如何使用凌空從MySQL數據庫中獲取JSON數據？

Question

我正在嘗試從MySQL數據庫獲取JSON數據，但這給了我一個錯誤。 我正在使用本地計算機，並且已將端口配置為8080。因此，我看不到錯誤在哪里。

PHP腳本：

<?php

$username = "root";
$password = "";
$host = "localhost";
$db_name = "user_info";

$conn = mysqli_connect($host,$username,$password,$db_name);

$sql = "select * from users where name like 'Rashmi';";
$result = mysqli_query($conn,$sql);

if(mysqli_num_rows($result)>0)
{

    $row = mysqli_fetch_assoc($result);
    echo json_encode(array("Name"=>$row["name"],"Email"=>$row["email"],"Mobile"=>$row["mobile"]));
}

?>

這是android代碼，可從數據庫中以JSON格式獲取數據。

Android代碼：

public void onClick(View v) {

    JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, json_url, null, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {

            try {
                name.setText(response.getString("Name"));
                email.setText(response.getString("Email"));
                mobile.setText(response.getString("Mobile"));
            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {

            Toast.makeText(MainActivity.this,"Error",Toast.LENGTH_LONG).show();
            error.printStackTrace();
        }
    });

    MySingleton.getmInstance(MainActivity.this).addToRequestque(jsonObjectRequest);

}

Answer 1

當您可以使用AsyncTask從MySQL數據庫檢索所有數據時，我將為您提供解決方案。 嘗試以下代碼： PHP腳本：首先將數據庫中的所有元素添加到數組中：

<?php
$con = mysqli_connect("localhost", "db_username", "password", "database_name");

$query = mysqli_query($con, "SELECT username, email FROM users");

if($query)
{
    while($row = mysqli_fetch_array($query))
    {
        $arrRow["username"] = $row["username"];
        $arrRow["email"] = $row["email"];
        $users[] = $arrRow;
    }
    print(json_encode($users));
}
mysqli_close($con);

？>您應該在JSON Array中獲得所有結果。 接下來創建AsyncTask：

//Get Http Connection with async
private class RetrieveTask extends AsyncTask<Void, Void, String> {

    @Override
    protected String doInBackground(Void... voids) {
        String strUrl = "your url with php file";
        URL url = null;
        StringBuffer sb = new StringBuffer();

        try {
            url = new URL(strUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.connect();
            InputStream iStream = connection.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(iStream));
            String line = "";

            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }

            reader.close();
            iStream.close();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return sb.toString();
    }

    @Override
    protected void onPostExecute(String result) {

        ArrayList<HashMap<String, String>> location = null;
        try {

            JSONArray data = new JSONArray(result);

            location = new ArrayList<HashMap<String, String>>();
            HashMap<String, String> map;

            for (int i = 0; i < data.length(); i++) {
                JSONObject c = data.getJSONObject(i);

                map = new HashMap<String, String>();
                map.put("username", c.getString("username"));
                map.put("email", c.getString("email")
                location.add(map);
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        if (location != null) {

            for (int i = 0; i < location.size(); i++) {
                username = location.get(i).get("username").toString();
                email = location.get(i).get("email").toString();

            //Here you can add these values to ArrayList and display it later
            }
        }
    }
}

不要忘記在您的onCreate方法中或要開始下載數據的任何地方對其進行初始化。