问题描述

Android 中new ObjectInputStream无法创建对象

//程序在这里报错了；
 this.ois = new ObjectInputStream(this.socket.getInputStream());
程序报错说空指针异常，表面上看是下面的第二条语句in在调用方法时出错的，实际上是Client.getInstance().getClientInputThread()返回了空对象，也即是ClientInputThread构造方法中的
this.ois = new ObjectInputStream(this.socket.getInputStream());
未能成功创建ois对象
这在后面打印出来的log信息也可以看出来。打印信息显示ois == null是 true,而oos == null 是 false;

事故语句块之语句1  final ClientInputThread in = Client.getInstance().getClientInputThread();
事故语句块之语句2  in.setMessageListener(new MsgListener(...){}); 

//输入线程
 public class ClientInputThread  extends Thread
{

    @SuppressWarnings("unused")
    private Socket socket;
    private ObjectInputStream ois;
    private TransEntity transEn;
    private MsgListener msgListener;
    private boolean isStart = true;
    public ClientInputThread(Socket socket)
    { 

        this.socket = socket;
        try
        {
            this.ois = new ObjectInputStream(this.socket.getInputStream());
        }
        catch (StreamCorruptedException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public TransEntity getMsg()
    {
        if(transEn!=null)
        {

            synchronized (this)
            {
                    try
                    {
                        wait();
                    }
                    catch (InterruptedException e)
                    {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }

            }

            return transEn;

        }
        return null;

    }

    public void setMessageListener(MsgListener msgListener)
    {
        this.msgListener = msgListener;
    }

    public void releaseResource()
    {
        try
        {
            ois.close();
            socket.close();
        }
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void run()
    {
        while(isStart)
        {
            //if(ois == null)
                System.out.println("ois == null  : "+(ois == null));
            try
            {
                transEn = (TransEntity) ois.readObject();
                if(transEn!=null)
                {
                    synchronized (this)
                    {
                        notify();
                    }
                }

            //  msgListener.Message(transEn);
            }
            catch (OptionalDataException e)
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            catch (ClassNotFoundException e)
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            catch (IOException e)
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
        releaseResource();
    }

}

 //输出线程
public class OutputThread extends Thread
{
        private Socket socket;
        private OutputThread  outputThread;
        private ObjectOutputStream oos;
        private TransEntity transEn;
        private boolean isStart = true;
        public OutputThread(Socket socket)
        {
            this.socket = socket;
            try
            {
                oos = new ObjectOutputStream(socket.getOutputStream());
            }
            catch (IOException e)
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
     // 设置了消息之后，唤醒写线程
        public void setMessage(TransEntity transEn)
        {
            this.transEn = transEn;
            synchronized (this)
            {
                notify();
            }
        }
        public void releaseResouce()
        {
            try
            {
                if (oos != null)
                oos.close();
                if (socket != null)
                socket.close();
            }
            catch (IOException e)
            {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        public void run()
        {
            while(isStart)
            {
            synchronized (this)
            {
                try
                {
                    if (transEn != null)
                    {
                            wait();
                            try
                            {
                                oos.writeObject(transEn);
                                oos.flush();
                                //oos.reset();
                            }
                            catch (IOException e)
                            {
                                // TODO Auto-generated catch block
                                e.printStackTrace();
                            }
                    }
                }
                catch (InterruptedException e)
                {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

            }
            releaseResouce();
        }
}

//客户端线程，在客户端线程启动输出和输入线程
 public class  ClientThread extends Thread
{

        private ClientOutputThread out;
        private ClientInputThread in;
        private Socket socket;
        public ClientThread(Socket socket)
        {
            this.socket = socket;

        }

        public void run()
        {   

            out = new ClientOutputThread(socket);
            in = new ClientInputThread(socket);
            out.start();
            in.start();

        }

        public ClientInputThread getIn()
        {

            return in;

        }
        public ClientOutputThread getOut()
        {

            return out;

        }
}

//客户端
 public class Client
{
        private static Client client;
      //  private boolean isLogin  = false;
        private Socket socket;
        private ClientThread clientThread;
        private Client()
        {

        }

        public static synchronized Client getInstance()
        { 

                if (client == null)
                {
                    client = new Client();
                }
                return client;
        }  

        public boolean startClient()
        {
            try
            {
                socket = new Socket();
                socket.connect(new InetSocketAddress("10.0.2.2",5345),2000);
                if (socket.isConnected())
                {
                    System.out.println("Connecting...");
                    clientThread = new ClientThread(socket);
                    clientThread.start();
                }
            }
            catch (IOException e)
            {
                e.printStackTrace();
                return false;
            }
            return true;
        }

     // 直接通过client得到读线程
        public ClientInputThread getClientInputThread()
        {
            return clientThread.getIn();
        }

        // 直接通过client得到写线程
        public ClientOutputThread getClientOutputThread()
        {
            return clientThread.getOut();
        }

}

//在onResume里头启动service，由service启动客户端
     protected void onResume()
    {
        // TODO Auto-generated method stub
        super.onResume();
        if (!GetMsgService.isStart)
        {
             Intent service = new Intent(FirstActivity.this, GetMsgService.class);
             startService(service);
            //isServiceRunning = true;
        } 

    }

报错信息

解决方案

http://www.oschina.net/question/2245161_2175113

解决方案二：

this.ois = new ObjectInputStream(this.socket.getInputStream()); this.socket.getInputStream()==null 出现的null指针吧

解决方案三：

this.ois = new ObjectInputStream(this.socket.getInputStream());
你传进来的 socket 有问题；