Question

我是android studio的新手。目前，我正在尝试使用Volley从mysql中获取数据。不幸的是，数据只获取第一个ID而其他信息仍为空。我试图只获取ID并且它有效，它显示所有ID。但是，当我获取chapter_num和chapter_title时，输出为空。输出应该有ID，chapter_num，chapter_title。

<?php

$db_name = "spmsejarahrevisionapp";
$mysql_username = "root";
$mysql_password = "";
$server_name = "localhost";
$conn = mysqli_connect($server_name, $mysql_username, $mysql_password, $db_name);

if (mysqli_connect_errno($conn)) {
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

$res = mysqli_query($conn, "SELECT id, chapter_num, chapter_title FROM spmtopic WHERE form='4' ORDER BY chapter_num");

$result = array();

while($row = mysqli_fetch_array($res)){
    array_push($result,
    array(
        'id'=>$row[0],
        'chapter_num'=>$row[1],
        'chapter_title'=>$row[2]
    ));
}

echo json_encode(array("result"=>$result));

mysqli_close($conn);

这是数据：

{
  "result": [
    {
      "id": "3",
      "chapter_num": "1",
      "chapter_title": "Kemunculan Tamadun Awal Manusia"
    },
    {
      "id": "4",
      "chapter_num": "2",
      "chapter_title": "Peningkatan Tamadun"
    },
    {
      "id": "5",
      "chapter_num": "3",
      "chapter_title": "Tamadun Awal Asia Tenggara"
    },
    {
      "id": "21",
      "chapter_num": "4",
      "chapter_title": "Kemunculan Tamadun Islam di Makkah"
    },
    {
      "id": "6",
      "chapter_num": "5",
      "chapter_title": "Kerajaan Islam Di Madinah"
    },
    {
      "id": "7",
      "chapter_num": "6",
      "chapter_title": "Kerajaan Islam dan Sumbangannya"
    },
    {
      "id": "8",
      "chapter_num": "7",
      "chapter_title": "Islam di Asia Tenggara"
    },
    {
      "id": "9",
      "chapter_num": "8",
      "chapter_title": "Pengaruh Islam di Malaysia"
    },
    {
      "id": "10",
      "chapter_num": "9",
      "chapter_title": "Perkembangan di Eropah"
    },
    {
      "id": "11",
      "chapter_num": "10",
      "chapter_title": "Dasar British dan Kesannya Terhadap Ekonomi Negara"
    }
  ]
}

MainActivity.java

public class MMapf4Activity extends CodeReuse {

public static final String JSON_URL = "http://10.0.2.2/conn.php";
public ListView listView;
private ProgressDialog loading;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_mmapf4);

    barRule();
    getSupportActionBar().setHomeAsUpIndicator(R.mipmap.ic_arrow_left_white);

    sendRequest();

    listView = (ListView) findViewById(R.id.listView);
}

private void sendRequest(){
    loading = ProgressDialog.show(this,"Please wait...","Fetching...",false,false);
    StringRequest stringRequest = new StringRequest(JSON_URL,
        new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                showJSON(response);
                loading.dismiss();
            }
        },
        new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Toast.makeText(MMapf4Activity.this,error.getMessage(),Toast.LENGTH_LONG).show();
            }
        });

    RequestQueue requestQueue = Volley.newRequestQueue(this);
    requestQueue.add(stringRequest);
}

private void showJSON(String json){
    ParseJSON pj = new ParseJSON(json);
    pj.parseJSON();
    CustomList cl = new CustomList(this, ParseJSON.ids,ParseJSON.nums,ParseJSON.titles);
    listView.setAdapter(cl);
}
}

ParseJson：

public class ParseJSON {
public static String[] ids;
public static String[] nums;
public static String[] titles;

public static final String JSON_ARRAY = "result";
public static final String KEY_ID = "id";
public static final String KEY_NUM = "nums";
public static final String KEY_TITLE = "titles";

private JSONArray users = null;

private String json;

public ParseJSON(String json){
    this.json = json;
}

protected void parseJSON(){
    JSONObject jsonObject = null;
    try {
        jsonObject = new JSONObject(json);
        users = jsonObject.getJSONArray(JSON_ARRAY);

        ids = new String[users.length()];
        nums = new String[users.length()];
        titles = new String[users.length()];

        for(int i=0;i < users.length();i++){
            JSONObject jo = users.getJSONObject(i);
            ids[i] = jo.getString(KEY_ID);
            nums[i] = jo.getString(KEY_NUM);
            titles[i] = jo.getString(KEY_TITLE);
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
}
}

CustomList.java

public class CustomList extends ArrayAdapter<String> {
private String[] ids;
private String[] nums;
private String[] titles;
private Activity context;

public CustomList(Activity context, String[] ids, String[] nums, String[] titles) {
    super(context, R.layout.spmtopic_list, ids);
    this.context = context;
    this.ids = ids;
    this.nums = nums;
    this.titles = titles;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = context.getLayoutInflater();
    View listViewItem = inflater.inflate(R.layout.spmtopic_list, null, true);
    TextView textViewId = (TextView) listViewItem.findViewById(R.id.id);
    TextView textViewNum = (TextView) listViewItem.findViewById(R.id.chapter_num);
    TextView textViewTitle = (TextView) listViewItem.findViewById(R.id.chapter_title);

    textViewId.setText(ids[position]);
    textViewNum.setText(nums[position]);
    textViewTitle.setText(titles[position]);

    return listViewItem;
}
}

spmtopic.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical">

<TextView
    android:id="@+id/id"
    android:text="New Text"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>

<TextView
    android:id="@+id/chapter_num"
    android:text="New Text"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>

<TextView
    android:id="@+id/chapter_title"
    android:text="New Text"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>

</LinearLayout>

MainActivity.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.foong.spmsejerahscore.MMapf4Activity">

<include
    layout="@layout/app_bar_2_reuse"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/include" />

<ProgressBar
    android:id="@+id/progressBar"
    style="?android:attr/progressBarStyle"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true" />

<ListView
    android:id="@+id/listView"
    android:layout_width="match_parent"
    android:layout_height="507dp"
    android:scrollbars="vertical"
    android:layout_below="@+id/include"
    android:layout_alignParentStart="true"
    android:layout_alignParentBottom="true" />


</RelativeLayout>

我的输出：

Answer 1

不确定为什么你认为它卡住了，但你的JSON键不匹配，所以它可能在第一条消息后引发异常

public static final String KEY_ID = "id";
// these aren't in your data 
public static final String KEY_NUM = "nums";
public static final String KEY_TITLE = "titles";

另外，适配器的推荐模式是

public class CustomList extends ArrayAdapter<Chapter> {
    private Chapter[] chapters;
    private Context context;

Answer 2

public static final String KEY_ID = "id";
public static final String KEY_NUM = "nums";
public static final String KEY_TITLE = "titles";

使用

更改密钥

public static final String KEY_ID = "id";
public static final String KEY_NUM = "chapter_num";
public static final String KEY_TITLE = "chapter_title";

Volley停留在ParseJSON循环上

2 个答案: