(Added an example to BukkitScheduler, for tasks that only run once (instead of repeating).) |
UltraFireFX-gpuser (talk | contribs) m (Fixing return typo) |
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This tutorial will guide you in using the scheduler provided by bukkit. It will allow you to defer the execution of code to a later time. This is not the same as registering a [http://jd.bukkit.org/apidocs/index.html?org/bukkit/event/Listener.html Listener], a block of code which is executed in response to an [http://wiki.bukkit.org/Event_API_Reference event] in the game. Blocks of code may also be scheduled to be executed repeatedly at a fixed interval, with or without a delay. They will continue to execute until completed, or canceled, or your plugin is disabled. |
This tutorial will guide you in using the scheduler provided by bukkit. It will allow you to defer the execution of code to a later time. This is not the same as registering a [http://jd.bukkit.org/apidocs/index.html?org/bukkit/event/Listener.html Listener], a block of code which is executed in response to an [http://wiki.bukkit.org/Event_API_Reference event] in the game. Blocks of code may also be scheduled to be executed repeatedly at a fixed interval, with or without a delay. They will continue to execute until completed, or canceled, or your plugin is disabled. |
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− | When using [[#BukkitRunnable|BukkitRunnable]], with separate |
+ | When using [[#BukkitRunnable|BukkitRunnable]], with a separate class, scheduling work occurs in two steps for the programmer. |
# Define the work to be done, see the section [[#Defining_work|Defining Work]] |
# Define the work to be done, see the section [[#Defining_work|Defining Work]] |
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# Notify Bukkit when the work should be executed, see the section [[#Scheduling_Work|Scheduling Work]] |
# Notify Bukkit when the work should be executed, see the section [[#Scheduling_Work|Scheduling Work]] |
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+ | Alternatively, work can be scheduled directly with the scheduler, this also occurs in two steps for the programmer. |
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− | This can also be done with the [[#BukkitScheduler|BukkitScheduler]], using less code. |
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+ | # Define the work to be done, in a Runnable or Callable |
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+ | # Then directly scheduling the work with the Bukkit Scheduler, see the section [[#BukkitScheduler|BukkitScheduler]] |
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= BukkitRunnable = |
= BukkitRunnable = |
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private final JavaPlugin plugin; |
private final JavaPlugin plugin; |
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− | public ExampleTask(JavaPlugin plugin) { |
+ | public void ExampleTask(JavaPlugin plugin) { |
this.plugin = plugin; |
this.plugin = plugin; |
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} |
} |
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this.plugin = plugin; |
this.plugin = plugin; |
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if (counter < 1) { |
if (counter < 1) { |
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− | throw new |
+ | throw new IllegalArgumentException("counter must be greater than 1"); |
} else { |
} else { |
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this.counter = counter; |
this.counter = counter; |
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plugin.getServer().broadcastMessage("Commence greeting in " + counter--); |
plugin.getServer().broadcastMessage("Commence greeting in " + counter--); |
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} else { |
} else { |
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− | plugin.getServer().broadcastMessage("Welcome to Bukkit! Remember to read the documentation!") |
+ | plugin.getServer().broadcastMessage("Welcome to Bukkit! Remember to read the documentation!"); |
this.cancel(); |
this.cancel(); |
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} |
} |
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Line 103: | Line 105: | ||
@EventHandler |
@EventHandler |
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public void onJoin(PlayerJoinEvent event) { |
public void onJoin(PlayerJoinEvent event) { |
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− | // Create the task and schedule to run once |
+ | // Create the task and schedule to run it once, after 20 ticks |
BukkitTask task = new ExampleTask(this.plugin).runTaskLater(this.plugin, 20); |
BukkitTask task = new ExampleTask(this.plugin).runTaskLater(this.plugin, 20); |
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} |
} |
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Line 173: | Line 175: | ||
@EventHandler |
@EventHandler |
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public void onJoin(PlayerJoinEvent event) { |
public void onJoin(PlayerJoinEvent event) { |
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− | // Create the task anonymously and schedule to run once |
+ | // Create the task anonymously and schedule to run it once, after 20 ticks |
new BukkitRunnable() { |
new BukkitRunnable() { |
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Line 194: | Line 196: | ||
===Example=== |
===Example=== |
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− | Example for directly scheduling |
+ | Example for directly scheduling an anonymous Runnable with the BukkitScheduler to run after 20 ticks. |
<blockquote><source lang="java"> |
<blockquote><source lang="java"> |
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import org.bukkit.Bukkit; |
import org.bukkit.Bukkit; |
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===Repeating Example=== |
===Repeating Example=== |
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− | Example for directly scheduling |
+ | Example for directly scheduling an anonymous Runnable with the BukkitScheduler to run every twenty ticks, forever, starting from when you schedule it. |
<blockquote><source lang="java"> |
<blockquote><source lang="java"> |
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import org.bukkit.Bukkit; |
import org.bukkit.Bukkit; |
Revision as of 03:16, 26 March 2015
This tutorial will guide you in using the scheduler provided by bukkit. It will allow you to defer the execution of code to a later time. This is not the same as registering a Listener, a block of code which is executed in response to an event in the game. Blocks of code may also be scheduled to be executed repeatedly at a fixed interval, with or without a delay. They will continue to execute until completed, or canceled, or your plugin is disabled.
