Java 界面-焦点事件类

[ 相关信息]
焦点事件类(FocusEvent)是指用户程序界面的组件失去焦点(即焦点从一个对象转移到另外一个对象)时，就会发生焦点事件。
使用焦点事件必须给组件增加一个 FocusListener 接口的事件处理器,该接口包含以下两个方法：
1）void focusGained(FocusEvent e)：当获得焦点时发生。
2）void focusLost(FocusEvent e)：当失去焦点时发生。

[具体程序实现]

package sup.orange.learn;



import java.awt.*;

import java.awt.event.*;



/**

 * Created by re-x on 10/28/14.

 */

public class FocusEventDemo extends Frame{

    TextArea textarea;

    TextField textfield;



    public FocusEventDemo () {

        super();

        init();

    }



    public static void main(String[] args) {

        new FocusEventDemo();

    }



    public void init() {

        setLayout(new GridLayout(2, 1));

        textarea = new TextArea();

        textarea.addFocusListener(new FocusListener() {

            @Override

            public void focusGained(FocusEvent e) {

                textarea.setText("gained");

            }



            @Override

            public void focusLost(FocusEvent e) {

                textarea.setText("lost");

            }

        });



        textfield = new TextField();

        textfield.addFocusListener(new FocusListener() {

            @Override

            public void focusGained(FocusEvent e) {

                textfield.setText("textfield gained");

            }



            @Override

            public void focusLost(FocusEvent e) {

                textfield.setText("textfield lost");

            }

        });



        add(textarea);

        add(textfield);

        addWindowListener(new WindowAdapter() {

            @Override

            public void windowClosing(WindowEvent e) {

                super.windowClosing(e);

                dispose();

                System.exit(0);

            }

        });

        setSize(200, 500);

        setVisible(true);

    }

}