Message dialogs provide information to the user. Message dialogs are created with the JOptionPane.showMessageDialog() method.
We call the static showMessageDialog() method of the JOptionPane class to create a message dialog. We provide the dialog’s parent, message text, title, and message type. The message type is one of the following constants :
- ERROR_MESSAGE
- WARNING_MESSAGE
- QUESTION_MESSAGE
- INFORMATION_MESSAGE
Methods Used :
- setLayout(…): method helps us to set the layout of the container, often a JPanel, to say FlowLayout, BorderLayout, GridLayout, null layout, or whatever layout we want to add on container.
- setBounds(…): method is used to set the location and size of components like JButton, and is only useful if null layout is used in JFrame.
- setVisible(…): method is used to set the Visibility status of JFrame.
- setVisible(true) will set JFrame visible to user.
- setVisible(false) will set JFrame not visible to user.
- getSource(): An event object contains a reference to the component that generated the event. To extract that reference from the event object we use getSource() Method.
- add(): It is used to add components like JButton etc, to the container of JFrame.
Below is the implementation of above discussed method to show Message Dialogs :
Tóm Tắt
Java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Demo extends JFrame implements ActionListener
{
JButton b1;
Demo()
{
this.setLayout(null);
b1 = new JButton("Button 1");
b1.setBounds(130, 05, 100, 50);
this.add(b1);
b1.addActionListener(this);
}
public void actionPerformed(ActionEvent evt)
{
if (evt.getSource() == b1)
{
JOptionPane.showMessageDialog(this, "Enter a valid Number",
"ERROR", JOptionPane.ERROR_MESSAGE);
}
}
}
class MessageDialogs1 {
public static void main(String args[])
{
Demo f = new Demo();
f.setBounds(200, 200, 400, 300);
f.setResizable(false);
f.setVisible(true);
}
}
Output :
Java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Demo extends JFrame implements ActionListener
{
JButton b1;
Demo()
{
this.setLayout(null);
b1 = new JButton("Button 2");
b1.setBounds(130, 05, 100, 50);
this.add(b1);
b1.addActionListener(this);
}
public void actionPerformed(ActionEvent evt)
{
if (evt.getSource() == b1) {
JOptionPane.showMessageDialog(this, "Enter a valid String",
"WARNING", JOptionPane.WARNING_MESSAGE);
}
}
}
class MessageDialogs2 {
public static void main(String args[])
{
Demo f = new Demo();
f.setBounds(200, 200, 400, 300);
f.setResizable(false);
f.setVisible(true);
}
}
Output :
Java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Demo extends JFrame implements ActionListener
{
JButton b1;
Demo()
{
this.setLayout(null);
b1 = new JButton("Button 3");
b1.setBounds(130, 05, 100, 50);
this.add(b1);
b1.addActionListener(this);
}
public void actionPerformed(ActionEvent evt)
{
if (evt.getSource() == b1)
{
JOptionPane.showMessageDialog(this, "Do you want to quit",
"Question", JOptionPane.QUESTION_MESSAGE);
}
}
}
class MessageDialogs3 {
public static void main(String args[])
{
Demo f = new Demo();
f.setBounds(200, 200, 400, 300);
f.setResizable(false);
f.setVisible(true);
}
}
Output :
Java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Demo extends JFrame implements ActionListener
{
JButton b1;
Demo()
{
this.setLayout(null);
b1 = new JButton("Button 4");
b1.setBounds(130, 05, 100, 50);
this.add(b1);
b1.addActionListener(this);
}
public void actionPerformed(ActionEvent evt)
{
if (evt.getSource() == b1)
{
JOptionPane.showMessageDialog(this, "You Pressed Button FOUR",
"INFORMATION",
JOptionPane.INFORMATION_MESSAGE);
}
}
}
class MessageDialogs4 {
public static void main(String args[])
{
Demo f = new Demo();
f.setBounds(200, 200, 400, 300);
f.setResizable(false);
f.setVisible(true);
}
}
Output :
My Personal Notes
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