Package edu.wpi.first.wpilibj.command

Class Command

java.lang.Object
edu.wpi.first.wpilibj.command.Command
All Implemented Interfaces:
Sendable, AutoCloseable
Direct Known Subclasses:
CommandGroup, ConditionalCommand, InstantCommand, PIDCommand, TimedCommand, WaitForChildren, WaitUntilCommand
public abstract class Command
extends Object
implements Sendable, AutoCloseable
The Command class is at the very core of the entire command framework. Every command can be started with a call to start(). Once a command is started it will call initialize(), and then will repeatedly call execute() until the isFinished() returns true. Once it does, end() will be called.

However, if at any point while it is running cancel() is called, then the command will be stopped and interrupted() will be called.

If a command uses a Subsystem, then it should specify that it does so by calling the requires(...) method in its constructor. Note that a Command may have multiple requirements, and requires(...) should be called for each one.

If a command is running and a new command with shared requirements is started, then one of two things will happen. If the active command is interruptible, then cancel() will be called and the command will be removed to make way for the new one. If the active command is not interruptible, the other one will not even be started, and the active one will continue functioning.

See Also:
Subsystem, CommandGroup, IllegalUseOfCommandException

  • Constructor Summary

    Constructors 
    Constructor Description
    Command()
    Creates a new command.
    Command​(double timeout)
    Creates a new command with the given timeout and a default name.
    Command​(double timeout, Subsystem subsystem)
    Creates a new command with the given timeout and a default name.
    Command​(Subsystem subsystem)
    Creates a new command with the given timeout and a default name.
    Command​(String name)
    Creates a new command with the given name.
    Command​(String name, double timeout)
    Creates a new command with the given name and timeout.
    Command​(String name, double timeout, Subsystem subsystem)
    Creates a new command with the given name and timeout.
    Command​(String name, Subsystem subsystem)
    Creates a new command with the given name.

  • Method Summary

    Modifier and Type Method Description
    void cancel()
    This will cancel the current command.
    protected void clearRequirements()
    Clears list of subsystem requirements.
    void close()  
    boolean doesRequire​(Subsystem system)
    Checks if the command requires the given Subsystem.
    protected void end()
    Called when the command ended peacefully.
    protected void execute()
    The execute method is called repeatedly until this Command either finishes or is canceled.
    CommandGroup getGroup()
    Returns the CommandGroup that this command is a part of.
    String getName()
    Gets the name of this Command.
    String getSubsystem()
    Gets the subsystem name of this Command.
    protected void initialize()
    The initialize method is called the first time this Command is run after being started.
    void initSendable​(SendableBuilder builder)
    Initializes this Sendable object.
    protected void interrupted()
    Called when the command ends because somebody called cancel() or another command shared the same requirements as this one, and booted it out.
    boolean isCanceled()
    Returns whether or not this has been canceled.
    boolean isCompleted()
    Whether or not this command has completed running.
    protected abstract boolean isFinished()
    Returns whether this command is finished.
    boolean isInterruptible()
    Returns whether or not this command can be interrupted.
    boolean isRunning()
    Returns whether or not the command is running.
    protected boolean isTimedOut()
    Returns whether or not the timeSinceInitialized() method returns a number which is greater than or equal to the timeout for the command.
    protected void requires​(Subsystem subsystem)
    This method specifies that the given Subsystem is used by this command.
    protected void setInterruptible​(boolean interruptible)
    Sets whether or not this command can be interrupted.
    void setName​(String name)
    Sets the name of this Command.
    void setRunWhenDisabled​(boolean run)
    Sets whether or not this Command should run when the robot is disabled.
    void setSubsystem​(String subsystem)
    Sets the subsystem name of this Command.
    protected void setTimeout​(double seconds)
    Sets the timeout of this command.
    void start()
    Starts up the command.
    double timeSinceInitialized()
    Returns the time since this command was initialized (in seconds).
    String toString()
    The string representation for a Command is by default its name.
    boolean willRunWhenDisabled()
    Returns whether or not this Command will run when the robot is disabled, or if it will cancel itself.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Command

      public Command()
      Creates a new command. The name of this command will be set to its class name.

