如何初始化OutputStream

Question

我正在開發一款應用程序，它可以控制arduino和藍牙，一切都可以正常工作，我可以連接到arduino藍牙橋，但是當我點擊控制arduino的botton時，我的應用程序崩潰了，崩潰日誌說它在OutputStream中發生空點異常，但即時通訊新的這一點，我不知道如何初始化它，我的OutputStream應該傳輸命令（寫入命令字符串）到arduino。我懷疑是如何初始化OutputStream？如果問題不清楚或缺乏信息，請告訴我。

import android.app.Activity; 
import android.bluetooth.BluetoothAdapter; 
import android.bluetooth.BluetoothDevice; 
import android.bluetooth.BluetoothSocket; 

import android.content.Intent; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.MotionEvent; 
import android.view.View; 
import android.widget.Button; 
import android.widget.Toast; 

import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.OutputStream; 
import java.util.UUID; 



public class MainActivity extends AppCompatActivity { 

    Button forward_btn,forward_left_btn , forward_right_btn , reverse_btn , reverse_right_btn , reverse_left_btn , btnConexao ; 
    public static final int SOLICITA_ATIVACAO = 1; // é o codigo numero 1 , é diferenciado o codigo pq pode haver varias solicitações na msma tela 
    public static final int SOLICITA_CONEXAO = 2; 

    BluetoothAdapter meuBluetoothAdapter=null; //declarar o meu adptador bluetooth 
    BluetoothDevice meuDevice=null; 
    BluetoothSocket meuSocket=null;// faz transiçao dos dados 



    boolean conexao = false; //variavel para a conexao que indica se a conexao está em andamento ou nao 

    private OutputStream outputStream ; 

    private static String MAC = null; 
    String command; //string variable that will store value to be transmitted to the bluetooth module 

    UUID MEU_UUID = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb"); // canal de comunicaçao bluetooth , UUID- ID do canal 
//protocolo Rfcomm 



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

     forward_btn = (Button) findViewById(R.id.forward_btn); //definir botoes e associar ao ficheiro xml 
     forward_left_btn = (Button) findViewById(R.id.forward_left_btn); 
     forward_right_btn = (Button) findViewById(R.id.forward_right_btn); 
     reverse_btn = (Button) findViewById(R.id.reverse_btn); 
     reverse_left_btn = (Button) findViewById(R.id.reverse_left_btn); 
     reverse_right_btn = (Button) findViewById(R.id.reverse_right_btn); 
     btnConexao = (Button) findViewById(R.id.btnConexao); 




     forward_btn.setOnTouchListener(new View.OnTouchListener() { 
      @Override 
      // comando para o botao frente , forward button 
      public boolean onTouch(View v, MotionEvent event) { // comandos bluetooth correspondentes do arduino 

       if (event.getAction() == MotionEvent.ACTION_DOWN) //MotionEvent.ACTION_DOWN é quando botao é segurado 
       { 
        command = "1"; 

        try 
        { 
         outputStream.write(command.getBytes()); //transmite o valor do comando para o modulo bluetooth 
        } 
        catch (IOException e) 
        { 
         e.printStackTrace(); 
        } 
        return true; 
       } 
       else if(event.getAction() == MotionEvent.ACTION_UP) 
       { 
        command = "10"; 
        try 
        { 
         outputStream.write(command.getBytes()); 
        } 
        catch(IOException e) 
        { 
         e.printStackTrace(); 
        } 

       } 

       return false; 
      } 

     }); 

     //OnTouchListener para o botao recuar (reverse button) (pressionar alongado) 
     reverse_btn.setOnTouchListener(new View.OnTouchListener(){ 
      @Override 
      public boolean onTouch(View v, MotionEvent event) 
      { 
       if(event.getAction() == MotionEvent.ACTION_DOWN) 
       { 
        command = "2"; 

        try 
        { 
         outputStream.write(command.getBytes()); 
        } 
        catch (IOException e) 
        { 
         e.printStackTrace(); 
        } 
       } 
       else if(event.getAction() == MotionEvent.ACTION_UP) 
       { 
        command = "10"; 
        try 
        { 
         outputStream.write(command.getBytes()); 
        } 
        catch(IOException e) 
        { 

        } 

       } 
       return false; 
      } 
     }); 

Answer 1

對於同樣的問題，開發商，解決方案已經給我的代碼用於初始化「的OutputStream」，並尋找答案的源線下面寫：

來源： https://developer.android.com/reference/java/io/OutputStream.html

行代碼： 的OutputStream =新ByteArrayOutputStream（1024; //大小