FocusListener焦點監聽器

【FocusListener焦點監聽器】

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() );//調用自定義焦點監聽方法類 
        sk2.addFocusListener(new myFocusListener());
        sk3.addFocusListener(new myFocusListener());

 setVisible(true); } //在myFocusListener 上 ，按Alt+Ins導入Java類快捷鍵 implements FocusListener
      class  myFocusListener implements FocusListener{//實現焦點監聽 有光標點擊為綠色，無光標點擊為紅色。
 @Override public void focusGained(FocusEvent e) { JTextField sk=(JTextField) e.getSource();//獲取觸發焦點事件的控件，強制轉換為文本
 sk.setBorder(BorderFactory.createLineBorder(Color.green)); } @Override public void focusLost(FocusEvent e) { JTextField sk=(JTextField) e.getSource();//獲取焦點事件觸發的控件。強制轉換為文本
 sk.setBorder(BorderFactory.createLineBorder(Color.RED)); } } public static void main(String[] args) { new Demo(); } }