我看过类似的问题但是这些例子和答案都太复杂了,我无法理解。
我正在研究项目,基本上需要能够从组合框菜单中选择项目,这样我就可以在JDBC中运行查询。我得到了JDBC部分的帮助。
问题:我很困惑天气使用ActionListener,ItemStateChanged或两者兼而有之!
还需要在上述方法中添加哪些代码。
谢谢你的帮助。
package userProfile;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
public class Database extends GUI implements ActionListener {
JFrame frame;
JButton search;
JComboBox fromLoc, toLoc, fromDate, fromTime;
JLabel fromLabel, toLabel, fromDateLabel, fromTimeLabel;
PreparedStatement ps = null;
Connection link;
ResultSet rs = null;
public Database() {
frame = new JFrame("Make a Reservation");
frame.getContentPane().setLayout(null);
//Arrival date/time comboBoxes and labels
fromDateLabel = new JLabel("Departure Date");
fromDateLabel.setBounds(50,230,100,30);
fromDate = new JComboBox(new String[]{"12/15/2015",
"12/21/2015", "12/21/2015", "12/24/2015"});
fromDate.addActionListener(this);
fromDate.setBounds(50,200,100,30);
fromTimeLabel = new JLabel("Departure Time");
fromTimeLabel.setBounds(160,230,100,30);
fromTime = new JComboBox(new String[]{"13:00",
"15:00", "15:30", "08:00"});
fromTime.addActionListener(this);
fromTime.setBounds(160,200,100,30);
//Departure label and comboBox
fromLabel = new JLabel("Departure");
fromLabel.setBounds(50,300,100,30);
fromLoc = new JComboBox(new String[]{"Atlanta",
"Charleston", "New York", "Los Angeles",
"Orlando", "San Francisco"});
fromLoc.addActionListener(this);
fromLoc.setBounds(50,270,100,30);
toLabel = new JLabel("Arrival");
toLabel.setBounds(160,300,100,30);
toLoc = new JComboBox(new String[]{"Atlanta",
"Charleston", "New York", "Los Angeles", "Orlando", "San Francisco"});
toLoc.addActionListener(this);
toLoc.setBounds(160,270,100,30);
search = new JButton("Ok");
search.addActionListener(this);
search.setBounds(270,270,100,30);
//adding the buttons in frame
frame.getContentPane().add(fromDateLabel);
frame.getContentPane().add(fromDate);
frame.getContentPane().add(fromTimeLabel);
frame.getContentPane().add(fromTime);
frame.getContentPane().add(fromLabel);
frame.getContentPane().add(fromLoc);
frame.getContentPane().add(toLabel);
frame.getContentPane().add(toLoc);
frame.getContentPane().add(search);
frame.setSize(400,400);
frame.setVisible(true);
StateChange state = new StateChange();
try {
// Driver for mysql
Class.forName("com.mysql.jdbc.Driver");
// connection link obj
link = DriverManager.getConnection("jdbc:mysql://localhost:3306/world", "root", "root");
// query statement obj
ps = link.prepareStatement("select * from flights where from_date = ? and from_loc = ? and to_loc = ?");
ps.setString(1, fromD);
ps.setString(2, fromL);
ps.setString(3, toL);
rs = ps.executeQuery();
while (rs.next()) {
}
} catch (SQLException sqle) {
System.out.println("An error occurred.Maybe user/password is invalid");
sqle.printStackTrace();
} catch (ClassNotFoundException cfne) {
cfne.printStackTrace();
}
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
private class StateChange implements ItemListener {
@Override
public void itemStateChanged(ItemEvent e) {
// TODO Auto-generated method stub
// if (e.getStateChange() == ItemEvent.SELECTED) {
// String toLoc = (String)e.getItem();
// System.out.println(s);
// here i just used strings to get content from comboBox
String fromL = fromLoc.getSelectedItem().toString();
String fromD = fromDate.getSelectedItem().toString();
String toL = toLoc.getSelectedItem().toString();
}
}
}
答案 0 :(得分:0)
你只需要覆盖actionPerformed()方法,这里是获取所选选项文本的方法
public void actionPerformed(ActionEvent e) {
JComboBox fromL = (JComboBox)e.getSource();
String fromL = (String) fromLoc.getSelectedItem();
// do whatever you want with the values
...
}
现在您可以从相应的组合框中选择文本,现在您可以使用这些文本。请参阅链接https://docs.oracle.com/javase/tutorial/uiswing/components/combobox.html中的处理组合框上的事件部分 如果你还有任何疑问。