Получение Bluetooth-устройств

Question

Я искал Google и нашел код в stackoverflow. Я начал использовать его, но строка list.setAdapter(aa); генерирует NullPointerException. Как я могу это решить? Вот мой MainActivity.java:

public class MainActivity extends Activity { 
    private static int DISCOVERY_REQUEST = 1; 

    private Handler handler = new Handler(); 
    private ArrayList<BluetoothDevice> foundDevices; 
    private ArrayAdapter<BluetoothDevice> aa; 
    private ListView list; 

    private BluetoothAdapter bluetooth; 
    private BluetoothSocket socket; 
    private UUID uuid = UUID.fromString("a60f35f0-b93a-11de-8a39-08002009c666"); 

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

     configureBluetooth(); 
     setupListView(); 
     setupSearchButton(); 
     setupListenButton(); 
    } 

    private void configureBluetooth() { 
     bluetooth = BluetoothAdapter.getDefaultAdapter(); 
    } 

    private void setupListenButton() { 
     Button listenButton = (Button) findViewById(R.id.button_listen); 
     listenButton.setOnClickListener(new OnClickListener() { 
      public void onClick(View view) { 
       Intent disc = new Intent(
         BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE); 
       startActivityForResult(disc, DISCOVERY_REQUEST); 
      } 
     }); 
    } 

    @Override 
    protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
     if (requestCode == DISCOVERY_REQUEST) { 
      boolean isDiscoverable = resultCode > 0; 
      if (isDiscoverable) { 
       String name = "bluetoothserver"; 
       try { 
        final BluetoothServerSocket btserver = bluetooth 
          .listenUsingRfcommWithServiceRecord(name, uuid); 

        AsyncTask<Integer, Void, BluetoothSocket> acceptThread = new AsyncTask<Integer, Void, BluetoothSocket>() { 

         @Override 
         protected BluetoothSocket doInBackground(
           Integer... params) { 
          try { 
           socket = btserver.accept(params[0] * 1000); 
           return socket; 
          } catch (IOException e) { 
           Log.d("BLUETOOTH", e.getMessage()); 
          } 
          return null; 
         } 

         @Override 
         protected void onPostExecute(BluetoothSocket result) { 
          if (result != null) 
           switchUI(); 
         } 
        }; 
        acceptThread.execute(resultCode); 
       } catch (IOException e) { 
        Log.d("BLUETOOTH", e.getMessage()); 
       } 
      } 
     } 
    } 

    private void setupListView() { 
     aa = new ArrayAdapter<BluetoothDevice>(this, 
       android.R.layout.simple_list_item_1, foundDevices); 
     list = (ListView) findViewById(R.id.list_discovered); 
     list.setAdapter(aa); //the error comes from this line 

     list.setOnItemClickListener(new OnItemClickListener() { 
      public void onItemClick(AdapterView<?> arg0, View view, int index, 
        long arg3) { 
       AsyncTask<Integer, Void, Void> connectTask = new AsyncTask<Integer, Void, Void>() { 
        @Override 
        protected Void doInBackground(Integer... params) { 
         try { 
          BluetoothDevice device = foundDevices 
            .get(params[0]); 
          socket = device 
            .createRfcommSocketToServiceRecord(uuid); 
          socket.connect(); 
         } catch (IOException e) { 
          Log.d("BLUETOOTH_CLIENT", e.getMessage()); 
         } 
         return null; 
        } 

        @Override 
        protected void onPostExecute(Void result) { 
         switchUI(); 
        } 
       }; 
       connectTask.execute(index); 
      } 
     }); 
    } 

    private void setupSearchButton() { 
     Button searchButton = (Button) findViewById(R.id.button_search); 

     searchButton.setOnClickListener(new OnClickListener() { 
      public void onClick(View view) { 
       registerReceiver(discoveryResult, new IntentFilter(
         BluetoothDevice.ACTION_FOUND)); 

       if (!bluetooth.isDiscovering()) { 
        foundDevices.clear(); 
        bluetooth.startDiscovery(); 
       } 
      } 
     }); 
    } 

    private void switchUI() { 
     final TextView messageText = (TextView) findViewById(R.id.text_messages); 
     final EditText textEntry = (EditText) findViewById(R.id.text_message); 

     messageText.setVisibility(View.VISIBLE); 
     list.setVisibility(View.GONE); 
     textEntry.setEnabled(true); 

