Slim: Stop Writing and Rewriting Boilerplate Code

Slim is an annotation library whose main purpose is to remove common boilerplate associated with Android development. You can find it here on GitHub.

Features

  • Assignment of ‘extras’ passed through to an Activity or Fragment
  • Casting of an Activity to an interface callback within a Fragment
  • Easily call through to an Activity through an interface callback
  • Layout declaration at the top of the class
  • Base class implementations that remove having to call through to the Slim methods
  • Pairs well with other Annotation-based libraries, such as ButterKnife
  • Check out GitHub for more

 

Usage

@Extra

public class MyActivity extends Activity {    public static final String EXTRA_DATA = "data";    @Extra(EXTRA_DATA)    Data mData;    public void onCreate(Bundle savedInstanceState) {      super.onCreate(savedInstanceState);      Slim.injectExtras(getIntent().getExtras(), this);    }}

An exception will be thrown by default if an extra is not found. You can mark an extra as optional by setting optional = true inside the annotation parameters. This will also allow you to set a default value:

@Extra(value = EXTRA_DATA, optional = true)Data mData = Data.newInstance();

mData will be set to Data.newInstance() if an extra was not found matching key EXTRA_DATA.

 

@Callback

public class MyFragment extends Fragment {    @Callback    MyCallback mMyCallback;    public void onAttach(Activity activity) {        super.onAttach(activity);        Slim.injectCallback(this);    }    public interface MyCallback {        public void doStuff();    }}

This will cast the Activity to your callback for you automatically. If the Activity does not implement the Fragment interface, a ClassCastException will be thrown with an appropriate error message in the logs.

 

@CallbackClick

public class MyFragment extends Fragment {    @Callback    MyCallback mMyCallback;    public void onAttach(Activity activity) {        super.onAttach(activity);        Slim.injectCallbacks(this);    }    public void onViewCreated(View view, Bundle savedInstanceState) {        super.onViewCreated(view, savedInstanceState);        Slim.injectCallbacksMethods(this);    }    public interface MyCallback {        @CallbackClick(R.id.do_stuff)        public void doStuff();    }}

This will automatically assign a click listener from a View represented by its id to your callback’s methods. Due to limitations with Java annotations, this will only work with zero argument methods.

 

 

@Layout

@Layout(R.layout.fragment_main)public class MyFragment extends Fragment {    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {        return Slim.createLayout(getActivity(), this, container);    }}

This will work anywhere you have access to a Context.

@Layout(R.layout.list_item)public class MyAdapter extends BaseAdapter {    @Override    public View getView(int position, View convertView, ViewGroup parent) {        View view = convertView;        if(view == null) {            view = Slim.createLayout(parent.getContext(), this, parent);        }        // ...        return view;    }}

 

 

Other

@Layout(R.layout.fragment_example)public class ExampleFragment extends SlimFragment {    public static final String EXTRA_TEXT = "extra_text";    @Extra(EXTRA_TEXT)    String mText;    @Callback    ExampleCallback mCallback;    @Override    public void onViewCreated(View view, Bundle savedInstanceState) {        super.onViewCreated(view, savedInstanceState);        TextView textView = (TextView) view.findViewById(R.id.text);        textView.setText(mText);    }    public interface ExampleCallback {        @CallbackClick(R.id.example_Button)        public void goToNextScreen();    }}

 

 

Author avatar
Jason Robinson
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