After understanding the use of various basic components and the handling of common events, this case will synthesize the text box. Button and Drop-down list Component to implement a constellation selector program. The program allows the user to be in the ____________ Drop-down list Choose one of your own constellations, if not in the list can also add constellations, you can also delete constellations. The implementation process is as follows.
(1) create a SampeDemo class and call its construction method in the main() method. The code is as follows:
package my;
public class SampeDemo
{
public static void main(String[] args)
{
// TODO Auto-generated method stub
new SampeDemo();//Call the constructor
}
}
(2) Create a SampeDemo construction method to complete the creation of windows, add buttons and drop-down lists, and listen for the corresponding events. The code is as follows:
private JPanel panel=new JPanel();
private JComboBox cmb=new JComboBox();//Create JComboBox
private JLabel label1=new JLabel("Add new constellations");
private JLabel showInfo=new JLabel();//Used for displaying information
private JTextField jtf=new JTextField(16);//Used for input information
private JButton buttonADD=new JButton();//Newly added
private JButton buttonDel=new JButton();//delete
public SampeDemo()
{
JFrame frame=new JFrame("Choose your constellation");
cmb.addItem("--Please choose--");
cmb.addItem("Taurus");
cmb.addItem("Gemini");
cmb.addItem("Aries");
panel.add(cmb);
panel.add(label1);
panel.add(jtf);
panel.add(buttonADD);
panel.add(buttonDel);
frame.add(panel);
cmb.addItemListener(new MyItemListener());//Dropdown List Events
frame.setBounds(300,200,600,200);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}The drop-down list created by the above program is cmb, and two options are added to it by calling its addItem() method. The program listens for selected events when selecting items in the drop-down list.
(3) Create MyItemListener class and implement the ItemListener interface to process the selected events. At this time, the selected items are displayed in the text box. The implementation code is as follows:
//Monitor selected events
class MyItemListener implements ItemListener
{
@Override
public void itemStateChanged(ItemEvent e)
{
// TODO Auto-generated method stub
String str=e.getItem().toString();
panel.add(showInfo);
showInfo.setText("The constellation you choose is:"+str);
}
}(4) To monitor the event processing of adding and deleting buttons, the code is as follows:
// Listen for add and delete button events
buttonADD.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent e)
{
String command=e.getActionCommand();
//Add button processing
if(command.equals("Newly added"))
{
if(jtf.getText().length()!=0)
{
cmb.addItem(jtf.getText()); //Add item
panel.add(showInfo);
showInfo.setText("Successful additions, new additions:"+jtf.getText());
}
else
{
panel.add(showInfo);
showInfo.setText("Please enter the constellation you want to add.");
}
}
}
});
//Delete button processing
buttonDel.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent e)
{
// TODO Auto-generated method stub
String command=e.getActionCommand();
if(command.equals("delete"))
{
if(cmb.getSelectedIndex()!=-1)
{
//Get the value of the item to be deleted first
String strDel=cmb.getSelectedItem().toString();
cmb.removeItem(strDel); //Delete item
panel.add(showInfo);
showInfo.setText("Delete successfully, delete:"+strDel);
}
else
{
panel.add(showInfo);
showInfo.setText("Please select the constellation to delete");
}
}
}
}); The overall code is implemented as follows:
package my;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import com.sun.java.swing.plaf.motif.MotifButtonListener;
public class SampeDemo
{
private JPanel panel=new JPanel();
private JComboBox cmb=new JComboBox();//Create JComboBox
private JLabel label1=new JLabel("Add new constellations");
private JLabel showInfo=new JLabel();//Used for displaying information
private JTextField jtf=new JTextField(16);//Used for input information
private JButton buttonADD=new JButton("Newly added");//Newly added
private JButton buttonDel=new JButton("delete");//delete
public SampeDemo()
{
JFrame frame=new JFrame("Choose your constellation");
cmb.addItem("--Please choose--");
cmb.addItem("Taurus");
cmb.addItem("Gemini");
cmb.addItem("Aries");
panel.add(cmb);
panel.add(label1);
panel.add(jtf);
panel.add(buttonADD);
panel.add(buttonDel);
frame.add(panel);
cmb.addItemListener(new MyItemListener());//Dropdown List Events
frame.setBounds(300,200,600,200);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Monitor selected events
class MyItemListener implements ItemListener
{
@Override
public void itemStateChanged(ItemEvent e)
{
// TODO Auto-generated method stub
String str=e.getItem().toString();
panel.add(showInfo);
showInfo.setText("The constellation you choose is:"+str);
}
}
// Listen for add and delete button events
buttonADD.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent e)
{
String command=e.getActionCommand();
//Add button processing
if(command.equals("Newly added"))
{
if(jtf.getText().length()!=0)
{
cmb.addItem(jtf.getText()); //Add item
panel.add(showInfo);
showInfo.setText("Successful additions, new additions:"+jtf.getText());
}
else
{
panel.add(showInfo);
showInfo.setText("Please enter the constellation you want to add.");
}
}
}
});
//Delete button processing
buttonDel.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent e)
{
// TODO Auto-generated method stub
String command=e.getActionCommand();
if(command.equals("delete"))
{
if(cmb.getSelectedIndex()!=-1)
{
//Get the value of the item to be deleted first
String strDel=cmb.getSelectedItem().toString();
cmb.removeItem(strDel); //Delete item
panel.add(showInfo);
showInfo.setText("Delete successfully, delete:"+strDel);
}
else
{
panel.add(showInfo);
showInfo.setText("Please select the constellation to delete");
}
}
}
});
}
public static void main(String[] args)
{
// TODO Auto-generated method stub
new SampeDemo();//Call the constructor
}
}
The operation procedure is as follows:
