Android tcp/ip 从主代码中读取和写入缓冲区

Question

我可以通过按钮在 Main 布局和 MainActivity java 上读写 TCP/IP 缓冲区。

但不能在不同的片段或不同的布局上这样做。

错误信息是：

java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.murat.ev.TcpClient.sendMessage(java.lang.String)' on a null object reference

我的代码：

MainActivity.java

public class MainActivity extends AppCompatActivity {
public TcpClient mTcpClient;
public Thread send_data;
public Button button;
public byte data[]=new byte[1024];

public DatabaseConstruction db;

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

    db = new DatabaseConstruction(getApplicationContext());
    new datasync().execute("");

    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    Fragment1 fragment1=new Fragment1();
    fragmentTransaction.replace(R.id.container, fragmen1_layout);
    fragmentTransaction.commit();

    button=(Button)findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            send_data_pre();
        }
    });
}

public class datasync extends AsyncTask<String, String, TcpClient>
{
    @Override
    protected TcpClient doInBackground(String... message)
    {
        //we create a TCPClient object and
        mTcpClient = new TcpClient(new TcpClient.OnMessageReceived()
        {
            @Override
            //here the messageReceived method is implemented
            public void messageReceived(String message)
            {
                Log.i("Debug","Input message: " + message);
                publishProgress(message);
            }
        });

        mTcpClient.run();
        return null;
    }

    @Override
    protected void onProgressUpdate(String... values)
    {
        super.onProgressUpdate(values);
        Log.i("onProgressUpdate",values[0]);
    }
}


public void send_data_pre()
{
    send_data = new Thread(new send_data("hello"));
    send_data.start();
}

public class send_data implements Runnable
{
    private String message;
    public send_data (String message)
    {
        this.message = message;
    }
    @Override
    public void run()
    {
        mTcpClient.sendMessage(message);
        Log.i("Debug", "mesaj did send");
    }
  }
}

Fragment1.java

public class Fragment1 extends Fragment {
Button button1;
MainActivity main=new MainActivity();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState)
{
    View view = inflater.inflate(R.layout.fragment1_layout, container, false);
    button1 =(Button)view.findViewById(R.id.buton_1);
    button1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            main.send_data();   ////THIS HERE IS APP STOP AND ERROR
        }
    });
    return view;
  }
}

Answer 1

也许在你想做的片段中 main.send_data_pre(); 而不是 main.send_data(); 如果我很好地理解你的问题，就像你在 MainActivity 的 OnCreate() 中所做的那样。

Android tcp/ip 从主代码中读取和写入缓冲区

Android tcp/ip read and write buffer out of main code

android

android-activity

nullpointerexception

fragment

tcpclient