Actions and Sequencing

Prepare autonomous code for Road Runner action composition.

Autonomous FoundationsAdvanced

In this lesson, you will:

Write instant and running actions.
Return completion correctly.
Compose actions safely.

Concept narrative

Actions are reusable autonomous behaviors that continue until they report completion. This model aligns with Road Runner 1.0 and command-based robot thinking.

Robot mental model

An action is a cooperative task. It must do a small amount of work each time run is called, report telemetry, and finish when its condition is satisfied.

Implementation walkthrough

Create one instant servo action and one encoder-wait action. Then compose them sequentially. Keep run calls short; do not hide sleeps inside custom actions.

MechanismAction.javaJava

public Action liftTo(int target) {
    return new Action() {
        private boolean initialized;
        private final ElapsedTime timer = new ElapsedTime();

        @Override
        public boolean run(@NonNull TelemetryPacket packet) {
            boolean stopRequested = !opModeIsActive();
            if (stopRequested) {
                lift.setPower(0.0);
                packet.put("liftStopRequested", true);
                packet.put("liftExit", "stop");
                return false;
            }

            if (!initialized) {
                lift.setTargetPosition(target);
                lift.setMode(DcMotor.RunMode.RUN_TO_POSITION);
                lift.setPower(0.4);
                timer.reset();
                initialized = true;
            }

            int error = target - lift.getCurrentPosition();
            boolean timedOut = timer.seconds() >= 2.0;
            boolean running = Math.abs(error) > 25 && !timedOut;

            packet.put("liftError", error);
            packet.put("liftTimedOut", timedOut);
            packet.put("liftStopRequested", stopRequested);
            if (!running) {
                lift.setPower(0.0);
                packet.put("liftExit", timedOut ? "timeout" : "target");
            }
            return running;
        }
    };
}

try {
    Actions.runBlocking(liftTo(targetTicks));
} finally {
    lift.setPower(0.0); // Cover OpMode interruption as well as normal completion.
}

Common mistakes and debugging

Returning false too soon starts the next action early; returning true forever stalls auto. Long blocking calls starve parallel actions.

Practice

Write an action that moves a lift until error is small, then use it in a sequence with a claw action.

Checkpoint

Each run call returns promptly so other actions can continue.
The lift action initializes mode and power exactly once.
The action ends on tolerance or a documented timeout and reports the reason.
Lift power returns to zero after completion and after OpMode interruption.
A teammate can reproduce the sequence from the saved target, timeout, and telemetry.

Reflection check

Check your understanding before moving on.

For a Road Runner 1.0 Action, what does returning true from run(packet) mean?

The action completed and should be removed.

The action needs another scheduler call to continue.

The OpMode should restart initialization.

Before a lift action waits for encoder error to shrink, what setup must it perform?

Only read the encoder once.

Call Thread.sleep inside run(packet).

Set its target, choose the appropriate motor mode, command safe power, and define a timeout.

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References

Road Runner 1.0 ActionsAction composition, custom actions, and autonomous structure.FIRST FTC DocsOfficial SDK, Robot Controller, and programming reference.