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 {@link java.beans.XMLEncoder}. | 