问答题

本程序的功能是用按钮来控制文本框中文本的颜色。窗口中有两个带有文字标题的“Sample text”和“Text color control”面板，窗ISl的底部还有一个“Disable changes”复选框。在“Sample text”面板中有一个带有字符串的文本框，而在“Text color control”面板中有“Black”、“Red”和“Green”三个按钮，并且每个按钮上都有一个对应颜色的圆。单击任意按钮，文本框中的文本变成对应的颜色，如果选中“Disable changes”复选框，则三个颜色按钮变为不可用，如果取消选中复选框，则三个按钮变为可用，如图所示。


import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class exam_11 extends JFrame {
private JPanel upper, middle, lower;
private JTextField text;
private JButton black, red, green;
private JCheckBox disable;
public exam_11( String titleText ) {
super( titleText );
addWindowListener( new WindowAdapter() {
public void
windowClosing( WindowEvent e ) {
System.exit(0);
}
}
);
upper=new JPanel();
upper.setBorder(BorderFactory.createTitledBorder("Sample text" ) );
upper.setlayout(_new_BorderLayout()__);
text=new JTextField( "Change the color of this text" );
upper.add( text, BorderLayout.CENTER );
middle=new JPanel();
middle.setBorder( BorderFactory.createTitledBorder("Text color
control" ) );
middle.setLayout( new FlowLayout( FlowLayout.CENTER ) );
black=new JButton( "Black",new ColorIcon( Color.black ) );
black.addActionListener( new ButtonListener( Color.black ) );
middle.add( black );
red=new JButton( "Red",new ColorIcon( Color.red ) );
red.addActionListener(new ButtonListener( Color.red ) );
middle.add( red );
green=new JButton( "Green",new ColorIcon( Color.green ) ;
green.addActionListener(new ButtonListener( Color.green );
middle.add( green );
lower=new JPanel();
lower.setLayout( new FlowLayout( FlowLayout.RIGHT ) );
disable=new JCheckBox( "Disable changes" );
disable.addItemListener( new ItemListener() {
public void itemStateChanged( ItemEvent e ) {
boolean enabled
=(e.getStateChange()
== ItemEvent. DESELECTED );
black.setEnabled( enabled );
red.setEnabled( enabled );
green.setEnabled( enabled );
}
}
);
lower.add( disable );
Container cp=getContentPane();
cp.add( upper, BorderLayout.NORTH );
cp.add( middle, BorderLayout.CENTER );
cp.add( lower, BorderLayout. SOUTH );
pack();
setVisible( true );
}
class ButtonListener extends ActionListener {
private Color c;
public ButtonListener( Color c ) {
this.c=c;
}
public void actionPerformed( ActionEvent e ) {
text.setForeground( c );
}
}
class ColorIcon implements Icon {
private Color c;
private static final int DIAMETER=10;
public ColorIcon( Color c ) {
c=c;
}
public void paintIcon( Component cp, Graphics g,
int x, int y ) {
g.setColor( c );
g.fillOval( x, y, DIAMETER, DIAMETER );
g.setColor( Color.black );
g.drawOval( x, y, DIAMETER, DIAMETER );
}
public int getIconHeight()
return DIAMETER;
}
public int getIconWidth()
return DIAMETER;
}
}
public static void main( String[] args ) {
new exam_11( "exam_11" );
}
}