我写了一个程序来计算每加仑输入的英里数。它也可以通过下拉菜单切换到公里。我正在努力做到这一点，以便当我选择下拉菜单时，每次切换时图片都可以切换。所以英里和公里的图片不同。它很愚蠢，但它是作业的要求之一。我该怎么做呢？这是我目前拥有的，我只想让图片在我拥有的两个之间切换。
import java.awt.Component;
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
import static javax.swing.GroupLayout.Alignment.*;
import net.miginfocom.swing.MigLayout;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
public class mpg_mig extends JFrame {
public mpg_mig() {
JLabel titleLabel = new JLabel("Fuel Calculator");
titleLabel.setFont(new Font("Serif", Font.BOLD, 18));
titleLabel.setForeground(Color.blue);
final JLabel distLabel = new JLabel("Miles:");
final JTextField distText = new JTextField(10);
JLabel traveledLabel = new JLabel("traveled");
final JLabel fuelLabel = new JLabel("Gas:");
final JTextField fuelText = new JTextField(10);
final JLabel mpgLabel = new JLabel("Miles per gallon:");
final JTextField mpgText = new JTextField(10);
JButton clearButton = new JButton("Clear");
JButton calcButton = new JButton("Calculate");
String[] actStrings = { "Miles", "kiloMeters" };
JComboBox jComboBox1 = new JComboBox(actStrings);
jComboBox1.setEditable(true);
String sFileName = "circuit1.png";
BufferedImage image = null;
try {
image = ImageIO.read(new File(sFileName));
} catch (IOException ex) {
System.out.println (ex.toString());
System.out.println(sFileName);
JOptionPane.showMessageDialog(null,ex.toString() + " " + sFileName);
System.exit(0);
}
JLabel labelPic1 = new JLabel(new ImageIcon(image));
setResizable( false );
JPanel p = new JPanel(new MigLayout("", "[] [] []",
"[] [] [] [] []"));
p.setBackground(Color.WHITE);
setContentPane(p);
p.add(labelPic1, "cell 0 0 1 3"); //(column 0, row 0, width 1, height 3)
p.add(clearButton, "cell 0 3"); //(column 0, row 3)
p.add(calcButton, "cell 0 4"); //(column 0, row 4)
p.add(titleLabel, "cell 1 0"); //(column 1, row 0)
p.add(distLabel, "cell 1 1"); //(column 1, row 1)
p.add(fuelLabel, "cell 1 2"); //(column 1, row 2)
p.add(mpgLabel, "cell 1 3"); //(column 1, row 3)
p.add(jComboBox1, "cell 1 4"); //(column 1, row 4)
p.add(distText, "cell 2 1"); //(column 2, row 1)
p.add(fuelText, "cell 2 2"); //(column 2, row 2)
p.add(mpgText, "cell 2 3"); //(column 2, row 3)
clearButton.addActionListener(new ActionListener()
{ public void actionPerformed(ActionEvent event)
{
distText.setText("");
fuelText.setText("");
mpgText.setText("");
}
});
calcButton.addActionListener(new ActionListener()
{ public void actionPerformed(ActionEvent event)
{
if(isNumeric(distText.getText()) &&
isNumeric(fuelText.getText()))
{
double fuel;
double dist;
double result;
fuel = Double.parseDouble(fuelText.getText());
dist = Double.parseDouble(distText.getText());
result = dist/fuel;
result = Round(result,2);
mpgText.setText(String.format("%f", result));
}
else
{
JOptionPane.showMessageDialog(null, "Enter distance traveled and fuel used");
}
}
});
jComboBox1.addActionListener(new ActionListener()
{ public void actionPerformed(ActionEvent event)
{
//JComboBox jComboBox1 = (JComboBox)event.getSource();
JComboBox jComboBox1 = (JComboBox)event.getSource();
if(jComboBox1.getSelectedItem() == "Miles")
{
distLabel.setText("Miles");
mpgLabel.setText("Miles per gallon:");
}
else
{
distLabel.setText("KiloMeters");
mpgLabel.setText("KM per liter:");
}
}
});
setTitle("MPG and KML");
pack(); //pack disables setting frames size...
setLocationRelativeTo(null);//center frame and showMessageDialog
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
}
private static boolean isNumeric(String text)
{ try
{ Double.parseDouble(text); }
catch (Exception e)
{ return false; }
return true;
}
public double Round(double val, int plc)
{
double pwr = Math.pow(10,plc);
val = val * pwr; //shift to the left
double tmp = (int) val;
if( ((int)(val + .5)) == (int) val)
return (tmp/pwr); //don't round up
else
return((tmp + 1.0)/pwr); //round up
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
try {
UIManager.setLookAndFeel(
UIManager.getCrossPlatformLookAndFeelClassName());
} catch (Exception ex) {
ex.printStackTrace();
}
new mpg_mig().setVisible(true);
}
});
}
}
