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package com.mapswithme.util;
import android.support.annotation.NonNull;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
/**
* `Registrator` pattern implementation which allows to maintain the list of listeners,
* offers safe adding/removing of listeners during iteration.
* <br/>{@link #finishIterate()} must be called after iteration is complete.
*/
public final class Listeners<T> implements Iterable<T>
{
private final Set<T> mListeners = new LinkedHashSet<>();
private final Set<T> mListenersToAdd = new LinkedHashSet<>();
private final Set<T> mListenersToRemove = new LinkedHashSet<>();
private boolean mIterating;
@Override
public @NonNull Iterator<T> iterator()
{
if (mIterating)
throw new RuntimeException("finishIterate() must be called before new iteration");
mIterating = true;
return mListeners.iterator();
}
/**
* Completes listeners iteration. Must be called after iteration is done.
*/
public void finishIterate()
{
if (!mListenersToRemove.isEmpty())
mListeners.removeAll(mListenersToRemove);
if (!mListenersToAdd.isEmpty())
mListeners.addAll(mListenersToAdd);
mListenersToAdd.clear();
mListenersToRemove.clear();
mIterating = false;
}
/**
* Safely registers new listener. If registered during iteration, new listener will NOT be called before current iteration is complete.
*/
public void register(T listener)
{
if (mIterating)
{
mListenersToRemove.remove(listener);
if (!mListeners.contains(listener))
mListenersToAdd.add(listener);
}
else
mListeners.add(listener);
}
/**
* Safely unregisters listener. If unregistered during iteration, old listener WILL be called in the current iteration.
*/
public void unregister(T listener)
{
if (mIterating)
{
mListenersToAdd.remove(listener);
if (mListeners.contains(listener))
mListenersToRemove.add(listener);
}
else
mListeners.remove(listener);
}
public int getSize()
{
int res = mListeners.size();
if (mIterating)
{
res += mListenersToAdd.size();
res -= mListenersToRemove.size();
}
return res;
}
public boolean isEmpty()
{
return (getSize() <= 0);
}
}
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