Timer (Java 2 Platform SE v1.4.1_"07")

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JavaTM 2 Platform
Std. Ed. v1.4.1_"07"

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## javax.swing
Class Timer

    java.lang.Object
      |
      +--javax.swing.Timer

All Implemented Interfaces:
  Serializable

public class Timer
extends Object
implements Serializable

Fires one or more action events after a specified delay. For example, an animation object can use 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();

Each `Timer` has one or more action listeners and a delay (the time between action events). When delay milliseconds have passed, the `Timer` fires an action event to its listeners. By default, this cycle repeats until the `stop` method is called. If you want the timer to fire only once, invoke `setRepeats(false)` on the timer. To make the delay before the first action event different from the delay between events, use the `setInitialDelay` method.

Although all `Timer`s perform their waiting using a single, shared thread (created by the first `Timer` object that executes), the action event handlers for `Timer`s execute on another thread -- the event-dispatching thread. This means that the action handlers for `Timer`s 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 `XMLEncoder`.

See Also:
  ``java.util.Timer``

Field Summary
`protected EventListenerList` | `listenerList`

Constructor Summary
`Timer(int delay, ActionListener listener)` Creates a `Timer` that will notify its listeners every `delay` milliseconds.

Method Summary
`void` | `addActionListener(ActionListener listener)` Adds an action listener to the `Timer`.
`protected void` | `fireActionPerformed(ActionEvent e)` Notifies all listeners that have registered interest for notification on this event type.
`ActionListener[]` | `getActionListeners()` Returns an array of all the action listeners registered on this timer.
`int` | `getDelay()` Returns the delay, in milliseconds, between firings of action events.
`int` | `getInitialDelay()` Returns the `Timer`'s initial delay.
`EventListener[]` | `getListeners(Class listenerType)` Returns an array of all the objects currently registered as `FooListener`s upon this `Timer`.
`static boolean` | `getLogTimers()` Returns `true` if logging is enabled.
`boolean` | `isCoalesce()` Returns `true` if the `Timer` coalesces multiple pending action events.
`boolean` | `isRepeats()` Returns `true` (the default) if the `Timer` will send an action event to its listeners multiple times.
`boolean` | `isRunning()` Returns `true` if the `Timer` is running.
`void` | `removeActionListener(ActionListener listener)` Removes the specified action listener from the `Timer`.
`void` | `restart()` Restarts the `Timer`, canceling any pending firings and causing it to fire with its initial delay.
`void` | `setCoalesce(boolean flag)` Sets whether the `Timer` coalesces multiple pending `ActionEvent` firings.
`void` | `setDelay(int delay)` Sets the `Timer`'s delay, the number of milliseconds between successive action events.
`void` | `setInitialDelay(int initialDelay)` Sets the `Timer`'s initial delay, which by default is the same as the between-event delay.
`static void` | `setLogTimers(boolean flag)` Enables or disables the timer log.
`void` | `setRepeats(boolean flag)` If `flag` is `false`, instructs the `Timer` to send only one action event to its listeners.
`void` | `start()` Starts the `Timer`, causing it to start sending action events to its listeners.
`void` | `stop()` Stops the `Timer`, causing it to stop sending action events to its listeners.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### listenerList

    protected EventListenerList listenerList

Constructor Detail

### Timer

    public Timer(int delay,
                 ActionListener listener)

  Creates a `Timer` that will notify its listeners every `delay` milliseconds. If `delay` is less than or equal to zero the timer will fire as soon as it is started. If `listener` is not `null`, it's registered as an action listener on the timer.

Parameters:
  `delay` - the number of milliseconds between action events
  `listener` - an initial listener; can be `null`
See Also:
  `addActionListener(java.awt.event.ActionListener)`, `setInitialDelay(int)`, `setRepeats(boolean)`

Method Detail

### addActionListener

    public void addActionListener(ActionListener listener)

  Adds an action listener to the `Timer`.

  Parameters:
    `listener` - the listener to add
  See Also:
    `Timer(int, java.awt.event.ActionListener)`

### removeActionListener

    public void removeActionListener(ActionListener listener)

  Removes the specified action listener from the `Timer`.

