HttpURLConnection工作在Java中，但不是Android

Question

我們一直在嘗試發送POST請求到一個android應用程序中的node.js服務器。由於舊的apache依賴關係被棄用（我似乎無法訪問它們 - 我試過），我們一直在使用HttpURLConnection類。我們在java中編寫了一個類，它只是一個獨立的類（Request.java），但是當它在android程序中運行時，它每次都會引發一個錯誤，當試圖獲取錯誤消息時，它只返回null。

Request.java

package andrewmmattb.beacongame; 

/** 
* Created by matt on 05/03/2016. 
*/ 

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

public class Request { 

    public static void main(String[] args) throws Exception { 
     Request http = new Request(); 

     System.out.println("POST"); 
     http.sendPost("{\"username\": \"matt\",\"newPoints\":5}"); 
    } 

    public static void sendPost(String json) throws Exception { 

     String url = "http://ec2-54-187-69-193.us-west-2.compute.amazonaws.com/points"; 
     URL obj = new URL(url); 
     HttpURLConnection con = (HttpURLConnection) obj.openConnection(); 

     //add reuqest header 
     con.setRequestMethod("POST"); 
     con.setRequestProperty("User-Agent", ""); 
     con.setRequestProperty("Accept-Language", "en-US,en;q=0.5"); 
     con.setRequestProperty("Content-Type", "application/json"); 

     String urlParameters = ""; 

     // Send post request 
     con.setDoOutput(true); 
     DataOutputStream wr = new  DataOutputStream(con.getOutputStream()); 
     wr.writeBytes(json); 
     wr.flush(); 
     wr.close(); 

     int responseCode = con.getResponseCode(); 
     System.out.println("\nSending 'POST' request to URL : " + url); 
     System.out.println("Post parameters : " + urlParameters); 
     System.out.println("Response Code : " + responseCode); 

     BufferedReader in = new BufferedReader(
       new InputStreamReader(con.getInputStream())); 
     String inputLine; 
     StringBuffer response = new StringBuffer(); 

     while ((inputLine = in.readLine()) != null) { 
      response.append(inputLine); 
     } 
     in.close(); 

     //print result 
     System.out.println(response.toString()); 
    } 
} 

GameActivity.java

package andrewmmattb.beacongame; 

import android.app.Activity; 
import android.app.DownloadManager; 
import android.content.Intent; 
import android.os.Bundle; 
import android.os.Debug; 
import android.os.Handler; 
import android.util.Base64; 
import android.util.JsonWriter; 
import android.util.Log; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.widget.TextView; 
import android.widget.Toast; 

import org.json.*; 

import java.io.BufferedOutputStream; 
import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.InputStreamReader; 
import java.io.OutputStream; 
import java.io.OutputStreamWriter; 
import java.net.HttpURLConnection; 
import java.net.MalformedURLException; 
import java.net.URL; 
import java.util.ArrayList; 
import java.util.Collection; 
import java.util.HashMap; 
import java.util.Map; 
import java.util.Set; 

public class GameActivity extends Activity { 

String username; 
String serverPath = "THE PATH TO THE SERVER"; 

int score = 0; 
int prevScore = 0; 

TextView usernameTextView; 
TextView scoreTextView; 

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

    usernameTextView = (TextView)findViewById(R.id.textViewGameUsername); 
    scoreTextView = (TextView)findViewById(R.id.textViewGameScore); 

    Intent intent = getIntent(); 
    username = intent.getStringExtra("username"); 
    usernameTextView.setText(username); 

    try { 
     makeSeverPost(); 
    } 
    catch (IOException e) { 
     Toast.makeText(GameActivity.this,"There was an IO error, called after function call (line 56)",Toast.LENGTH_LONG).show(); 
     e.printStackTrace(); 
    } 
} 

void makeSeverPost() throws IOException { 
    // creates a map object with username and the additional points to the previous sent score 
    Map<String,Object> values = new HashMap<String,Object>(); 
    values.put("username",username); 
    values.put("newPoints",score-prevScore); 
    // sets the previous score to equal the current score 
    prevScore = score; 

