I'm doing a small program with Java GUI here is mu code:
// DebugFourteen3
// User selects pizza topping and sees price
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
//use correct spelling of class name
public class DebugFourteen3 extends JFrame
{
FlowLayout flow = new FlowLayout();
JComboBox pizzaBox = new JComboBox();
JLabel toppingList = new JLabel("Topping List");
JLabel aLabel = new JLabel("Paulos's American Pie");
JTextField totPrice = new JTextField(10);
int[] pizzaPrice = {7,10,10,8,8,8,8};
int totalPrice = 0;
String output;
int pizzaNum;
public DebugFourteen3()
{
super("Pizza List");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(flow);
add(toppingList);
pizzaBox.addItem("cheese");
pizzaBox.addItem("sausage");
pizzaBox.addItem("pepperoni");
pizzaBox.addItem("onion");
pizzaBox.addItem("green pepper");
pizzaBox.addItem("green olive");
pizzaBox.addItem("black olive");
add(pizzaBox);
add(aLabel);
add(totPrice);
itemStateChanged(this);
}
public static void main(String[] arguments)
{
JFrame frame = new DebugFourteen3();
frame.setSize(200, 150);
frame.setVisible(true);
}
public void itemStateChanged(ItemEvent[] list)
{
Object source = list.getSource();
if(source == pizzaBox)
{
int pizzaNum = pizzaBox.getSelectedIndex();
totalPrice = pizzaPrice[pizzaNum];
output = "Pizza Price $" + totalPrice;
totPrice.setText(output);
}
}
}
the compiler gets me error on line 35, it says itemStateChanged() should receive a argument which type is ItemEvent[] but I'm passing "this"(the class it self)
can anyone explain how the itemStateChanged works with the JComboBox? thanks
You have to add the listener on the combo box instead of calling the itemStateChanged
method directly. Adding the listener will enable the callbacks when the click event happens, and jvm will call the itemStateChanged
method automatically as combo box is registered for the event. Replace this line
itemStateChanged(this);
with
pizzaBox.addItemListener(this);
At first, you need to implements ItemListener
with JFrame
. Than add following line with pizzaBox
, this will notify overrided public void itemStateChanged(ItemEvent ev)
method ItemListener
.
pizzaBox.addItemListener(this);
For details, see this tutorial .
Problem :
1.you are not registering itemListener
for JComboBox
2. itemStateChanged
event takes ItemEvent
as argument not ItemEvent[]
array
1.Replace this :
itemStateChanged(this);
with this:
pizzaBox.addItemListener(this);
2.Replace This:
public void itemStateChanged(ItemEvent[] list)
With this:
public void itemStateChanged(ItemEvent list)
Complete Code:
// DebugFourteen3
// User selects pizza topping and sees price
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
//use correct spelling of class name
public class DebugFourteen3 extends JFrame
{
FlowLayout flow = new FlowLayout();
JComboBox pizzaBox = new JComboBox();
JLabel toppingList = new JLabel("Topping List");
JLabel aLabel = new JLabel("Paulos's American Pie");
JTextField totPrice = new JTextField(10);
int[] pizzaPrice = {7,10,10,8,8,8,8};
int totalPrice = 0;
String output;
int pizzaNum;
public DebugFourteen3()
{
super("Pizza List");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(flow);
add(toppingList);
pizzaBox.addItem("cheese");
pizzaBox.addItem("sausage");
pizzaBox.addItem("pepperoni");
pizzaBox.addItem("onion");
pizzaBox.addItem("green pepper");
pizzaBox.addItem("green olive");
pizzaBox.addItem("black olive");
add(pizzaBox);
add(aLabel);
add(totPrice);
pizzaBox.addItemListener(this);
}
public static void main(String[] arguments)
{
JFrame frame = new DebugFourteen3();
frame.setSize(200, 150);
frame.setVisible(true);
}
public void itemStateChanged(ItemEvent list)
{
Object source = list.getSource();
if(source == pizzaBox)
{
int pizzaNum = pizzaBox.getSelectedIndex();
totalPrice = pizzaPrice[pizzaNum];
output = "Pizza Price $" + totalPrice;
totPrice.setText(output);
}
}
}
Here this
ie DebugFourteen3
is not a type ItemEvent
. Thats why
itemStateChanged(ItemEvent[] list)
gives error.
If you want to handle itemStateChanged
then you need to implement ItemLisntener
and add actionListner
to it as
pizzaBox.addItemListener(this);
also add Handler method of ItemLisntener
as
public void itemStateChanged(....)
{
//Handling Code goes here
}
Or you can implement ActionListner
also For more information on how to use combobox you can visit here
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.