  Parameters:
    `listener` - the listener to remove

### getActionListeners

    public ActionListener[] getActionListeners()

  Returns an array of all the action listeners registered on this timer.

  Returns:
    all of the timer's `ActionListener`s or an empty array if no action listeners are currently registered
  Since:
    1.4
  See Also:
    `addActionListener(java.awt.event.ActionListener)`, `removeActionListener(java.awt.event.ActionListener)`

### fireActionPerformed

    protected void fireActionPerformed(ActionEvent e)

  Notifies all listeners that have registered interest for notification on this event type.

  Parameters:
    `e` - the action event to fire
  See Also:
    `EventListenerList`

### getListeners

    public EventListener[] getListeners(Class listenerType)

  Returns an array of all the objects currently registered as `FooListener`s upon this `Timer`. `FooListener`s 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.

  Parameters:
    `listenerType` - the type of listeners requested; this parameter should specify an interface that descends from `java.util.EventListener`
  Returns:
    an array of all objects registered as `FooListener`s on this timer, or an empty array if no such listeners have been added
  Throws:
    `ClassCastException` - if `listenerType` doesn't specify a class or interface that implements `java.util.EventListener`
  Since:
    1.3
  See Also:
    `getActionListeners()`, `addActionListener(java.awt.event.ActionListener)`, `removeActionListener(java.awt.event.ActionListener)`

### setLogTimers

    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.

  Parameters:
    `flag` - `true` to enable logging
  See Also:
    `getLogTimers()`

### getLogTimers

    public static boolean getLogTimers()

  Returns `true` if logging is enabled.

  Returns:
    `true` if logging is enabled; otherwise, false
  See Also:
    `setLogTimers(boolean)`

### setDelay

    public void setDelay(int delay)

  Sets the `Timer`'s delay, the number of milliseconds between successive action events.

  Parameters:
    `delay` - the delay in milliseconds
  See Also:
    `setInitialDelay(int)`

### getDelay

    public int getDelay()

  Returns the delay, in milliseconds, between firings of action events.

  See Also:
    `setDelay(int)`, `getInitialDelay()`

### setInitialDelay

    public void setInitialDelay(int initialDelay)

  Sets the `Timer`'s initial delay, which by default is the same as the between-event delay. This is used only for the first action event. Subsequent action events are spaced using the delay property.

  Parameters:
    `initialDelay` - the delay, in milliseconds, between the invocation of the `start` method and the first action event fired by this timer
  See Also:
    `setDelay(int)`

### getInitialDelay

    public int getInitialDelay()

  Returns the `Timer`'s initial delay.

  See Also:
    `setInitialDelay(int)`, `setDelay(int)`

### setRepeats

    public void setRepeats(boolean flag)

  If `flag` is `false`, instructs the `Timer` to send only one action event to its listeners.

  Parameters:
    `flag` - specify `false` to make the timer stop after sending its first action event

### isRepeats

    public boolean isRepeats()

  Returns `true` (the default) if the `Timer` will send an action event to its listeners multiple times.

  See Also:
    `setRepeats(boolean)`

### setCoalesce

    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. `Timer`s coalesce events by default.

  Parameters:
    `flag` - specify `false` to turn off coalescing

### isCoalesce

    public boolean isCoalesce()

  Returns `true` if the `Timer` coalesces multiple pending action events.

  See Also:
    `setCoalesce(boolean)`

### start

    public void start()

  Starts the `Timer`, causing it to start sending action events to its listeners.

  See Also:
    `stop()`

### isRunning

    public boolean isRunning()

  Returns `true` if the `Timer` is running.

  See Also:
    `start()`

### stop

    public void stop()

  Stops the `Timer`, causing it to stop sending action events to its listeners.

  See Also:
    `start()`

### restart

    public void restart()

  Restarts the `Timer`, canceling any pending firings and causing it to fire with its initial delay.

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JavaTM 2 Platform
Std. Ed. v1.4.1_"07"

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Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.