What is Proton?

A lightweight dependency injection framework for Android.

Inspired by MiniGuice and RoboGuice

Getting Started

Initialize App

public class MyApplication extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        Proton.initialize(this, new MyModule());
    }
}

Define Module

public class MyModule extends DefaultModule {
    @Override
    protected void configure() {
        super.configure();
        bind(Greeting.class).to(GreetingImpl.class);
    }
}

Field Injection

public class MainActivity extends ProtonActivity {
    @Inject private Greeting mGreeting;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView textView = (TextView) findViewById(R.id.greeting_text);
        textView.setText(mGreeting.greet());
    }
}

Context-scoped Injection

Proton supports context-scoped injection.

@ContextScoped
public class GreetingImpl extends Greeting {
    ...
}

or

public class MyModule extends DefaultModule {
    @Override
    protected void configure() {
        super.configure();
        bind(Greeting.class).to(GreetingImpl.class).in(ContextScoped.class);
    }
}

• @ApplicationScoped => is injected as application singleton.
• @ContextScoped => is injected as context singleton.
• @Dependent => is injected as new object every time.

Tips

On-demand Injection

Injector injector = Proton.getInjector(...);
Greeting greeting = new GreetingImpl();
injector.inject(greeting);

Provider Injection

public class BigCoffeeMaker {
    @Inject Provider<Filter> mFilterProvider;

    public void brew(int numberOfPots) {
        ...
        for (int p = 0; p < numberOfPots; p++) {
            maker.addFileter(filterProvider.get()); // new filter every time.
            maker.addCoffee(...);
            maker.percolate();
            ...
        }
    }
}

RetainState

@RetainState saves value automatically when the android system call onSaveInstanceState.

Proguard Settings

You need to add the following lines to your proguard configuration file.

-keepattributes *Annotation*
-keepclassmembers class * {
   @javax.inject.Inject <init>(...);
}
-keepclassmembers class * {
   void *(**On*Event);
}

Todo

• Test utility

License

    Copyright 2013 Hirofumi Nakagawa.

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.