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标题:Swing FocusAdapter类

FocusAdapter类是一个抽象(适配器)类,用于接收键盘焦点事件。此类的所有方法都是空的,此类是用于创建侦听器对象的便捷类。

类声明

以下是java.awt.event.FocusAdapter类的声明 -

public abstract class FocusAdapter
   extends Object
      implements FocusListener

类构造函数

编号 构造函数 描述
1 FocusAdapter() 无参数构造函数

类方法

编号 类方法 描述
1 void focusGained(FocusEvent e) 当组件获得键盘焦点时调用。

方法继承

该类继承以下类中的方法 -

  • java.lang.Object

FocusAdapter示例

使用编辑器创建以下Java程序:FocusAdapterExample.java

package com.yiibai.swing.listener;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class FocusAdapterExample {
    private JFrame mainFrame;
    private JLabel headerLabel;
    private JLabel statusLabel;
    private JPanel controlPanel;

    public FocusAdapterExample() {
        prepareGUI();
    }

    public static void main(String[] args) {
        FocusAdapterExample swingAdapterDemo = new FocusAdapterExample();
        swingAdapterDemo.showFocusAdapterDemo();
    }

    private void prepareGUI() {
        mainFrame = new JFrame("Java SWING FocusAdapter示例(yiibai.com)");
        mainFrame.setSize(400, 400);
        mainFrame.setLayout(new GridLayout(3, 1));

        headerLabel = new JLabel("", JLabel.CENTER);
        statusLabel = new JLabel("", JLabel.CENTER);
        statusLabel.setSize(350, 100);

        mainFrame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent windowEvent) {
                System.exit(0);
            }
        });
        controlPanel = new JPanel();
        controlPanel.setLayout(new FlowLayout());

        mainFrame.add(headerLabel);
        mainFrame.add(controlPanel);
        mainFrame.add(statusLabel);
        mainFrame.setVisible(true);
    }

    private void showFocusAdapterDemo() {
        headerLabel.setText("Listener in action: FocusAdapter");
        JButton okButton = new JButton("确定");
        JButton cancelButton = new JButton("取消");

        okButton.addFocusListener(new FocusAdapter() {
            public void focusGained(FocusEvent e) {
                statusLabel.setText(
                        statusLabel.getText() + e.getComponent().getClass().getSimpleName() + " gained focus. ");
            }
        });
        cancelButton.addFocusListener(new FocusAdapter() {
            public void focusLost(FocusEvent e) {
                statusLabel
                        .setText(statusLabel.getText() + e.getComponent().getClass().getSimpleName() + " lost focus. ");
            }
        });
        controlPanel.add(okButton);
        controlPanel.add(cancelButton);
        mainFrame.setVisible(true);
    }
}

执行上面示例代码,得到以下结果:


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