java - 向服务器发送 POST 请求

Question

我目前第一次在 android studio 上的应用程序中工作。我目前面临一个问题，我不知道从哪里开始......我搜索了几个小时的文档和所有内容，但我没有找到适合我的东西。

所以我的应用程序是一个订购汉堡的应用程序。我通过我构建的 API 从服务器获取数据(一个简单的 php 文件，用于连接到数据库并获取我提供给应用程序的汉堡)，然后我使用获取的数据创建 View 。

当我在这里时，用户可以选择他想要的订单数量，然后他需要将命令发送到服务器。但我不知道如何执行应用程序的这一部分。我尝试了在互联网上找到的东西，但我从未收到服务器或任何东西的响应。没有看到任何东西就工作有点困难。这是我的应用程序设计: App View from user perspective

这是我的代码:

1. 主要 Activity

public class MainActivity extends AppCompatActivity {
        ListView listView;

            @Override
            protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_main);
                listView = findViewById(R.id.listView);
                downLoadJson("http://192.168.0.5/API/burger.php");
            }

            private void downLoadJson(final String urlWebService) {
                DownLoadJson getJson = new DownLoadJson(urlWebService, this);
                getJson.execute();
            }

        }

这是我的 DownLoadJson 类

import android.app.Activity;
import android.os.AsyncTask;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ListView;

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

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;

public class DownLoadJson extends AsyncTask<Void, Void, String> {
    final String urlWebService;
    final Activity activity;
    private ArrayList<Burger> burgersList;

    public DownLoadJson(String url, Activity activity) {
        this.urlWebService = url;
        this.activity = activity;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        //Toast.makeText(activity.getApplicationContext(),"DOWNLOADING",Toast.LENGTH_LONG).show();
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        try {
            renderView(s);
            Button btnSend = activity.findViewById(R.id.btnSend);
            btnSend.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Log.d("ENVOYER", ""+burgersList.toString());
                    new SendPostRequestToServer().execute("http://192.168.0.5/API/ServiceCommandes.php",burgersList.toString());
                }
            });
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected String doInBackground(Void... voids) {
        try {
            // Ouverture de la connexion avec l'api
            URL url = new URL(urlWebService);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            StringBuilder stringBuilder = new StringBuilder();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String json;
            while ((json = bufferedReader.readLine()) != null) {
                stringBuilder.append(json + "\n");
            }
            return stringBuilder.toString().trim();
        } catch (MalformedURLException e) {
            Log.d("ERROR", "WRONG URL");
            e.printStackTrace();
            return null;
        } catch (IOException e) {
            Log.d("ERROR", "Connection I/O error ");
            e.printStackTrace();
            return null;
        } catch (Exception e) {
            return null;
        }
    }

    private void renderView(String json) throws JSONException {
        JSONArray jsonArray = new JSONArray(json);
        JSONObject jsonObject = jsonArray.getJSONObject(0);
        if (jsonObject.has("recette")) {
            burgersList = Burger.fromJson(jsonArray);
            BurgerAdapter adapter = new BurgerAdapter(activity, burgersList);
            ListView listView = (ListView) activity.findViewById(R.id.listView);
            listView.setAdapter(adapter);
            //adapter.addAll(burgersList);
            Log.d("DEBUG", "BURGER LIST = " + burgersList.size());
        }
    }

    public ArrayList<Burger> returnArrayList() {
        return burgersList;
    }
}

这是我找到互联网的 SendPostRequestToServer

    import android.os.AsyncTask;
    import android.util.Log;

    import java.io.DataOutputStream;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    import java.net.HttpURLConnection;
    import java.net.URL;

    public class SendPostRequestToServer extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... params) {

            String data = "";

            HttpURLConnection httpURLConnection = null;
            try {

                httpURLConnection = (HttpURLConnection) new URL(params[0]).openConnection();
                httpURLConnection.setRequestMethod("POST");

                httpURLConnection.setDoOutput(true);

