Android Java 访问 ROOM 数据库的对象

Question

I am trying to write an android app with a room database implemented. i followed a tutorial to setup the Database (honestly not fully understanding everything that i have done).

From the Database i am getting a "LiveData< List< Player>>" Object with all "Player"s in my Table. Each player has a Name and a Price.

I want to add up all prices and get a average value when adding a new player. But the code from me always disregards the last entry and only does the calculation for everything in the List except the last player. Where is my error?

public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == NEW_WORD_ACTIVITY_REQUEST_CODE && resultCode == RESULT_OK) {

       // Add a New Player to the Database
            int preis = data.getExtras().getInt("EXTRA_REPLY_PREIS");
            String name = data.getExtras().getString("EXTRA_REPLY_NAME");
            Player player = new Player(name, preis);
            mPlayerViewModel.insert(player);

      // Populate the TextView "durchschnitt" with the average Value of all players, calculated in durchschnittspreis()
            TextView durchschnitt = findViewById(R.id.tvPreis);
            LiveData<List<Player>> alleSpieler = mPlayerViewModel.getAllPlayers();
            durchschnitt.setText("" + durschnittspreis(alleSpieler));

        } else {
            Toast.makeText(
                    getApplicationContext(),
                    R.string.empty_not_saved,
                    Toast.LENGTH_LONG).show();
        }
    }

 public int durschnittspreis(LiveData<List<Player>> players) {
        int durchschnittspreis = 0;
        int preis = 0;
        for (int i = 0; i < players.getValue().size(); i++) {
            preis = preis + players.getValue().get(i).getPreis();
            System.out.println(preis);
            durchschnittspreis = preis / players.getValue().size();
        }
        return durchschnittspreis;
    }

Answer 1

I don't have enough reputation to comment but did you try changing the loop condition in durschnittspreis function like:

for (int i = 0; i <= players.getValue().size(); i++)