Chief Delphi - extending CANJaguar subclass

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extending CANJaguar subclass

I am trying to add methods to help with reading our robots actual speed off of a CANJaguar in fps. The issue I am having now is that it is not building becasue it needs a constructor, but if I am inheriting the class shouldn't they already exist. What i want to be able to do is when i call a CANJaguar object, e.g. leftMotor.getFps(), it will return the fps data to me. This is my code so far.

Any help is greatly appreciated.

Code:

/*

 * To change this template, choose Tools | Templates

 * and open the template in the editor.

 */

package edu.wpi.first.wpilibj;

import edu.wpi.first.wpilibj.can.CANTimeoutException;

import edu.wpi.first.wpilibj.can.JaguarCANProtocol;





/**

 *

 * @author rudun

 */

public class fps extends CANJaguar {



    final static double PI = Math.PI;

    private double WheelSize;

     /**

     * Get the speed of your robot.

     *

     * @return The speed of the robot in fps.

     */

    public double getFps() throws CANTimeoutException {

        byte[] dataBuffer = new byte[8];

        byte dataSize;

        double rpms;



        dataSize = getTransaction(JaguarCANProtocol.LM_API_STATUS_SPD, dataBuffer);

        if (dataSize == 4) {

            rpms = unpackFXP16_16(dataBuffer);

        } else {

            rpms = 0.0;

        }

        

        double fps = 0;

        fps = (rpms *(WheelSize * PI))/(60 * 12);

        return fps;

    }

    

    public void setWheelSize(double WheelSizeInInches) {

        WheelSize = WheelSizeInInches;

        }

}

and this is my current compiler output

Code:

init:

clean:

init:

clean:

Created dir: C:\Users\kyle\Documents\NetBeansProjects\fpstest\build

Compiling 2 source files to C:\Users\kyle\Documents\NetBeansProjects\fpstest\build

C:\Users\kyle\Documents\NetBeansProjects\fpstest\src\edu\wpi\first\wpilibj\fps.java:13: error: no suitable constructor found for CANJaguar()

public class fps extends CANJaguar {

    constructor CANJaguar.CANJaguar(int,ControlMode) is not applicable

      (actual and formal argument lists differ in length)

    constructor CANJaguar.CANJaguar(int) is not applicable

      (actual and formal argument lists differ in length)

1 error

C:\Users\kyle\sunspotfrcsdk\ant\compile.xml:48: Compile failed; see the compiler error output for details.

BUILD FAILED (total time: 8 seconds)

Re: extending CANJaguar subclass

Quote:

Originally Posted by rudun (Post 1085890)

The issue I am having now is that it is not building becasue it needs a constructor, but if I am inheriting the class shouldn't they already exist.

In this case you need to explicitly define at least one constructor for your subclass (fps).

Why? Because if you don't specify a constructor in a subclass, Java makes a default one for you that doesn't take any arguments. But that default no-argument constructor expects to call the no-argument constructor for all of the superclasses (CANJaguar in your case). CANJaguar doesn't have a no-argument constructor, only the two constructors CANJaguar(int, ControlMode) and CANJaguar(int). That's what the compiler error message is telling you - that CANJaguar has "no suitable constructor" for a default no-argument subclass constructor to call.

So you need to do something like this:

Code:

public class fps extends CANJaguar {

   

   public fps(int id) throws Exception {

         super(id);

   }



...

}

Hope that helps!

- Ron
Team #2607 controls mentor

Re: extending CANJaguar subclass

Thanks Ron. It now works, and even my math which is always a culprit in slowing me down was right. Here is what the whole thing is to anyone intrested in using the encoder on the Jaguar to calculate fps.

Code:

/*

 * To change this template, choose Tools | Templates

 * and open the template in the editor.

 */

package edu.wpi.first.wpilibj;

import edu.wpi.first.wpilibj.can.CANTimeoutException;

import edu.wpi.first.wpilibj.can.JaguarCANProtocol;





/**

 *

 * @author rudun, 1203

 */

public class FPS extends CANJaguar{



    final static double PI = Math.PI;

    private double WheelSize;

    

    public FPS(int id) throws CANTimeoutException {

        super(id);

   }

     /**

     * Get the speed of your robot.

     *

     * @return The speed of the robot in fps.

     */

    public double getFps() throws CANTimeoutException {

        byte[] dataBuffer = new byte[8];

        byte dataSize;

        double rpms;



        dataSize = getTransaction(JaguarCANProtocol.LM_API_STATUS_SPD, dataBuffer);

        if (dataSize == 4) {

            rpms = unpackFXP16_16(dataBuffer);

        } else {

            rpms = 0.0;

        }

        

        double fps = 0;

        fps = (rpms *(WheelSize * PI))/(60 * 12);

        return fps;

    }

    

    public void setWheelSize(double WheelSizeInInches) {

        WheelSize = WheelSizeInInches;

        }

}