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A very simple animation loop that can be paused and stopped.
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/**************************** | |
* | |
* The MIT License (MIT) | |
* | |
* Copyright (c) 2015 Claude Martin | |
* | |
* Permission is hereby granted, free of charge, to any person obtaining a copy | |
* of this software and associated documentation files (the "Software"), to deal | |
* in the Software without restriction, including without limitation the rights | |
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
* copies of the Software, and to permit persons to whom the Software is | |
* furnished to do so, subject to the following conditions: | |
* | |
* The above copyright notice and this permission notice shall be included in | |
* all copies or substantial portions of the Software. | |
* | |
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | |
* THE SOFTWARE. | |
* | |
****************************/ | |
package ch.claude_martin.util; | |
import java.util.concurrent.ThreadFactory; | |
import java.util.concurrent.TimeUnit; | |
import java.util.concurrent.atomic.AtomicInteger; | |
import java.util.concurrent.locks.Condition; | |
import java.util.concurrent.locks.Lock; | |
import java.util.concurrent.locks.ReentrantLock; | |
import java.util.function.LongConsumer; | |
import java.util.function.LongPredicate; | |
/** | |
* A very simple animation loop that can be paused and stopped. This allows timing control for | |
* animations. The action is executed in a thread that is created on construction. | |
* <code>System.nanoTime()</code> is used as the high-resolution time source. However, the actual | |
* number of frames per second will not be precise at all. The given action callback to render a | |
* single frame will get the approximate time since the first start in nanoseconds. | |
* | |
* <p> | |
* The created thread will have a hard reference to the animation loop. An instance will not be | |
* garbage collected until it is {@link #stop() stopped}. | |
* | |
* @author Claude Martin | |
* | |
*/ | |
public final class AnimationLoop { | |
private static final AtomicInteger counter = new AtomicInteger(); | |
private final Lock lock = new ReentrantLock(); | |
private boolean isPaused = true; | |
private boolean isStopped = false; | |
private final Condition running = this.lock.newCondition(); | |
/** Time between frames in nanoseconds. */ | |
private final double delay; | |
/** Start of the animation. */ | |
private long timeStarted = -1; | |
/** When the current pause was started, or -1. */ | |
private long timePaused = -1; | |
/** Total duration (nanos) of all pauses after the first start. */ | |
private long durationOfPauses = 0; | |
private final Thread thread; | |
final static ThreadFactory DEFAULT_THREAD_FACTORY = r -> { | |
final Thread t = new Thread(r); | |
t.setName(AnimationLoop.class.getSimpleName() + "-" + counter.getAndIncrement()); | |
t.setDaemon(true); | |
return t; | |
}; | |
/** | |
* Creates a new animation loop from a {@link Runnable} with a default thread factory, creating | |
* daemon threads. The loop is paused and needs to be {@link #start() started}. | |
*/ | |
public AnimationLoop(final Runnable action, final double fps) { | |
this(time -> { | |
action.run(); | |
return true; | |
}, fps); | |
} | |
/** | |
* Creates a new animation loop with a default thread factory. The loop is paused and needs to be | |
* {@link #start() started}. | |
* | |
* @param action | |
* The callback that is invoked each time the animation needs to repaint. The action has | |
* one single argument, the nanoseconds of unpaused animation since the first start. The | |
* animation loop will {@link #pause} if the action returns <code>false</code>. | |
* @param fps | |
* Frames per second. This will regulate the timeout before each new animation step. | |
* | |
*/ | |
public AnimationLoop(final LongPredicate action, final double fps) { | |
this(action, (long) (1_000_000_000 / fps), DEFAULT_THREAD_FACTORY); | |
} | |
/** | |
* Creates a new animation loop. The loop is paused and needs to be {@link #start() started}. | |
* | |
* @param action | |
* The callback that is invoked each time the animation needs to repaint. The action has | |
* one single argument, the nanoseconds of unpaused animation since the first start. The | |
* animation loop will {@link #pause} if the action returns <code>false</code>. | |
* @param delay | |
* The delay between frames in nano seconds. | |
* @param threadFactory | |
* A thread factory for the thread used by this animation loop. | |
*/ | |
public AnimationLoop(final LongPredicate action, final long delay, | |
final ThreadFactory threadFactory) { | |
this.delay = delay; | |
this.thread = threadFactory.newThread(() -> { | |
while (!this.isStopped) { | |
final long timeToSleep; | |
this.lock.lock(); | |
try { | |
while (this.isPaused && !this.isStopped) | |
try { | |
this.running.await(); | |
} catch (final InterruptedException e) { | |
this.stop(); | |
return; | |
} | |
if (this.isStopped) | |
return; | |
// Now it's not paused and not stopped. | |
final long now1 = System.nanoTime(); | |
final long param = now1 - this.timeStarted - this.durationOfPauses; | |
