Why I am getting this

Question

java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.shopgroc.controller.ProductController.addProduct(com.example.shopgroc.model.Product)' on a null object reference at com.example.shopgroc.fragment.store.addItemToStore.setModel(addItemToStore.java:384) at com.example.shopgroc.fragment.store.addItemToStore.onClick(addItemToStore.java:350)

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(addItemToStore.java:350)
 public void onClick(View v) {
        int id = v.getId();
        if(id == R.id.btnAddStoreItem){
            setModel();
        }
    }

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(addItemToStore.java:384)
productController.addProduct(product);