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Nishant Srivastava The A,B and C of Lifecycle Components

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Nishant Srivastava twitter.com/nisrulz github.com/nisrulz www.nisrulz.com

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Soundbrenner

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The Challenge @nisrulz #DCBERLIN18

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The Challenge Android activity lifecycle.. @nisrulz #DCBERLIN18

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The Challenge Android activity lifecycle @nisrulz #DCBERLIN18

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The Challenge Android activity lifecycle - Many states @nisrulz #DCBERLIN18

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The Challenge Android activity lifecycle - Many states - Repeats on configuration changes @nisrulz #DCBERLIN18

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The Challenge Android activity lifecycle - Many states - Repeats on configuration changes Not to forget... @nisrulz #DCBERLIN18

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The Challenge ...the Fragment lifecycle. @nisrulz #DCBERLIN18

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The Challenge ...the Fragment lifecycle. @nisrulz #DCBERLIN18

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Architecture Components @nisrulz #DCBERLIN18

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Lifecycle Components @nisrulz #DCBERLIN18

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Lifecycle Components Series of classes designed to help deal with lifecycles in a more consistent fashion. @nisrulz #DCBERLIN18

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Lifecycle Components Series of classes designed to help deal with lifecycles in a more consistent fashion. - Lifecycle - LifecycleOwner - LifecycleObserver @nisrulz #DCBERLIN18

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Lifecycle @nisrulz #DCBERLIN18

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Lifecycle Series of states an object can be in. For Android: Object that defines Android lifecycle states. i.e. Activity & Fragment @nisrulz #DCBERLIN18

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Lifecycle @nisrulz #DCBERLIN18

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Lifecycle dependencies { def lifecycle_version = "1.1.1" // Support library already depends on this (since v26.1.0) // Both AppCompatActivity & Support Fragment implement // LifecycleOwner interface. // Lifecycles only implementation "android.arch.lifecycle:runtime:$lifecycle_version" ... } @nisrulz #DCBERLIN18

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Lifecycle // Source code public abstract class Lifecycle { // Adds a LifecycleObserver addObserver(@NonNull LifecycleObserver observer) // Removes the given observer from the observers list removeObserver(@NonNull LifecycleObserver observer) // Current state of the Lifecycle getCurrentState() // Compares the lifecycle states isAtLeast(@NonNull State state) ... } @nisrulz #DCBERLIN18

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Lifecycle // Source code public abstract class Lifecycle { // Adds a LifecycleObserver addObserver(@NonNull LifecycleObserver observer) // Removes the given observer from the observers list removeObserver(@NonNull LifecycleObserver observer) // Current state of the Lifecycle getCurrentState() // Compares the lifecycle states isAtLeast(@NonNull State state) ... } @nisrulz #DCBERLIN18

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Lifecycle // Source code public abstract class Lifecycle { // Adds a LifecycleObserver addObserver(@NonNull LifecycleObserver observer) // Removes the given observer from the observers list removeObserver(@NonNull LifecycleObserver observer) // Current state of the Lifecycle getCurrentState() // Compares the lifecycle states isAtLeast(@NonNull State state) ... } @nisrulz #DCBERLIN18

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LifecycleOwner @nisrulz #DCBERLIN18

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LifecycleOwner Interface that goes through Android Lifecycle. @nisrulz #DCBERLIN18

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LifecycleOwner Interface that goes through Android Lifecycle. // Source code public interface LifecycleOwner { // Returns the Lifecycle of the provider. @NonNull Lifecycle getLifecycle(); } @nisrulz #DCBERLIN18

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LifecycleOwner class MainActivity : AppCompatActivity() { // Missing myLifecycleObserver override fun onResume() { // Add lifecycle observer lifecycle.addObserver(myLifecycleObserver) } override fun onStop() { // Remove lifecycle observer lifecycle.removeObserver(myLifecycleObserver) } } @nisrulz #DCBERLIN18

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LifecycleOwner Fun Fact: Activities & fragments are not the only things with lifecycle by default @nisrulz #DCBERLIN18

