我正在做一个GUI程序,但得到一个奇怪的错误
问题描述:
我为我的作业做了这个程序,我必须添加一个GUI选择到另一个。我正在做一个GUI程序,但得到一个奇怪的错误
这两个选择的总和没有出现在每学期总费用按钮中。
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
/**
The Main class creates the GUI for the Dorm and
Meal charges.
*/
public class Main extends JFrame
{
private JPanel dormPanel;
private JComboBox dormBox;
private JPanel mealPanel;
private JComboBox mealBox;
private JPanel totalChargesPanel;
private JPanel selectedMealPanel;
private JPanel buttonPanel;
private JButton calcButton;
private JLabel label1;
private JTextField totalCharges;
private String[] dorm = { "Allen Hall: $1,500 per semester",
"Pike Hall: $1,600 per semester",
"Farthing Hall: $1,200 per semester",
"University Suites: $1,800 pe r semester"};
private String[] meal = { "7 meals per week: $650 per semester",
"14 meals per week: $1,095 per semester",
"Unlimited meals: $1,500 per semester"};
/**
Constructor
*/
public Main()
{
super("Dormitory and Meal Plan");
// Specify an action for the close button.
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create a BorderLayout manager.
setLayout(new BorderLayout());
// Create the dorm and meal panel.
buildDormPanel();
buildMealPanel();
buildSelectedTotalChargesPanel();
buildButtonPanel();
// Add the components to the content pane.
add(dormPanel, BorderLayout.WEST);
add(mealPanel, BorderLayout.EAST);
add(totalChargesPanel, BorderLayout.SOUTH);
add(buttonPanel, BorderLayout.NORTH);
// Pack the contents of the window and display it.
pack();
setVisible(true);
}
// The buildDormPanel method builds the dorm panel.
private void buildDormPanel()
{
// Create the dorm panel.
dormPanel = new JPanel();
dormBox = new JComboBox(dorm);
// Register the action listener.
dormBox.addActionListener(new ComboBoxListener());
// Add the dorm panel to the panel.
dormPanel.add(dormBox);
}
// The buildMealPanel method builds the meal panel.
private void buildMealPanel()
{
// Create the meal panel.
mealPanel = new JPanel();
mealBox = new JComboBox(meal);
// Register the action listener.
mealBox.addActionListener(new ComboBoxListener());
// Add the meal panel to the panel.
mealPanel.add(mealBox);
}
// The buttonPanel method builds the bottun panel.
private void buildButtonPanel()
{
// Create a panel.
buttonPanel = new JPanel();
// Create a button.
calcButton = new JButton("Calculate");
// Register an action listener with the button.
calcButton.addActionListener(new ButtonListener());
// Add the button to the panel.
buttonPanel.add(calcButton);
}
// The buildSelectedDormPanel builds the selected totalCharges panel.
private void buildSelectedTotalChargesPanel()
{
// Create the totalChargesPanel for the label.
totalChargesPanel = new JPanel();
label1 = new JLabel("Total charges per semester: ");
// Create the totalCharges textfield.
totalCharges = new JTextField (25);
totalCharges.setEditable(false);
// Add the totalChargesPanel to the panel.
totalChargesPanel.add(label1);
totalChargesPanel.add(totalCharges);
}
/** Private inner class that handles the event when the user
selects the dorm and meal boxes.
*/
private class ComboBoxListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
// Variables to hold the dorm, meal, and total charges.
String dorm = (String) dormBox.getSelectedItem();
String meal = (String) mealBox.getSelectedItem();
// Calculates the total.
totalCharges.setText(meal + dorm);
}
}
private class ButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
// Add code below
}
}
public static void main(String[] args)
{
new Main();
}
}
答
在你的动作监听我发现下面的代码:
// Variables to hold the dorm, meal, and total charges.
String dorm = (String) dormBox.getSelectedItem();
String meal = (String) mealBox.getSelectedItem();
// Calculates the total.
totalCharges.setText(meal + dorm);
您阅读每个组合框的字符串,然后尝试计算总。不幸的是,术语meal+dorm
并不意味着添加如果应用于字符串,但字符串连接。
要解决此问题,您可以选择一个适当的数据结构,以保存组合框中每个条目的显示文本+值,然后计算actionlistener中的所有值的总数,然后再将此总数转换为文本格式。
你是否从组合框中选择了任何东西? – 2011-02-10 17:40:17