Types of OpModes

In the FTC SDK, there are two primary classes you can inherit from to write your robot controller programs: OpMode and LinearOpMode. Choosing which one to use depends on how you want to structure your code and logic.

OpMode

An OpMode (often called an Iterative OpMode) acts like a state machine. It has specific methods (init(), init_loop(), start(), loop(), and stop()) that are repeatedly called by the system in a non-blocking loop. You must avoid using loops like while() or Thread.sleep() inside loop(), because it will freeze the robot and crash the app.

Linear OpMode

A LinearOpMode runs your code linearly from top to bottom. Everything happens inside a single runOpMode() method. To keep the program running continuously throughout the match, you must manually use a loop (usually while (opModeIsActive())). It’s easier for beginners to grasp because it acts like a traditional linear program and permits blocking code (like sleep()).

The Difference in Code

Here is a side-by-side comparison of a simple robot waiting for start and then driving forward. Notice the structural and syntax differences between the two.

// ITERATIVE OPMODE EXAMPLE
@TeleOp(name="Basic Iterative")
public class BasicIterative extends OpMode {
    DcMotor motor;

    @Override
    public void init() {
        motor = hardwareMap.get(DcMotor.class, "motor");
    }

    @Override
    public void loop() {
        // This repeatedly runs incredibly fast! No while loops here.
        motor.setPower(1.0);
    }
}

// LINEAR OPMODE EXAMPLE 
@TeleOp(name="Basic Linear")
public class BasicLinear extends LinearOpMode {
    DcMotor motor;

    @Override
    public void runOpMode() throws InterruptedException {
        // 1. Initialization code
        motor = hardwareMap.get(DcMotor.class, "motor");
        
        // 2. Wait for the play button
        waitForStart();

        // 3. Loop while the match is running
        while (opModeIsActive()) {
            motor.setPower(1.0);
        }
    }
}