An X-Drive chassis can be programmed using the same holonomic/omni-directional drive code structure as a mecanum drivetrain 11. The following code is based on the official FTC SDK sample for a 4-motor omni-directional robot 11.

Because the official sample in the documentation is truncated, the class below has been closed with the necessary brackets to compile. You will need to add setPower() calls at the end of the loop to apply the calculated powers to your motors.

package org.firstinspires.ftc.robotcontroller.external.samples;

import com.qualcomm.robotcore.eventloop.opmode.Disabled;
import com.qualcomm.robotcore.eventloop.opmode.LinearOpMode;
import com.qualcomm.robotcore.eventloop.opmode.TeleOp;
import com.qualcomm.robotcore.hardware.DcMotor;
import com.qualcomm.robotcore.util.ElapsedTime;

@TeleOp(name="Basic: Omni Linear OpMode", group="Linear OpMode")
@Disabled
public class BasicOmniOpMode_Linear extends LinearOpMode {

    // Declare OpMode members for each of the 4 motors.
    private ElapsedTime runtime = new ElapsedTime();
    private DcMotor frontLeftDrive = null;
    private DcMotor backLeftDrive = null;
    private DcMotor frontRightDrive = null;
    private DcMotor backRightDrive = null;

    @Override
    public void runOpMode() {

        // Initialize the hardware variables. Note that the strings used here must correspond
        // to the names assigned during the robot configuration step on the DS or RC devices.
        frontLeftDrive = hardwareMap.get(DcMotor.class, "front_left_drive");
        backLeftDrive = hardwareMap.get(DcMotor.class, "back_left_drive");
        frontRightDrive = hardwareMap.get(DcMotor.class, "front_right_drive");
        backRightDrive = hardwareMap.get(DcMotor.class, "back_right_drive");

        // ########################################################################################
        // !!!            IMPORTANT Drive Information. Test your motor directions.            !!!!!
        // ########################################################################################
        // Most robots need the motors on one side to be reversed to drive forward.
        // The motor reversals shown here are for a "direct drive" robot (the wheels turn the same direction as the motor shaft)
        // If your robot has additional gear reductions or uses a right-angled drive, it's important to ensure
        // that your motors are turning in the correct direction.  So, start out with the reversals here, BUT
        // when you first test your robot, push the left joystick forward and observe the direction the wheels turn.
        // Reverse the direction (flip FORWARD <-> REVERSE ) of any wheel that runs backward
        // Keep testing until ALL the wheels move the robot forward when you push the left joystick forward.
        frontLeftDrive.setDirection(DcMotor.Direction.REVERSE);
        backLeftDrive.setDirection(DcMotor.Direction.REVERSE);
        frontRightDrive.setDirection(DcMotor.Direction.FORWARD);
        backRightDrive.setDirection(DcMotor.Direction.FORWARD);

        // Wait for the game to start (driver presses START)
        telemetry.addData("Status", "Initialized");
        telemetry.update();

        waitForStart();
        runtime.reset();

        // run until the end of the match (driver presses STOP)
        while (opModeIsActive()) {
            double max;

            // POV Mode uses left joystick to go forward & strafe, and right joystick to rotate.
            double axial   = -gamepad1.left_stick_y;  // Note: pushing stick forward gives negative value
            double lateral =  gamepad1.left_stick_x;
            double yaw     =  gamepad1.right_stick_x;

            // Combine the joystick requests for each axis-motion to determine each wheel's power.
            // Set up a variable for each drive wheel to save the power level for telemetry.
            double frontLeftPower  = axial + lateral + yaw;
            double frontRightPower = axial - lateral - yaw;
            double backLeftPower   = axial - lateral + yaw;
            double backRightPower  = axial + lateral - yaw;

            // Normalize the values so no wheel power exceeds 100%
            // This ensures that the robot maintains the desired motion.
            max = Math.max(Math.abs(frontLeftPower), Math.abs(frontRightPower));
            max = Math.max(max, Math.abs(backLeftPower));
            max = Math.max(max, Math.abs(backRightPower));

            if (max > 1.0) {
                frontLeftPower  /= max;
                frontRightPower /= max;
                backLeftPower   /= max;
                backRightPower  /= max;
            }

            // This is test code:
            //
            // Uncomment the foll
        }
    }
}

What to Tune and What Will Break

• Motor Directions: The default configuration assumes a direct-drive setup where the left-side motors are reversed 11. If your robot uses a different gear reduction or a right-angled drive, the wheels may spin in the wrong directions 11. You must test and flip the FORWARD and REVERSE directions of any motor that runs backward when pushing the left joystick forward 11.
• Missing Motor Power Calls: Because the source sample is truncated, the code calculates the power variables (frontLeftPower, frontRightPower, etc.) but does not apply them to the motors. You must add setPower() calls (e.g., frontLeftDrive.setPower(frontLeftPower);) inside the while(opModeIsActive()) loop for the robot to physically move.