简单的客户端服务器应用程序android

Question

您好，我正在尝试在 android 中编写简单的客户端-服务器应用程序。这是我的客户端代码。

package com.sudarshan.client;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;


import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

import android.app.Activity;
import android.os.AsyncTask;

import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;


public class MainActivity extends Activity {
private Socket client;
private PrintWriter printwriter;
private EditText textField;
private Button button;
private String messsage;

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

    textField = (EditText) findViewById(R.id.editText1); // reference to the text field
    button = (Button) findViewById(R.id.button1); // reference to the send button

    // Button press event listener
    button.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {
            messsage = textField.getText().toString(); // get the text message on the text field
            textField.setText(""); // Reset the text field to blank
            SendMessage sendMessageTask = new SendMessage();
            sendMessageTask.execute();
        }
    });
}

private class SendMessage extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... params) {
        try {

            client = new Socket("10.0.2.2", 4444); // connect to the server
            printwriter = new PrintWriter(client.getOutputStream(), true);
            printwriter.write(messsage); // write the message to output stream

            printwriter.flush();
            printwriter.close();
            client.close(); // closing the connection

        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

}

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

}

这是服务器的代码

package com.sudarshan.server;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class MainActivity extends AppCompatActivity {

    private static ServerSocket serverSocket;
    private static Socket clientSocket;
    private static InputStreamReader inputStreamReader;
    private static BufferedReader bufferedReader;
    private static String message;

    @Override

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        try {
            serverSocket = new ServerSocket(4444); // Server socket

        } catch (IOException e) {
            System.out.println("Could not listen on port: 4444");
        }

        System.out.println("Server started. Listening to the port 4444");

        while (true) {
            try {

                clientSocket = serverSocket.accept(); // accept the client connection
                inputStreamReader = new InputStreamReader(clientSocket.getInputStream());
                bufferedReader = new BufferedReader(inputStreamReader); // get the client message
                message = bufferedReader.readLine();

                System.out.println(message);
                inputStreamReader.close();
                clientSocket.close();

            } catch (IOException ex) {
                System.out.println("Problem in message reading");
            }
        }
    }
}

服务器代码崩溃。它给出错误“java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sudarshan.server/com.sudarshan.server.MainActivity}: android.os.NetworkOnMainThreadException”。

我做错了什么？

Answer 1

解决了。

“android.os.NetworkOnMainThreadException”表示网络相关的任务不能直接在主线程上完成，即。 Activity 类。所以，需要在主线程下做一个线程，然后做这个工作。