    • Command

      public Command​(String name)
      Creates a new command with the given name.
      Parameters:
      name - the name for this command
      Throws:
      IllegalArgumentException - if name is null

    • Command

      public Command​(double timeout)
      Creates a new command with the given timeout and a default name. The default name is the name of the class.
      Parameters:
      timeout - the time (in seconds) before this command "times out"
      Throws:
      IllegalArgumentException - if given a negative timeout
      See Also:
      isTimedOut()

    • Command

      public Command​(Subsystem subsystem)
      Creates a new command with the given timeout and a default name. The default name is the name of the class.
      Parameters:
      subsystem - the subsystem that this command requires
      Throws:
      IllegalArgumentException - if given a negative timeout
      See Also:
      isTimedOut()

    • Command

      public Command​(String name, Subsystem subsystem)
      Creates a new command with the given name.
      Parameters:
      name - the name for this command
      subsystem - the subsystem that this command requires
      Throws:
      IllegalArgumentException - if name is null

    • Command

      public Command​(double timeout, Subsystem subsystem)
      Creates a new command with the given timeout and a default name. The default name is the name of the class.
      Parameters:
      timeout - the time (in seconds) before this command "times out"
      subsystem - the subsystem that this command requires
      Throws:
      IllegalArgumentException - if given a negative timeout
      See Also:
      isTimedOut()

    • Command

      public Command​(String name, double timeout)
      Creates a new command with the given name and timeout.
      Parameters:
      name - the name of the command
      timeout - the time (in seconds) before this command "times out"
      Throws:
      IllegalArgumentException - if given a negative timeout or name was null.
      See Also:
      isTimedOut()

    • Command

      public Command​(String name, double timeout, Subsystem subsystem)
      Creates a new command with the given name and timeout.
      Parameters:
      name - the name of the command
      timeout - the time (in seconds) before this command "times out"
      subsystem - the subsystem that this command requires
      Throws:
      IllegalArgumentException - if given a negative timeout
      IllegalArgumentException - if given a negative timeout or name was null.
      See Also:
      isTimedOut()

  • Method Details

    • close

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

    • setTimeout

      protected final void setTimeout​(double seconds)
      Sets the timeout of this command.
      Parameters:
      seconds - the timeout (in seconds)
      Throws:
      IllegalArgumentException - if seconds is negative
      See Also:
      isTimedOut()

    • timeSinceInitialized

      public final double timeSinceInitialized()
      Returns the time since this command was initialized (in seconds). This function will work even if there is no specified timeout.
      Returns:
      the time since this command was initialized (in seconds).

    • requires

      protected void requires​(Subsystem subsystem)
      This method specifies that the given Subsystem is used by this command. This method is crucial to the functioning of the Command System in general.

      Note that the recommended way to call this method is in the constructor.

      Parameters:
      subsystem - the Subsystem required
      Throws:
      IllegalArgumentException - if subsystem is null
      IllegalUseOfCommandException - if this command has started before or if it has been given to a CommandGroup
      See Also:
      Subsystem

    • initialize

      protected void initialize()
      The initialize method is called the first time this Command is run after being started.

    • execute

      protected void execute()
      The execute method is called repeatedly until this Command either finishes or is canceled.

    • isFinished

      protected abstract boolean isFinished()
      Returns whether this command is finished. If it is, then the command will be removed and end() will be called.

      It may be useful for a team to reference the isTimedOut() method for time-sensitive commands.

      Returning false will result in the command never ending automatically. It may still be canceled manually or interrupted by another command. Returning true will result in the command executing once and finishing immediately. We recommend using InstantCommand for this.

