InventoryRetriever.java

package com.mozu.mozuandroidinstoreassistant.app.loaders;

import com.mozu.api.MozuApiContext;
import com.mozu.api.contracts.productadmin.LocationInventoryCollection;
import com.mozu.api.contracts.productruntime.Product;
import com.mozu.api.resources.commerce.catalog.admin.products.LocationInventoryResource;

import rx.Observable;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;

public class InventoryRetriever {

    public Observable<LocationInventoryCollection> getInventoryData(final Product product, int tenantId, int siteId) {
        final LocationInventoryResource inventoryResource = new LocationInventoryResource(new MozuApiContext(tenantId, siteId));

        return Observable
                .create(new Observable.OnSubscribe<LocationInventoryCollection>() {
                        @Override
                        public void call(Subscriber<? super LocationInventoryCollection> subscriber) {
                            try {
                                subscriber.onNext(inventoryResource.getLocationInventories(product.getProductCode()));
                                subscriber.onCompleted();
                            } catch (Exception e) {
                                subscriber.onError(e);
                            }
                        }
                    })
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeOn(Schedulers.io());

    }

}

ProductDetailInventoryFragment.java

package com.mozu.mozuandroidinstoreassistant.app.fragments;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

import com.crashlytics.android.Crashlytics;
import com.mozu.api.contracts.productadmin.LocationInventory;
import com.mozu.api.contracts.productadmin.LocationInventoryCollection;
import com.mozu.api.contracts.productruntime.Product;
import com.mozu.mozuandroidinstoreassistant.app.R;
import com.mozu.mozuandroidinstoreassistant.app.adapters.ProdDetailLocationInventoryAdapter;
import com.mozu.mozuandroidinstoreassistant.app.loaders.InventoryRetriever;

import java.util.List;

import butterknife.ButterKnife;
import butterknife.InjectView;
import rx.Observer;
import rx.Subscription;
import rx.android.observables.AndroidObservable;

public class ProductDetailInventoryFragment extends Fragment implements Observer<LocationInventoryCollection> {

    private Product mProduct;

    private int mTenantId;
    private int mSiteId;

    private List<LocationInventory> mInventory;

    @InjectView(R.id.inventory_list) ListView mInventoryList;
    @InjectView(R.id.inventory_progress) ProgressBar mProgress;
    @InjectView(R.id.dialog_header) LinearLayout mDialogLayout;

    private Subscription mSubscription;

    public ProductDetailInventoryFragment() {
        // Required empty public constructor

        setRetainInstance(true);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mSubscription = AndroidObservable.bindFragment(this, new InventoryRetriever().getInventoryData(mProduct, mTenantId, mSiteId)).subscribe(this);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.product_detail_inventory_fragment, null);

        ButterKnife.inject(this, view);

        if (mInventory == null) {
            mProgress.setVisibility(View.VISIBLE);
            mInventoryList.setVisibility(View.GONE);
        } else {
            onCompleted();
        }

        return view;
    }

    @Override
    public void onDestroyView() {
        mSubscription.unsubscribe();

        super.onDestroyView();
    }

    public void onNext(LocationInventoryCollection inventoryCollection) {
        mInventory = inventoryCollection.getItems();
    }

    @Override
    public void onCompleted() {
        mProgress.setVisibility(View.GONE);
        mInventoryList.setVisibility(View.VISIBLE);

        mInventoryList.setAdapter(new ProdDetailLocationInventoryAdapter(getActivity(), mInventory,mTenantId,mSiteId));
    }

    public void onError(Throwable error) {

        Crashlytics.logException(error);
    }

    public void setProduct(Product product) {
        mProduct = product;
    }

    public void setTenantId(int tenantId) {
        mTenantId = tenantId;
    }

    public void setSiteId(int siteId) {
        mSiteId = siteId;
    }

}

Two thoughts:

1. Usually you don't need to call Observable.create(). I understand the problem you're trying to solve here; you can't just use Observable.just() since your long-running call will happen immediately. Good news: combine it with Observable.defer() and it'll work great!

   Observable.defer(new Func0<Observable<?>>() {
       @Override
       public Observable<?> call() {
           return Observable.just(inventoryResource.getLocationInventories(product.getProductCode()));
       }
   });
   

2. You should let the subscriber call subscribeOn() and observeOn(). Instead of calling it before returning the Observable, you should leave it be and call it right before subscribe().

One minor note. I typically like to let the client set the observeOn and subscribeOn.

So your fragment code sets subscribeOn(Schedulers.IO).observeOn(AndroidSchedulers.mainThread).

Then later if you ever wish to write tests using Mockito you can use the same InventoryRetriever API and set the threads accordingly. (Typically you don't set any threads so it runs synchronously which simplifies testing)

Thanks @dlew and @zsiegel, I've moved the observerOn and subscribeOn to the client.

@dlew, I've changed Observable.create to use defer/just, but with defer/just, how would you call your subscribers error callback?

@dlew im interested to know why you use defer instead of create? Is this something new that was updated recently?

One other thing you might want to change is to make your subscribe/unscubsribe calls in methods such as onResume/onPause... the AndroidObservable.bindFragment insulates this from you a bit but typically when possible I always like to ensure the points where I subscribe and unsubscribe are in matching lifecycle methods.

This also helps for example when the user might background or resume your app you can suspend or refresh work when needed.

I responded on Twitter, but any Exceptions should just be naturally passed along to onError().

One other thing I might change: I'm personally used to creating my own anonymous inner classes for Subscribers. The reason being that there could be many, many different subscribers in one class.

Actually one more thing i just noticed.

You should change the line

Subscription mSubscription

to something like

Subscription mSubscription = Subscriptions.empty()

This should insulate you from any NPE errors if you decide to change where you subscribe and unsubscribe