zxing onActivityResult not called in Fragment only in Activity

As Martynnw pointed out the issue is to call fragment.startActivityForResult instead of activity.startActivityForResult. So just use next wrapper:

import android.content.Intent;
import android.support.v4.app.Fragment;

import com.google.zxing.integration.android.IntentIntegrator;

public final class FragmentIntentIntegrator extends IntentIntegrator {

    private final Fragment fragment;

    public FragmentIntentIntegrator(Fragment fragment) {
        super(fragment.getActivity());
        this.fragment = fragment;
    }

    @Override
    protected void startActivityForResult(Intent intent, int code) {
        fragment.startActivityForResult(intent, code);
    }
}

integrator.initiateScan();

Change the above line as

integrator.forSupportFragment(fragment_name.this).initiateScan();