2回印刷した後、Bluetoothプリンタが例外をスローします。

Question

私はBluetoothプリンタから請求書を印刷するためのアンドロイドアプリケーションを開発しました。私のコードでは「java.lang.NullPointerException：仮想メソッドを呼び出そうとしています」という例外がスローされます。「void java.io.OutputStream.write（byte []）」ヌルオブジェクト参照 "。

接続Bluetoothプリンタをし、印刷するデータを送信するための私のコードのように怒鳴るです：

enter code here 

//これは、印刷するBluetoothプリンタデバイス

void findBT() 
{ 
    try { 
     mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); 

     if (mBluetoothAdapter == null) { 
      //myLabel.setText("No bluetooth adapter available"); 

      Utilities.showToast("No bluetooth adapter available", true); 
     } 

     if (!mBluetoothAdapter.isEnabled()) 
     { 

      Utilities.showToast("Bluetooth is not On, Please Turn on Blueetooth", true); 

     } 

     Set<BluetoothDevice> pairedDevices = mBluetoothAdapter 
       .getBondedDevices(); 
     if (pairedDevices.size() > 0) { 
      for (BluetoothDevice device : pairedDevices) { 

       //Toast.makeText(PrintMain.this, "Device Name : " + device.getName(), Toast.LENGTH_SHORT).show(); 

       // MP300 is the name of the bluetooth printer device 
       if (device.getName().equals("PTP-III")) { 
        mmDevice = device; 
        break; 
       } 
      } 
     } 
     // myLabel.setText("Bluetooth Device Found"); 

     Utilities.showToast("Bluetooth Device is Found", true); 

    } catch (NullPointerException e) { 
     e.printStackTrace(); 
    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
} 


enter code here 

void openBT() throws IOException { 
try { 
      UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb"); 
     //UUID uuid = UUID.fromString("fa87c0d0-afac-11de-8a39-0800200c9a66"); 
     mmSocket = mmDevice.createRfcommSocketToServiceRecord(uuid); 
     mmSocket.connect(); 
     mmOutputStream = mmSocket.getOutputStream(); 
     mmInputStream = mmSocket.getInputStream(); 

     beginListenForData(); 

     // myLabel.setText("Bluetooth Opened"); 

     Utilities.showToast("Bluetooth connection is Open now", true); 

    } catch (NullPointerException e) { 
     e.printStackTrace(); 
    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
} 

enter code here 

void beginListenForData() { 
    try { 
     final Handler handler = new Handler(); 

     // This is the ASCII code for a newline character 
     final byte delimiter = 10; 

     stopWorker = false; 
     readBufferPosition = 0; 
     readBuffer = new byte[1024]; 

     workerThread = new Thread(new Runnable() { 
      public void run() { 
       while (!Thread.currentThread().isInterrupted() 
         && !stopWorker) { 

        try { 

         int bytesAvailable = mmInputStream.available(); 
         if (bytesAvailable > 0) { 
          byte[] packetBytes = new byte[bytesAvailable]; 
          mmInputStream.read(packetBytes); 
          for (int i = 0; i < bytesAvailable; i++) { 
           byte b = packetBytes[i]; 
           if (b == delimiter) { 
            byte[] encodedBytes = new byte[readBufferPosition]; 
            System.arraycopy(readBuffer, 0, 
              encodedBytes, 0, 
              encodedBytes.length); 
            final String data = new String(
              encodedBytes, "US-ASCII"); 
            readBufferPosition = 0; 

            handler.post(new Runnable() { 
             public void run() { 
              // myLabel.setText(data); 
             } 
            }); 
           } else { 
            readBuffer[readBufferPosition++] = b; 
           } 
          } 
         } 

        } catch (IOException ex) { 
         stopWorker = true; 
        } 

       } 
      } 
     }); 

     workerThread.start(); 
    } catch (NullPointerException e) { 
     e.printStackTrace(); 
    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
} 
enter code here 

void sendData(String VoucherNumber, String ConnectedCmpName, String EntryUserName, String PartyName, String VoucherDate, Context mContext1, String[] InvItemDtls) throws IOException 
{ 

    try 
    { 
     String StrVisitAgain = "VISIT AGAIN  \n"; 
     mmOutputStream.write(StrVisitAgain.getBytes()); 


     mmOutputStream.flush(); 

    } catch (Exception e) { 
     Log.e("Main", "Exe ", e); 
     System.out.println("Excelption is : " + e.toString()); 
    } 
} 

enter code here 

void closeBT() throws IOException { 
    try { 
     stopWorker = true; 
     mmOutputStream.close(); 
     mmInputStream.close(); 
     mmSocket.close(); 
     Utilities.showToast("Bluetootj is now Closed", true); 
     // myLabel.setText("Bluetooth Closed"); 
    } catch (NullPointerException e) { 
     e.printStackTrace(); 
    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
} 

enter code here 

//コードを見つけますデータ

 PrintSalesInvoice p = new PrintSalesInvoice(); 
     try { 
      p.findBT(); 
      p.openBT(); 
      p.sendData(VoucherNumber, ConnectedCmpName, EntryUserName, PartyName, VoucherDate, getApplicationContext(),InvItemDtls); 
      p.closeBT(); 
     } catch (IOException ex) { 


     } 

Answer 1

SendData関数（データを出力する関数）に蛇コードを追加するh問題を解決しました。

enter code here 

try { 
      Thread.sleep(1000); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     }