当我尝试从数据库检索数据并将其保存到数组列表中时，出现以下错误： com.google.firebase.database.DatabaseException: Expected a List while deserializing, but got a class java.util.HashMap ```
@Override
public List getPlayers(String gameId) {
final List commentKeys = new ArrayList<>();
DatabaseReference nishi = FirebaseDatabase.getInstance().getReference("players");
Query query = nishi.orderByChild("game_id").equalTo(gameId);
query.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
for (DataSnapshot childSnapshot : snapshot.getChildren()) {
commentKeys.add((Player) childSnapshot.getValue());
}
Log.d("Data:", commentKeys.toString());

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
    return commentKeys;
}

这是我的 `Player` 班级：

public class Player {

private String playerId;
private String name;
private String color;
private int points;
private String gameId;

public Player() {
}

public Player(String id, String name, String color, int points, String gameId) {
    this.playerId = id;
    this.name = name;
    this.color = color;
    this.points = points;
    this.gameId = gameId;
}

public String getPlayerId() {
    return playerId;
}

public void setPlayerId(String playerId) {
    this.playerId = playerId;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getColor() {
    return color;
}

public void setColor(String color) {
    this.color = color;
}

public int getPoints() {
    return points;
}

public void setPoints(int points) {
    this.points = points;
}

public String getGameId() {
    return gameId;
}

public void setGameId(String gameId) {
    this.gameId = gameId;
}

}

我做错什么了？