RamseteCommand in SequentialCommandGroup Errors Java

Technical Java
1

New to Java programing. Working on planning some Auto routines. We have successfully followed a path from PathWeaver with RamseteCommand created in the getAutonomousCommand and returning that command (like the wpilib documents show). We are attempting to implement a SequentialCommandGroup so that we can run the shooter for a time and then follow a path using RamseteCommand to pick up some additional cargo and make more complex routines. I have used the exact same RamseteCommand that worked when in the getAutonomousCommand, but it is generating an error every time it goes to start running the command.

I am getting this error:

Unhandled exception: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
from: java.base/jdk.internal.util.Preconditions.outOfBounds(Unknown Source)
at: at java.base/jdk.internal.util.Preconditions.outOfBounds(Unknown Source)
at: at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Unknown Source)
at: at java.base/jdk.internal.util.Preconditions.checkIndex(Unknown Source)
at: at java.base/java.util.Objects.checkIndex(Unknown Source)
at: at java.base/java.util.ArrayList.get(Unknown Source)
at: at edu.wpi.first.math.trajectory.Trajectory.sample(Trajectory.java:99)
at: at edu.wpi.first.wpilibj2.command.RamseteCommand.initialize(RamseteCommand.java:137)
at: at edu.wpi.first.wpilibj2.command.SequentialCommandGroup.execute(SequentialCommandGroup.java:72)
at: at edu.wpi.first.wpilibj2.command.CommandScheduler.run(CommandScheduler.java:280)
at: at frc.robot.Robot.robotPeriodic(Robot.java:74)
at: at edu.wpi.first.wpilibj.IterativeRobotBase.loopFunc(IterativeRobotBase.java:328)
at: at edu.wpi.first.wpilibj.TimedRobot.startCompetition(TimedRobot.java:131)
at: at edu.wpi.first.wpilibj.RobotBase.runRobot(RobotBase.java:373)
at: at edu.wpi.first.wpilibj.RobotBase.startRobot(RobotBase.java:463)
at: at frc.robot.Main.main(Main.java:23)

Error at java.base/jdk.internal.util.Preconditions.outOfBounds(Unknown Source): Unhandled exception: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
at java.base/jdk.internal.util.Preconditions.outOfBounds(Unknown Source)
at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Unknown Source)
at java.base/jdk.internal.util.Preconditions.checkIndex(Unknown Source)

Here is a link to the github for the TestAuto command. The rest of the code is there as well.

There is alot of cleanup and unused imports and things as this is a work in progress so go easy we are new to Java :wink:

2

At first glance your trajectory might be empty. The error message basically shows ramsete getting the first step of the trajectory, and that fails.

1 Like
3

Agreed, the trajectory is empty when the autonomous command is created.
In the constructor for RobotContainer on line 93, testAuto variable gets set to a new instance of the command group with the trajectory from Robot. However, in Robot.java on line 42 the robotContainer variable is initialized to a new robot container before the trajectories are loaded, which means the testTrajectory is still an empty trajectory when the autonomous command is created.
I would try loading the trajectory before initializing the robot container. (so move lines 44 through 49 in Robot.java above line 42)
Sorry this reply was in two parts, I sent it before I was done typing by accident lol.

1 Like
4

That makes perfect sense. I will give it a try and post back on here tomorrow… getAutonomousCommand wasnt run until well after the paths were imported.

Thanks! Wish I understood the error messages better

5

Wish I understood the error messages better

Don’t be deterred by the error’s stack trace being that long. The key elements are

Unhandled exception:
java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
...
java.base/java.util.ArrayList.get(Unknown Source)
...
edu.wpi.first.wpilibj2.command.RamseteCommand.initialize(RamseteCommand.java:137)

So the RamseteCommand has trouble early on in initialize, something related to an array.
If you check the source code for RamseteCommand.java line 137, it’s this:

    var initialState = m_trajectory.sample(0);

So for some reason the trajectory must be empty, and it’s downhill from there on.

3 Likes
6

Thanks for that… makes some more sense… I am now getting a new error message…

  • Loop time of 0.02s overrun
  • Warning at edu.wpi.first.wpilibj.IterativeRobotBase.printLoopOverrunMessage(IterativeRobotBase.java:359): Loop time of 0.02s overrun
  • Unhandled exception: java.lang.NullPointerException
  • Error at java.base/java.util.ImmutableCollections$Set12.(Unknown Source): Unhandled exception: java.lang.NullPointerException
  • at java.base/java.util.ImmutableCollections$Set12.(Unknown Source)
  • at java.base/java.util.Set.of(Unknown Source)
  • at edu.wpi.first.wpilibj2.command.CommandGroupBase.requireUngrouped(CommandGroupBase.java:57)
  • at edu.wpi.first.wpilibj2.command.ParallelRaceGroup.addCommands(ParallelRaceGroup.java:37)
  • at edu.wpi.first.wpilibj2.command.ParallelRaceGroup.(ParallelRaceGroup.java:32)
  • at frc.robot.commands.TestAuto.(TestAuto.java:28)
  • at frc.robot.RobotContainer.getAutonomousCommand(RobotContainer.java:134)
  • at frc.robot.Robot.autonomousInit(Robot.java:95)
  • at edu.wpi.first.wpilibj.IterativeRobotBase.loopFunc(IterativeRobotBase.java:294)
  • at edu.wpi.first.wpilibj.TimedRobot.startCompetition(TimedRobot.java:131)
  • at edu.wpi.first.wpilibj.RobotBase.runRobot(RobotBase.java:373)
  • at edu.wpi.first.wpilibj.RobotBase.startRobot(RobotBase.java:463)
  • at frc.robot.Main.main(Main.java:23)
  • DifferentialDrive… Output not updated often enough.
  • Error at edu.wpi.first.wpilibj.MotorSafety.check(MotorSafety.java:96): DifferentialDrive… Output not updated often enough.

I am struggling to figure out why it is doing this only in Autonomous Mode. When I enable during teleoperated no error is given. I updated the github with new code. The auto I am trying is the TestAuto Command

This has worked great. Thanks!!!

7

Your trying to add a command that is a null pointer: startShooter.

8

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