I am working on an app which uses the NavigationDrawer. Different fragments are placed into the content view of the MainActivity whenever a menu item in the drawer is selected.
To inform the MainActivity that a Fragment successfully attached the following callback is executed:
public class CustomFragment extends Fragment {
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
((MainActivity) activity).onSectionAttached();
}
}
Since I am started using Otto with Dagger in the project I am curious how I can substitute the callback with a .post() event such as:
mBus.post(new CustomFragmentAttachedEvent);
The problem is that mBus is null in onAttach(). It gets initialized in onCreate().
#Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
((MyApp) getActivity().getApplication()).getObjectGraph().inject(this);
}
Here is an example of such a Fragment class.
References:
Complete Android Fragment & Activity Lifecycle
You can easily try out the example yourself: Create a new project from the NavigationDrawer template available in Android Studio, add Dagger and Otto and try to substitute the mentioned callback.
Working solution:
Here is the example Fragment in the final working version.
You can create a provider for your Otto bus with Dagger as follows:
#Module(injects = {
YourFragment.class,
MainActivity.class
},complete = true)
public class EventBusModule {
#Provides
#Singleton
Bus provideBus() {
return new Bus();
}
}
Then you register the EventBusModule when you create your ObjectGraph. You can create your graph in the Application's onCreate():
public class MyApplication extends Application{
public void onCreate() {
Object[] modules = new Object[]{new EventBusModule()};
Injector.init(modules);
}
}
You would need to create an Injector that has some static methods and a reference to the ObjectGraph so you can manipulate it without having a reference to the Application. Something like this:
public final class Injector {
private static ObjectGraph objectGraph = null;
public static void init(final Object... modules) {
if (objectGraph == null) {
objectGraph = ObjectGraph.create(modules);
}
else {
objectGraph = objectGraph.plus(modules);
}
// Inject statics
objectGraph.injectStatics();
}
public static final void inject(final Object target) {
objectGraph.inject(target);
}
public static <T> T resolve(Class<T> type) {
return objectGraph.get(type);
}
}
Then you just use #Inject in your Fragment to let Dagger give you a Bus instance and inject the Fragment:
public class MyFragment extends Fragment{
#Inject Bus mBus;
public void onAttach(){
Injector.inject(this);
}
}
Related
I am trying to make an injection using Dagger 2, but it always returns null. I think I am doing all right, but anyway it does not work.
Here is the application class:
public class ApplicationSA extends Application {
private static AppComponent appComponent;
#Override
public void onCreate() {
super.onCreate();
appComponent = DaggerAppComponent.create();
}
public static AppComponent getComponent() {
return appComponent;
}
}
The component interface:
#Component(modules = {
SnoreDetectorClass.class,
AudioRecorderClass.class
})
public interface AppComponent {
void injectsMainFunctionalityActivity(Activity activity);
}
An the main class where I am trying to get the object:
public class MainFunctionalityActivity extends AppCompatActivity {
#Inject
AudioRecorderClass audioRecorderClass;
#Inject
SnoreDetectorClass snoreDetectorClass;
#Override
protected void onCreate(Bundle savedInstanceState) {
ApplicationSA.getComponent().injectsMainFunctionalityActivity(this);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d("TESTING","audioRecorderClass= "+audioRecorderClass); // always null
Log.d("TESTING","snoreDetectorClass= "+snoreDetectorClass); // always null
...
}
And here are the module classes:
#Module
public class AudioRecorderClass {
public interface AudioRecorderInterface {
void AudioRecorder_hasUpdate(double amplitude_in_dB);
}
public AudioRecorderInterface delegate = null;
#Provides
AudioRecorderClass provideAudioRecorderClass(Activity activity) {
delegate = (AudioRecorderInterface)activity;
return new AudioRecorderClass();
}
...
#Module
public class SnoreDetectorClass {
#Provides
SnoreDetectorClass provideSnoreDetectorClass() {
return new SnoreDetectorClass();
}
...
What am I doing wrong ? Why the objects are always null ?
