JDK8/Java8源码在线阅读
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package javax.swing;
import java.util.*;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.*;
import java.awt.*;
import java.awt.event.*;
import java.io.Serializable;
import java.io.*;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import javax.swing.event.EventListenerList;
/**
* Fires one or more {@code ActionEvent}s at specified
* intervals. An example use is an animation object that uses a
* <code>Timer</code> as the trigger for drawing its frames.
*<p>
* Setting up a timer
* involves creating a <code>Timer</code> object,
* registering one or more action listeners on it,
* and starting the timer using
* the <code>start</code> 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 <code>Timer</code> constructor).
* The second argument to the <code>Timer</code> constructor
* specifies a listener to receive the timer's action events.
*
*<pre>
* int delay = 1000; //milliseconds
* ActionListener taskPerformer = new ActionListener() {
* public void actionPerformed(ActionEvent evt) {
* <em>//...Perform a task...</em>
* }
* };
* new Timer(delay, taskPerformer).start();</pre>
*
* <p>
* {@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 <code>ActionEvent</code> to registered listeners.
* After this first event, it continues to fire events
* every time the between-event delay has elapsed, until it
* is stopped.
* <p>
* After construction, the initial delay and the between-event
* delay can be changed independently, and additional
* <code>ActionListeners</code> may be added.
* <p>
* If you want the timer to fire only the first time and then stop,
* invoke <code>setRepeats(false)</code> on the timer.
* <p>
* Although all <code>Timer</code>s perform their waiting
* using a single, shared thread
* (created by the first <code>Timer</code> object that executes),
* the action event handlers for <code>Timer</code>s
* execute on another thread -- the event-dispatching thread.
* This means that the action handlers for <code>Timer</code>s
* can safely perform operations on Swing components.
* However, it also means that the handlers must execute quickly
* to keep the GUI responsive.
*
* <p>
* In v 1.3, another <code>Timer</code> class was added
* to the Java platform: <code>java.util.Timer</code>.
* Both it and <code>javax.swing.Timer</code>
* provide the same basic functionality,
* but <code>java.util.Timer</code>
* is more general and has more features.
* The <code>javax.swing.Timer</code> 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.
*
* <p>
* You can find further documentation
* and several examples of using timers by visiting
* <a href="https://docs.oracle.com/javase/tutorial/uiswing/misc/timer.html"
* target = "_top">How to Use Timers</a>,
* a section in <em>The Java Tutorial.</em>
* For more examples and help in choosing between
* this <code>Timer</code> class and
* <code>java.util.Timer</code>,
* see
* <a href="http://java.sun.com/products/jfc/tsc/articles/timer/"
* target="_top">Using Timers in Swing Applications</a>,
* an article in <em>The Swing Connection.</em>
* <p>
* <strong>Warning:</strong>
* 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 JavaBeans™
* has been added to the <code>java.beans</code> package.
* Please see {@link java.beans.XMLEncoder}.
*
* @see java.util.Timer <code>java.util.Timer</code>
*
*
* @author Dave Moore
*/
@SuppressWarnings("serial")
public class Timer implements Serializable
{
/*
* NOTE: all fields need to be handled in readResolve
*/
protected EventListenerList listenerList = new EventListenerList();
// The following field strives to maintain the following:
// If coalesce is true, only allow one Runnable to be queued on the
// EventQueue and be pending (ie in the process of notifying the
// ActionListener). If we didn't do this it would allow for a
// situation where the app is taking too long to process the
// actionPerformed, and thus we'ld end up queing a bunch of Runnables
// and the app would never return: not good. This of course implies
// you can get dropped events, but such is life.
// notify is used to indicate if the ActionListener can be notified, when
// the Runnable is processed if this is true it will notify the listeners.
// notify is set to true when the Timer fires and the Runnable is queued.
// It will be set to false after notifying the listeners (if coalesce is
// true) or if the developer invokes stop.
private transient final AtomicBoolean notify = new AtomicBoolean(false);
private volatile int initialDelay, delay;
private volatile boolean repeats = true, coalesce = true;
private transient final Runnable doPostEvent;
private static volatile boolean logTimers;
private transient final Lock lock = new ReentrantLock();
// This field is maintained by TimerQueue.
