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Add call to onDataChanged when adding first listener #736

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Merged
merged 3 commits into from
Jun 8, 2017
Merged

Add call to onDataChanged when adding first listener #736

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6ff024d
Add call to onDataChanged when adding first listener
SUPERCILEX Jun 5, 2017
7ebf519
Fix onDataChanged being called even if no data was added
SUPERCILEX Jun 5, 2017
42b40d0
Reset state when all listeners are removed
SUPERCILEX Jun 5, 2017
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11 changes: 11 additions & 0 deletions database/src/main/java/com/firebase/ui/database/ObservableSnapshotArray.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,8 @@ public abstract class ObservableSnapshotArray<E> extends ImmutableList<DataSnaps
protected final List<ChangeEventListener> mListeners = new CopyOnWriteArrayList<>();
protected final SnapshotParser<E> mParser;

private boolean mHasDataChanged = false;

/**
* Create an ObservableSnapshotArray where snapshots are parsed as objects of a particular
* class.
Expand Down Expand Up @@ -56,6 +58,9 @@ public ChangeEventListener addChangeEventListener(@NonNull ChangeEventListener l
for (int i = 0; i < size(); i++) {
listener.onChildChanged(ChangeEventListener.EventType.ADDED, get(i), i, -1);
}
if (mHasDataChanged) {
listener.onDataChanged();
}

return listener;
}
Expand All @@ -66,6 +71,11 @@ public ChangeEventListener addChangeEventListener(@NonNull ChangeEventListener l
@CallSuper
public void removeChangeEventListener(@NonNull ChangeEventListener listener) {
mListeners.remove(listener);

// Reset mHasDataChanged if there are no more listeners
if (!isListening()) {
mHasDataChanged = false;
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This block is a little surprising to me. Wouldn't you want the first listener attached to still fire immediately if the FirebaseArray contains data?

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@samtstern Yeah, that still happens. This just ensures that adding the first listener is the same whether or not this class was first created or is being reused. The contract for removeChangeEventListener is that the list must be cleared when there are no more listeners, as if the class was first created. Here's the FirebaseArray implementation:

// Clear data when all listeners are removed
if (!isListening()) {
    mQuery.removeEventListener((ValueEventListener) this);
    mQuery.removeEventListener((ChildEventListener) this);

    clearData();
}

}
}

/**
Expand Down Expand Up @@ -98,6 +108,7 @@ protected final void notifyChangeEventListeners(ChangeEventListener.EventType ty
}

protected final void notifyListenersOnDataChanged() {
mHasDataChanged = true;
for (ChangeEventListener listener : mListeners) {
listener.onDataChanged();
}
Expand Down