Firebase java.lang.IllegalArgumentException：未找到密钥

Question

这是我第一次学习在Android中使用Firebase。一切都很好，直到突然间我开始崩溃，我只是不知道为什么会这样。这是我的日志

06-08 19:39:55.064 28217-28217/k.cook.com E/AndroidRuntime: FATAL EXCEPTION: 
main
Process: k.cook.com, PID: 28217
java.lang.IllegalArgumentException: Key not found
    at com.firebase.ui.database.FirebaseArray.getIndexForKey(FirebaseArray.java:125)
    at 
com.firebase.ui.database.FirebaseArray.onChildMoved(FirebaseArray.java:97)
    at com.google.android.gms.internal.zzegg.zza(Unknown Source:43)
    at com.google.android.gms.internal.zzelk.zza(Unknown Source:2)
    at com.google.android.gms.internal.zzelq.run(Unknown Source:71)
    at android.os.Handler.handleCallback(Handler.java:789)
    at android.os.Handler.dispatchMessage(Handler.java:98)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6938)
    at java.lang.reflect.Method.invoke(Native Method)
    at 
  com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)

每当我尝试在活动中的两个片段之间切换时，就会发生此错误

这是代码。它发生在firebaseArray类

中

public class FirebaseArray<T> extends ObservableSnapshotArray<T>
    implements ChildEventListener, ValueEventListener {
private final Query mQuery;
private final List<DataSnapshot> mSnapshots = new ArrayList<>();

/**
 * Create a new FirebaseArray with a custom {@link SnapshotParser}.
 *
 * @param query The Firebase location to watch for data changes. Can also be a slice of a
 *              location, using some combination of {@code limit()}, {@code startAt()}, and
 *              {@code endAt()}.
 * @see ObservableSnapshotArray#ObservableSnapshotArray(SnapshotParser)
 */
public FirebaseArray(@NonNull Query query, @NonNull SnapshotParser<T> parser) {
    super(parser);
    mQuery = query;
}

@Override
protected void onCreate() {
    super.onCreate();
    mQuery.addChildEventListener(this);
    mQuery.addValueEventListener(this);
}

@Override
protected void onDestroy() {
    super.onDestroy();
    mQuery.removeEventListener((ValueEventListener) this);
    mQuery.removeEventListener((ChildEventListener) this);
}

@Override
public void onChildAdded(DataSnapshot snapshot, String previousChildKey) {
    int index = 0;
    if (previousChildKey != null) {
        index = getIndexForKey(previousChildKey) + 1;
    }

    mSnapshots.add(index, snapshot);
    notifyOnChildChanged(ChangeEventType.ADDED, snapshot, index, -1);
}

@Override
public void onChildChanged(DataSnapshot snapshot, String previousChildKey) {
    int index = getIndexForKey(snapshot.getKey());

    mSnapshots.set(index, snapshot);
    notifyOnChildChanged(ChangeEventType.CHANGED, snapshot, index, -1);
}

@Override
public void onChildRemoved(DataSnapshot snapshot) {
    int index = getIndexForKey(snapshot.getKey());

    mSnapshots.remove(index);
    notifyOnChildChanged(ChangeEventType.REMOVED, snapshot, index, -1);
}

@Override
public void onChildMoved(DataSnapshot snapshot, String previousChildKey) {
    int oldIndex = getIndexForKey(snapshot.getKey());
    mSnapshots.remove(oldIndex);

    int newIndex = previousChildKey == null ? 0 : getIndexForKey(previousChildKey) + 1;
    mSnapshots.add(newIndex, snapshot);

    notifyOnChildChanged(ChangeEventType.MOVED, snapshot, newIndex, oldIndex);
}

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
    notifyOnDataChanged();
}

@Override
public void onCancelled(DatabaseError error) {
    notifyOnError(error);
}
//the error is thrown here 
private int getIndexForKey(String key) {
    int index = 0;
    for (DataSnapshot snapshot : mSnapshots) {
        if (snapshot.getKey().equals(key)) {
            return index;
        } else {
            index++;
        }
    }
    throw new IllegalArgumentException("Key not found");
}

@NonNull
@Override
protected List<DataSnapshot> getSnapshots() {
    return mSnapshots;
}

}