// eventQueued can also be reset by the TimerQueue, but will only ever
// happen in applet case when TimerQueues thread is destroyed.
// access to this field is synchronized on getLock() lock.
transient TimerQueue.DelayedTimer delayedTimer = null;
private volatile String actionCommand;
/**
* Creates a {@code Timer} and initializes both the initial delay and
* between-event delay to {@code delay} milliseconds. If {@code delay}
* is less than or equal to zero, the timer fires as soon as it
* is started. If <code>listener</code> is not <code>null</code>,
* it's registered as an action listener on the timer.
*
* @param delay milliseconds for the initial and between-event delay
* @param listener an initial listener; can be <code>null</code>
*
* @see #addActionListener
* @see #setInitialDelay
* @see #setRepeats
*/
public Timer(int delay, ActionListener listener) {
super();
this.delay = delay;
this.initialDelay = delay;
doPostEvent = new DoPostEvent();
if (listener != null) {
addActionListener(listener);
}
}
/*
* The timer's AccessControlContext.
*/
private transient volatile AccessControlContext acc =
AccessController.getContext();
/**
* Returns the acc this timer was constructed with.
*/
final AccessControlContext getAccessControlContext() {
if (acc == null) {
throw new SecurityException(
"Timer is missing AccessControlContext");
}
return acc;
}
/**
* DoPostEvent is a runnable class that fires actionEvents to
* the listeners on the EventDispatchThread, via invokeLater.
* @see Timer#post
*/
class DoPostEvent implements Runnable
{
public void run() {
if (logTimers) {
System.out.println("Timer ringing: " + Timer.this);
}
if(notify.get()) {
fireActionPerformed(new ActionEvent(Timer.this, 0, getActionCommand(),
System.currentTimeMillis(),
0));
if (coalesce) {
cancelEvent();
}
}
}
Timer getTimer() {
return Timer.this;
}
}
/**
* Adds an action listener to the <code>Timer</code>.
*
* @param listener the listener to add
*
* @see #Timer
*/
public void addActionListener(ActionListener listener) {
listenerList.add(ActionListener.class, listener);
}
/**
* Removes the specified action listener from the <code>Timer</code>.
*
* @param listener the listener to remove
*/
public void removeActionListener(ActionListener listener) {
listenerList.remove(ActionListener.class, listener);
}
/**
* Returns an array of all the action listeners registered
* on this timer.
*
* @return all of the timer's <code>ActionListener</code>s or an empty
* array if no action listeners are currently registered
*
* @see #addActionListener
* @see #removeActionListener
*
* @since 1.4
*/
public ActionListener[] getActionListeners() {
return listenerList.getListeners(ActionListener.class);
}
/**
* Notifies all listeners that have registered interest for
* notification on this event type.
*
* @param e the action event to fire
* @see EventListenerList
*/
protected void fireActionPerformed(ActionEvent e) {
// Guaranteed to return a non-null array
Object[] listeners = listenerList.getListenerList();
// Process the listeners last to first, notifying
// those that are interested in this event
for (int i=listeners.length-2; i>=0; i-=2) {
if (listeners[i]==ActionListener.class) {
((ActionListener)listeners[i+1]).actionPerformed(e);
}
}
}
/**
* Returns an array of all the objects currently registered as
* <code><em>Foo</em>Listener</code>s
* upon this <code>Timer</code>.
* <code><em>Foo</em>Listener</code>s
* are registered using the <code>add<em>Foo</em>Listener</code> method.
* <p>
* You can specify the <code>listenerType</code> argument
* with a class literal, such as <code><em>Foo</em>Listener.class</code>.
* For example, you can query a <code>Timer</code>
* instance <code>t</code>
* for its action listeners
* with the following code:
*
* <pre>ActionListener[] als = (ActionListener[])(t.getListeners(ActionListener.class));</pre>
*
* If no such listeners exist,
* this method returns an empty array.
*
* @param listenerType the type of listeners requested;
* this parameter should specify an interface
* that descends from <code>java.util.EventListener</code>
* @return an array of all objects registered as
* <code><em>Foo</em>Listener</code>s
* on this timer,
* or an empty array if no such
* listeners have been added
* @exception ClassCastException if <code>listenerType</code> doesn't
* specify a class or interface that implements
* <code>java.util.EventListener</code>
*
* @see #getActionListeners
* @see #addActionListener
* @see #removeActionListener
*
* @since 1.3
*/
public <T extends EventListener> T[] getListeners(Class<T> listenerType) {
return listenerList.getListeners(listenerType);
}
/**
* Returns the timer queue.
