Package edu.wpi.first.wpilibj2.command

Interface Command

All Known Implementing Classes:
CommandBase, CommandGroupBase, ConditionalCommand, FunctionalCommand, InstantCommand, NotifierCommand, ParallelCommandGroup, ParallelDeadlineGroup, ParallelRaceGroup, PerpetualCommand, PIDCommand, PrintCommand, ProxyScheduleCommand, RunCommand, ScheduleCommand, SelectCommand, SequentialCommandGroup, StartEndCommand, WaitCommand, WaitUntilCommand
public interface Command
A state machine representing a complete action to be performed by the robot. Commands are run by the CommandScheduler, and can be composed into CommandGroups to allow users to build complicated multi-step actions without the need to roll the state machine logic themselves.

Commands are run synchronously from the main robot loop; no multithreading is used, unless specified explicitly from the command implementation.

  • Method Summary

    Modifier and Type Method Description
    default Command alongWith​(Command... parallel)
    Decorates this command with a set of commands to run parallel to it, ending when the last command ends.
    default Command andThen​(Command... next)
    Decorates this command with a set of commands to run after it in sequence.
    default Command asProxy()
    Decorates this command to run "by proxy" by wrapping it in a ProxyScheduleCommand.
    default Command beforeStarting​(java.lang.Runnable toRun)
    Decorates this command with a runnable to run before this command starts.
    default void cancel()
    Cancels this command.
    default Command deadlineWith​(Command... parallel)
    Decorates this command with a set of commands to run parallel to it, ending when the calling command ends and interrupting all the others.
    default void end​(boolean interrupted)
    The action to take when the command ends.
    default void execute()
    The main body of a command.
    default java.lang.String getName()
    Gets the name of this Command.
    java.util.Set<Subsystem> getRequirements()
    Specifies the set of subsystems used by this command.
    default boolean hasRequirement​(Subsystem requirement)
    Whether the command requires a given subsystem.
    default void initialize()
    The initial subroutine of a command.
    default Command interruptOn​(java.util.function.BooleanSupplier condition)
    Decorates this command with an interrupt condition.
    default boolean isFinished()
    Whether the command has finished.
    default boolean isScheduled()
    Whether or not the command is currently scheduled.
    default Command perpetually()
    Decorates this command to run perpetually, ignoring its ordinary end conditions.
    default Command raceWith​(Command... parallel)
    Decorates this command with a set of commands to run parallel to it, ending when the first command ends.
    default boolean runsWhenDisabled()
    Whether the given command should run when the robot is disabled.
    default void schedule()
    Schedules this command, defaulting to interruptible.
    default void schedule​(boolean interruptible)
    Schedules this command.
    default Command whenFinished​(java.lang.Runnable toRun)
    Decorates this command with a runnable to run after the command finishes.
    default Command withTimeout​(double seconds)
    Decorates this command with a timeout.

  • Method Details

    • initialize

      default void initialize()
      The initial subroutine of a command. Called once when the command is initially scheduled.

    • execute

      default void execute()
      The main body of a command. Called repeatedly while the command is scheduled.

    • end

      default void end​(boolean interrupted)
      The action to take when the command ends. Called when either the command finishes normally, or when it interrupted/canceled.
      Parameters:
      interrupted - whether the command was interrupted/canceled

    • isFinished

      default boolean isFinished()
      Whether the command has finished. Once a command finishes, the scheduler will call its end() method and un-schedule it.
      Returns:
      whether the command has finished.

    • getRequirements

      java.util.Set<Subsystem> getRequirements()
      Specifies the set of subsystems used by this command. Two commands cannot use the same subsystem at the same time. If the command is scheduled as interruptible and another command is scheduled that shares a requirement, the command will be interrupted. Else, the command will not be scheduled. If no subsystems are required, return an empty set.

      Note: it is recommended that user implementations contain the requirements as a field, and return that field here, rather than allocating a new set every time this is called.

