Add MainActivity.kt

app/src/main/java/chat/rocket/android/chatrooms/ui/MainActivity.kt

+package chat.rocket.android.chatrooms.ui
+
+import android.os.Bundle
+import android.support.v4.app.Fragment
+import android.support.v7.app.AppCompatActivity
+import chat.rocket.android.R
+import chat.rocket.android.util.addFragment
+import dagger.android.AndroidInjection
+import dagger.android.AndroidInjector
+import dagger.android.DispatchingAndroidInjector
+import dagger.android.support.HasSupportFragmentInjector
+import javax.inject.Inject
+
+class MainActivity : AppCompatActivity(), HasSupportFragmentInjector {
+    @Inject lateinit var fragmentDispatchingAndroidInjector: DispatchingAndroidInjector<Fragment>
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_main)
+
+        AndroidInjection.inject(this)
+
+        addFragment("ChatRoomsFragment", R.id.fragment_container) {
+            ChatRoomsFragment.newInstance()
+        }
+    }
+
+    override fun supportFragmentInjector(): AndroidInjector<Fragment> {
+        return fragmentDispatchingAndroidInjector
+    }
+}
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