When using BukkitRunnable, with a separate class, scheduling work occurs in two steps for the programmer.
- Define the work to be done, see the section Defining Work
- Notify Bukkit when the work should be executed, see the section Scheduling Work
Alternatively, work can be scheduled directly with the scheduler, this also occurs in two steps for the programmer.
- Define the work to be done, in a Runnable or Callable
- Then directly scheduling the work with the Bukkit Scheduler, see the section BukkitScheduler
BukkitRunnable
BukkitRunnable is an abstract implementation of Runnable. It also supports additional operations that a Runnable is not capable of, most conveniently, BukkitRunnables can schedule and cancel their own execution. However, if the BukkitRunnable did not schedule itself for execution, it cannot cancel itself from execution. BukkitRunnables are not schedulers, do not contain any scheduler logic, and are not expensive to create. Plugins should prefer defining a BukkitRunnable and calling the appropriate run method over directly scheduling a Runnable with the BukkitScheduler.
- For more information on BukkitRunnable, see the BukkitRunnable JavaDocs
Defining work
Plugins should first extend BukkitRunnable to define work that needs to be done. In other words, the definition of the run method is what you want executed in accordance to a schedule.
Basic Example
This is an example definition of a task that can be scheduled.
import org.bukkit.Bukkit; import org.bukkit.plugin.java.JavaPlugin; import org.bukkit.scheduler.BukkitRunnable; public class ExampleTask extends BukkitRunnable { private final JavaPlugin plugin; public void ExampleTask(JavaPlugin plugin) { this.plugin = plugin; } @Override public void run() { // What you want to schedule goes here plugin.getServer().broadcastMessage("Welcome to Bukkit! Remember to read the documentation!"); } }
Self-Canceling Example
This is an example of a definition of a task that will cancel itself when it has executed the specified number of times
import org.bukkit.plugin.java.JavaPlugin; import org.bukkit.scheduler.BukkitRunnable; public class ExampleSelfCancelingTask extends BukkitRunnable { private final JavaPlugin plugin; private int counter; public ExampleSelfCancelingTask(JavaPlugin plugin, int counter) { this.plugin = plugin; if (counter < 1) { throw new IllegalArgumentException("counter must be greater than 1"); } else { this.counter = counter; } } @Override public void run() { // What you want to schedule goes here if (counter > 0) { plugin.getServer().broadcastMessage("Commence greeting in " + counter--); } else { plugin.getServer().broadcastMessage("Welcome to Bukkit! Remember to read the documentation!"); this.cancel(); } } }
Scheduling Work
After defining the task, the plugin needs to schedule the task. BukkitRunnables are scheduled when the desired run method is invoked on an instance of the task. The list of methods for BukkitRunnable can be found in the Javadocs for BukkitRunnable. The different run methods all return a BukkitTask object
Warning: | Asynchronous tasks should never access any API in Bukkit |
Example
This is an example of a plugin which registers a listener and when a player joins, schedules a task to be run 20 ticks later.
import org.bukkit.event.EventHandler; import org.bukkit.event.Listener; import org.bukkit.event.player.PlayerJoinEvent; import org.bukkit.plugin.java.JavaPlugin; import org.bukkit.scheduler.BukkitRunnable; import org.bukkit.scheduler.BukkitTask; public final class ExamplePlugin extends JavaPlugin { @Override public void onEnable() { new ExampleListener(this); } } class ExampleListener implements Listener { private final ExamplePlugin plugin; public ExampleListener(ExamplePlugin plugin) { this.plugin = plugin; plugin.getServer().getPluginManager().registerEvents(this, plugin); } @EventHandler public void onJoin(PlayerJoinEvent event) { // Create the task and schedule to run it once, after 20 ticks BukkitTask task = new ExampleTask(this.plugin).runTaskLater(this.plugin, 20); } }
Self-Canceling Example
This is example takes the above ExampleSelfCancelingTask and scheules it to run every 20 ticks after waiting 10 ticks.
