Package com.google.gwt.core.client

Class Scheduler

java.lang.Object

com.google.gwt.core.client.Scheduler

Direct Known Subclasses:

StubScheduler

public abstract class Scheduler
extends Object

This class provides low-level task scheduling primitives. Any exceptions thrown by the command objects executed by the scheduler will be passed to the GWT.UncaughtExceptionHandler if one is installed.

NOTE: If you are using a timer to schedule a UI animation, use AnimationScheduler instead. The browser can optimize your animation for maximum performance.

See Also:

• StubScheduler

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	Scheduler.RepeatingCommand	General-purpose Command interface for tasks that repeat.
static interface	Scheduler.ScheduledCommand	General-purpose Command interface.

Constructor Summary

Constructors

Constructor	Description
Scheduler()

Method Summary

Modifier and Type	Method	Description
static Scheduler	get()	Returns the default implementation of the Scheduler API.
abstract void	scheduleDeferred(Scheduler.ScheduledCommand cmd)	A deferred command is executed after the browser event loop returns.
abstract void	scheduleEntry(Scheduler.RepeatingCommand cmd)	An "entry" command will be executed before GWT-generated code is invoked by the browser's event loop.
abstract void	scheduleEntry(Scheduler.ScheduledCommand cmd)	An "entry" command will be executed before GWT-generated code is invoked by the browser's event loop.
abstract void	scheduleFinally(Scheduler.RepeatingCommand cmd)	A "finally" command will be executed before GWT-generated code returns control to the browser's event loop.
abstract void	scheduleFinally(Scheduler.ScheduledCommand cmd)	A "finally" command will be executed before GWT-generated code returns control to the browser's event loop.
abstract void	scheduleFixedDelay(Scheduler.RepeatingCommand cmd, int delayMs)	Schedules a repeating command that is scheduled with a constant delay.
abstract void	scheduleFixedPeriod(Scheduler.RepeatingCommand cmd, int delayMs)	Schedules a repeating command that is scheduled with a constant periodicity.
abstract void	scheduleIncremental(Scheduler.RepeatingCommand cmd)	Schedules a repeating command that performs incremental work.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Scheduler

public Scheduler()

Method Details

get

public static Scheduler get()

Returns the default implementation of the Scheduler API.

scheduleDeferred

public abstract void scheduleDeferred(Scheduler.ScheduledCommand cmd)

A deferred command is executed after the browser event loop returns.

scheduleEntry

public abstract void scheduleEntry(Scheduler.RepeatingCommand cmd)

An "entry" command will be executed before GWT-generated code is invoked by the browser's event loop. The Scheduler.RepeatingCommand will be called once per entry from the event loop until false is returned. This type of command is appropriate for instrumentation or code that needs to know when "something happens."

If an entry command schedules another entry command, the second command will be executed before control flow continues to the GWT-generated code.

scheduleEntry

public abstract void scheduleEntry(Scheduler.ScheduledCommand cmd)

An "entry" command will be executed before GWT-generated code is invoked by the browser's event loop. This type of command is appropriate for code that needs to know when "something happens."

If an entry command schedules another entry command, the second command will be executed before control flow continues to the GWT-generated code.

scheduleFinally

public abstract void scheduleFinally(Scheduler.RepeatingCommand cmd)

A "finally" command will be executed before GWT-generated code returns control to the browser's event loop. The Scheduler.RepeatingCommand.execute() method will be called once per exit to the event loop until false is returned. This type of command is appropriate for instrumentation or cleanup code.

If a finally command schedules another finally command, the second command will be executed before control flow returns to the browser.

scheduleFinally

public abstract void scheduleFinally(Scheduler.ScheduledCommand cmd)

A "finally" command will be executed before GWT-generated code returns control to the browser's event loop. This type of command is used to aggregate small amounts of work before performing a non-recurring, heavyweight operation.

If a finally command schedules another finally command, the second command will be executed before control flow returns to the browser.

Consider the following:

 try {
   nativeEventCallback(); // Calls scheduleFinally one or more times
 } finally {
   executeFinallyCommands();
 }
 

See Also:

• StyleInjector

scheduleFixedDelay

public abstract void scheduleFixedDelay(Scheduler.RepeatingCommand cmd,
 int delayMs)

Schedules a repeating command that is scheduled with a constant delay. That is, the next invocation of the command will be scheduled for delayMs milliseconds after the last invocation completes.

For example, assume that a command takes 30ms to run and a 100ms delay is provided. The second invocation of the command will occur at 130ms after the first invocation starts.

Parameters:

cmd - the command to execute

delayMs - the amount of time to wait after one invocation ends before the next invocation

scheduleFixedPeriod

public abstract void scheduleFixedPeriod(Scheduler.RepeatingCommand cmd,
 int delayMs)

Schedules a repeating command that is scheduled with a constant periodicity. That is, the command will be invoked every delayMs milliseconds, regardless of how long the previous invocation took to complete.

Parameters:

cmd - the command to execute

delayMs - the period with which the command is executed

scheduleIncremental

public abstract void scheduleIncremental(Scheduler.RepeatingCommand cmd)

Schedules a repeating command that performs incremental work. This type of command is encouraged for long-running processes that perform computation or that manipulate the DOM. The commands in this queue are invoked many times in rapid succession and are then deferred to allow the browser to process its event queue.

Parameters:

cmd - the command to execute