Method 'onCheckboxClicked(android.view.View)' is never used

I'm coding in a Fragment. The rest of the code is okay but I got a small error. The error says:

Method 'onCheckboxClicked(android.view.View)' is never used.

Does anyone know what the problem is?

public void onCheckboxClicked(View view) {
    boolean checked = ((CheckBox) view).isChecked();

    checkOne = '0';
    checkTwo = '0';
    checkThree = '0';

    switch (view.getId()) {

        case R.id.checkboxbak:

            if (checked) {
                checkOne = '1';
                changeImage(); }

            else {
                checkOne = '0';
                changeImage(); }
            break;


        case R.id.checkBox2:
            if (checked) {
                checkTwo = '1';
                changeImage(); }
            else {
                checkTwo = '0';
                changeImage(); }
            break;

        case R.id.checkBox3:
            if (checked) {
                checkThree = '1';
                changeImage(); }
            else {
                checkThree = '0';
                changeImage(); }
            break;
    }