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LifecycleOwner Fun Fact: Activities & fragments are not the only things with lifecycle by default You also have - LifecycleService - ProcessLifecycleOwner @nisrulz #DCBERLIN18

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LifecycleService @nisrulz #DCBERLIN18

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LifecycleService A service that is also a LifecycleOwner @nisrulz #DCBERLIN18

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LifecycleService A service that is also a LifecycleOwner // Source code public class LifecycleService extends Service implements LifecycleOwner { ... } @nisrulz #DCBERLIN18

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ProcessLifecycleOwner @nisrulz #DCBERLIN18

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ProcessLifecycleOwner - Class that tracks the lifecycle of @nisrulz #DCBERLIN18

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ProcessLifecycleOwner - Class that tracks the lifecycle of - whole application process or - all the activities combined @nisrulz #DCBERLIN18

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ProcessLifecycleOwner - Class that tracks the lifecycle of - whole application process or - all the activities combined - Useful for reacting to app coming to foreground or going to background @nisrulz #DCBERLIN18

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ProcessLifecycleOwner dependencies { def lifecycle_version = "1.1.1" // For ProcessLifecycleOwner implementation "android.arch.lifecycle:extensions:$lifecycle_version" ... } @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ON_CREATE ON_START & ON_RESUME ON_PAUSE & ON_STOP ON_DESTROY @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ON_CREATE (Only 1 time) ON_START & ON_RESUME ON_PAUSE & ON_STOP ON_DESTROY @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ON_CREATE (Only 1 time) ON_START & ON_RESUME (First Activity pass) ON_PAUSE & ON_STOP ON_DESTROY @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ON_CREATE (Only 1 time) ON_START & ON_RESUME (First Activity pass) ON_PAUSE & ON_STOP (after 700ms delay) ON_DESTROY @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ON_CREATE (Only 1 time) ON_START & ON_RESUME (First Activity pass) ON_PAUSE & ON_STOP (after 700ms delay) ON_DESTROY @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ON_CREATE (Only 1 time) ON_START & ON_RESUME (First Activity pass) ON_PAUSE & ON_STOP (after 700ms delay) ON_DESTROY @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ON_PAUSE & ON_STOP (after 700ms delay) @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ON_PAUSE & ON_STOP (after 700ms delay) // Source code public class ProcessLifecycleOwner implements LifecycleOwner { static final long TIMEOUT_MS = 700; //mls ... } @nisrulz #DCBERLIN18

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ProcessLifecycleOwner Guarantee that ProcessLifecycleOwner won’t send any events if activities are - Destroyed - Recreated due to configuration change @nisrulz #DCBERLIN18

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ProcessLifecycleOwner Comes with cost: @nisrulz #DCBERLIN18

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ProcessLifecycleOwner Comes with cost: extension artifact automatically adds element to your manifest @nisrulz #DCBERLIN18

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ProcessLifecycleOwner ... @nisrulz #DCBERLIN18

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ProcessLifecycleOwner // Source code // Internal class to initialize Lifecycles. public class ProcessLifecycleOwnerInitializer extends ContentProvider { @Override public boolean onCreate() { ... ProcessLifecycleOwner.init(getContext()); return true; } ... } @nisrulz #DCBERLIN18

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ProcessLifecycleOwner Side-effect: @nisrulz #DCBERLIN18

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ProcessLifecycleOwner Side-effect: Inits ProcessLifecycleOwner even if your app does not use it! @nisrulz #DCBERLIN18

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ProcessLifecycleOwner Side-effect: Inits ProcessLifecycleOwner even if your app does not use it! Why? @nisrulz #DCBERLIN18

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ProcessLifecycleOwner Side-effect: Inits ProcessLifecycleOwner even if your app does not use it! Why? So that ProcessLifecycleOwner can be invoked as soon as process starts @nisrulz #DCBERLIN18

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@nisrulz #DCBERLIN18 Application.ActivityLifecycleCallback vs ProcessLifecycleOwner

