Ricardo's Blog

  • 03:43:16 pm on January 19, 2011 | 3
    Tags: , ,

    The Problem: Adapters cannot be injected into Activities because the BaseAdapter constructor requires a Context be passed to it.

    The Solution: Create a new Guice @InjectAdapter annotation and TypeListener that dynamically creates an adapter on injection, passing the inject Activity to the adapter’s constructor.

    So, our activity code might look something like this:

    public class SampleActivity extends GuiceListActivity {

 @Inject
 List<Integer> items;

 @InjectAdapter
 @Override
 public void setListAdapter(ListAdapter adapter) {
  super.setListAdapter(adapter);
 }

 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  Log.i(TAG, "searching for local profiles");
  setContentView(R.layout.main);
 }
}

    Out module might then have the following code:

    bindListener(Matchers.any(), new AdapterTypeListener(binder()));
bind(ListAdapter.class).to(LocalProfilesAdapter.class);

    Where AdapterTypeListener is defined as follows:

    public <T> void hear(TypeLiteral<T> typeLiteral, TypeEncounter<T> typeEncounter) {

Class<T> type = typeLiteral.getRawType();

for (Field field : type.getDeclaredFields()) {
	if (Adapter.class.isAssignableFrom(field.getType()) && field.isAnnotationPresent(InjectAdapter.class)) {
		typeEncounter.register(new AdapterMembersInjector<T>(field));
	}
}

for (Method method : type.getDeclaredMethods()) {
	if(method.isAnnotationPresent(InjectAdapter.class)) {
		typeEncounter.register(new AdapterMembersInjector<T>(method));
	}
}
}

    Last we could define AdapterMembersInjector as follows:

    public class AdapterMembersInjector<T> implements MembersInjector<T> {

	private Field field;
	private Method setter;
	TypeEncounter<T> typeEncounter;

	AdapterMembersInjector(Field field, TypeEncounter<T> typeEncounter) {
		this.field = field;
		field.setAccessible(true);
	}

	AdapterMembersInjector(Method setter, TypeEncounter<T> typeEncounter) {
		this.setter = setter;
		setter.setAccessible(true);
	}

	public void injectMembers(T activity) {
		Adapter adapter;

		if(field != null) {
			try {
				field.set(activity, adapter);
			} catch (IllegalAccessException e) {
				throw new RuntimeException(e);
			}
		} else if(setter != null) {
			try {
				setter.invoke(activity, adapter);
			} catch (IllegalArgumentException e) {
				throw new RuntimeException(e);
			} catch (IllegalAccessException e) {
				throw new RuntimeException(e);
			} catch (InvocationTargetException e) {
				throw new RuntimeException(e);
			}
		}
	}

}

    The problem is how do we create a reference to Adapter in the above MembersInjector, with all the correct dependencies including the Activity context injected into it’s constructor?

     

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