     textEntry.setOnKeyListener(new OnKeyListener() { 
      public boolean onKey(View view, int keyCode, KeyEvent keyEvent) { 
       if ((keyEvent.getAction() == KeyEvent.ACTION_DOWN) 
         && (keyCode == KeyEvent.KEYCODE_DPAD_CENTER)) { 
        sendMessage(socket, textEntry.getText().toString()); 
        textEntry.setText(""); 
        return true; 
       } 
       return false; 
      } 
     }); 
     BluetoothSocketListener bsl = new BluetoothSocketListener(socket, 
       handler, messageText); 
     Thread messageListener = new Thread(bsl); 
     messageListener.start(); 
    } 

    private void sendMessage(BluetoothSocket socket, String msg) { 
     OutputStream outStream; 
     try { 
      outStream = socket.getOutputStream(); 
      byte[] byteString = (msg + " ").getBytes(); 
      byteString[byteString.length - 1] = 0; 
      outStream.write(byteString); 
     } catch (IOException e) { 
      Log.d("BLUETOOTH_COMMS", e.getMessage()); 
     } 
    } 

    BroadcastReceiver discoveryResult = new BroadcastReceiver() { 
     @Override 
     public void onReceive(Context context, Intent intent) { 
      BluetoothDevice remoteDevice; 
      remoteDevice = intent 
        .getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); 
      if (bluetooth.getBondedDevices().contains(remoteDevice)) { 
       foundDevices.add(remoteDevice); 
       aa.notifyDataSetChanged(); 
      } 
     } 
    }; 

    private class MessagePoster implements Runnable { 
     private TextView textView; 
     private String message; 

     public MessagePoster(TextView textView, String message) { 
      this.textView = textView; 
      this.message = message; 
     } 

     public void run() { 
      textView.setText(message); 
     } 
    } 

    private class BluetoothSocketListener implements Runnable { 

     private BluetoothSocket socket; 
     private TextView textView; 
     private Handler handler; 

     public BluetoothSocketListener(BluetoothSocket socket, Handler handler, 
       TextView textView) { 
      this.socket = socket; 
      this.textView = textView; 
      this.handler = handler; 
     } 

     public void run() { 
      int bufferSize = 1024; 
      byte[] buffer = new byte[bufferSize]; 
      try { 
       InputStream instream = socket.getInputStream(); 
       int bytesRead = -1; 
       String message = ""; 
       while (true) { 
        message = ""; 
        bytesRead = instream.read(buffer); 
        if (bytesRead != -1) { 
         while ((bytesRead == bufferSize) 
           && (buffer[bufferSize - 1] != 0)) { 
          message = message 
            + new String(buffer, 0, bytesRead); 
          bytesRead = instream.read(buffer); 
         } 
         message = message 
           + new String(buffer, 0, bytesRead - 1); 

         handler.post(new MessagePoster(textView, message)); 
         socket.getInputStream(); 
        } 
       } 
      } catch (IOException e) { 
       Log.d("BLUETOOTH_COMMS", e.getMessage()); 
      } 
     } 
    } 

} 

И ошибка:

Caused by: java.lang.NullPointerException 
at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330) 
at android.widget.ListView.setAdapter(ListView.java:464) 
at com.example.testbluetooth.MainActivity.setupListView(MainActivity.java:113) 

Вот мой activity_main.xml:

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" > 

    <EditText 
     android:id="@+id/text_message" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:layout_alignParentBottom="true" 
     android:enabled="false" /> 

    <Button 
     android:id="@+id/button_search" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:layout_above="@id/text_message" 
     android:text="Search for listener" /> 

    <Button 
     android:id="@+id/button_listen" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:layout_above="@id/button_search" 
     android:text="Listen for connection" /> 

    <ListView 
     android:id="@+id/list_discovered" 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" 
     android:layout_above="@id/button_listen" 
     android:layout_alignParentTop="true" /> 

    <TextView 
     android:id="@+id/text_messages" 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" 
     android:layout_above="@id/button_listen" 
     android:layout_alignParentTop="true" 
     android:visibility="gone" /> 

</RelativeLayout> 

Answer 1

У вас есть пустой список, вы настраиваете список массива, прежде чем иметь список с устройствами.

Попробуйте удалить

setupListView() из onCreate()

и поставить его на место после того, как список с создания устройств.

Вы можете попробовать сделать это таким образом:

1. коллекция Initialize в вашем случае просто написать private ArrayList<BluetoothDevice> foundDevices = new ArrayList<BluetoothDevice>();
2. Когда вы вещать foundDevices.add(remoteDevice);
3. aa.addAll(foundDevices), а затем вызвать aa.notifyDataSetChanged();

Список литературы: ArrayAdapter.AddAll()