java - Firebase:类 java.util.List 具有通用类型参数

Question

我正在为我的 android 应用程序使用 firebase，并将我自己的用户对象存储在数据库中。但是，每当我尝试从数据库中的信息创建用户对象时，我都会收到以下错误:

com.google.firebase.database.DatabaseException: Class java.util.List has generic type parameters, please use GenericTypeIndicator instead
        at com.google.android.gms.internal.zzear.zzb(Unknown Source)
        at com.google.android.gms.internal.zzear.zza(Unknown Source)
        at com.google.android.gms.internal.zzear.zza(Unknown Source)
        at com.google.android.gms.internal.zzear.zzb(Unknown Source)
        at com.google.android.gms.internal.zzeas.zze(Unknown Source)
        at com.google.android.gms.internal.zzear.zzb(Unknown Source)
        at com.google.android.gms.internal.zzear.zza(Unknown Source)
        at com.google.android.gms.internal.zzear.zza(Unknown Source)
        at com.google.android.gms.internal.zzear.zza(Unknown Source)
        at com.google.android.gms.internal.zzear.zzb(Unknown Source)
        at com.google.android.gms.internal.zzeas.zze(Unknown Source)
        at com.google.android.gms.internal.zzear.zzb(Unknown Source)
        at com.google.android.gms.internal.zzear.zza(Unknown Source)
        at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
        at christophershae.stats.CreateRoster$1.onDataChange(CreateRoster.java:88)
        at com.google.android.gms.internal.zzduz.zza(Unknown Source)
        at com.google.android.gms.internal.zzdwu.zzbvb(Unknown Source)
        at com.google.android.gms.internal.zzdxa.run(Unknown Source)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:7325)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

这是我的用户类:

public class User implements Serializable {
    public String email;

    public Map<String, List<BasketballPlayer>> userRosters = new 
   HashMap<String, List<BasketballPlayer>>();


    public User(){

    }

    public User(String email){
        this.email = email;
    }

}

这是我尝试创建新对象的代码:

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
    user = dataSnapshot.child(userId).getValue(User.class);

}

Answer 1

改变这个:-

user = dataSnapshot.child(userId).getValue(User.class);

进入这个:-

List<BasketBallPlayer> retrievedata=dataSnapshot.child(userId).getValue(userRosters);