Java语言程序设计(郑莉)第九章课后习题答案

jTextField = new JTextField(\输入\); // 窗体加入各组件 this.add(label1); this.add(jTextField); this.add(label2); this.add(label3); this.add(buttonOfSure); this.add(buttonOfExit); // 显示窗体

this.setVisible(true);

System.out.println(numberOfRandom);// 偷偷看看随机数，哈哈 }

// 事件处理

public void eventHandle() {

//捕获非整型输入异常 try {

numberOfUser = Integer.parseInt(jTextField.getText());//获得

用户输入数 if (numberOfUser < 1 || numberOfUser > 100) {

JOptionPane.showMessageDialog(this, \请输入1到100之间的整

数\);

}

} else { }

JOptionPane.showMessageDialog(this, \请输入整数\, \输入错误\, JOptionPane.WARNING_MESSAGE); jTextField.requestFocus();

if (numberOfUser > numberOfRandom) {

label3.setText(\偏大\);

jTextField.requestFocus();//清空文本框并使重新获得焦点

}

if (numberOfUser < numberOfRandom) { }

if (numberOfUser == numberOfRandom) { }

label3.setText(\恭喜你，答对了。\); jTextField.requestFocus(); label3.setText(\偏小\);

jTextField.requestFocus();

} catch (NumberFormatException e) {

}

public static void main(String[] args) { }

new GuessNumber().init(); }

//按钮触发选择

public void actionPerformed(ActionEvent e) {

if (e.getActionCommand() == \确定\) { this.eventHandle(); }

if (e.getActionCommand() == \退出\) { System.exit(0); } }

运行结果：

7.练习使用JscrollPane。使用BorderLayout将JFrame布局分为左右两块；左边又使用

GridLayout，包含三个按钮，右边在JLabel里显示一幅图画，按钮控制JLabel是否显示滚动条。 //test9_7

import java.awt.BorderLayout; import java.awt.Button; import java.awt.Container; import java.awt.GridLayout;

import java.awt.event.ActionEvent; import java.awt.event.ActionListener;

import javax.swing.ImageIcon; import javax.swing.JFrame;

import javax.swing.JLabel; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JScrollPane;

import javax.swing.ScrollPaneConstants;

public class test9_7 extends JFrame implements ActionListener {

// 将左右两边的中间容器放弃JFrame中

// 读取图片作为图标

picture = new ImageIcon(\); // 将图标赋给标签label

label = new JLabel(picture);

// 定义滚动框,总是显示滚动条

jscrollPane = new JScrollPane(label,

ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);

// 定义左边镶板JPanel框和三个按钮

jPanel = new JPanel(new GridLayout(3, 1, 0, 30)); button1 = new Button(\滚动\);

button1.addActionListener(this); button2 = new Button(\试试\);

button2.addActionListener(this); button3 = new Button(\退出\);

button3.addActionListener(this); jPanel.add(button1); jPanel.add(button2); jPanel.add(button3);

private JPanel jPanel;//左边panel框 private Button button1; private Button button2; private Button button3;

private JScrollPane jscrollPane;//右边滚动框 private JLabel label;//滚动框中的标签

public ImageIcon picture = null;//标签中的图标

public boolean whetherCroll = true;//用于切换滚动条的显示 public void init() {

JFrame jFrame = new JFrame(\练习使用JscrollPane\); Container pane = jFrame.getContentPane();

this.setDefaultCloseOperation((JFrame.EXIT_ON_CLOSE));

}

pane.add(jPanel, BorderLayout.WEST); pane.add(jscrollPane, BorderLayout.EAST); //排版显示

jFrame.pack();

jFrame.setVisible(true);

@Override

public void actionPerformed(ActionEvent e) {

// TODO Auto-generated method stub if (e.getActionCommand() == \滚动\) { if (whetherCroll) {

jscrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROL

LBAR_NEVER);//垂直不显示

jscrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);//水平不显示 whetherCroll = false;

} else {

jscrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROL

LBAR_ALWAYS);//垂直显示

jscrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);//水平显示 whetherCroll = true;

public static void main(String[] args) { }

new test9_7().init(); }

}

if (e.getActionCommand() == \试试\) { JOptionPane.showMessageDialog(this, }

if (e.getActionCommand() == \退出\) { System.exit(0); }

\);

}

}

运行结果： 显示滚动条

点击“滚动”按钮后，没显示滚动条

8.练习使用JList。建立两个JList，双击其中任何一个中的某一项，此项就会跑到另外一个JList