爲什麼我的緩衝區在此代碼中返回爲空？

Question

代碼從http://rxtx.qbang.org/wiki/index.php/Event_Based_Two_Way_Communication

適應我試圖讀取與SerialReader類常見的緩衝區和發送緩衝區out了通過SerialWriter類系列，但緩衝區顯示爲空每次作家被調用。該代碼是使用TwoWaySerialCommTest的連接方法初始化（下面粘貼供參考）

public SerialWriter (OutputStream out) 
      { 
       this.out = out; 
      } 

      public SerialWriter (OutputStream out, byte[] buffer) 
      { 
        this.out = out; 
        this.buffer = buffer; 
      } 

      public void run() 
      { 
        while(true) 
        { 
          lock.lock(); 
          try 
         { 
          dataAvailable.await(); 
          System.out.println("Waking up"); 
          int i = 0; 
          if (this.buffer != null) 
          { 
            System.out.println("Buffer isn't empty"); 
            while(buffer[i] != ((byte)'\n') && i < buffer.length - 1) 
            { 
              this.out.write(buffer[i]); 
            } 
          } 
          else 
          { 
            System.out.println("Buffer is null"); 
            System.out.println(this.buffer.toString()); 
          } 
         } 
         catch (IOException e) 
         { 
          e.printStackTrace(); 
          System.exit(-1); 
         } 
         catch(Exception e) 
         { 
          e.printStackTrace(); 
         } 

          finally 
          { 
            lock.unlock(); 
          } 
        } 
      } 
     } 

串行Reader類

public static class SerialReader implements SerialPortEventListener 
     { 
      private InputStream in; 
      byte[] buffer; 

      public SerialReader (InputStream in) 
      { 
       this.in = in; 
      } 

      public SerialReader (InputStream in, byte[] buffer) 
      { 
        this.in = in; 
        this.buffer = buffer; 
      } 

      public void serialEvent(SerialPortEvent arg0) { 
       lock.lock(); 
        int data; 
        if (buffer != null) 
        { 
        for(int i = 0; i < buffer.length; i++) 
        { 
          if (buffer[i] != 0) 
          { 
            System.out.print((char)buffer[i]); 
          } 
        } 
        } 
        buffer = new byte[1024]; 

       try 
       { 
        int len = 0; 
        while ((data = in.read()) > -1) 
        { 
         if (data == '\n') { 
          break; 
         } 
         buffer[len++] = (byte) data; 
        } 
        System.out.println(new String(buffer,0,len)); 
        for(int i = 0; i < buffer.length; i++) 
        { 
          if (buffer[i] != 0) 
          { 
            System.out.print((char)buffer[i]); 
          } 
        } 
        System.out.println(); 
        dataAvailable.signal(); 
       } 
       catch (IOException e) 
       { 
        e.printStackTrace(); 
        System.exit(-1); 
       } 
       finally 
       { 
        lock.unlock(); 
       } 
      } 

     } 

TwoWaySerialCommTest（截斷）

import gnu.io.SerialPortEvent; 
    import gnu.io.SerialPortEventListener; 

    import java.io.IOException; 
    import java.io.InputStream; 
    import java.io.OutputStream; 
    import java.util.concurrent.locks.*; 

    /** 
    * This version of the TwoWaySerialComm example makes use of the 
    * SerialPortEventListener to avoid polling. 
    * 
    */ 
    public class TwoWaySerialCommTest 
    { 
      static Lock lock = new ReentrantLock(); 
      static Condition dataAvailable = lock.newCondition(); 
      public volatile byte[] buffer; 

      public TwoWaySerialCommTest() 
     { 
      super(); 
     } 


     void connect (String portName) throws Exception 
     { 
      CommPortIdentifier portIdentifier = CommPortIdentifier.getPortIdentifier(portName); 
      if (portIdentifier.isCurrentlyOwned()) 
      { 
       System.out.println("Error: Port is currently in use"); 
      } 
      else 
      { 
       CommPort commPort = portIdentifier.open(this.getClass().getName(),2000); 

       if (commPort instanceof SerialPort) 
       { 
        SerialPort serialPort = (SerialPort) commPort; 
        serialPort.setSerialPortParams(57600,SerialPort.DATABITS_8,SerialPort.STOPBITS_1,SerialPort.PARITY_NONE); 

        InputStream in = serialPort.getInputStream(); 
        OutputStream out = serialPort.getOutputStream(); 

        (new Thread(new SerialWriter(out , buffer))).start(); 

        serialPort.addEventListener(new SerialReader(in , buffer)); 
        serialPort.notifyOnDataAvailable(true); 

       } 
       else 
       { 
        System.out.println("Error: Only serial ports are handled by this example."); 
       } 
      } 
     } 

Answer 1

一個問題似乎是這樣的line：

buffer = new byte[1024]; 

我不認爲你想分配本地buffer到一個新的字節數組。這導致作者寫入它自己的數組中，並且而不是傳入的內容由讀者共享。指定buffer僅影響寫入器內部的局部變量。

此外，什麼停止輸入流覆蓋buffer？如果行長度大於1024，那麼你將得到一個數組越界異常。

最後，您並未將\n字符寫入buffer。因此，讀者將在輸出中打印多個\0空字符。