java - 如何在 firebase 事务中使用快照结果

Question

0

我的数据库中有一个分数节点。目前，我可以在比赛结束后更新比分。出于创建排行榜的目的，我还想将用户用户名添加到节点。我尝试使用拍摄快照的事务来获取当前登录的用户名，当分数更新时，该名称也将添加到分数节点。

我可以使用我的事务检索用户名，但无法弄清楚如何将此值传递给 Scores 节点。

这是我到目前为止所拥有的，这段代码允许我更新分数节点中的“积分”，并允许我检索登录用户的名称，但不能在数据库的分数节点中设置这个值：

package com.example.securityapp;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.MutableData;
import com.google.firebase.database.Transaction;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.Collections;

public class industry_standards_questions extends AppCompatActivity {

    DatabaseReference databaseUsers, databaseUsername;
    FirebaseDatabase database = FirebaseDatabase.getInstance();
    FirebaseAuth mAuth;
    TextView stmnt;
    ImageView image_true, image_false;
    Button points, finished;
    Statements tfStatements;
    int statementsLength;
    ArrayList<Item> statementList;
    int currentStatement = 0;
    int grade = 0;
    String name;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_industry_standards_questions);

        databaseUsers = database.getReference("Scores");
        databaseUsername = database.getReference("Users");

        mAuth = FirebaseAuth.getInstance();
        FirebaseUser user = mAuth.getCurrentUser();
        stmnt = (TextView) findViewById(R.id.statement_TV);
        image_true = (ImageView) findViewById(R.id.trueImage);
        image_true.setFocusable(false);
        image_false = (ImageView) findViewById(R.id.falseImage);
        image_false.setFocusable(false);
        tfStatements = new Statements();
        statementsLength = tfStatements.tfStatements.length;
        statementList = new ArrayList<>();
        finished = (Button) findViewById(R.id.finish);
        points = (Button) findViewById(R.id.final_score);

        for (int i = 0; i < statementsLength; i++)
        {
            statementList.add(new Item(tfStatements.getStatement(i), tfStatements.getAnswer(i)));
        }
        Collections.shuffle(statementList);
        setStmnt(currentStatement);



    }

    // show Statement
    private void setStmnt(int number) {
        stmnt.setText(statementList.get(number).getStatement());
    }

    //check is answer is right
    private boolean checkAnswer(int number) {
        String answer = statementList.get(number).getAnswer();
        return answer.equals("true");
    }

    public void trueClicked(View view) {
        if (checkAnswer(currentStatement)) {
            grade++;
        }
        currentStatement++;
        if (currentStatement >= statementsLength) {
            score();
            return;
        }
        if (currentStatement <= statementsLength )
            setStmnt(currentStatement);
    }

    public void falseClicked(View view) {
        if (!checkAnswer(currentStatement)) {
            grade++;
        }
        currentStatement++;
        if (currentStatement >= statementsLength) {
            score();
            return;
        }
        if (currentStatement <= statementsLength )
            setStmnt(currentStatement);
    }



    public void score() {


        String id = mAuth.getCurrentUser().getUid();
        DatabaseReference score = databaseUsers.child(id).child("Points");
        DatabaseReference set_username = databaseUsers.child(id).child("Username");
        final DatabaseReference get_user_name = databaseUsername.child(id).child("username");



        final int pointsEarned = grade;


        score.runTransaction(new Transaction.Handler() {
                                 @Override
                                 public Transaction.Result doTransaction(MutableData mutableData) {
                                     System.out.println("You scored: " + pointsEarned);
                                     System.out.println("The current score is: " + mutableData.getValue(Integer.class));
                                     mutableData.setValue((mutableData.getValue() == null ? 0 : mutableData.getValue(Integer.class)) + pointsEarned);
                                     System.out.println("The new score is: " + mutableData.getValue(Integer.class));
                                     return Transaction.success(mutableData);
                                 }

                                 @Override
                                 public void onComplete(@Nullable DatabaseError databaseError, boolean b, @Nullable DataSnapshot dataSnapshot) {

                                 }
                             }
        );


        get_user_name.runTransaction(new Transaction.Handler() {

            @NonNull
            @Override
            public Transaction.Result doTransaction(@NonNull MutableData mutableData) {
                String name = mutableData.getValue(String.class);
                return Transaction.success(mutableData);
            }

            @Override
            public void onComplete(@Nullable DatabaseError databaseError, boolean b, @Nullable DataSnapshot dataSnapshot) {
                String username = dataSnapshot.getValue().toString();
            }

        });

        set_username.runTransaction(new Transaction.Handler() {
            @NonNull
            @Override
            public Transaction.Result doTransaction(@NonNull MutableData mutableData) {
                mutableData.setValue(name);
                return Transaction.success(mutableData);

            }

            @Override
            public void onComplete(@Nullable DatabaseError databaseError, boolean b, @Nullable DataSnapshot dataSnapshot) {


            }
        });


        Toast.makeText(this, "You scored " + grade + " points!", Toast.LENGTH_LONG).show();
        grade = 0;
    }






    public void FinishedOnClick (View view)
    {
        Intent intent_finished = new Intent(industry_standards_questions.this, industry_standards_rating_screen.class);
        startActivity(intent_finished);
        finish();
    }


}

标签： javaandroidfirebase-realtime-database