getOutputStream在一個空套接字上？

Question

我是新來的，我在這裏問一個關於Sockets和Thread的問題。我有這樣的代碼，它給了我下面的錯誤：

public class Conferma extends AppCompatActivity { 

    private final String TAG = "Conferma"; 
    public Socket socket; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.conferma); 

     final EditText etTavolo = (EditText) findViewById(R.id.etTavolo); 
     final RadioButton rbSi = (RadioButton) findViewById(R.id.rbSi); 
     RadioButton rbNo = (RadioButton) findViewById(R.id.rbNo); 
     Button bInvia = (Button) findViewById(R.id.bInvia); 

     Thread t = new Thread(new ClientThread()); 
     t.start(); 

     bInvia.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       String ordine = getIntent().getExtras().getString("ordine"); 
       if(etTavolo.getText().toString().equals("")){ 
        AlertDialog.Builder builder = new AlertDialog.Builder(Conferma.this); 
        builder.setMessage("Inserire il numero del tavolo!").setNegativeButton("Riprova!", null).create().show(); 
       } 
       ordine = ordine + "Tavolo: " + etTavolo.getText().toString() + "/"; 
       if(rbSi.isChecked()) { 
        ordine = ordine + "Coperto: Sì/"; 
       } 
       else{ 
        ordine = ordine + "Coperto: No/"; 
       } 
       Log.d(TAG, ordine); 

       //invio informazione 
       inviaStringa(view, ordine); 
      } 
     }); 
    } 

    private void inviaStringa(View view, String ordine) { 

     try{ 
      OutputStream s = socket.getOutputStream(); 
      OutputStreamWriter outputStreamWriter = new OutputStreamWriter(s); 
      BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter); 
      PrintWriter out = new PrintWriter(bufferedWriter, true); 
      out.println(ordine); 
     } catch (Exception e) { 
      Log.e(TAG, "Errore: " + e); 
     } 
    } 

    private class ClientThread implements Runnable { 

     private static final int SERVER_PORT = 6000; 
     private static final String SERVER_IP = "109.115.84.90"; 
     private static final String TAG = "ClientThread"; 

     @Override 
     public void run() { 
      try { 
       InetAddress serverAddress = InetAddress.getByName(SERVER_IP); 
       Log.d(TAG, "creato"); 
       socket = new Socket(serverAddress, SERVER_PORT); 
      } catch (UnknownHostException e) { 
       Log.e(TAG, "Errore: " + e); 
      } catch (IOException e) { 
       Log.e(TAG, "Errore: " + e); 
      } 
     } 
    } 
} 

錯誤：現在

java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.OutputStream java.net.Socket.getOutputStream()' on a null object reference

，從錯誤中我認爲這個問題是在插座，這意味着未初始化。但是如果我在創建簡單線程的時候調用ClientThread方法，爲什麼不初始化呢？感謝您的幫助，並且抱歉，如果我不能比這更清楚！ ：（（

Answer 1

實現這一目標的最好的（也是最正確的）的方法是使用一個AsyncTask（正如我在評論中寫道）

如果你想使用這個類，然後有很多種解決方案，在這裏。我只是建議一個我認爲是更清潔，在另一個文件中創建類ClientThread並添加到該方法inviaStringa：

ClientThread：

private class ClientThread implements Runnable {  
    private static final int SERVER_PORT = 6000; 
     private static final String SERVER_IP = "109.115.84.90"; 
      private static final String TAG = "ClientThread"; 
     private Socket socket; 

    public ClientThread(){ 
       try { 
        InetAddress serverAddress = InetAddress.getByName(SERVER_IP); 
        Log.d(TAG, "creato"); 
        socket = new Socket(serverAddress, SERVER_PORT); 
       } catch (UnknownHostException e) { 
        Log.e(TAG, "Errore: " + e); 
       } catch (IOException e) { 
        Log.e(TAG, "Errore: " + e); 
       } 
      } 

    } 

      @Override 
      public void run() { 
    } 
      private void inviaStringa(View view, String ordine) { 

      try{ 
       OutputStream s = socket.getOutputStream(); 
       OutputStreamWriter outputStreamWriter = new OutputStreamWriter(s); 
       BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter); 
       PrintWriter out = new PrintWriter(bufferedWriter, true); 
       out.println(ordine); 
      } catch (Exception e) { 
       Log.e(TAG, "Errore: " + e); 
      } 
     } 

     } 

然後裏面Conferma你不需要更多的申報插座，但只做到這一點

Thread t = new Thread(new ClientThread()); 
     t.start(); 

...//when you've to send the String 

t.inviaStringa(view, ordine);