introduction.rst

Introduction

Developing an Android app includes a number of repetitive tasks. Like SQLite interactions or Model <=> JSON conversions or findViewsById() and then casting.

Eventually I ended up with a number of helper classes that were copied from project to project. That's how DroidParts started.

The vision for DroidParts is a minimalistic framework with clean API that eliminates the most common boilerplate code.

Some Code

The code below:

1. Displays a list of Postings from EntityCursorAdapter which is backed by ORM.
2. Injects a Button and sets OnClickListener.
3. Fetches, caches & attaches pics in a single line of code.
4. Serializes Postings to JSON & http POSTs the resulting JSONArray.

public class PostingListFragment extends ListFragment implements
      View.OnClickListener, AlterableContent<Select<Posting>>,
      AsyncTaskResultListener<HTTPResponse> {

   private EntityCursorAdapter<Posting> adapter;

   @InjectDependency
   private DialogFactory dialogFactory;

   @InjectView(id = R.id.btn_submit, click = true)
   private Button submitBtn;

   private Select<Posting> select;

   @Override
   public void onActivityCreated(Bundle savedInstanceState) {
      super.onActivityCreated(savedInstanceState);
      adapter = new PostingCursorAdapter(getActivity());
      setListAdapter(adapter);
   }

   @Override
   public void onClick(View v) {
      if (v == submitBtn) {
         submitPostings();
      }
   }

   @Override
   public void setContent(Select<Posting> select) {
      this.select = select;
      adapter.changeData(select);
   }

   private void submitPostings() {
      new SubmitPostingsTask(getActivity(), this, select).execute();
   }

   @Override
   public void onAsyncTaskSuccess(HTTPResponse resp) {
      dialogFactory.showToast("Response: " + resp.body);
   }

   @Override
   public void onAsyncTaskFailure(Exception e) {
      L.w(e);
      dialogFactory.showErrorToast();
   }

}

public class PostingCursorAdapter extends EntityCursorAdapter<Posting> {

   public PostingCursorAdapter(Context ctx) {
      super(Posting.class, ctx);
   }

   @InjectDependency
   private ImageFetcher imageFetcher;

   @Override
   public void bindView(Context context, View view, Posting item) {
      PostingViewHolder holder = (PostingViewHolder) view.getTag();
      holder.titleView.setText(item.title);
      imageFetcher.attachImage(holder.iconView, item.iconUrl);
   }

   // ...
}

public class SubmitPostingsTask extends SimpleAsyncTask<HTTPResponse> {

   private final Select<Posting> select;

   private final EntityManager<Posting> entityManager;
   private final JSONSerializer<Posting> jsonSerializer;

   @InjectDependency
   private RESTClient2 restClient;

   public SubmitPostingsTask(Context ctx,
         AsyncTaskResultListener<HTTPResponse> resultListener,
         Select<Posting> select) {
      super(ctx, resultListener);
      this.select = select;
      entityManager = new EntityManager<Posting>(Posting.class, ctx);
      jsonSerializer = new JSONSerializer<Posting>(Posting.class, ctx);
   }

   @Override
   protected HTTPResponse executeInBackground() throws Exception {
      ArrayList<Posting> list = entityManager.readAll(select);
      JSONArray arr = jsonSerializer.serialize(list);
      return restClient.post("http://example.com", arr);
   }

}

TL;DR DroidParts saves a lot of keystrokes & helps write elegant code.