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@nisrulz #DCBERLIN18 Application.ActivityLifecycleCallback vs or ProcessLifecycleOwner

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Application.ActivityLifecycleCallback // Source code public interface ActivityLifecycleCallbacks { void onActivityCreated(Activity var1, Bundle var2); ... void onActivitySaveInstanceState(Activity var1, Bundle var2); void onActivityDestroyed(Activity var1); } @nisrulz #DCBERLIN18

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Application.ActivityLifecycleCallback // Register for the callback application .registerActivityLifecycleCallbacks(object: Application.ActivityLifecycleCallbacks{ override fun onActivityCreated(activity: Activity?, bundle: Bundle?) {} ... }) @nisrulz #DCBERLIN18

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ProcessLifecycleOwner // Source code public class ProcessLifecycleOwner implements LifecycleOwner { ... void attach(Context context) { ... Application app = (Application) context.getApplicationContext(); app.registerActivityLifecycleCallbacks (new EmptyActivityLifecycleCallbacks() { @Override public void onActivityCreated(Activity activity, Bundle savedInstanceState) { .. } ... }); } } @nisrulz #DCBERLIN18

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ProcessLifecycleOwner // Source code public class ProcessLifecycleOwner implements LifecycleOwner { ... void attach(Context context) { ... Application app = (Application) context.getApplicationContext(); app.registerActivityLifecycleCallbacks (new EmptyActivityLifecycleCallbacks() { @Override public void onActivityCreated(Activity activity, Bundle savedInstanceState) { .. } ... }); } } @nisrulz #DCBERLIN18

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ProcessLifecycleOwner // Source code public class ProcessLifecycleOwner implements LifecycleOwner { ... void attach(Context context) { ... Application app = (Application) context.getApplicationContext(); app.registerActivityLifecycleCallbacks (new EmptyActivityLifecycleCallbacks() { @Override public void onActivityCreated(Activity activity, Bundle savedInstanceState) { .. } ... }); } } @nisrulz #DCBERLIN18

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ProcessLifecycleOwner // Source code class EmptyActivityLifecycleCallbacks implements Application.ActivityLifecycleCallbacks { @Override public void onActivityCreated(Activity activity, Bundle savedInstanceState) { //Empty method body } ... } @nisrulz #DCBERLIN18

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ProcessLifecycleOwner // Source code class EmptyActivityLifecycleCallbacks implements Application.ActivityLifecycleCallbacks { @Override public void onActivityCreated(Activity activity, Bundle savedInstanceState) { //Empty method body } ... } @nisrulz #DCBERLIN18

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LifecycleRegistry @nisrulz #DCBERLIN18

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LifecycleRegistry Implementation of Lifecycle that can handle multiple observers @nisrulz #DCBERLIN18

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LifecycleRegistry Implementation of Lifecycle that can handle multiple observers // Source code public class LifecycleRegistry extends Lifecycle { ... } @nisrulz #DCBERLIN18

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LifecycleRegistry Implementation of Lifecycle that can handle multiple observers // Source code public class LifecycleRegistry extends Lifecycle { ... } However, you need to dispatch the events yourself. @nisrulz #DCBERLIN18

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LifecycleRegistry class MyLifecycleOwner : LifecycleOwner { private var registry: LifecycleRegistry = LifecycleRegistry(this) init { registry.handleLifecycleEvent(Lifecycle.Event.ON_CREATE) } override fun getLifecycle(): Lifecycle = registry fun startListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_START) } fun stopListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_STOP) } } @nisrulz #DCBERLIN18

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LifecycleRegistry class MyLifecycleOwner : LifecycleOwner { private var registry: LifecycleRegistry = LifecycleRegistry(this) init { registry.handleLifecycleEvent(Lifecycle.Event.ON_CREATE) } override fun getLifecycle(): Lifecycle = registry fun startListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_START) } fun stopListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_STOP) } } @nisrulz #DCBERLIN18