if (!action.test(param)) { | |
this.pause(); | |
return; | |
} | |
final long now2 = System.nanoTime(); | |
timeToSleep = (long) (this.delay - (now2 - now1)); | |
} finally { | |
this.lock.unlock(); | |
} | |
try { | |
if (timeToSleep > 0) { | |
final int ns = (int) (timeToSleep % 1_000_000); | |
final long ms = (timeToSleep - ns) / 1_000_000; | |
Thread.sleep(ms, ns); | |
} | |
} catch (final InterruptedException e) { | |
this.stop(); | |
return; | |
} | |
} | |
}); | |
// The thread will start and then sleep until start() is invoked from any thread. | |
this.thread.start(); | |
} | |
/** | |
* Starts the animation loop. Calling this method when it's already started has no side effects, | |
* but it could slow down animation. | |
* | |
* @throws IllegalStateException | |
* If the loop is already stopped. | |
*/ | |
public void start() throws IllegalStateException { | |
this.lock.lock(); | |
assert this.isPaused || this.timePaused == -1; | |
try { | |
if (this.isStopped) | |
throw new IllegalStateException("Already stopped."); | |
if (!this.isPaused) | |
return; | |
this.isPaused = false; | |
final long now = System.nanoTime(); | |
if (this.timeStarted == -1) | |
this.timeStarted = now; | |
else | |
this.durationOfPauses += now - this.timePaused; | |
this.timePaused = -1; | |
this.running.signalAll(); | |
} finally { | |
this.lock.unlock(); | |
} | |
} | |
/** | |
* Pause the animation. The current frame will be rendered and execution is then paused. Calling | |
* this method when it's already paused has no side effects. | |
* | |
* @throws IllegalStateException | |
* If the loop is already stopped. | |
*/ | |
public void pause() throws IllegalStateException { | |
this.lock.lock(); | |
assert this.isPaused || this.timePaused == -1; | |
try { | |
if (this.isStopped) | |
throw new IllegalStateException("Already stopped."); | |
this.timePaused = System.nanoTime(); | |
this.isPaused = true; | |
} finally { | |
this.lock.unlock(); | |
} | |
} | |
/** | |
* Permanently stops this animation loop. It then can not be started again. | |
*/ | |
public void stop() { | |
this.lock.lock(); | |
try { | |
this.isStopped = true; | |
// Signal needed if loop is waiting: | |
if (this.isPaused) | |
this.running.signalAll(); | |
} finally { | |
this.lock.unlock(); | |
} | |
} | |
/** A builder for an animation loop. */ | |
public static final class Builder implements Cloneable { | |
private LongPredicate action = null; | |
private ThreadFactory threadFactory = DEFAULT_THREAD_FACTORY; | |
private long delay = Long.MIN_VALUE; | |
private boolean autostart = false; | |
/** | |
* The action to render one frame. The action has one single argument, the nanoseconds of | |
* unpaused animation since the first start. The animation loop will | |
* {@link AnimationLoop#pause() pause} if the action returns <code>false</code> | |
*/ | |
public Builder action(@SuppressWarnings("hiding") final LongPredicate action) { | |
this.action = action; | |
return this; | |
} | |
/** The action to render one frame. */ | |
public Builder runnable(final Runnable runnable) { | |
this.action = time -> { | |
runnable.run(); | |
return true; | |
}; | |
return this; | |
} | |
/** | |
* The action to render one frame. The action has one single argument, the nanoseconds of | |
* unpaused animation since the first start. | |
*/ | |
public Builder consumer(final LongConsumer consumer) { | |
this.action = time -> { | |
consumer.accept(time); | |
return true; | |
}; | |
return this; | |
} | |
/** Delay between frames in nano seconds. */ | |
public Builder delay(final long nanos) { | |
this.delay = nanos; | |
return this; | |
} | |
/** Delay between frames in any time unit. */ | |
public Builder delay(final long duration, final TimeUnit unit) { | |
this.delay = unit.toNanos(duration); | |
return this; | |
} | |
/** Frames per second (instead of delay in nano seconds). */ | |
public Builder fps(final double fps) { | |
this.delay = (long) (1_000_000_000 / fps); | |
return this; | |
} | |
/** | |
* Set the thread factory for the anmation loop. | |
* <p> | |
* Default value: A default thread factory that creats daemon threads. | |
*/ | |
public Builder threadFactory(final ThreadFactory factory) { | |
this.threadFactory = factory; | |
return this; | |
} | |
/** | |
* Set autostart. The animation loop will not start unless this is set to true or | |
* <code>start()</code> is invoked. | |
* <p> | |
* Default value: <code>false</code> | |
*/ | |
public Builder autostart(final boolean auto) { | |
this.autostart = auto; | |
return this; | |
} | |
/** Builds the animation loop. */ | |
public AnimationLoop build() { | |
if (this.action == null) | |
throw new IllegalStateException("no action"); | |
if (this.delay < 0) | |
throw new IllegalStateException("no delay"); | |
final AnimationLoop al = new AnimationLoop(this.action, this.delay, this.threadFactory); | |
if (this.autostart) | |
al.start(); | |
return al; | |
} | |
@Override | |
public Builder clone() { | |
try { | |
return (Builder) super.clone(); | |
} catch (final CloneNotSupportedException e) { | |
throw new RuntimeException(e); | |
} | |
} | |
} | |
} |
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