从 JSON 读取整数并将其添加到数组列表

Question

我想从 URL（JSON 格式）读取数据并将这些值添加到 ArrayList。我测试了 URL 部分的读数，这有效。但出于某种原因，我无法将读取的值添加到 ArrayList

有人知道为什么会发生这种情况以及我该如何解决它吗？

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.concurrent.TimeUnit;

public class SaldoActivity extends AppCompatActivity {
    private RequestQueue requestQueue;
    private ArrayList<String> names;
    private ArrayList<Integer> payList;
    private ArrayList<Integer> totalList;
    private ArrayList<Integer> debtList = new ArrayList<Integer>();
    private int offset = 1;
    private String email;
    private int previousID;
    private int loginID;
    private int totalPerPerson;
    private int info;

    private static final String GET_LAST_URL = "https://studev.groept.be/api/a21pt120/getPreviousIDFromGroup/";
    private static final String QUEUE_URL_LOGIN_ID = "https://studev.groept.be/api/a21pt120/getLoginID/";
    private static final String GET_PAY_AMOUNT_PER_NAME = "https://studev.groept.be/api/a21pt120/payedPerPerson/";
    private static final String GET_TOTAL_AMOUNT = "https://studev.groept.be/api/a21pt120/totalPayed/";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        //READING FROM DATABASE DOESNT WORK -> SOMETHING ABOUT THE ARRAYLIST
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_saldo);
        getPayList();

        Bundle extras = getIntent().getExtras();
        email = (String) extras.get("email");
        names = GroupActivity.getNamesList();
        //######## TRANSACTIONS ###########
        Button newTransaction = findViewById(R.id.button3);
        newTransaction.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                onAddTransaction_Clicked();
            }
        });
        //##################################

        ListView saldoList = findViewById(R.id.saldoList);
        TextView lblGroup = findViewById(R.id.lblGroup);



        ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(getApplicationContext(),
                android.R.layout.simple_list_item_1, names);
        saldoList.setAdapter(arrayAdapter);
        arrayAdapter.notifyDataSetChanged();


        //######### DELETE BUTTON ###########
        JsonArrayRequest loginIDRequest = new JsonArrayRequest(Request.Method.GET, QUEUE_URL_LOGIN_ID + email,null,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        for (int i=0; i<response.length(); ++i) {
                            loginID = 0;
                            JSONObject o = null;
                            try {
                                loginID += response.getJSONObject(i).getInt("id");
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }

                        JsonArrayRequest previousIDRequest = new JsonArrayRequest(Request.Method.GET,GET_LAST_URL + Integer.toString(loginID),null,
                                new Response.Listener<JSONArray>() {
                                    @Override
                                    public void onResponse(JSONArray response) {
                                        for (int i=0; i<response.length(); ++i) {
                                            previousID = 0;
                                            JSONObject o = null;
                                            try {
                                                previousID += response.getJSONObject(i).getInt("id");
                                            } catch (JSONException e) {
                                                e.printStackTrace();
                                            }
                                        }

                                    }
                                }, new Response.ErrorListener() {
                                    @Override
                                    public void onErrorResponse(VolleyError error) {
                                        Toast.makeText(SaldoActivity.this, "Unable to communicate with the server", Toast.LENGTH_LONG).show();
                            }
                        });

                        requestQueue.add(previousIDRequest);
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(SaldoActivity.this, "Unable", Toast.LENGTH_LONG).show();
            }
        });
        requestQueue.add(loginIDRequest);

        calculateTotalPerPerson();
        calculateDebtList();

        lblGroup.setText(Integer.toString(payList.get(0)));

        saldoList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                int amount = debtList.get(i);
                Toast.makeText(SaldoActivity.this, Integer.toString(amount), Toast.LENGTH_LONG).show();

            }
        });

    }

    public void onAddTransaction_Clicked() {
        Intent intent = new Intent(this, AddTransaction.class);
        startActivity(intent);
    }

    public void onDeleteGroup_Clicked(View caller) throws InterruptedException {
        if(previousID == GroupActivity.getID()){
            offset++;
        }
        String url = "https://studev.groept.be/api/a21pt120/deleteGroup/" + GroupActivity.getID();
        httpCall(url);
        String url_offset = "https://studev.groept.be/api/a21pt120/deleted_input/" + offset;
        httpCall(url_offset);
        Intent intent = new Intent(this, GroupActivity.class);
        timeout();
        intent.putExtra("email", email);
        startActivity(intent);
    }

    private void calculateDebtList() {
        for(int i = 0; i < payList.size(); i++){
            int debt = payList.get(i) - totalPerPerson;
            debtList.add(debt);
        }
    }

    private void calculateTotalPerPerson() {
        if(names.size() > 0) {
            totalPerPerson = calculateSum()/names.size();
        }
        else{
            totalPerPerson = calculateSum();;
        }
    }

    private int calculateSum() {
        int sum = 0;
        for(int i = 0; i < totalList.size(); i++)
            sum += totalList.get(i);
        return sum;
    }

    private void timeout() {
        try {
            TimeUnit.SECONDS.sleep(3);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public void getPayList(){
        RequestQueue requestQueue = Volley.newRequestQueue(GroupActivity.returnContext());
        String url = GET_PAY_AMOUNT_PER_NAME + GroupActivity.getID();
        StringRequest submitRequest = new StringRequest(Request.Method.GET, url,
                response -> {
                    try {
                        JSONArray responseArray = new JSONArray(response);
                        payList = new ArrayList<>();
                        for(int i = 0; i<responseArray.length(); i++) {
                            JSONObject curObject = responseArray.getJSONObject(i);
                            payList.add(curObject.getInt("totalPerPerson"));
                        }
                    }
                    catch (JSONException e)
                    {
                        Log.e("Error", e.toString());
                    }
                },
                error -> Log.e("Error", "Could not reach database"));
        requestQueue.add(submitRequest);
    }
}

我想将 int 值添加到 payList 中。但是 add() 并不能解决问题。当我尝试使用 lblGroup.setText(Integer.toString(payList.get(0))) 从支付列表中获取第一个元素时；（我用的例子里面应该有3个），app崩溃是因为paylist里面没有元素。

这是我从 URL 得到的 JSON。我想在名为 payList

的 ArrayList 中设置值 200、3、10

[ { "totalPerPerson": "200" }, { "totalPerPerson": "3" }, { "totalPerPerson": "10" } ]

Answer 1

我认为您是直接尝试将字符串数字值添加到 Int 数组 payList 所以首先使用 Integer.parseInt()

转换为 Parse int

试试下面的代码，这可能会有帮助

               try {
                    JSONArray responseArray = new JSONArray(response);
                    payList = new ArrayList<>();
                    for(int i = 0; i<responseArray.length(); i++) {
                        JSONObject curObject = responseArray.getJSONObject(i);
                        payList.add(Integer.parseInt(curObject.getInt("totalPerPerson"))); //check here
                    }
                }
                catch (JSONException e)
                {
                    Log.e("Error", e.toString());
                }

从 JSON 读取整数并将其添加到数组列表

Read Integer from JSON and add it to an arraylist

java

android

json

arraylist