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LifecycleRegistry class MyLifecycleOwner : LifecycleOwner { private var registry: LifecycleRegistry = LifecycleRegistry(this) init { registry.handleLifecycleEvent(Lifecycle.Event.ON_CREATE) } override fun getLifecycle(): Lifecycle = registry fun startListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_START) } fun stopListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_STOP) } } @nisrulz #DCBERLIN18

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LifecycleRegistry class MyLifecycleOwner : LifecycleOwner { private var registry: LifecycleRegistry = LifecycleRegistry(this) init { registry.handleLifecycleEvent(Lifecycle.Event.ON_CREATE) } override fun getLifecycle(): Lifecycle = registry fun startListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_START) } fun stopListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_STOP) } } @nisrulz #DCBERLIN18

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LifecycleRegistry class MyLifecycleOwner : LifecycleOwner { private var registry: LifecycleRegistry = LifecycleRegistry(this) init { registry.handleLifecycleEvent(Lifecycle.Event.ON_CREATE) } override fun getLifecycle(): Lifecycle = registry fun startListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_START) } fun stopListening() { registry.handleLifecycleEvent(Lifecycle.Event.ON_STOP) } } @nisrulz #DCBERLIN18

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LifecycleRegistry val myLifecycleOwner = MyLifecycleOwner() // Missing myLifecycleObserver // Add lifecycle observer myLifecycleOwner.lifecycle.addObserver(myLifecycleObserver) // Remove lifecycle observer myLifecycleOwner.lifecycle.removeObserver(myLifecycleObserver) @nisrulz #DCBERLIN18

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LifecycleObserver @nisrulz #DCBERLIN18

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LifecycleObserver An interface for observing a Lifecycle // Source code public interface LifecycleObserver { // Empty } @nisrulz #DCBERLIN18

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LifecycleObserver Two ways to implement - Annotation - Callback Interface @nisrulz #DCBERLIN18

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LifecycleObserver dependencies { def lifecycle_version = "1.1.1" // For Annotation Support annotationProcessor "android.arch.lifecycle:compiler:$lifecycle_version" ... } @nisrulz #DCBERLIN18

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LifecycleObserver class MyLifecycleObserver : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_CREATE) fun init() {} @OnLifecycleEvent(Lifecycle.Event.ON_START) fun onStart() {} ... @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY) fun cleanup() {} } @nisrulz #DCBERLIN18

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LifecycleObserver val myLifecycleOwner = MyLifecycleOwner() // Add lifecycle observer myLifecycleOwner.lifecycle.addObserver(myLifecycleObserver) // Remove lifecycle observer myLifecycleOwner.lifecycle.removeObserver(myLifecycleObserver) @nisrulz #DCBERLIN18

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LifecycleObserver val myLifecycleOwner = MyLifecycleOwner() val myLifecycleObserver = MyLifecycleObserver() // Add lifecycle observer myLifecycleOwner.lifecycle.addObserver(myLifecycleObserver) // Remove lifecycle observer myLifecycleOwner.lifecycle.removeObserver(myLifecycleObserver) @nisrulz #DCBERLIN18

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LifecycleObserver val myLifecycleOwner = MyLifecycleOwner() val myLifecycleObserver = MyLifecycleObserver() // Add lifecycle observer myLifecycleOwner.lifecycle.addObserver(myLifecycleObserver) // Remove lifecycle observer myLifecycleOwner.lifecycle.removeObserver(myLifecycleObserver) @nisrulz #DCBERLIN18

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DefaultLifecycleObserver @nisrulz #DCBERLIN18

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DefaultLifecycleObserver Callback interface for listening to LifecycleOwner state changes. @nisrulz #DCBERLIN18

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DefaultLifecycleObserver Callback interface for listening to LifecycleOwner state changes. Recommended over annotations if using Java 8 language. @nisrulz #DCBERLIN18

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DefaultLifecycleObserver android { compileOptions { sourceCompatibility JavaVersion.VERSION_1_8 targetCompatibility JavaVersion.VERSION_1_8 } } dependencies { def lifecycle_version = "1.1.1" // For DefaultLifecycleObserver implementation "android.arch.lifecycle:common-java8:$lifecycle_version" ... } @nisrulz #DCBERLIN18

