Firebase更新儿童字段的值 [英] Firebase updating value for a field in a child

问题描述

  {
posts：{ 
-KNnbTHJGm83zpSELWwB：{
.priority：6gydj46kg0，
branch：Branch，
category：Categoria，
expiration：24h，
g：6gydj46kg0，
l：[-23.5415083，-46.88642]，
photo：mPostPic_20160728192627.jpeg ，
price：10，
priority：0，
product：ipad，
userKey：BNd8RP5qHoc0q7f9gn8cLjPy5Ux1，
 offerMessage：Valido吃了14:00 hs，
likeCount：0 
} 
} 
} 
  pre> 
 
 
我只需要读取likeCount值，并在特定情况下将其值加1即可。
 
 
 
阅读了大量的Firebase文档和示例，其中大部分示例与推送数据或读取数据和处理值有关。 
 
 
我只需要读取值，增量， SA ve值，但我是新手在Firebase中，并没有找到一个有效的方式来做到这一点。
解决方案
 2文件，现在下面的代码工作正如我所料。
  public void writeUserSawPost（final String postkey，int mode）{
 
 
最终DatabaseReference mPostsRef = mDatabase.child（posts /+ postkey）; 
 String user = mAuth.getCurrentUser（）。getUid（）; 
 final DatabaseReference mPostUser = mDatabase.child（posts-user /+ user +/+ postkey +/ sentiment）; 
 
 if（mode == Constants.LIKE）{
 
 
 
 mPostsRef.runTransaction（new Transaction.Handler（）{
 @覆盖
 public Transaction.Result doTransaction（MutableData mutableData）{
 Post p = mutableData.getValue（Post.class）; 
 if（p == null）{
 return Transaction。成功（mutableData）; 
} 
 p.likeCount = p.likeCount + 1; 
 mutableData.setValue（p）; 
返回Transaction.success（mutableData）; 
 
 $ b @Override 
 public void onComplete（DatabaseError databaseError，boolean b，
 DataSnapshot dataSnapshot）{
 //完成的事务
 
 
} 
}）; 
 
 
 mPostUser.setValue（like）; 
 
} else if（mode == Constants.DISLIKE）{
 mPostUser.setValue（dislike）; 
} 
 
 
 
} 
  
 
I have a Child in Firebase like this in my ANDROID project:
{
  "posts" : {
    "-KNnbTHJGm83zpSELWwB" : {
      ".priority" : "6gydj46kg0",
      "branch" : "Branch",
      "category" : "Categoria",
      "expiration" : "24h",
      "g" : "6gydj46kg0",
      "l" : [ -23.5415083, -46.88642 ],
      "photo" : "mPostPic_20160728192627.jpeg",
      "price" : 10,
      "priority" : 0,
      "product" : "ipad",
      "userKey" : "BNd8RP5qHoc0q7f9gn8cLjPy5Ux1",
      "offerMessage": "Valido ate as 14:00 hs",
      "likeCount": 0
    }
  }
}
I just need to read the likeCount value and increment it by 1 in specific situation.

I have read a lot of Firebase documentation and sample and most part of examples is related to push data or read data and handle value changed.

I just need to read value, increment, save value again but I am newbie in Firebase and not finding a efficient way to do that.
解决方案
I have splited my Json in 2 files and now the code below is working as i expected.
public void writeUserSawPost(final String postkey, int mode){


        final DatabaseReference mPostsRef = mDatabase.child("posts/" + postkey);
        String user = mAuth.getCurrentUser().getUid();
        final DatabaseReference mPostUser = mDatabase.child("posts-user/" + user + "/" + postkey + "/sentiment");

        if (mode == Constants.LIKE) {



            mPostsRef.runTransaction(new Transaction.Handler() {
                @Override
                public Transaction.Result doTransaction(MutableData mutableData) {
                    Post p = mutableData.getValue(Post.class);
                    if (p == null) {
                        return Transaction.success(mutableData);
                    }
                    p.likeCount = p.likeCount + 1;
                    mutableData.setValue(p);
                    return Transaction.success(mutableData);
                }

                @Override
                public void onComplete(DatabaseError databaseError, boolean b,
                                       DataSnapshot dataSnapshot) {
                    // Transaction completed


                }
            });


            mPostUser.setValue("like");

        } else if (mode == Constants.DISLIKE){
            mPostUser.setValue("dislike");
        }



    }


                        
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