Ah, I see what is going on here. You cannot inject into a subclass. So in your AppComponent you cannot have
void injectsMainFunctionalityActivity(Activity activity);
you must inject with
void injectsMainFunctionalityActivity(MainFunctionalityActivity activity);
As a side note I would suggest not combining your injector and your model class. Better to have separation of concerns. Keep them separate
You have to specifically tell dagger which activity will be injected here, not use the super class Activity but rather your own implementation of the Activity class :
void injectsMainFunctionalityActivity(Activity activity);
change to:
void injectsMainFunctionalityActivity(MainFunctionalityActivity activity);
Android Studio 3.0 Canary 8
I am trying to inject my MainActivity into my Adapter. However, my solution works ok, but I think its a code smell and not the right way to do it.
My adapter snippet looks like this the but I don't like about this is that I have to cast the Activity to MainActivity:
public class RecipeAdapter extends RecyclerView.Adapter<RecipeListViewHolder> {
private List<Recipe> recipeList = Collections.emptyList();
private Map<Integer, RecipeListViewHolderFactory> viewHolderFactories;
private MainActivity mainActivity;
public RecipeAdapter(Activity activity, Map<Integer, RecipeListViewHolderFactory> viewHolderFactories) {
this.recipeList = new ArrayList<>();
this.viewHolderFactories = viewHolderFactories;
this.mainActivity = (MainActivity)activity;
}
#Override
public RecipeListViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
/* Inject the viewholder */
final RecipeListViewHolder recipeListViewHolder = viewHolderFactories.get(Constants.RECIPE_LIST).createViewHolder(viewGroup);
recipeListViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
/* Using the MainActivity to call a callback listener */
mainActivity.onRecipeItemClick(getRecipe(recipeListViewHolder.getAdapterPosition()));
}
});
return recipeListViewHolder;
}
}
In my Module, I pass the Activity in the module's constructor and pass it to the Adapter.
#Module
public class RecipeListModule {
private Activity activity;
public RecipeListModule() {}
public RecipeListModule(Activity activity) {
this.activity = activity;
}
#RecipeListScope
#Provides
RecipeAdapter providesRecipeAdapter(Map<Integer, RecipeListViewHolderFactory> viewHolderFactories) {
return new RecipeAdapter(activity, viewHolderFactories);
}
}
In My Application class I create the components and I am using a SubComponent for the adapter. Here I have to pass the Activity which I am not sure is a good idea.
#Override
public void onCreate() {
super.onCreate();
applicationComponent = createApplicationComponent();
recipeListComponent = createRecipeListComponent();
}
public BusbyBakingComponent createApplicationComponent() {
return DaggerBusbyBakingComponent.builder()
.networkModule(new NetworkModule())
.androidModule(new AndroidModule(BusbyBakingApplication.this))
.exoPlayerModule(new ExoPlayerModule())
.build();
}
public RecipeListComponent createRecipeListComponent(Activity activity) {
return recipeListComponent = applicationComponent.add(new RecipeListModule(activity));
}
My Fragment I inject like this:
#Inject RecipeAdapter recipeAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
((BusbyBakingApplication)getActivity().getApplication())
.createRecipeListComponent(getActivity())
.inject(this);
}
Even though the above design works, I think it's a code smell as I have to cast the Activity to the MainActivity. The reason I use the Activity as I want to make this module more generic.