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DefaultLifecycleObserver // Source code public interface DefaultLifecycleObserver extends FullLifecycleObserver { @Override default void onCreate(@NonNull LifecycleOwner owner) { ... } ... @Override default void onDestroy(@NonNull LifecycleOwner owner) { ... } } @nisrulz #DCBERLIN18

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DefaultLifecycleObserver // Source code interface FullLifecycleObserver extends LifecycleObserver { void onCreate(LifecycleOwner owner); void onStart(LifecycleOwner owner); ... void onDestroy(LifecycleOwner owner); } @nisrulz #DCBERLIN18

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DefaultLifecycleObserver class MyLifecycleObserver : DefaultLifecycleObserver { override fun onCreate(owner: LifecycleOwner) {} ... override fun onDestroy(owner: LifecycleOwner) {} } @nisrulz #DCBERLIN18

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LiveData @nisrulz #DCBERLIN18

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LiveData A lifecycle aware base class for encapsulating loading data @nisrulz #DCBERLIN18

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LiveData A lifecycle aware base class for encapsulating loading data Lightweight implementation of Observer pattern @nisrulz #DCBERLIN18

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LiveData dependencies { def lifecycle_version = "1.1.1" // For LiveData implementation "android.arch.lifecycle:livedata:$lifecycle_version" ... } @nisrulz #DCBERLIN18

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LiveData // Source Code public abstract class LiveData { ... protected void postValue(T value) {...} ... @MainThread protected void setValue(T value) {...} ... protected void onActive() {...} protected void onInactive() {...} } @nisrulz #DCBERLIN18

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LiveData // Source Code public abstract class LiveData { ... protected void postValue(T value) {...} // Sets the value async ... @MainThread protected void setValue(T value) {...} ... protected void onActive() {...} protected void onInactive() {...} } @nisrulz #DCBERLIN18

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LiveData // Source Code public abstract class LiveData { ... protected void postValue(T value) {...} // Sets the value async ... @MainThread protected void setValue(T value) {...} // Sets the value sync ... protected void onActive() {...} protected void onInactive() {...} } @nisrulz #DCBERLIN18

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LiveData // Source Code public abstract class LiveData { ... protected void postValue(T value) {...} // Sets the value async ... @MainThread protected void setValue(T value) {...} // Sets the value sync ... protected void onActive() {...} // Has active observers i.e in Start/Resume state protected void onInactive() {...} } @nisrulz #DCBERLIN18

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LiveData // Source Code public abstract class LiveData { ... protected void postValue(T value) {...} // Sets the value async ... @MainThread protected void setValue(T value) {...} // Sets the value sync ... protected void onActive() {...} // Has active observers i.e in Start/Resume state protected void onInactive() {...} // Has 0 active observers } @nisrulz #DCBERLIN18

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LiveData class MySensorLiveData(context: Context?) : LiveData() { val sensorManager: SensorManager? = context? .getSystemService(Service.SENSOR_SERVICE) as SensorManager val sensorListener: SensorEventListener = object : SensorEventListener { override fun onSensorChanged(event: SensorEvent?) { // Set Value setValue(event?.values?.get(0)) } ... } } @nisrulz #DCBERLIN18

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LiveData class MySensorLiveData(context: Context?) : LiveData() { val sensorManager: SensorManager? = context? .getSystemService(Service.SENSOR_SERVICE) as SensorManager val sensorListener: SensorEventListener = object : SensorEventListener { override fun onSensorChanged(event: SensorEvent?) { // Set Value setValue(event?.values?.get(0)) } ... } } @nisrulz #DCBERLIN18

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LiveData class MySensorLiveData(context: Context?) : LiveData() { ... override fun onActive() { ... sensorManager?.registerListener(sensorListener, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_FASTEST) } override fun onInactive() { ... sensorManager.unregisterListener(sensorListener) } } @nisrulz #DCBERLIN18

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LiveData class MySensorLiveData(context: Context?) : LiveData() { ... override fun onActive() { ... sensorManager?.registerListener(sensorListener, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_FASTEST) } override fun onInactive() { ... sensorManager.unregisterListener(sensorListener) } } @nisrulz #DCBERLIN18

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LiveData val mySensorLiveData = MySensorLiveData(this) // Observe for values mySensorLiveData.observe(this, Observer{ floatVal -> // Update the UI }) @nisrulz #DCBERLIN18

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ViewModel @nisrulz #DCBERLIN18

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ViewModel - Hold & manage UI related data in Lifecycle conscious way - Survives configuration changes - Prevents unnecessary reloading of data @nisrulz #DCBERLIN18

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ViewModel dependencies { def lifecycle_version = "1.1.1" // For ViewModel implementation "android.arch.lifecycle:viewmodel:$lifecycle_version" ... } @nisrulz #DCBERLIN18

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ViewModel // Source code public abstract class ViewModel { // Called when ViewModel is destroyed protected void onCleared() { } } @nisrulz #DCBERLIN18

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ViewModel class MyViewModel : ViewModel() { private val username = MutableLiveData() fun initExpensiveOperation() { // expensive operation, e.g. network request username.value = "Nishant" // username.setValue(“Nishant”) } fun getUsername(): LiveData { return username } } @nisrulz #DCBERLIN18

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ViewModel class MyViewModel : ViewModel() { private val username = MutableLiveData() fun initExpensiveOperation() { // expensive operation, e.g. network request username.value = "Nishant" // username.setValue(“Nishant”) } fun getUsername(): LiveData { return username } } @nisrulz #DCBERLIN18

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ViewModel class MyViewModel : ViewModel() { private val username = MutableLiveData() fun initExpensiveOperation() { // expensive operation, e.g. network request username.value = "Nishant" // username.setValue(“Nishant”) } fun getUsername(): LiveData { return username } } @nisrulz #DCBERLIN18

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ViewModel class MyViewModel : ViewModel() { private val username = MutableLiveData() fun initExpensiveOperation() { // expensive operation, e.g. network request username.value = "Nishant" // username.setValue(“Nishant”) } fun getUsername(): LiveData { return username } } @nisrulz #DCBERLIN18

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ViewModel class MyViewModel : ViewModel() { private val username = MutableLiveData() fun initExpensiveOperation() { // expensive operation, e.g. network request username.value = "Nishant" // username.setValue(“Nishant”) } fun getUsername(): LiveData { return username } } @nisrulz #DCBERLIN18

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ViewModel class MyViewModel : ViewModel() { private val username = MutableLiveData() fun initExpensiveOperation() { // expensive operation, e.g. network request username.value = "Nishant" // username.setValue(“Nishant”) } fun getUsername(): LiveData { return username } } @nisrulz #DCBERLIN18

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ViewModel val viewModel = ViewModelProviders .of(this) .get(MyViewModel::class.java) viewModel.getUsername().observe(this, Observer { text -> //Update the UI }) @nisrulz #DCBERLIN18

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ViewModel val viewModel = ViewModelProviders .of(this) .get(MyViewModel::class.java) viewModel.getUsername().observe(this, Observer { text -> //Update the UI }) @nisrulz #DCBERLIN18

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Thank You twitter.com/nisrulz github.com/nisrulz www.nisrulz.com

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More Info Is your Android Library, Lifecycle-Aware? https://android.jlelse.eu/is-your-android-library-lifecycle-aware-127629d32dcc Official documentation about lifecycle components d.android.com/topic/libraries/architecture/lifecycle Using ProcessLifecycleOwner for libraries example https://github.com/nisrulz/android-examples/tree/develop/UsingProcessLifecycleOwnerForLibs Using Lifecycle Components for libraries example https://github.com/nisrulz/android-examples/tree/develop/LifeCycleCompForLib @nisrulz #DCBERLIN18

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The A,B and C of Lifecycle Components twitter.com/nisrulz github.com/nisrulz www.nisrulz.com