      Returns:
      whether this command is finished.
      See Also:
      isTimedOut()

    • end

      protected void end()
      Called when the command ended peacefully. This is where you may want to wrap up loose ends, like shutting off a motor that was being used in the command.

    • interrupted

      protected void interrupted()
      Called when the command ends because somebody called cancel() or another command shared the same requirements as this one, and booted it out.

      This is where you may want to wrap up loose ends, like shutting off a motor that was being used in the command.

      Generally, it is useful to simply call the end() method within this method, as done here.

    • isTimedOut

      protected boolean isTimedOut()
      Returns whether or not the timeSinceInitialized() method returns a number which is greater than or equal to the timeout for the command. If there is no timeout, this will always return false.
      Returns:
      whether the time has expired

    • clearRequirements

      protected void clearRequirements()
      Clears list of subsystem requirements. This is only used by ConditionalCommand so canceling the chosen command works properly in CommandGroup.

    • start

      public void start()
      Starts up the command. Gets the command ready to start.

      Note that the command will eventually start, however it will not necessarily do so immediately, and may in fact be canceled before initialize is even called.

      Throws:
      IllegalUseOfCommandException - if the command is a part of a CommandGroup

    • isRunning

      public boolean isRunning()
      Returns whether or not the command is running. This may return true even if the command has just been canceled, as it may not have yet called interrupted().
      Returns:
      whether or not the command is running

    • cancel

      public void cancel()
      This will cancel the current command.

      This will cancel the current command eventually. It can be called multiple times. And it can be called when the command is not running. If the command is running though, then the command will be marked as canceled and eventually removed.

      A command can not be canceled if it is a part of a command group, you must cancel the command group instead.

      Throws:
      IllegalUseOfCommandException - if this command is a part of a command group

    • isCanceled

      public boolean isCanceled()
      Returns whether or not this has been canceled.
      Returns:
      whether or not this has been canceled

    • isCompleted

      public boolean isCompleted()
      Whether or not this command has completed running.
      Returns:
      whether or not this command has completed running.

    • isInterruptible

      public boolean isInterruptible()
      Returns whether or not this command can be interrupted.
      Returns:
      whether or not this command can be interrupted

    • setInterruptible

      protected void setInterruptible​(boolean interruptible)
      Sets whether or not this command can be interrupted.
      Parameters:
      interruptible - whether or not this command can be interrupted

    • doesRequire

      public boolean doesRequire​(Subsystem system)
      Checks if the command requires the given Subsystem.
      Parameters:
      system - the system
      Returns:
      whether or not the subsystem is required, or false if given null

    • getGroup

      public CommandGroup getGroup()
      Returns the CommandGroup that this command is a part of. Will return null if this Command is not in a group.
      Returns:
      the CommandGroup that this command is a part of (or null if not in group)

    • setRunWhenDisabled

      public void setRunWhenDisabled​(boolean run)
      Sets whether or not this Command should run when the robot is disabled.

      By default a command will not run when the robot is disabled, and will in fact be canceled.

      Parameters:
      run - whether or not this command should run when the robot is disabled

    • willRunWhenDisabled

      public boolean willRunWhenDisabled()
      Returns whether or not this Command will run when the robot is disabled, or if it will cancel itself.
      Returns:
      True if this command will run when the robot is disabled.

    • getName

      public String getName()
      Gets the name of this Command.
      Returns:
      Name

    • setName

      public void setName​(String name)
      Sets the name of this Command.
      Parameters:
      name - name

    • getSubsystem

      public String getSubsystem()
      Gets the subsystem name of this Command.
      Returns:
      Subsystem name

    • setSubsystem

      public void setSubsystem​(String subsystem)
      Sets the subsystem name of this Command.
      Parameters:
      subsystem - subsystem name

    • toString

      public String toString()
      The string representation for a Command is by default its name.
      Overrides:
      toString in class Object
      Returns:
      the string representation of this object

    • 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