Android 对象输出流

Question

我需要发送到我的服务器 java 程序（它在 PC 上运行）从 android 应用程序获取的电子邮件地址和密码，但是当我点击登录按钮时服务器没有收到我的消息并且应用程序崩溃

这是安卓代码：

    public class MainActivity extends Activity {

    private TextView tv;
    private Button button;
    private EditText editText1;
    private EditText editText2;
    Socket client;

    private class myTask extends AsyncTask<String, String, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

        }

        @Override
        protected String doInBackground(String... params) {

           try {
                 client = new Socket("192.168.1.3", 4444);  //connect to server

           }catch (UnknownHostException e){
               return "Host not found";
           }catch (IOException e) {
               return "Exception Caught";
           }
            return null;
        }

        @Override
        protected void onPostExecute(String result) {

            super.onPostExecute(result);   



            if ("Host not found".equalsIgnoreCase(result)){
                Toast.makeText(getApplicationContext(), "Host not found" ,Toast.LENGTH_LONG).show();
            }else if("Exception Caught".equalsIgnoreCase(result)){
                Toast.makeText(getApplicationContext(), "Connection error" ,Toast.LENGTH_LONG).show();
            }else{
                 Toast.makeText(getApplicationContext(), "Connection established" ,Toast.LENGTH_LONG).show();
             }
        }
    }

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tv = (TextView)findViewById(R.id.register);
        button = (Button)findViewById(R.id.login);

        new myTask().execute();

        tv.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View arg0) {
                startActivity(new Intent(MainActivity.this, Register.class));
            }
        });

        button.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View arg0) {
                ObjectInputStream ois = null;
                ObjectOutputStream oos = null;

                try {

                    oos = new ObjectOutputStream(client.getOutputStream());

                    oos.writeUTF("LOGIN");

                    String emailText = editText1.getText().toString();
                    oos.writeUTF(emailText);
                    oos.flush();

                    String passwordText = editText2.getText().toString();
                    oos.writeUTF(passwordText);
                    oos.flush();

                        client.close();

                } catch (IOException ex) {
                    Logger.getLogger(MainActivity.class.getName()).log(Level.SEVERE, null, ex);                 
                }

            }

        });


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

服务器崩溃：

Exception in thread "main" java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:196)
at java.net.SocketInputStream.read(SocketInputStream.java:122)
at java.net.SocketInputStream.read(SocketInputStream.java:210)
at java.io.ObjectInputStream$PeekInputStream.peek(ObjectInputStream.java:2293)
at java.io.ObjectInputStream$BlockDataInputStream.readBlockHeader(ObjectInputStream.java:2473)
at java.io.ObjectInputStream$BlockDataInputStream.refill(ObjectInputStream.java:2543)
at java.io.ObjectInputStream$BlockDataInputStream.read(ObjectInputStream.java:2615)
at java.io.DataInputStream.readUnsignedShort(DataInputStream.java:337)
at java.io.ObjectInputStream$BlockDataInputStream.readUnsignedShort(ObjectInputStream.java:2808)
at java.io.ObjectInputStream$BlockDataInputStream.readUTF(ObjectInputStream.java:2864)
at java.io.ObjectInputStream.readUTF(ObjectInputStream.java:1072)

android 应用程序日志：

    06-02 10:42:56.948: E/AndroidRuntime(5383): FATAL EXCEPTION: main
06-02 10:42:56.948: E/AndroidRuntime(5383): java.lang.NullPointerException
06-02 10:42:56.948: E/AndroidRuntime(5383):     at com.example.social_network.MainActivity$2.onClick(MainActivity.java:106)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at android.view.View.performClick(View.java:4240)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at android.view.View$PerformClick.run(View.java:17721)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at android.os.Handler.handleCallback(Handler.java:730)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at android.os.Handler.dispatchMessage(Handler.java:92)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at android.os.Looper.loop(Looper.java:137)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at android.app.ActivityThread.main(ActivityThread.java:5103)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at java.lang.reflect.Method.invokeNative(Native Method)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at java.lang.reflect.Method.invoke(Method.java:525)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
06-02 10:42:56.948: E/AndroidRuntime(5383):     at dalvik.system.NativeStart.main(Native Method)

我需要使用 ObjectOutputStream 因为服务器设置为接收这个对象..我错了什么？ 谢谢

Answer 1

虽然我不完全确定它为什么会因 NullPointerException 而崩溃，但我不认为 ObjectOutputStream 旨在在同一流上发送多个对象。我建议不要使用多个字符串，而是使用单个类来保存数据。

另外，我会使用 KryoNet 序列化库，而不是使用默认的 ObjectOutputStream，因为它可以节省您使用 AsyncTasks（默认情况下它是异步的和基于侦听器的）的工作量，并使这个过程更容易。它也是桌面和 Android 之间的跨平台。

https://github.com/EsotericSoftware/kryonet

它的工作方式是你必须在Server和Client的Kryo对象中注册你要发送的类，然后你可以使用sendTCP(object)命令发送数据。反序列化为对象是自动的，有关更多详细信息，请参见该站点。使用起来真的很简单！ :)