*/
private TimerQueue timerQueue() {
return TimerQueue.sharedInstance();
}
/**
* Enables or disables the timer log. When enabled, a message
* is posted to <code>System.out</code> whenever the timer goes off.
*
* @param flag <code>true</code> to enable logging
* @see #getLogTimers
*/
public static void setLogTimers(boolean flag) {
logTimers = flag;
}
/**
* Returns <code>true</code> if logging is enabled.
*
* @return <code>true</code> if logging is enabled; otherwise, false
* @see #setLogTimers
*/
public static boolean getLogTimers() {
return logTimers;
}
/**
* Sets the <code>Timer</code>'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.
*
* @param delay the delay in milliseconds
* @see #setInitialDelay
*/
public void setDelay(int delay) {
if (delay < 0) {
throw new IllegalArgumentException("Invalid delay: " + delay);
}
else {
this.delay = delay;
}
}
/**
* Returns the delay, in milliseconds,
* between firings of action events.
*
* @see #setDelay
* @see #getInitialDelay
*/
public int getDelay() {
return delay;
}
/**
* Sets the <code>Timer</code>'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.
*
* @param initialDelay the initial delay, in milliseconds
* @see #setDelay
*/
public void setInitialDelay(int initialDelay) {
if (initialDelay < 0) {
throw new IllegalArgumentException("Invalid initial delay: " +
initialDelay);
}
else {
this.initialDelay = initialDelay;
}
}
/**
* Returns the <code>Timer</code>'s initial delay.
*
* @see #setInitialDelay
* @see #setDelay
*/
public int getInitialDelay() {
return initialDelay;
}
/**
* If <code>flag</code> is <code>false</code>,
* instructs the <code>Timer</code> to send only one
* action event to its listeners.
*
* @param flag specify <code>false</code> to make the timer
* stop after sending its first action event
*/
public void setRepeats(boolean flag) {
repeats = flag;
}
/**
* Returns <code>true</code> (the default)
* if the <code>Timer</code> will send
* an action event
* to its listeners multiple times.
*
* @see #setRepeats
*/
public boolean isRepeats() {
return repeats;
}
/**
* Sets whether the <code>Timer</code> coalesces multiple pending
* <code>ActionEvent</code> firings.
* A busy application may not be able
* to keep up with a <code>Timer</code>'s event generation,
* causing multiple
* action events to be queued. When processed,
* the application sends these events one after the other, causing the
* <code>Timer</code>'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.
* <code>Timer</code>s
* coalesce events by default.
*
* @param flag specify <code>false</code> to turn off coalescing
*/
public void setCoalesce(boolean flag) {
boolean old = coalesce;
coalesce = flag;
if (!old && coalesce) {
// We must do this as otherwise if the Timer once notified
// in !coalese mode notify will be stuck to true and never
// become false.
cancelEvent();
}
}
/**
* Returns <code>true</code> if the <code>Timer</code> coalesces
* multiple pending action events.
*
* @see #setCoalesce
*/
public boolean isCoalesce() {
return coalesce;
}
/**
* Sets the string that will be delivered as the action command
* in <code>ActionEvent</code>s fired by this timer.
* <code>null</code> is an acceptable value.
*
* @param command the action command
* @since 1.6
*/
public void setActionCommand(String command) {
this.actionCommand = command;
}
/**
* Returns the string that will be delivered as the action command
* in <code>ActionEvent</code>s fired by this timer. May be
* <code>null</code>, which is also the default.
*
* @return the action command used in firing events
* @since 1.6
*/
public String getActionCommand() {
return actionCommand;
}
/**
* Starts the <code>Timer</code>,
* causing it to start sending action events
* to its listeners.
*
* @see #stop
*/
public void start() {
timerQueue().addTimer(this, getInitialDelay());
}
/**
* Returns <code>true</code> if the <code>Timer</code> is running.
*
* @see #start
*/
public boolean isRunning() {
return timerQueue().containsTimer(this);
}
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