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Dagger2 and Android Lifecycle
with Kotlin
@takuji31
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@takuji31
(Takuji Nishibayashi)
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Loves Kotlin
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Dagger2
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de facto standard of DI container for
Android (may be)
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Compile )me dependency
resolu)on
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Scoped singleton
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Example of use
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Inject context
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Inject presenter
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Inject Realm
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Two Headaches
for Android
of the life cycle
with injected instances
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Headaches
• Handle lifecycle events
• Retain some instance during configura7on change
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Handle lifecycle events
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Stop UI refreshing in presenter
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Cancel API request
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Close Realm instance
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Unsubscribe RxJava subscrip1on
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Retain some instance
during
screen rota0on
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Keep API request
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Loaded model instances
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But, Loader is difficult !
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Solu%on
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Headaches
• Handle lifecycle events !
• Retain some instance during configura7on change
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Create lifecycle provider
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Lifecycle provider
interface ActivityLifecycle {
fun onCreate(savedInstanceStete: Bundle?) {}
fun onSaveInstanceState(outState: Bundle?) {}
fun onDestroy() {}
//...
}
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Lifecycle provider
object Lifecycles {
fun activity(vararg lifecycles: ActivityLifecycle): ActivityLifecycle {
return object : ActivityLifecycle {
override fun onCreate(savedInstanceStete: Bundle?) {
lifecycles.forEach { it.onCreate(savedInstanceStete = savedInstanceStete) }
}
override fun onStart() {
lifecycles.forEach { it.onStart() }
}
//...
}
}
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Provide Lifecycle provider
@Module
class UserModule() {
@Provides @PerActivity fun lifecycle(presenter: UserPresenter) : ActivityLifecycle {
return presenter
//or return Lifecycles.activity(presenter, some, lifecycle, objects)
}
}
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Use lifecycle provider
class UserActivity : AppCompatActivity() {
@Inject
lateinit var lifecycle : ActivityLifecycle
var component : UserComponent by Delegates.notNull()
override fun onCreate(savedInstanceState: Bundle?) {
lifecycle.onCreate(savedInstanceStete = savedInstanceState)
}
override fun onDestroy() {
lifecycle.onDestroy()
}
}
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Headaches
• Handle lifecycle events
• Retain some instance during configura7on change !
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Use retain fragment
for keep
component
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Retain fragment
class UserComponentFragment : Fragment() {
var component: UserComponent? = null
init {
retainInstance = true
}
companion object {
val TAG = "UserComponentFragment"
}
}
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Use retain fragment
class UserActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
var storeFragment = supportFragmentManager
.findFragmentByTag(UserComponentFragment.TAG) as? UserComponentFragment
if (storeFragment == null) {
storeFragment = UserComponentFragment()
supportFragmentManager
.beginTransaction()
.add(storeFragment, UserComponentFragment.TAG)
.commit()
}
if (storeFragment.component == null) {
//init component
}
storeFragment.component.inject(this)
}
}
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see. takuji31/Dagger2Android
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Enjoy Dagger2
and
Android life !