YassinAJDI/MaterialJournal

package com.ajdi.yassin.materialjournal.utils;

import java.util.concurrent.atomic.AtomicBoolean;

import androidx.annotation.MainThread;
import androidx.annotation.Nullable;
import androidx.lifecycle.LifecycleOwner;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.Observer;
import timber.log.Timber;

/**
 * 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().
 */
public class SingleLiveEvent<T> extends MutableLiveData<T> {

    private final AtomicBoolean mPending = new AtomicBoolean(false);

    @MainThread
    public void observeEvent(LifecycleOwner owner, final Observer<T> observer) {

        if (hasActiveObservers()) {
            Timber.w("Multiple observers registered but only one will be notified of changes.");
        }

        // Observe the internal MutableLiveData
        super.observe(owner, new Observer<T>() {
            @Override
            public void onChanged(@Nullable T t) {
                if (mPending.compareAndSet(true, false)) {
                    observer.onChanged(t);
                }
            }
        });
    }

    @MainThread
    public void setValue(@Nullable T t) {
        mPending.set(true);
        super.setValue(t);
    }

    /**
     * Used for cases where T is Void, to make calls cleaner.
     */
    @MainThread
    public void call() {
        setValue(null);
    }
}