Just wondering if there is a better way
=============== UPDATE USING INTERFACE
Interface
public interface RecipeItemClickListener {
void onRecipeItemClick(Recipe recipe);
}
Implementation
public class RecipeItemClickListenerImp implements RecipeItemClickListener {
#Override
public void onRecipeItemClick(Recipe recipe, Context context) {
final Intent intent = Henson.with(context)
.gotoRecipeDetailActivity()
.recipe(recipe)
.build();
context.startActivity(intent);
}
}
In my module, I have the following providers
#Module
public class RecipeListModule {
#RecipeListScope
#Provides
RecipeItemClickListener providesRecipeItemClickListenerImp() {
return new RecipeItemClickListenerImp();
}
#RecipeListScope
#Provides
RecipeAdapter providesRecipeAdapter(RecipeItemClickListener recipeItemClickListener, Map<Integer, RecipeListViewHolderFactory> viewHolderFactories) {
return new RecipeAdapter(recipeItemClickListener, viewHolderFactories);
}
}
Then I use it through constructor injection in the RecipeAdapter
public class RecipeAdapter extends RecyclerView.Adapter<RecipeListViewHolder> {
private List<Recipe> recipeList = Collections.emptyList();
private Map<Integer, RecipeListViewHolderFactory> viewHolderFactories;
private RecipeItemClickListener recipeItemClickListener;
#Inject /* IS THIS NESSESSARY - AS IT WORKS WITH AND WITHOUT THE #Inject annotation */
public RecipeAdapter(RecipeItemClickListener recipeItemClickListener, Map<Integer, RecipeListViewHolderFactory> viewHolderFactories) {
this.recipeList = new ArrayList<>();
this.viewHolderFactories = viewHolderFactories;
this.recipeItemClickListener = recipeItemClickListener;
}
#Override
public RecipeListViewHolder onCreateViewHolder(final ViewGroup viewGroup, int i) {
/* Inject the viewholder */
final RecipeListViewHolder recipeListViewHolder = viewHolderFactories.get(Constants.RECIPE_LIST).createViewHolder(viewGroup);
recipeListViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
recipeItemClickListener.onRecipeItemClick(getRecipe(recipeListViewHolder.getAdapterPosition()), viewGroup.getContext());
}
});
return recipeListViewHolder;
}
}
Just one question, is the #Inject annotation need for the constructor in the RecipeAdapter. As it works with or without the #Inject.
Do not pass Activities into Adapters - This is a really bad practice.
Inject only the fields you care about.
In your example: Pass an interface into the adapter to track the item click.
If you need a MainActivity then you should also provide it. Instead of Activity declare MainActivity for your module.
#Module
public class RecipeListModule {
private MainActivity activity;
public RecipeListModule(MainActivity activity) {
this.activity = activity;
}
}
And your Adapter should just request it (Constructor Injection for non Android Framework types!)
#RecipeListScope
class RecipeAdapter {
#Inject
RecipeAdapter(MainActivity activity,
Map<Integer, RecipeListViewHolderFactory> viewHolderFactories) {
// ...
}
}
If you want your module to use Activity and not MainActivity then you will need to declare an interface as already mentioned. You adapter would then declare the interface as its dependency.
But in some module you will still have to bind that interface to your MainActivity and one module needs to know how to provide the dependency.
// in some abstract module
#Binds MyAdapterInterface(MainActivity activity) // bind the activity to the interface
Addressing the updated part of the question
Just one question, is the #Inject annotation need for the constructor in the RecipeAdapter. As it works with or without the #Inject.
It works without it because you're still not using constructor injection. You're still calling the constructor yourself in providesRecipeAdapter(). As a general rule of thumb—if you want to use Dagger properly—don't ever call new yourself. If you want to use new ask yourself if you could be using constructor injection instead.
The same module you show could be written as follows, making use of #Binds to bind an implementation to the interface, and actually using constructor injection to create the adapter (which is why we don't have to write any method for it! Less code to maintain, less errors, more readable classes)
As you see I don't need to use new myself—Dagger will create the objects for me.
