Class CommandScheduler

java.lang.Object
edu.wpi.first.wpilibj2.command.CommandScheduler
All Implemented Interfaces:
Sendable, AutoCloseable

public final class CommandScheduler
extends Object
implements Sendable, AutoCloseable
The scheduler responsible for running Commands. A Command-based robot should call run() on the singleton instance in its periodic block in order to run commands synchronously from the main loop. Subsystems should be registered with the scheduler using registerSubsystem(Subsystem...) in order for their Subsystem.periodic() methods to be called and for their default commands to be scheduled.
  • Method Details

    • getInstance

      public static CommandScheduler getInstance()
      Returns the Scheduler instance.
      Returns:
      the instance
    • setPeriod

      public void setPeriod​(double period)
      Changes the period of the loop overrun watchdog. This should be be kept in sync with the TimedRobot period.
      Parameters:
      period - Period in seconds.
    • close

      public void close()
      Specified by:
      close in interface AutoCloseable
    • addButton

      public void addButton​(Runnable button)
      Adds a button binding to the scheduler, which will be polled to schedule commands.
      Parameters:
      button - The button to add
    • clearButtons

      public void clearButtons()
      Removes all button bindings from the scheduler.
    • schedule

      public void schedule​(boolean interruptible, Command... commands)
      Schedules multiple commands for execution. Does nothing if the command is already scheduled. If a command's requirements are not available, it will only be started if all the commands currently using those requirements have been scheduled as interruptible. If this is the case, they will be interrupted and the command will be scheduled.
      Parameters:
      interruptible - whether the commands should be interruptible
      commands - the commands to schedule
    • schedule

      public void schedule​(Command... commands)
      Schedules multiple commands for execution, with interruptible defaulted to true. Does nothing if the command is already scheduled.
      Parameters:
      commands - the commands to schedule
    • run

      public void run()
      Runs a single iteration of the scheduler. The execution occurs in the following order:

      Subsystem periodic methods are called.

      Button bindings are polled, and new commands are scheduled from them.

      Currently-scheduled commands are executed.

      End conditions are checked on currently-scheduled commands, and commands that are finished have their end methods called and are removed.

      Any subsystems not being used as requirements have their default methods started.

    • registerSubsystem

      public void registerSubsystem​(Subsystem... subsystems)
      Registers subsystems with the scheduler. This must be called for the subsystem's periodic block to run when the scheduler is run, and for the subsystem's default command to be scheduled. It is recommended to call this from the constructor of your subsystem implementations.
      Parameters:
      subsystems - the subsystem to register
    • unregisterSubsystem

      public void unregisterSubsystem​(Subsystem... subsystems)
      Un-registers subsystems with the scheduler. The subsystem will no longer have its periodic block called, and will not have its default command scheduled.
      Parameters:
      subsystems - the subsystem to un-register
    • setDefaultCommand

      public void setDefaultCommand​(Subsystem subsystem, Command defaultCommand)
      Sets the default command for a subsystem. Registers that subsystem if it is not already registered. Default commands will run whenever there is no other command currently scheduled that requires the subsystem. Default commands should be written to never end (i.e. their Command.isFinished() method should return false), as they would simply be re-scheduled if they do. Default commands must also require their subsystem.
      Parameters:
      subsystem - the subsystem whose default command will be set
      defaultCommand - the default command to associate with the subsystem
    • getDefaultCommand

      public Command getDefaultCommand​(Subsystem subsystem)
      Gets the default command associated with this subsystem. Null if this subsystem has no default command associated with it.
      Parameters:
      subsystem - the subsystem to inquire about
      Returns:
      the default command associated with the subsystem
    • cancel

      public void cancel​(Command... commands)
      Cancels commands. The scheduler will only call Command.end(boolean) method of the canceled command with true, indicating they were canceled (as opposed to finishing normally).

      Commands will be canceled even if they are not scheduled as interruptible.

      Parameters:
      commands - the commands to cancel
    • cancelAll

      public void cancelAll()
      Cancels all commands that are currently scheduled.
    • timeSinceScheduled

      public double timeSinceScheduled​(Command command)
      Returns the time since a given command was scheduled. Note that this only works on commands that are directly scheduled by the scheduler; it will not work on commands inside of commandgroups, as the scheduler does not see them.
      Parameters:
      command - the command to query
      Returns:
      the time since the command was scheduled, in seconds
    • isScheduled

      public boolean isScheduled​(Command... commands)
      Whether the given commands are running. Note that this only works on commands that are directly scheduled by the scheduler; it will not work on commands inside of CommandGroups, as the scheduler does not see them.
      Parameters:
      commands - the command to query
      Returns:
      whether the command is currently scheduled
    • requiring

      public Command requiring​(Subsystem subsystem)
      Returns the command currently requiring a given subsystem. Null if no command is currently requiring the subsystem
      Parameters:
      subsystem - the subsystem to be inquired about
      Returns:
      the command currently requiring the subsystem, or null if no command is currently scheduled
    • disable

      public void disable()
      Disables the command scheduler.
    • enable

      public void enable()
      Enables the command scheduler.
    • onCommandInitialize

      public void onCommandInitialize​(Consumer<Command> action)
      Adds an action to perform on the initialization of any command by the scheduler.
      Parameters:
      action - the action to perform
    • onCommandExecute

      public void onCommandExecute​(Consumer<Command> action)
      Adds an action to perform on the execution of any command by the scheduler.
      Parameters:
      action - the action to perform
    • onCommandInterrupt

      public void onCommandInterrupt​(Consumer<Command> action)
      Adds an action to perform on the interruption of any command by the scheduler.
      Parameters:
      action - the action to perform
    • onCommandFinish

      public void onCommandFinish​(Consumer<Command> action)
      Adds an action to perform on the finishing of any command by the scheduler.
      Parameters:
      action - the action to perform
    • initSendable

      public void initSendable​(SendableBuilder builder)
      Description copied from interface: Sendable
      Initializes this Sendable object.
      Specified by:
      initSendable in interface Sendable
      Parameters:
      builder - sendable builder