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public class: Timer [javadoc | source]

All Implemented Interfaces:

Direct Known Subclasses:

Fires one or more {@code ActionEvent}s at specified intervals. An example use is an animation object that uses a Timer as the trigger for drawing its frames.

Setting up a timer involves creating a Timer object, registering one or more action listeners on it, and starting the timer using the start method. For example, the following code creates and starts a timer that fires an action event once per second (as specified by the first argument to the Timer constructor). The second argument to the Timer constructor specifies a listener to receive the timer's action events.

 int delay = 1000; //milliseconds
 ActionListener taskPerformer = new ActionListener() {
     public void actionPerformed(ActionEvent evt) {
         //...Perform a task...
 new Timer(delay, taskPerformer).start();

{@code Timers} are constructed by specifying both a delay parameter and an {@code ActionListener}. The delay parameter is used to set both the initial delay and the delay between event firing, in milliseconds. Once the timer has been started, it waits for the initial delay before firing its first ActionEvent to registered listeners. After this first event, it continues to fire events every time the between-event delay has elapsed, until it is stopped.

After construction, the initial delay and the between-event delay can be changed independently, and additional ActionListeners may be added.

If you want the timer to fire only the first time and then stop, invoke setRepeats(false) on the timer.

Although all Timers perform their waiting using a single, shared thread (created by the first Timer object that executes), the action event handlers for Timers execute on another thread -- the event-dispatching thread. This means that the action handlers for Timers can safely perform operations on Swing components. However, it also means that the handlers must execute quickly to keep the GUI responsive.

In v 1.3, another Timer class was added to the Java platform: java.util.Timer. Both it and javax.swing.Timer provide the same basic functionality, but java.util.Timer is more general and has more features. The javax.swing.Timer has two features that can make it a little easier to use with GUIs. First, its event handling metaphor is familiar to GUI programmers and can make dealing with the event-dispatching thread a bit simpler. Second, its automatic thread sharing means that you don't have to take special steps to avoid spawning too many threads. Instead, your timer uses the same thread used to make cursors blink, tool tips appear, and so on.

You can find further documentation and several examples of using timers by visiting How to Use Timers, a section in The Java Tutorial. For more examples and help in choosing between this Timer class and java.util.Timer, see Using Timers in Swing Applications, an article in The Swing Connection.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeansTM has been added to the java.beans package. Please see java.beans.XMLEncoder .

Nested Class Summary:
class  Timer.DoPostEvent  DoPostEvent is a runnable class that fires actionEvents to the listeners on the EventDispatchThread, via invokeLater. 
Field Summary
protected  EventListenerList listenerList     
transient  DelayedTimer delayedTimer     
 public Timer(int delay,
    ActionListener listener) 
Method from javax.swing.Timer Summary:
addActionListener,   cancelEvent,   fireActionPerformed,   getAccessControlContext,   getActionCommand,   getActionListeners,   getDelay,   getInitialDelay,   getListeners,   getLock,   getLogTimers,   isCoalesce,   isRepeats,   isRunning,   post,   removeActionListener,   restart,   setActionCommand,   setCoalesce,   setDelay,   setInitialDelay,   setLogTimers,   setRepeats,   start,   stop
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from javax.swing.Timer Detail:
 public  void addActionListener(ActionListener listener) 
    Adds an action listener to the Timer.
  void cancelEvent() 
    Resets the internal state to indicate this Timer shouldn't notify any of its listeners. This does not stop a repeatable Timer from firing again, use stop for that.
 protected  void fireActionPerformed(ActionEvent e) 
    Notifies all listeners that have registered interest for notification on this event type.
 final AccessControlContext getAccessControlContext() 
    Returns the acc this timer was constructed with.
 public String getActionCommand() 
    Returns the string that will be delivered as the action command in ActionEvents fired by this timer. May be null, which is also the default.
 public ActionListener[] getActionListeners() 
    Returns an array of all the action listeners registered on this timer.
 public int getDelay() 
    Returns the delay, in milliseconds, between firings of action events.
 public int getInitialDelay() 
    Returns the Timer's initial delay.
 public T[] getListeners(Class<T> listenerType) 
    Returns an array of all the objects currently registered as FooListeners upon this Timer. FooListeners are registered using the addFooListener method.

    You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a Timer instance t for its action listeners with the following code:

    ActionListener[] als = (ActionListener[])(t.getListeners(ActionListener.class));
    If no such listeners exist, this method returns an empty array.
 Lock getLock() 
 public static boolean getLogTimers() 
    Returns true if logging is enabled.
 public boolean isCoalesce() 
    Returns true if the Timer coalesces multiple pending action events.
 public boolean isRepeats() 
    Returns true (the default) if the Timer will send an action event to its listeners multiple times.
 public boolean isRunning() 
    Returns true if the Timer is running.
  void post() 
 public  void removeActionListener(ActionListener listener) 
    Removes the specified action listener from the Timer.
 public  void restart() 
    Restarts the Timer, canceling any pending firings and causing it to fire with its initial delay.
 public  void setActionCommand(String command) 
    Sets the string that will be delivered as the action command in ActionEvents fired by this timer. null is an acceptable value.
 public  void setCoalesce(boolean flag) 
    Sets whether the Timer coalesces multiple pending ActionEvent firings. A busy application may not be able to keep up with a Timer's event generation, causing multiple action events to be queued. When processed, the application sends these events one after the other, causing the Timer's listeners to receive a sequence of events with no delay between them. Coalescing avoids this situation by reducing multiple pending events to a single event. Timers coalesce events by default.
 public  void setDelay(int delay) 
    Sets the Timer's between-event delay, the number of milliseconds between successive action events. This does not affect the initial delay property, which can be set by the {@code setInitialDelay} method.
 public  void setInitialDelay(int initialDelay) 
    Sets the Timer's initial delay, the time in milliseconds to wait after the timer is started before firing the first event. Upon construction, this is set to be the same as the between-event delay, but then its value is independent and remains unaffected by changes to the between-event delay.
 public static  void setLogTimers(boolean flag) 
    Enables or disables the timer log. When enabled, a message is posted to System.out whenever the timer goes off.
 public  void setRepeats(boolean flag) 
    If flag is false, instructs the Timer to send only one action event to its listeners.
 public  void start() 
    Starts the Timer, causing it to start sending action events to its listeners.
 public  void stop() 
    Stops the Timer, causing it to stop sending action events to its listeners.