Dagger2: no injector factory bound for fragment

Question

I'm trying to convert a project that I'm building to use the dagger-android API for the DI framework, but I'm running into a dead end with an IllegalArgumentException when trying to inject a fragment using @ContributesAnroidInjector.

The relevant modules and components are included below:

ApplicationComponent.java

@Singleton
@Component(modules = {AndroidSupportInjectionModule.class,
    ApplicationModule.class,
    ActivityBindingModule.class,
    DataManagerModule.class})
public interface ApplicationComponent extends AndroidInjector<MyApplication> {

DataManagerContract getDataManager();

void inject(MyApplication application);

@Component.Builder
interface Builder {

    @BindsInstance
    ApplicationComponent.Builder application(Application application);

    ApplicationComponent build();
    }
}

my ActivityBindingModule.java:

@Module
public abstract class ActivityBindingModule {

    @ActivityScope
    @ContributesAndroidInjector(modules = MainActivityModule.class)
    abstract MainActivity bindMainActivity();

    @ActivityScope
    @ContributesAndroidInjector(modules = SplashActivityModule.class)
    abstract SplashActivity bindSplashActivity();

    @ActivityScope
    @ContributesAndroidInjector(modules = LoginActivityModule.class)
    abstract LoginActivity bindLoginActivity();
}

MainActivityModule.java

@Module
public abstract class MainActivityModule {

    @ActivityScope
    @Binds
    abstract MainActivityContract.Presenter provideMainActivityPresenter(MainActivityPresenter presenter);

    @FragmentScope
    @ContributesAndroidInjector
    abstract HomeFragment provideHomeFragment();

    @FragmentScope
    @Binds
    abstract HomeFragmentContract.Presenter provideHomeFragmentPresenter(HomeFragmentPresenter presenter);

    // Inject other fragments and presenters
}

SplashActivity and LoginActivity only depend on their respective presenters, and dagger works fine in these. But my MainActivity can contain numerous fragments and causes a crash when trying to inject one of those fragments using:

HomeFragment.java

public class HomeFragment extends Fragment {
    ....
    @Override
    public void onAttach(Context context) {
        AndroidSupportInjection.inject(this);
        super.onAttach(context);
    }
    ....
}

Here is my logcat for this crash:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp/com.myapp.main.MainActivity}: java.lang.IllegalArgumentException: No injector factory bound for Class<com.myapp.ui.main.Home.HomeFragment>
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.IllegalArgumentException: No injector factory bound for Class<com.myapp.ui.main.Home.HomeFragment>
        at dagger.android.DispatchingAndroidInjector.inject(DispatchingAndroidInjector.java:104)
        at dagger.android.support.AndroidSupportInjection.inject(AndroidSupportInjection.java:74)
        at com.myapp.ui.main.Home.HomeFragment.onAttach(HomeFragment.java:65)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1363)
        at android.support.v4.app.FragmentTransition.addToFirstInLastOut(FragmentTransition.java:1109)
        at android.support.v4.app.FragmentTransition.calculateFragments(FragmentTransition.java:996)
        at android.support.v4.app.FragmentTransition.startTransitions(FragmentTransition.java:99)
        at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2364)
        at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2322)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2229)
        at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3221)
        at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:3171)
        at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:192)
        at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:560)
        at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:177)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1248)
        at android.app.Activity.performStart(Activity.java:6696)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2628)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
        at android.app.ActivityThread.-wrap12(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6119) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

I'm not sure where the problem in the code is. If I move the bindings for HomeFragment to the ActivityBindingModule, the app runs fine, but the crash comes back if I bring those bindings back into the MainActivityModule. What am I doing wrong here?

