如何使用 Ion 在 sql php android 中进行搜索？

编程问答 2022-05-20

问题描述

我正在做一个项目，试图从微调器的数据中进行数据库搜索，但即使我的 php 脚本正在运行，它仍然给我 nullPointer 异常。我已经看过 JSONArray 了，它准确地显示了它应该做什么，所以我真的不明白 Android 在哪里或为什么给我空指针异常。 P.S“数据”是葡萄牙语的日期，在我的数据库中，类型是时间戳，但即使去掉那部分也不起作用。 请帮帮我

PHP 脚本

<?php
include "conn.php";

$nome_prova = $_GET["nome"];
$id_prova = "";
$tempos = array();

//$nome_prova = "50 Freestyle";

$athleteQuery = mysqli_query($conn,"SELECT `id` FROM `prova` WHERE `nome` LIKE '$nome_prova'");
$row1 = mysqli_fetch_array($athleteQuery);
$id_prova = $row1['id'];

$selectTimes = mysqli_query($conn,"SELECT A.nome,A.genero,T.tempo,T.data FROM atleta A,tempos T WHERE T.Prova_id = '$id_prova' AND A.id = T.Atleta_id;");*/

while($row = mysqli_fetch_assoc($selectTimes)){
    array_push($tempos,$row);   
}

echo json_encode ($tempos);

?>

安卓脚本

package com.example.time2swim;

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import com.android.volley.AuthFailureError;
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.StringRequest;
import com.android.volley.toolbox.Volley;
import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.koushikdutta.async.future.FutureCallback;
import com.koushikdutta.ion.Ion;
import com.rengwuxian.materialedittext.MaterialEditText;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class VerTempos extends AppCompatActivity {

    Spinner eventspinner;
    Button search;
    ListView listView;
    List<Time> lista;
    List<String> listaevent = new ArrayList<String>();
    String HOST = "http://192.168.1.220/Time2Swim";
    Adapter timeAdapter;




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

        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        lista = new ArrayList<Time>();

        eventspinner = findViewById(R.id.event);
        listView = findViewById(R.id.listViewTimes);

        listaEvents();

        search = findViewById(R.id.search);
        search.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String eventText = String.valueOf(eventspinner.getSelectedItem());
                String url = HOST + "/Mostrar_Tempos.php?nome=" + eventText;
                Ion.with(getBaseContext())
                        .load(url)
                        .asJsonArray()
                        .setCallback(new FutureCallback<JsonArray>() {
                            @Override
                            public void onCompleted(Exception e,JsonArray result) {
                                for (int i = 0; i < result.size(); i++) {
                                    JsonObject obj = result.get(i).getAsJsonObject();
                                    Time t = new Time();

                                    t.setNome_atleta(obj.get("nome").getAsString());
                                    t.setGenero_atleta(obj.get("telefone").getAsString());
                                    t.setData(obj.get("data").getAsString());
                                    t.setTempo(obj.get("tempo").getAsString());

                                    lista.add(t);
                                }

                                listView = findViewById(R.id.listViewAthletes);
                                timeAdapter = new TimeAdapter(VerTempos.this,lista);
                                listView.setAdapter((ListAdapter) timeAdapter);
                            }
                        });
            }
        });
    }

控制台

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.time2swim,PID: 15141
    java.lang.NullPointerException: Attempt to invoke virtual method 'int com.google.gson.JsonArray.size()' on a null object reference
        at com.example.time2swim.VerTempos$1$1.onCompleted(VerTempos.java:107)
        at com.example.time2swim.VerTempos$1$1.onCompleted(VerTempos.java:104)
        at com.koushikdutta.async.future.SimpleFuture.handleCallbackUnlocked(SimpleFuture.java:107)
        at com.koushikdutta.async.future.SimpleFuture.setComplete(SimpleFuture.java:141)
        at com.koushikdutta.async.future.SimpleFuture.setComplete(SimpleFuture.java:124)
        at com.koushikdutta.ion.IonRequestBuilder$1.run(IonRequestBuilder.java:244)
        at com.koushikdutta.async.AsyncServer$RunnableWrapper.run(AsyncServer.java:60)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

解决方法

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