如何在firebase中保存用户分数并在Android studio中实时检索它 [英] How to save users score in firebase and retrieve it in real-time in Android studio

问题描述

我正在创建一个应用程序，其中单击按钮时点数会增加，并且这些点数应保存到 firebase.我设法将这些数据保存到 firebase.但是当我销毁我的应用程序并再次打开它时，点值显示相同但在单击按钮后.又是从0开始.

I am creating an app in which points increases on button click and those points should be saved to firebase. I managed to save those data to firebase. But when I destroy my app and open it again the points value is showing same but after clicking button. It again starts from 0.

例如:每次单击按钮时，点值都会增加到 10 点.现在，当我完全销毁应用程序并再次打开它时，点值显示相同，但​​是当再次单击按钮时，它会从初始状态开始.

For example: every time on button click the points value increases to 10 points. Now when I completely destroy the app and open it again, the points value shows same, but when button clicked it again starts from initial condition.

这是我的代码

    int amount = 0;

@Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

button_claim.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            amount = amount + 100;


            textView_points.setText(String.valueOf(amount));
            databaseReference.setValue(textView_points.getText().toString());

        }
    });


}


@Override
    protected void onStart() {
    super.onStart();
    if (mAuth.getCurrentUser() == null) {
        finish();
        Intent main = new Intent(this,MainActivity.class);
        main.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(main);
    }

    databaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            textView_points.setText(dataSnapshot.getValue(String.class));
            databaseReference.setValue(textView_points.getText().toString());
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

            Toast.makeText(Main2Activity.this,"error",Toast.LENGTH_LONG).show();
        }
    });



    }

在销毁应用程序之前请看图片，在销毁应用程序并上传到数据库之前点击按钮会增加积分请看图1

再次打开应用(关闭后)它显示相同的更新点请参见图 2

现在当我点击声明它返回到 100请参见图片编号 3

请帮我解决这个问题，我是新手谢谢

please help me on this problem, and i am a newbie Thanks

推荐答案

Edit: 29th, June 2020

现在不使用事务也可以解决这个问题.我们可以简单地使用以下方法增加一个值:

Now it's also possible to solve this problem without the use of a transaction. We can simply increment a value using:

rootRef.child("score").setValue(ServerValue.increment(1));

对于 decremenet，需要以下代码行:

And for decremenet, the following line of code is required:

rootRef.child("score").setValue(ServerValue.increment(-1));

---

这是在 Firebase 数据库中设置值的方式:

---

This is how you set a value in your Firebase database:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
rootRef.child("score").setValue(1);

假设你的score字段是Integer类型的，要解决这个问题，请使用以下方法:

Assuming that the your score field is of type Integer, to solve this, please use the following method:

public static void setScore(String operation) {
    DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
    DatabaseReference scoreRef = rootRef.child("score");
    scoreRef.runTransaction(new Transaction.Handler() {
        @Override
        public Transaction.Result doTransaction(MutableData mutableData) {
            Integer score = mutableData.getValue(Integer.class);
            if (score == null) {
                return Transaction.success(mutableData);
            }

            if (operation.equals("increaseScore")) {
                mutableData.setValue(score + 1);
            } else if (operation.equals("decreaseScore")){
                mutableData.setValue(score - 1);
            }

            return Transaction.success(mutableData);
        }

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

为此，我建议您绝对使用transactions.如果用户同时尝试增加/减少分数，您将避免错误的结果.因此，作为结论，请根据您的增减操作调用此方法.

For this, I recommend you definitely use transactions. You will avoid wrong results if users are trying to increase/decrease the score in the same time. So as a conclusion, call this method accordingly to your increase/decrease operation.

阅读方式如下:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference scoreRef = rootRef.child("score");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Integer score = ds.getValue(Integer.class);
        Log.d("TAG", score + "");
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
scoreRef.addListenerForSingleValueEvent(eventListener);

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