java - 将数据从Android中的另一个类发送到异步任务

Question

我有扩展异步任务的类和另一个扩展线程的类。

客户端.java

public class Client extends AsyncTask<String, Void, Void>
{
 Socket socket;
 private SocketClient socketClient;
 DataOutputStream out;

 @Override
 protected Void doInBackground(String... params) 
 {
    // TODO Auto-generated method stub
    Log.d("home","Client");
    connect();
    return null;
 }  
 protected void connect() 
 {
    // TODO Auto-generated method stub
    Log.d("home","Connect");
    if(socket!=null) 
    {
        disconnect();
        return;
    }       
    try
    {
        String host = "111.111.1.111";
        InetAddress in=InetAddress.getByName(host);
        socket = new Socket(in,21);
        socketClient=SocketClient.handle(this,socket);
        Log.d("home","Connection established");
    }
    catch(Exception e)
    {
        e.printStackTrace();
        Log.d("home","Not Connection established");
    }
 }  
 void disconnect() 
 {
    // TODO Auto-generated method stub
    try 
    {
        socketClient.setDesonnected(true);
        socket.close();
    } 
    catch (Exception e)
    {
        System.err.println("Error closing client : "+e);
    }
    socket=null;
}

protected void sendmessage(byte[] commandchannel1)
{
    // TODO Auto-generated method stub
    byte[] commandchannel=commandchannel1;
     try
     {
         if(out==null)
         {
             out=new DataOutputStream(socket.getOutputStream());
         }
//      out.writeInt(commandchannel.length);        
        out.write(commandchannel);
        out.flush();
     } 
     catch(Exception e)
     {
         e.printStackTrace();
         disconnect();
     }
}
public void setreceived(String got)
{
    // TODO Auto-generated method stub
      System.out.println(got);
}
}

SocketClient.java

public class SocketClient extends Thread
{

 private boolean desonnected=false;
 private static SocketClient socketClient=null;
 private Socket socket=null;
 private static Client parent;
 private DataInputStream in;
 customadapter customadapter;

 public synchronized void setDesonnected(boolean cr) 
 {
        desonnected=cr;

 }

 private SocketClient(Client parent, Socket s)
 {
     super("Client");
     this.parent = parent;
     socket=s;
     setDesonnected(false);
     start();
     System.out.println(this.parent);
 }

public static SocketClient handle(Client client, Socket socket) 
{
    // TODO Auto-generated method stub
      if(socketClient==null)
            socketClient=new SocketClient(parent, socket);
        else {
            if(socketClient.socket!=null) {
                try {
                    socketClient.socket.close();
                } catch (Exception e)   {

                }
            }
            socketClient.socket=null;
            socketClient=new SocketClient(parent,socket);
        }
        return socketClient;
}

 public void run() {
     InputStream is = null;
        try {
            is = socket.getInputStream();
            System.out.println(is);
            in = new DataInputStream(is);

        } catch(IOException e) {
            try {
                socket.close();
            } catch(IOException e2) {
                System.err.println("Socket not closed :"+e2);
            }
            System.out.println("Could not open socket : "+e.getMessage());
            parent.disconnect();
            return;
        }

        while(!desonnected) {
            try {
                String got = readInputStream(in); //in.readLine();

                if(got==null) {
                    //parent.error("Connection closed by client");
                    parent.disconnect();
                    break;
                }
              **parent.setreceived(got);**
            } catch(IOException e) 
            {
                if(!desonnected) 
                {
                    System.out.println(e.getMessage());                  
                    parent.disconnect();
                }
                break;
            }
        }//end of while
        try {
            is.close();
            in.close();
            //socket.close();
        } catch (Exception err) {}
        socket=null;
    }//end of run

    private static String readInputStream(DataInputStream _in) throws     IOException
    {
        StringBuilder sb=new StringBuilder();
        String data = "";
        int s = _in.read();
        if(s==-1)
            return null;
        data += ""+String.format("%X", s)+ " ";
        int len = _in.available();
        System.out.println("Len got : "+len);
        if(len > 0)
        {
            byte[] byteData = new byte[len];
            _in.read(byteData);
            for(byte b:byteData)
             {
                System.out.println(byteData);
                 sb.append(String.format("%02X",b));
                 sb.append(" ");
             }                      
        }
        data += sb.toString();
        System.out.println(data);
        return data;
    }       
}

当 setreceived(got) 被调用时，我收到异常，因为 Attempt to invoke virtual method on null pointer exception。我将如何克服这个异常。

我从另一个 Activity 调用异步任务作为

client=new Client();
client.execute();

我想最终将接收到的值返回给一个 Activity 。我怎样才能做到这一点。 请帮助。提前致谢

Answer 1

您必须更改handle 方法。至于初始化SocketClient，你已经传递了参数parent，它还没有被初始化。所以传递 'client' 而不是它。

public static SocketClient handle(Client client, Socket socket) 
{
  // Verify that the socket is open
  if(socketClient==null)
        socketClient=new SocketClient(client, socket);
    else {
        if(socketClient.socket!=null) {
            try {
                socketClient.socket.close();
            } catch (Exception e)   {

            }
        }
        socketClient.socket=null;
        socketClient=new SocketClient(client,socket);
    }
    return socketClient;
}