android - 当用户单击按钮时，我如何通过 android 应用程序永远增加 firebase 数据库中的计数器

Question

这是我的代码。

package com.example.manali.likeex;

import android.app.Activity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;



public class MainActivity2 extends Activity implements View.OnClickListener {
    Button senlike;
    private DatabaseReference mdatabase;
    private DatabaseReference user1;

     int c;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        Button sendlike = (Button) findViewById(R.id.b1);
        mdatabase= FirebaseDatabase.getInstance().getReference();
        user1=mdatabase.child("Teacher");
        sendlike.setOnClickListener(this);

    }

//当用户点击 firebase 上的按钮时计数器增加 public void onClick( View View ) {

        if(user1!=null)
        {
            c++;

        }



//sets value to user1 node
        user1.setValue(c);

    }
    public DatabaseReference getUser1()
    {
        return user1;

    }
}

此代码仅在应用处于 Activity 状态时增加计数器。当我们关闭应用程序，并重新启动它。计数器再次从 1 开始。因此我想维护这个计数器。

Answer 1

DatabaseReference upvotesRef = ref.child("server/saving-data/fireblog/posts/-JRHTHaIs-jNPLXOQivY/upvotes");
upvotesRef.runTransaction(new Transaction.Handler() {
    @Override
    public Transaction.Result doTransaction(MutableData mutableData) {
        Integer currentValue = mutableData.getValue(Integer.class);
        if (currentValue == null) {
            mutableData.setValue(1);
        } else {
            mutableData.setValue(currentValue + 1);
        }

        return Transaction.success(mutableData);
    }

    @Override
    public void onComplete(DatabaseError databaseError, boolean committed, DataSnapshot dataSnapshot) {
       System.out.println("Transaction completed");
    }
});