Class Command
- java.lang.Object
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- edu.wpi.first.wpilibj.command.Command
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- 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 tostart(). Once a command is started it will callinitialize(), and then will repeatedly callexecute()until theisFinished()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 andinterrupted()will be called.If a command uses a
Subsystem, then it should specify that it does so by calling therequires(...)method in its constructor. Note that a Command may have multiple requirements, andrequires(...)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
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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.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description voidcancel()This will cancel the current command.protected voidclearRequirements()Clears list of subsystem requirements.voidclose()booleandoesRequire(Subsystem system)Checks if the command requires the givenSubsystem.protected voidend()Called when the command ended peacefully.protected voidexecute()The execute method is called repeatedly until this Command either finishes or is canceled.CommandGroupgetGroup()Returns theCommandGroupthat this command is a part of.StringgetName()Gets the name of this Command.StringgetSubsystem()Gets the subsystem name of this Command.protected voidinitialize()The initialize method is called the first time this Command is run after being started.voidinitSendable(SendableBuilder builder)Initializes thisSendableobject.protected voidinterrupted()Called when the command ends because somebody calledcancel()or another command shared the same requirements as this one, and booted it out.booleanisCanceled()Returns whether or not this has been canceled.booleanisCompleted()Whether or not this command has completed running.protected abstract booleanisFinished()Returns whether this command is finished.booleanisInterruptible()Returns whether or not this command can be interrupted.booleanisRunning()Returns whether or not the command is running.protected booleanisTimedOut()Returns whether or not thetimeSinceInitialized()method returns a number which is greater than or equal to the timeout for the command.protected voidrequires(Subsystem subsystem)This method specifies that the givenSubsystemis used by this command.protected voidsetInterruptible(boolean interruptible)Sets whether or not this command can be interrupted.voidsetName(String name)Sets the name of this Command.voidsetRunWhenDisabled(boolean run)Sets whether or not thisCommandshould run when the robot is disabled.voidsetSubsystem(String subsystem)Sets the subsystem name of this Command.protected voidsetTimeout(double seconds)Sets the timeout of this command.voidstart()Starts up the command.doubletimeSinceInitialized()Returns the time since this command was initialized (in seconds).StringtoString()The string representation for aCommandis by default its name.booleanwillRunWhenDisabled()Returns whether or not thisCommandwill run when the robot is disabled, or if it will cancel itself.
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Constructor Detail
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Command
public Command()
Creates a new command. The name of this command will be set to its class name.
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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
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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()
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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()
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Command
public Command(String name, Subsystem subsystem)
Creates a new command with the given name.- Parameters:
name- the name for this commandsubsystem- the subsystem that this command requires- Throws:
IllegalArgumentException- if name is null
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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()
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Command
public Command(String name, double timeout)
Creates a new command with the given name and timeout.- Parameters:
name- the name of the commandtimeout- the time (in seconds) before this command "times out"- Throws:
IllegalArgumentException- if given a negative timeout or name was null.- See Also:
isTimedOut()
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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 commandtimeout- the time (in seconds) before this command "times out"subsystem- the subsystem that this command requires- Throws:
IllegalArgumentException- if given a negative timeoutIllegalArgumentException- if given a negative timeout or name was null.- See Also:
isTimedOut()
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Method Detail
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close
public void close()
- Specified by:
closein interfaceAutoCloseable
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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()
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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).
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requires
protected void requires(Subsystem subsystem)
This method specifies that the givenSubsystemis 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- theSubsystemrequired- Throws:
IllegalArgumentException- if subsystem is nullIllegalUseOfCommandException- if this command has started before or if it has been given to aCommandGroup- See Also:
Subsystem
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initialize
protected void initialize()
The initialize method is called the first time this Command is run after being started.
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execute
protected void execute()
The execute method is called repeatedly until this Command either finishes or is canceled.
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isFinished
protected abstract boolean isFinished()
Returns whether this command is finished. If it is, then the command will be removed andend()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 cancelled manually or interrupted by another command. Returning true will result in the command executing once and finishing immediately. We recommend using
InstantCommandfor this.- Returns:
- whether this command is finished.
- See Also:
isTimedOut()
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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.
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interrupted
protected void interrupted()
Called when the command ends because somebody calledcancel()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.
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isTimedOut
protected boolean isTimedOut()
Returns whether or not thetimeSinceInitialized()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
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clearRequirements
protected void clearRequirements()
Clears list of subsystem requirements. This is only used byConditionalCommandso cancelling the chosen command works properly inCommandGroup.
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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
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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 calledinterrupted().- Returns:
- whether or not the command is running
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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
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isCanceled
public boolean isCanceled()
Returns whether or not this has been canceled.- Returns:
- whether or not this has been canceled
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isCompleted
public boolean isCompleted()
Whether or not this command has completed running.- Returns:
- whether or not this command has completed running.
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isInterruptible
public boolean isInterruptible()
Returns whether or not this command can be interrupted.- Returns:
- whether or not this command can be interrupted
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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
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doesRequire
public boolean doesRequire(Subsystem system)
Checks if the command requires the givenSubsystem.- Parameters:
system- the system- Returns:
- whether or not the subsystem is required, or false if given null
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getGroup
public CommandGroup getGroup()
Returns theCommandGroupthat this command is a part of. Will return null if thisCommandis not in a group.- Returns:
- the
CommandGroupthat this command is a part of (or null if not in group)
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setRunWhenDisabled
public void setRunWhenDisabled(boolean run)
Sets whether or not thisCommandshould 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
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willRunWhenDisabled
public boolean willRunWhenDisabled()
Returns whether or not thisCommandwill run when the robot is disabled, or if it will cancel itself.- Returns:
- True if this command will run when the robot is disabled.
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getName
public String getName()
Gets the name of this Command.
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setName
public void setName(String name)
Sets the name of this Command.
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getSubsystem
public String getSubsystem()
Gets the subsystem name of this Command.- Specified by:
getSubsystemin interfaceSendable- Returns:
- Subsystem name
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setSubsystem
public void setSubsystem(String subsystem)
Sets the subsystem name of this Command.- Specified by:
setSubsystemin interfaceSendable- Parameters:
subsystem- subsystem name
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initSendable
public void initSendable(SendableBuilder builder)
Description copied from interface:SendableInitializes thisSendableobject.- Specified by:
initSendablein interfaceSendable- Parameters:
builder- sendable builder
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