import org.bukkit.event.EventHandler; import org.bukkit.event.Listener; import org.bukkit.event.player.PlayerJoinEvent; import org.bukkit.plugin.java.JavaPlugin; import org.bukkit.scheduler.BukkitRunnable; import org.bukkit.scheduler.BukkitTask; public final class ExamplePlugin extends JavaPlugin { @Override public void onEnable() { new ExampleListener(this); } } class ExampleListener implements Listener { private final ExamplePlugin plugin; public ExampleListener(ExamplePlugin plugin) { this.plugin = plugin; plugin.getServer().getPluginManager().registerEvents(this, plugin); } @EventHandler public void onJoin(PlayerJoinEvent event) { // Create the task and schedule BukkitTask task = new ExampleSelfCancelingTask(this.plugin, 5).runTaskTimer(this.plugin, 10, 20); } }
Anonymous BukkitRunnable Example
An anonymous BukkitRunnable will allow you to schedule a task, without creating a new class with a name. This examples combines the above two basic examples.
import org.bukkit.event.EventHandler; import org.bukkit.event.Listener; import org.bukkit.event.player.PlayerJoinEvent; import org.bukkit.plugin.java.JavaPlugin; import org.bukkit.scheduler.BukkitRunnable; import org.bukkit.scheduler.BukkitTask; public final class ExamplePlugin extends JavaPlugin { @Override public void onEnable() { new ExampleListener(this); } } class ExampleListener implements Listener { private final ExamplePlugin plugin; public ExampleListener(ExamplePlugin plugin) { this.plugin = plugin; plugin.getServer().getPluginManager().registerEvents(this, plugin); } @EventHandler public void onJoin(PlayerJoinEvent event) { // Create the task anonymously and schedule to run it once, after 20 ticks new BukkitRunnable() { @Override public void run() { // What you want to schedule goes here plugin.getServer().broadcastMessage( "Welcome to Bukkit! Remember to read the documentation!"); } }.runTaskLater(this.plugin, 20); } }
BukkitScheduler
The BukkitScheduler allows plugins to schedule a Runnable and/or a Callable , for execution at a later time. The list of methods for BukkitScheduler can be found in the Javadocs for BukkitScheduler.
- Note: Plugins should not schedule a BukkitRunnable with the scheduler, instead they should run the BukkitRunnable with the desired schedule.
Example
Example for directly scheduling an anonymous Runnable with the BukkitScheduler to run after 20 ticks.
import org.bukkit.Bukkit; import org.bukkit.plugin.java.JavaPlugin; import org.bukkit.scheduler.BukkitScheduler; public final class ExamplePlugin extends JavaPlugin { public void onEnable() { BukkitScheduler scheduler = Bukkit.getServer().getScheduler(); scheduler.scheduleSyncDelayedTask(this, new Runnable() { @Override public void run() { // Do something } }, 20L); } }
Repeating Example
Example for directly scheduling an anonymous Runnable with the BukkitScheduler to run every twenty ticks, forever, starting from when you schedule it.
import org.bukkit.Bukkit; import org.bukkit.plugin.java.JavaPlugin; import org.bukkit.scheduler.BukkitScheduler; public final class ExamplePlugin extends JavaPlugin { public void onEnable() { BukkitScheduler scheduler = Bukkit.getServer().getScheduler(); scheduler.scheduleSyncRepeatingTask(this, new Runnable() { @Override public void run() { // Do something } }, 0L, 20L); } }
Warning: | Asynchronous tasks should never access any API in Bukkit |
BukkitTask
A BukkitTask object is returned whenever a Runnable is scheduled. This object represents the task the scheduled task being executed by the scheduler. For more information see, Javadocs for BukkitTask.
Callable and Future
A Callable given to the scheduler to call synchronously returns a Future. These are standard Java classes, for more information see, Javadocs for Callable and Javadocs for Future
Tips for thread safety
The Bukkit API, with the exception of the scheduler package, is not thread safe nor guaranteed to be thread safe.
- Asynchronous tasks should never access any API in Bukkit.
- Do not access or modify shared collections from your asynchronous tasks. Normal collections are not thread-safe. This also applies to objects which are not thread safe.
- An asynchronous task can schedule a synchronous task.
- A synchronous task can schedule an asynchronous task.
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