如何更新Firebase中的數據

Question

我做了一個查詢以從我的Firebase中檢索特定數據。在這種情況下，它的用戶得分。我如何更新剛剛檢索的相同值？

感謝所有幫助

//check the leaders and their scores, get the score of the current user 
    DatabaseReference leadersRef = FirebaseDatabase.getInstance().getReference("Leaders"); 
    Query query = leadersRef.orderByChild("uID").equalTo(mCurrentUser.getUid()); 
    query.addListenerForSingleValueEvent(new ValueEventListener() { 
     @Override 
     public void onDataChange(DataSnapshot snapshot) { 

      if(snapshot.exists()){ 
        for (DataSnapshot child: snapshot.getChildren()) { 
         currentScore = child.child("Score").getValue(Integer.class); 
         Toast.makeText(RunningChallengeActivity.this,"Your current score: " + currentScore,Toast.LENGTH_LONG).show(); 
        } 
       } 
       else { 

       //if user has no points create new leader child and set score to 0 
       final DatabaseReference newResult = leaderBoard.push(); 
       String username = mCurrentUser.getEmail(); 

       //trim email leaving just username 
       int index = username.indexOf('@'); 
       username = username.substring(0,index); 

       newResult.child("UserName").setValue(username); 
       newResult.child("uID").setValue(mAuth.getCurrentUser().getUid()); 
       newResult.child("Score").setValue(0); 

       } 
      } 

     @Override 
     public void onCancelled(DatabaseError databaseError) { 
     } 
    }); 

Answer 1

事情是這樣的：

DatabaseReference leadersRef = FirebaseDatabase.getInstance().getReference("Leaders"); 
Query query = leadersRef.orderByChild("uID").equalTo(mCurrentUser.getUid()); 
query.addListenerForSingleValueEvent(new ValueEventListener() { 
    @Override 
    public void onDataChange(DataSnapshot snapshot) { 
     for (DataSnapshot child: snapshot.getChildren()) { 
      currentScore = child.child("Score").getValue(Integer.class); 
      child.getRef().child("Score").setValue(42); 
     } 
    } 

如果你想基於其電流值來設定分值的新的價值，你」而不是想要use a database transaction。

Answer 2

//check the leaders and their scores, get the score of the current user 
    final DatabaseReference leadersRef = FirebaseDatabase.getInstance().getReference("Leaders"); 
    final Query query = leadersRef.orderByChild("uID").equalTo(mCurrentUser.getUid()); 
    query.addListenerForSingleValueEvent(new ValueEventListener() { 
     @Override 
     public void onDataChange(DataSnapshot snapshot) { 

      if(snapshot.exists()){ 
       for (DataSnapshot child: snapshot.getChildren()) { 

        //get the key of the child node that has to be updated 
        String postkey = child.getRef().getKey(); 

        //update score 
        int new_score = currentScore + score; 
        leadersRef.child(postkey).child("Score").setValue(new_score); 
        Toast.makeText(RunningChallengeActivity.this,"Your current score: " + new_score +"",Toast.LENGTH_LONG).show(); 

       } 
      } 
     } 

     @Override 
     public void onCancelled(DatabaseError databaseError) { 
     } 
    });