Created
March 31, 2019 17:16
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| import androidx.annotation.MainThread | |
| import androidx.annotation.Nullable | |
| import androidx.lifecycle.LifecycleOwner | |
| import androidx.lifecycle.MutableLiveData | |
| import androidx.lifecycle.Observer | |
| import java.util.concurrent.atomic.AtomicBoolean | |
| /** | |
| * A lifecycle-aware observable that sends only new updates after subscription, used for events like | |
| * navigation and Snackbar messages. | |
| * <p> | |
| * This avoids a common problem with events: on configuration change (like rotation) an update | |
| * can be emitted if the observer is active. This LiveData only calls the observable if there's an | |
| * explicit call to setValue() or call(). | |
| * <p> | |
| * Note that only one observer is going to be notified of changes. | |
| */ | |
| class SingleLiveEvent<T> : MutableLiveData<T>() { | |
| private val mPending = AtomicBoolean(false) | |
| @MainThread | |
| override fun observe(owner: LifecycleOwner, observer: Observer<in T>) { | |
| // Observe the internal MutableLiveData | |
| super.observe(owner, Observer<T> { t -> | |
| if (mPending.compareAndSet(true, false)) { | |
| observer.onChanged(t) | |
| } | |
| }) | |
| } | |
| @MainThread | |
| override fun setValue(@Nullable t: T?) { | |
| mPending.set(true) | |
| super.setValue(t) | |
| } | |
| /** | |
| * Used for cases where T is Void, to make calls cleaner. | |
| */ | |
| @MainThread | |
| fun call() { | |
| value = null | |
| } | |
| } |
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