Question

我从firebase开始，我遇到了数据查询问题。我有这个firebase数据库：

  "Conversations" : {

    "-L9LJQiFKqGlNKKFEyvd" : {

      "-L9LJQiHrp1rU1pblNG_" : {
        "messageText" : "Hi there",
        "postTime" : 1522940321427,
        "senderId" : "GSJMlFA3pYMjYCfY6BA0AEyva9u2",
        "senderNickname" : "q"
      },
      "-L9LZ0O2rXHe-eh2iRgB" : {
        "messageText" : "f",
        "postTime" : 1522944447238,
        "senderId" : "GSJMlFA3pYMjYCfY6BA0AEyva9u2",
        "senderNickname" : "q"
      },
      "-L9LZ7uF9TPb4VZ-wJEO" : {
        "messageText" : "vvvv",
        "postTime" : 1522944478035,
        "senderId" : "GSJMlFA3pYMjYCfY6BA0AEyva9u2",
        "senderNickname" : "q"
      }
    }
  },

我想显示对那些“postTime”值高于某个特定值的push（）对象的引用，例如：1522944447230。我试过了：

mConversationId = "-L9LJQiFKqGlNKKFEyvd"
mLeaveTime = 1522944447230;

mUserConversationsReference = mFirebaseDatabase.getReference().child("Conversations");

mUserConversationsMessagesReference = mUserConversationsReference.child(mConversationId);

mLastMessageQuery  = mUserConversationsMessagesReference.orderByChild("postTime").orderByValue().startAt(mLeaveTime);

然后我得到：

java.lang.IllegalArgumentException：您无法组合多个orderBy 来电！

所以必须有另一种方法来解决这个问题。我会很感激任何建议。

Answer 1

要解决此问题，请使用代码行：

String mConversationId = "-L9LJQiFKqGlNKKFEyvd"
long mLeaveTime = 1522944447230;
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference mConversationIdRef = rootRef.child("Conversations").child(mConversationId);
Query query = mConversationIdRef.orderByChild("postTime").startAt(mLeaveTime);

.orderByValue()在此查询中与您无关。请注意，Firebase不允许您使用多个orderBy调用。所以要解决这个问题，只需一个即可。

如何通过特定子值查询Firebase中的数据？

1 个答案: