • 焦点监听事件FocusListener

    public class Demo extends JFrame {
        public Demo() {
            setBounds(100, 100, 200, 120);
            setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            Container c = getContentPane();
            c.setLayout(new FlowLayout());
            JTextField tf1 = new JTextField();
            JTextField tf2 = new JTextField();
            JTextField tf3 = new JTextField();
            tf1.setColumns(15);
            tf2.setColumns(15);
            tf3.setColumns(15);
            c.add(tf1);
            c.add(tf2);
            c.add(tf3);
            tf1.addFocusListener(new MyFocusListener());//调用自定义焦点监听方法类
            tf2.addFocusListener(new MyFocusListener());
            tf3.addFocusListener(new MyFocusListener());
            setVisible(true);
        }
    
        //在MyFocusListener上,Alt+Ins,Implement Methods,快速创建方法。有光标为绿,无为红
        class MyFocusListener implements FocusListener {//自定义类,实现焦点监听(一种接口)
    
            public void focusGained(FocusEvent e) {
                JTextField tf = (JTextField) e.getSource();//获取触发焦点事件的控件,强制转换为文本框
                tf.setBorder(BorderFactory.createLineBorder(Color.GREEN));//绿色边框
            }
    
            public void focusLost(FocusEvent e) {
                JTextField tf = (JTextField) e.getSource();//获取触发焦点事件的控件,强制转换为文本框
                tf.setBorder(BorderFactory.createLineBorder(Color.RED));//红色边框
            }
        }
    
        public static void main(String[] args) {
            new Demo();
        }
    }
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  • 原文地址:https://www.cnblogs.com/xixixing/p/9460470.html
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