    // writes the map into a string in JSON format 
    String jsonString = new JSONObject(values).toString(); 

    try { 
     Request.sendPost(jsonString); 
    } catch (Exception e) { 
     e.printStackTrace(); 
     Log.e("problem",""+e.getMessage()); 
    } 
    } 
} 

有由於所有其他努力做到這一點，我們已經做了很多多餘的依賴關係。

Answer 1

在主網上的android網絡是不允許的。

您必須從AsyncTask調用此方法。

---

實施例：

class MakeSeverPostTask extends AsyncTask<Void, String, JSONObject> 
{ 
    Map<String,Object> params; 

    public MakeSeverPostTask(Map<String,Object> params){ 
     this.params = params; 
    } 

    protected JSONObject doInBackground(Void... v) 
    { 
     String jsonString = new JSONObject(this.params).toString(); 
     return Request.sendPost(jsonString); 
    } 

    protected void onPostExecute(JSONObject result) 
    { 

    } 
} 

用法：

Map<String,Object> values = new HashMap<String,Object>(); 
values.put("username",username); 
values.put("newPoints",score-prevScore); 

new MakeSeverPostTask(values).execute(); 

Answer 2

下面是更詳細說明的解決方案：

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

     usernameTextView = (TextView)findViewById(R.id.textViewGameUsername); 
     scoreTextView = (TextView)findViewById(R.id.textViewGameScore); 

     // creates a map object with username and the additional points to the previous sent score 
     Map<String,Object> values = new HashMap<String,Object>(); 
     values.put("username",username); 
     values.put("newPoints",score-prevScore); 

     // writes the map into a string in JSON format 
     String jsonString = new JSONObject(values).toString(); 
     String url = "http://ec2-54-187-69-193.us-west-2.compute.amazonaws.com/points"; 

     // executing AsyncTask with passing string parameters. 
     ServerAsyncTask makeServerPost = new ServerAsyncTask(); 

     makeServerPost.execute(url, jsonString); 
    } 

    private class ServerAsyncTask extends AsyncTask<String, Void, JSONObject> { 

     private final String TAG = ServerAsyncTask.class.getSimpleName(); 

     @Override 
     protected JSONObject doInBackground(String... params) { 
      JSONObject result = null; 
      try { 
       URL obj = new URL(params[0]);      // added url 

       HttpURLConnection con = (HttpURLConnection) obj.openConnection(); 

       //add reuqest header 
       con.setRequestMethod("POST"); 
       con.setRequestProperty("User-Agent", ""); 
       con.setRequestProperty("Accept-Language", "en-US,en;q=0.5"); 
       con.setRequestProperty("Content-Type", "application/json"); 

       String urlParameters = ""; 

       // Send post request 
       con.setDoOutput(true); 
       DataOutputStream wr = new DataOutputStream(con.getOutputStream()); 
       wr.writeBytes(params[1]);      // Added json 
       wr.flush(); 
       wr.close(); 

       int responseCode = con.getResponseCode(); 

       Log.i(TAG, "\nSending 'POST' request to URL : " + params[0]); 
       Log.i(TAG, "Post parameters : " + urlParameters); 
       Log.i(TAG, "Response Code : " + responseCode); 

       // safer way to parse response 
       if(responseCode == HttpURLConnection.HTTP_OK){ 

        BufferedReader in = new BufferedReader(
          new InputStreamReader(con.getInputStream())); 
        String inputLine; 
        StringBuilder response = new StringBuilder(); 

        while ((inputLine = in.readLine()) != null) { 
         response.append(inputLine); 
        } 
        in.close(); 

        // print result 
        Log.i(TAG, response.toString()); 

        result = new JSONObject(response.toString()); 
       } 

      } catch (IOException | JSONException e) { 
       e.printStackTrace(); 
      } 

      return result; 
     } 

     @Override 
     protected void onPostExecute(JSONObject jsonObject) { 
      super.onPostExecute(jsonObject); 
      /* You get response jsonObject here, 
      you can now update your UI here*/ 

      // Example update your score. 
      try { 

       String score = (String) jsonObject.get("score"); 

       scoreTextView.setText(score); 

      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 
     } 
    }