Java GUI Programming – Tour III (Q and A)JOptionPane : Built-In Dialog of JAVA
JOptionPane allows to create pop-up window or dialog with predefined style.
It provides following types of Dialogs which can be used as per requirement.
① Dialog Type: MessageDialog
Method used: showMessageDialog();
It is used to inform user by displaying a message. It includes OK button only.
② Input Dialog
Method: showInputDialog();
Used to get user input using Text Field.
③ Confirm Dialog
Method: showConfirmDialog();
Used to ask a user to confirm some information with Yes/No or OK/Cancel buttons.
Q: Name the library or package to include in order to use JOptionPane.
Answer: To use the JoptionPane dialog control in the application, we must import the following class(s).
import.javax.swing.JOptionPane;
Q: What is the syntax of JOptionPane.showXXX methods? Also provide examples of each.
Answer:
In general, the following syntax of methods along with optional parameters can be used:
JoptionPane.show......([Frame name],<“Message”> [,<“Title”>] );
Frame Name: Generally null is used to indicate current frame.
Message: User given string to covey the message.
Title: Text to be displayed as Title on the Title bar.
Examples are:
JOptinPane.showMessageDialog(null,”JAVA Welcomes You”);
JOptinPane.showMessageDialog (null,”My Name is “+name);
String n= JOptinPane.showInputDialog (null,”Enter your Name ?”);
String n = JOptinPane.showInputDialog (null,”Enter your Name ?”, “Input Name”);
int ch=JOptinPane.showConfirmDialog(null,”Want to exit ?”);
int ch=JOptinPane.showConfirmDialog(null,”Want to exit ?”,”Confirm ?”);
Answer: ShowInputDialog() returns a string value which can be directly assigned on a string type variable. You may use parseXXX() method to convert it into other data types like int or float etc. for further use in the application.
e.g.
String strVal = JOptionPane.showInputDialog(null, ”Enter Name? ”);
Q: Write a Java program that accepts value of a radius using ShowInputDialog() and computes the area of the circle. showMessageDialog().
Answer:
/* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ import javax.swing.JOptionPane; /** * * @author eduvictors.com */ public class NewJFrame extends javax.swing.JFrame { /** * Creates new form NewJFrame */ public NewJFrame() { initComponents(); } /** * This method is called from within the constructor to initialize the form. * WARNING: Do NOT modify this code. The content of this method is always * regenerated by the Form Editor. */ @SuppressWarnings("unchecked") // <editor-fold defaultstate="collapsed" desc="Generated Code"> private void initComponents() { jLabel1 = new javax.swing.JLabel(); jLabel2 = new javax.swing.JLabel(); jButton1 = new javax.swing.JButton(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); setTitle("Demo App"); jLabel1.setText("Compute Area of Circle"); jLabel2.setText("Demo Of JOptionPane ShowXXX apis"); jButton1.setText("ClickMe"); jButton1.addActionListener(new java.awt.event.ActionListener() { public void actionPerformed(java.awt.event.ActionEvent evt) { jButton1ActionPerformed(evt); } }); javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); getContentPane().setLayout(layout); layout.setHorizontalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(55, 55, 55) .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addComponent(jLabel2) .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 233, javax.swing.GroupLayout.PREFERRED_SIZE))) .addGroup(layout.createSequentialGroup() .addGap(122, 122, 122) .addComponent(jButton1))) .addContainerGap(89, Short.MAX_VALUE)) ); layout.setVerticalGroup( layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) .addGroup(layout.createSequentialGroup() .addGap(37, 37, 37) .addComponent(jLabel1) .addGap(18, 18, 18) .addComponent(jLabel2) .addGap(41, 41, 41) .addComponent(jButton1) .addContainerGap(141, Short.MAX_VALUE)) ); pack(); }// </editor-fold> private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { // TODO add your handling code here: // Program to calculate area of circle using Input dialog String str=JOptionPane.showInputDialog(null, "Enter radius of circle ?"); int radius=Integer.parseInt(str); float area=(22/7)*(radius*radius); JOptionPane.showMessageDialog(null, "Area of circle="+area); } /** * @param args the command line arguments */ public static void main(String args[]) { /* Set the Nimbus look and feel */ //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) "> /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel. * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html */ try { for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) { if ("Nimbus".equals(info.getName())) { javax.swing.UIManager.setLookAndFeel(info.getClassName()); break; } } } catch (ClassNotFoundException ex) { java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); } catch (InstantiationException ex) { java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); } catch (IllegalAccessException ex) { java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); } catch (javax.swing.UnsupportedLookAndFeelException ex) { java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex); } //</editor-fold> /* Create and display the form */ java.awt.EventQueue.invokeLater(new Runnable() { public void run() { new NewJFrame().setVisible(true); } }); } // Variables declaration - do not modify private javax.swing.JButton jButton1; private javax.swing.JLabel jLabel1; private javax.swing.JLabel jLabel2; // End of variables declaration }
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