      Returns:
      the set of subsystems that are required

    • withTimeout

      default Command withTimeout​(double seconds)
      Decorates this command with a timeout. If the specified timeout is exceeded before the command finishes normally, the command will be interrupted and un-scheduled. Note that the timeout only applies to the command returned by this method; the calling command is not itself changed.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Parameters:
      seconds - the timeout duration
      Returns:
      the command with the timeout added

    • interruptOn

      default Command interruptOn​(java.util.function.BooleanSupplier condition)
      Decorates this command with an interrupt condition. If the specified condition becomes true before the command finishes normally, the command will be interrupted and un-scheduled. Note that this only applies to the command returned by this method; the calling command is not itself changed.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Parameters:
      condition - the interrupt condition
      Returns:
      the command with the interrupt condition added

    • whenFinished

      default Command whenFinished​(java.lang.Runnable toRun)
      Decorates this command with a runnable to run after the command finishes.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Parameters:
      toRun - the Runnable to run
      Returns:
      the decorated command

    • beforeStarting

      default Command beforeStarting​(java.lang.Runnable toRun)
      Decorates this command with a runnable to run before this command starts.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Parameters:
      toRun - the Runnable to run
      Returns:
      the decorated command

    • andThen

      default Command andThen​(Command... next)
      Decorates this command with a set of commands to run after it in sequence. Often more convenient/less-verbose than constructing a new SequentialCommandGroup explicitly.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Parameters:
      next - the commands to run next
      Returns:
      the decorated command

    • deadlineWith

      default Command deadlineWith​(Command... parallel)
      Decorates this command with a set of commands to run parallel to it, ending when the calling command ends and interrupting all the others. Often more convenient/less-verbose than constructing a new ParallelDeadlineGroup explicitly.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Parameters:
      parallel - the commands to run in parallel
      Returns:
      the decorated command

    • alongWith

      default Command alongWith​(Command... parallel)
      Decorates this command with a set of commands to run parallel to it, ending when the last command ends. Often more convenient/less-verbose than constructing a new ParallelCommandGroup explicitly.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Parameters:
      parallel - the commands to run in parallel
      Returns:
      the decorated command

    • raceWith

      default Command raceWith​(Command... parallel)
      Decorates this command with a set of commands to run parallel to it, ending when the first command ends. Often more convenient/less-verbose than constructing a new ParallelRaceGroup explicitly.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Parameters:
      parallel - the commands to run in parallel
      Returns:
      the decorated command

    • perpetually

      default Command perpetually()
      Decorates this command to run perpetually, ignoring its ordinary end conditions. The decorated command can still be interrupted or canceled.

      Note: This decorator works by composing this command within a CommandGroup. The command cannot be used independently after being decorated, or be re-decorated with a different decorator, unless it is manually cleared from the list of grouped commands with CommandGroupBase.clearGroupedCommand(Command). The decorated command can, however, be further decorated without issue.

      Returns:
      the decorated command

    • asProxy

      default Command asProxy()
      Decorates this command to run "by proxy" by wrapping it in a ProxyScheduleCommand. This is useful for "forking off" from command groups when the user does not wish to extend the command's requirements to the entire command group.
      Returns:
      the decorated command

    • schedule

      default void schedule​(boolean interruptible)
      Schedules this command.
      Parameters:
      interruptible - whether this command can be interrupted by another command that shares one of its requirements

    • schedule

      default void schedule()
      Schedules this command, defaulting to interruptible.

    • cancel

      default void cancel()
      Cancels this command. Will call the command's interrupted() method. Commands will be canceled even if they are not marked as interruptible.

    • isScheduled

      default boolean isScheduled()
      Whether or not the command is currently scheduled. Note that this does not detect whether the command is being run by a CommandGroup, only whether it is directly being run by the scheduler.
      Returns:
      Whether the command is scheduled.

    • hasRequirement

      default boolean hasRequirement​(Subsystem requirement)
      Whether the command requires a given subsystem. Named "hasRequirement" rather than "requires" to avoid confusion with Command.requires(edu.wpi.first.wpilibj.command.Subsystem) - this may be able to be changed in a few years.
      Parameters:
      requirement - the subsystem to inquire about
      Returns:
      whether the subsystem is required

    • runsWhenDisabled

      default boolean runsWhenDisabled()
      Whether the given command should run when the robot is disabled. Override to return true if the command should run when disabled.
      Returns:
      whether the command should run when the robot is disabled

    • getName

      default java.lang.String getName()
      Gets the name of this Command.
      Returns:
      Name