EDIT:

public class MyApp extends DaggerApplication {

    @Override
    protected AndroidInjector<? extends DaggerApplication> applicationInjector() {
        return DaggerApplicationComponent.builder().application(this).build();
    }
}

and my main activity:

public class MainActivity extends AppCompatActivity
    implements MainActivityContract.View,
    NavigationView.OnNavigationItemSelectedListener {

@Inject
MainActivityContract.Presenter mPresenter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    AndroidInjection.inject(this);
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Open home fragment on first start
    if (savedInstanceState == null) {
        // Create new instance of HomeFragment
        HomeFragment homeFragment = HomeFragment.newInstance();

        FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.content_main, homeFragment)
                .commit();
    }

// Other logic
}

Answer 1

When you inject using AndroidSupportInjection.inject(this) from your HomeFragment, Dagger will walk the parent-fragment hierarchy to find someone that implements HasSupportFragmentInjector. To make it work, make your MainActivity extends DaggerAppCompatActivity which implements HasSupportFragmentInjector.

From the doc of AndroidSupportInjection.inject(Fragment fragment):

Injects {@code fragment} if an associated {@link dagger.android.AndroidInjector} implementation can be found, otherwise throws an {@link IllegalArgumentException}.

Uses the following algorithm to find the appropriate {@code AndroidInjector} to use to inject {@code fragment}:

1. Walks the parent-fragment hierarchy to find the a fragment that implements {@link HasSupportFragmentInjector}, and if none do
2. Uses the {@code fragment}'s {@link Fragment#getActivity() activity} if it implements {@link HasSupportFragmentInjector}, and if not
3. Uses the {@link android.app.Application} if it implements {@link HasSupportFragmentInjector}.

If none of them implement {@link HasSupportFragmentInjector}, a {@link IllegalArgumentException} is thrown.

@throws IllegalArgumentException if no parent fragment, activity, or application implements {@link HasSupportFragmentInjector}.

With this, Dagger will use

@FragmentScope
@ContributesAndroidInjector
abstract HomeFragment provideHomeFragment();

from your MainActivityModule to inject inside your HomeFragment.

Answer 2

There could be other scenarious, where I got similar errors:

Possible case 1:
When you have a DialogFragment shown from a Fragment.
It's important to use the same FragmentManager.

For instance you have a "fragment-scoped screen":

@FragmentScope
@ContributesAndroidInjector(modules = [HomeInjectors::class])
abstract fun provideHomeFragment() HomeFragment

With a subcomponent

@Module
abstract class HomeInjectors {

    @ChildFragmentScope
    @ContributesAndroidInjector(modules = [DetailsModule::class])
    abstract fun provideDetailsFragment(): DetailsDialogFragment

}

Important here to note, that when you show a dialog fragment, you should use child fragment manager not the Activity's one.

in this case, if you show dialog from the HomeFragment,

detailsDialog.show(activity.supportFragmentManager, "some tag)

and

detailsDialog.show(requireFragmentManager(), "some tag)

will not work.

You should do instead:

detailsDialog.show(childFragmentManager, "some tag)

Possible case 2: Parent fragment with child fragments.

In order to make child fragments with "smaller" scope (Sample code is the same as above, but consider DetailsDialogFragment a regular fragment and a child of the HomeFragment).

In my case, the child fragment wasn't able to find Parent's fragment injector.

The reason was that while providing a child fragment injector, I mistakenly made my BaseFragment implement HasFragmentInjector.
However, since I use support fragments (AndroidX or whatever), I should have made BaseFragment implement HasSupportFragmentInjector

So the BaseFragment may look like:

import androidx.fragment.app.Fragment

abstract class BaseFragment : SometFragment(), HasSupportFragmentInjector {

    @Inject lateinit var childFragmentInjector: DispatchingAndroidInjector<Fragment>

    override fun supportFragmentInjector(): AndroidInjector<Fragment> {
        return childFragmentInjector
    }

    override fun onAttach(context: Context) {
        AndroidSupportInjection.inject(this)
        super.onAttach(context)
    }
}

It is useful when by certain reasons your "BaseFragment" must have other than DaggerFragment parent