S7 IWP notes -Timers in Java Swing

Timers in Java Swing

A Swing timer (an instance of javax.swing.Timer) fires one or more action events after a specified delay. Don't confuse Swing timers with the general-purpose timer facility that was added to the java.util package in release 1.3. This page describes only Swing timers.

In general, we recommend using Swing timers rather than general-purpose timers for GUI-related tasks because Swing timers all share the same, pre-existing timer thread and the GUI-related task automatically executes on the event-dispatch thread. However, you might use a general-purpose timer if you don't plan on touching the GUI from the timer, or need to perform lengthy processing.

You can use Swing timers in two ways:

To perform a task once, after a delay.For example, the tool tip manager uses Swing timers to determine when to show a tool tip and when to hide it.

To perform a task repeatedly.For example, you might perform animation or update a component that displays progress toward a goal.

Swing timers are very easy to use. When you create the timer, you specify an action listener to be notified when the timer "goes off". The actionPerformed method in this listener should contain the code for whatever task you need to be performed. When you create the timer, you also specify the number of milliseconds between timer firings. If you want the timer to go off only once, you can invoke setRepeats(false) on the timer. To start the timer, call its start method. To suspend it, call stop.

timer = new Timer(speed, this);

timer.setInitialDelay(pause);

timer.start();

import javax.swing.*;

import java.awt.event.*;

import java.awt.Graphics;

import java.util.Date;

import java.awt.Font;

import java.awt.Color;

public class TimerEx extends JFrame implements ActionListener

{ Timer t;

  JLabel l=new JLabel("  ",JLabel.CENTER);

  public TimerEx()

  {

 

   t=new Timer(1000,this);

   l.setOpaque(true);

   l.setBackground(new Color(100,50,50));

   l.setFont(new Font("Arial",Font.BOLD,60));

   l.setForeground(Color.yellow);

   getContentPane().add(l);

 

  t.start();

  setSize(400,200);

  setVisible(true);

  setLocationRelativeTo(null);

  }

  public void actionPerformed(ActionEvent ae){

   Date d=new Date();

   String s=(d.getHours()-12)+":"+d.getMinutes()+":"+d.getSeconds();

   l.setText(s);

 

  }

 

  public static void main(String ag[])

  { TimerEx te=new TimerEx();

  }

 }