public abstract class RecipeListModule {
#RecipeListScope
#Binds
RecipeItemClickListener providesRecipeClickListener(RecipeItemClickListenerImp listener);
}
Personally I would do the following trick
public class MainActivity extends AppCompatActivity {
private static final String TAG = "__ACTIVITY__";
public static MainActivity get(Context context) {
// noinspection ResourceType
return (MainActivity)context.getSystemService(TAG);
}
#Override
protected Object getSystemService(String name) {
if(TAG.equals(name)) {
return this;
}
return super.getSystemService(name);
}
}
public class RecipeAdapter extends RecyclerView.Adapter<RecipeListViewHolder> {
private List<Recipe> recipeList = Collections.emptyList();
private Map<Integer, RecipeListViewHolderFactory> viewHolderFactories;
public RecipeAdapter(Map<Integer, RecipeListViewHolderFactory> viewHolderFactories) {
this.recipeList = new ArrayList<>();
this.viewHolderFactories = viewHolderFactories;
}
#Override
public RecipeListViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
/* Inject the viewholder */
final RecipeListViewHolder recipeListViewHolder = viewHolderFactories.get(Constants.RECIPE_LIST).createViewHolder(viewGroup);
recipeListViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
MainActivity mainActivity = MainActivity.get(v.getContext());
if(recipeListViewHolder.getAdapterPosition() != -1) {
mainActivity.onRecipeItemClick(
getRecipe(recipeListViewHolder.getAdapterPosition()));
}
}
});
return recipeListViewHolder;
}
}
i'm trying to update this below code to dagger2, but i get error for ObjectGraph:
import dagger.ObjectGraph;
public class App extends Application {
private static App instance;
private ObjectGraph objectGraph;
public App() {
instance = this;
}
#Override
public void onCreate() {
super.onCreate();
objectGraph = ObjectGraph.create(new AppModule());
}
public static void injectMembers(Object object) {
getInstance().objectGraph.inject(object);
}
public static <T>T get(Class<T> klass) {
return getInstance().objectGraph.get(klass);
}
public static App getInstance() {
return instance;
}
}
how can i update that to and which class must be use instead of ObjectGraph?
injectMembers used in this class
public class MyJobManager extends JobManager {
public MyJobManager(Context context) {
super(context, new Configuration.Builder(context)
.injector(new DependencyInjector() {
#Override
public void inject(BaseJob baseJob) {
App.injectMembers(baseJob);
}
})
.build());
}
}
now how can i inject with component?
my component:
#ActivitiesScope
#Component(dependencies = GithubApplicationComponent.class)
public interface ApplicationComponent {
void inject(ActivityRegister activityRegister);
void inject(ActivityStartUpApplication activityStartUpApplication);
void inject(GetLatestRepositories getLatestRepositories);
}
Dagger 2 doesn't use an ObjectGraph. It doesn't use anything as its replacement. Dagger1 did injection at runtime via reflection and used the ObjectGraph to provide that functionality. Dagger 2 does injection at compile time, thus it doesn't need a runtime object to represent the graph. Instead you'd want to build a component that links the modules you with to provide. You can then inject using that component.
See https://google.github.io/dagger/dagger-1-migration.html for more details.
Let's say I have MainActivity where are few Fragments in ViewPager. I want to pass data from another Activity to one of these fragments. I'm doing this by BroadcastReceiver.
public class MyFragment extends Fragment {
private MyFragmentReceiver mReceiver;
public MyFragment() {
super();
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mReceiver = new MyFragmentReceiver();
getActivity().registerReceiver(mReceiver, new IntentFilter("fragmentUpdater"));
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_my, container, false);
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// My code here
}
public class MyFragmentReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
//My methods
}
}
#Override
public void onDestroy() {
super.onDestroy();
if (mReceiver != null)
getActivity().unregisterReceiver(mReceiver);
}
}
So in my AnotherActivity I'm doing something like this:
Intent data = new Intent("fragmentUpdater");
MyApplication.getInstance().getMainActivity().sendBroadcast(data);
Where MyApplication is singleton which contains MainActivity.
I noticed that BroadcastReceiver is putting something into logs, and I am wondering is that the best way to do it.
Are there better ways to pass data from another activity to specific Fragment or call methods in that Fragment?
Do I have to include something in AndroidManifest.xml related to BroadcastReceiver?
One alternative is using an interface for communicating between your activity and fragments. Example:
Interface
public interface MyInterface {
void setSomeValue(int someValue);
int getSomeValue();
}
Activity
public class MyActivity extends Activity implements MyInterface {
private int someValue;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// do the usual stuff
}
// implement from MyInterface
#Override
public void setSomeValue(int someValue) {
this.someValue = someValue;
}
// implement from MyInterface
#Override
public int getSomeValue() {
return someValue;
}
}
Fragment
public class MyFragment extends Fragment {
private MyInterface mi;
#Override
public void onAttach(Context context) {
super.onAttach(context);
mi = (MyInterface) context;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
mi.setSomeValue(20);
int someValue = mi.getSomeValue();
}
}
You can use the interface to communicate between one or more activities, multiple fragments, views, tasks, services, etc etc etc. If you were to go this route, I would create a base activity which implements MyInterface and its methods, and have all other activities extend the base activity. I would even create a base fragment which calls onAttach(), and have all my other fragments extend this base fragment (so that I don't need to call onAttach() in every fragment).
UPDATE...
A base fragment would simply look like this:
public class BaseFragment extends Fragment {
public MyInterface mi;
#Override
public void onAttach(Context context) {
super.onAttach(context);
mi = (MyInterface) context;
}
}
Now, MyFragment would just extend BaseFragment...
public class MyFragment extends BaseFragment {
...
}
There's no need now to attach or even declare MyInterface in any fragment extending BaseFragment, the base fragment already has a public instance of it. You just set/get/etc via your interface without any additional fuss:
mi.setSomeValue(20);
I would use LocalBroadcastManager instead, it gives you the following advantages :
You know that the data you are broadcasting won't leave your app, so
don't need to worry about leaking private data.
It is not possible for other applications to send these broadcasts
to your app, so you don't need to worry about having security holes
they can exploit.
It is more efficient than sending a global broadcast through the system.
This is directly from the official docs
You may pass the data using Extras.
Intent data = new Intent("fragmentUpdater");
data.putExtra("STRING_YOU_NEED", strName);
and you can get the data inside onReceive function by :
String data_needed_here= extras.getString("STRING_YOU_NEED");
I am attempting to add Dagger 2 to my Android Project. I think I understand the concepts up to the point of where I build the graph. At that point I'm shooting in the dark and that is where I'm going wrong.
Everything compiles, but the injected field is null at Runtime.
I am attempting to start simply by injecting the Presenter into my MainActivity. I have written the following code and would appreciate some help figuring out where I have gone wrong.
My PresenterModule.java:
#Module
public class PresenterModule {
#Provides MainActivityPresenter providesMainActivityPresenter() {
return new DefaultMainActivityPresenter();
}
}
My Application class which also includes my Component following the Dagger2 example code:
public class App extends Application {
private PresenterComponent component;
#Singleton
#Component(modules = PresenterModule.class)
public interface PresenterComponent {
void inject(App app);
void inject(MainActivity activity);
}
#Override public void onCreate() {
Log.d("App.java", "Starting Application");
super.onCreate();
component = DaggerApp_PresenterComponent.builder()
.presenterModule(new PresenterModule())
.build();
component.inject(this);
}
public PresenterComponent component() {
return component;
}
}
And finally my MainActivity.
public class DefaultMainActivity
extends ActionBarActivity
implements MainActivity
{
#Inject MainActivityPresenter mPresenter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
((App)getApplication()).component().inject(this);
mPresenter.getCurrentDetailLineNumber();
setContentView(R.layout.base_layout);
getSupportActionBar();
mContainer = (Container) findViewById(R.id.container);
mPresenter.requestCurrentScreen();
}
The actual object to be injected is an implementation of an interface but is other wise a POJO object:
public class DefaultMainActivityPresenter implements MainActivityPresenter {
private static final int SCREEN_BROWSER = 0;
private static final int SCREEN_DETAIL = 1;
LineNumber mCurrentDetailLineNumber;
int mCurrentScreen;
#Inject
public DefaultMainActivityPresenter() {
}
...
}
Changing PresenterComponent to following will fix your problem:
#Singleton
#Component(modules = PresenterModule.class)
public interface PresenterComponent {
void inject(App app);
void inject(DefaultMainActivity activity);
}
This is due to covariance:
While a members-injection method for a type will accept instances of its subtypes, only Inject-annotated members of the parameter type and its supertypes will be injected; members of subtypes will not. For example, given the following types, only a and b will be injected into an instance of Child when it is passed to the members-injection method injectSelf(Self instance):
class Parent {
#Inject A a;
}
class Self extends Parent {
#Inject B b;
}
class Child extends Self {
#Inject C c;
}