                DataOutputStream wr = new DataOutputStream(httpURLConnection.getOutputStream());
                wr.writeBytes("PostData=" + params[1]);
                wr.flush();
                wr.close();

                InputStream in = httpURLConnection.getInputStream();
                InputStreamReader inputStreamReader = new InputStreamReader(in);

                int inputStreamData = inputStreamReader.read();
                while (inputStreamData != -1) {
                    char current = (char) inputStreamData;
                    inputStreamData = inputStreamReader.read();
                    data += current;
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (httpURLConnection != null) {
                    httpURLConnection.disconnect();
                }
            }

            return data;
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            Log.e("POST :", result); // this is expecting a response code to be sent from your server upon receiving the POST data
        }
    }

PHP 文件:

<?php
// Headers
header("Access-Control-Allow-Origin: *");
header("Content-Type: application/json; charset=UTF-8");
header("Access-Control-Allow-Methods: POST");
$PostData = json_decode(file_get_contents("php://input"));
if(!empty(($PostData)){
    http_response_code(200);
    echo json_encode(array("message" => "DATA RECEIVE"));

}else{
    http_response_code(503);
    echo json_encode(array("message" => "DATA ERROR"));
}

$con=mysqli_connect("localhost","root","","fastfood");
// check erreur
if (mysqli_connect_errno())
{
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
mysqli_close($con);
?>

当我检查 file_get_contents("php://input");我明白了 :'''2020-06-16 15:16:06.174 12488-12488/com.example.fastfood D/POST::%5B%7B%22id%22%3A+%221%22%2C%22nom%22%3A+%22Hamburger%22 %2C%22quantite%22%3A+%220%22%7D%2C+%7B%22id%22%3A+%222%22%2C%22nom%22%3A+%22芝士汉堡%22%2C%22quantite%22%3A+%220 %22%7D%2C+%7B%22id%22%3A+%223%22%2C%22nom%22%3A+%22Giant%22%2C%22quantite%22%3A+%220%22%7D%2C+%7B%22id %22%3A+%224%22%2C%22nom%22%3A+%22巨型+最大%22%2C%22数量%22%3A+%220%22%7D%2C+%7B%22id%22%3A+%225% 22%2C%22nom%22%3A+%22培根+最大%22%2C%22数量%22%3A+%220%22%7D%2C+%7B%22id%22%3A+%226%22%2C%22nom%22 %3A+%22Supreme+奶酪%22%2C%22quantite%22%3A+%220%22%7D%2C+%7B%22id%22%3A+%227%22%2C%22nom%22%3A+%22Supreme+胡椒%22 %2C%22quantite%22%3A+%220%22%7D%2C+%7B%22id%22%3A+%228%22%2C%22nom%22%3A+%22至尊+鸡%22%2C%22quantite%22%3A+ %220%22%7D%2C+%7B%22id%22%3A+%229%22%2C%22nom%22%3A+%22鱼+汉堡%22%2C%22quantite%22%3A+%220%22%7D%2C+ %7B%22id%22%3A+%2210%22%2C%22nom%22%3A+%22鸡肉+汉堡%22%2C%22quantite%22%3A+%220%22%7D%2C+%7B%22id%22%3A+ %2211%22%2C%22nom%22%3A+%22空竹%22%2C%22quantite%22%3A+%220%22%7D%2C+%7B%22id%22%3A+%2212%22%2C%22nom%22 %3A+%22烧烤%22%2C%22定量%22%3A+%220%22%7D%5D

'''

我在互联网上检查，当我将其解码为 json 时，我得到: JSON DECODE

Answer 1

我有一个错误，因为我发送的是非 Json 数组。在 doinbackground 方法中，我使用 urlEncode，当我检查该功能正在做什么时，我读到:

The space character " " is converted into a plus sign "+".

这就是为什么当我对 file_get_contents("php://input") 进行 json_decode 时，我得到了错误的 jsonArray