Android / MySQL：微调器不填充来自 MySQL 的数据

Question

我的代码有问题。我已经创建了一个从 MySQL 数据库填充的微调器。PHP 代码似乎完全没有问题，因为我运行链接“localhost/latihan1/menu/php”，将显示 json 字符串。json显示如下：{"result":[{"username":"haha","name":"Bus Bisnis","course":"math","session":"20119"},{"username":"hihi", "name":"Bus Ace","course":"fizik","session":"12817"},{"username":"m_ridwan","name":"Ridwan","course":"Komputer" ,"session":"1920"},{"username":"m_iqbal","name":"Iqbal","course":"Sains","session":"2021"}]}但是当我打开应用程序时，微调器不显示数据。我不知道为什么。下面是我的代码JAVA公共类 MainActivity 扩展 AppCompatActivity 实现 Spinner.OnItemSelectedListener{<?php     require_once "koneksi.php";    $query = mysqli_query($con, "SELECT * FROM kendaraan ORDER BY id ASC");    $students = array();        while($row = mysqli_fetch_array($query)){        array_push($students,array(            'username'=>$row['username'],            'name'=>$row['name'],            'course'=>$row['course'],            'session'=>$row['session']        ));    }    echo json_encode(array('result'=>$students));    mysqli_close($con);?>

Answer 1

我在我的 android studio 中执行了你的代码。我看起来您的网络调用无法获取数据（结果仍然为空）。检查我的代码以供参考。我用静态数据替换了您的网络调用。

package com.attiq.testapp;

import android.os.Bundle;

import android.view.View;

import android.widget.AdapterView;

import android.widget.ArrayAdapter;

import android.widget.Spinner;

import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

import com.google.gson.Gson;

import com.google.gson.JsonArray;

import com.google.gson.JsonObject;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import java.util.ArrayList;

public class Main5Activity extends AppCompatActivity implements Spinner.OnItemSelectedListener {

private Spinner spinner;

private ArrayList<String> students;

//JSON Array

private JSONArray result;

private TextView textViewName;

private TextView textViewCourse;

private TextView textViewSession;

@Override

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main5);

    //Initializing the ArrayList

    students = new ArrayList<String>();

    spinner = findViewById(R.id.spinner);

    spinner.setOnItemSelectedListener(this);

    textViewName = findViewById(R.id.textViewName);

    textViewCourse = findViewById(R.id.textViewCourse);

    textViewSession = findViewById(R.id.textViewSession);

    getData();

}

private void getData(){

    String json= "{\"result\":[{\"username\":\"haha\",\"name\":\"Bus Bisnis\",\"course\":\"math\",\"session\":\"20119\"},{\"username\":\"hihi\",\"name\":\"Bus Ace\",\"course\":\"fizik\",\"session\":\"12817\"},{\"username\":\"m_ridwan\",\"name\":\"Ridwan\",\"course\":\"Komputer\",\"session\":\"1920\"},{\"username\":\"m_iqbal\",\"name\":\"Iqbal\",\"course\":\"Sains\",\"session\":\"2021\"}]}";

    try {

        JSONObject jsonObject = new JSONObject(json);

        result= jsonObject.getJSONArray("result");

        getStudents(result);

    } catch (Exception e){

        e.printStackTrace();

    }

}

private void getStudents(JSONArray j) {

    for (int i = 0; i < j.length(); i++) {

        try {

            JSONObject json = j.getJSONObject(i);

            students.add(json.getString(Config.TAG_USERNAME));

        } catch (JSONException e) {

            e.printStackTrace();

        }

    }

    spinner.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, students));

}

private String getName(int position) {

    String name = "";

    try {

        JSONObject json = result.getJSONObject(position);

        name = json.getString(Config.TAG_NAME);

    } catch (JSONException e) {

        e.printStackTrace();

    }

    return name;

}

private String getCourse(int position) {

    String course = "";

    try {

        JSONObject json = result.getJSONObject(position);

        course = json.getString(Config.TAG_COURSE);

    } catch (JSONException e) {

        e.printStackTrace();

    }

    return course;

}

private String getSession(int position) {

    String session = "";

    try {

        JSONObject json = result.getJSONObject(position);

        session = json.getString(Config.TAG_SESSION);

    } catch (JSONException e) {

        e.printStackTrace();

    }

    return session;

}

@Override

public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

    //Setting the values to textviews for a selected item

    textViewName.setText(getName(position));

    textViewCourse.setText(getCourse(position));

    textViewSession.setText(getSession(position));

}

@Override

public void onNothingSelected(AdapterView<?> parent) {

    textViewName.setText("");

    textViewCourse.setText("");

    textViewSession.setText("");

}

}