Hello, I ran into a problem in my application. There is a server using ServerSocket. In which there is a small UI with three JTextField and JButton. In which I fill in the information and on pressing the button I send information to the client, which is written under Andoid. The problem is the following, I do not understand how threads work in Android while the application is running. And as soon as I send the message to the client, textView immediately doesn’t fill it. The application starts to crash and as soon as I poke into some widget, it sort of decomposes and only then displays the message on the textView. As soon as I send something from the server, the following message is displayed in the log of Android Studio

Only this thread has been created.

Suppose I have an "send" Button on the activity and an EditText. So after I send a message to the client from the server, I open it and put the focus on EditText by clicking on it, it starts to lag as soon as I click on it to open the application completely and the textView server. Also, when re-sending a message from the server, the textView is not updated, perhaps the reason is that the code is in the onCreate () function;

What could be the problem and how to deal with it?

public class Server{ private static BufferedWriter bufferedWriter; JFrame frame; JButton sendButton; JPanel panel; JTextField nameTextField, serviceTextField, percentTextField; public Server(){ frame = new JFrame("AutoRate discount"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(410,100); frame.setVisible(true); frame.setLayout(new BorderLayout()); sendButton = new JButton("Send discount"); nameTextField = new JTextField(10); serviceTextField = new JTextField(10); percentTextField = new JTextField(10); panel = new JPanel(); panel.add(nameTextField); panel.add(serviceTextField); panel.add(percentTextField); panel.add(sendButton); frame.getContentPane().add(BorderLayout.CENTER,panel); frame.setLocationRelativeTo(null); sendButton.addActionListener(new MyListener()); } private static final int portNumber = 60123; public static void main(String[] args) { Server server = new Server(); ServerSocket serverSocket = null; try{ System.out.println("Server started at port number " + portNumber); serverSocket = new ServerSocket(portNumber); // Waiting for client connection System.out.println("Waiting for client connection"); Socket socket = serverSocket.accept(); System.out.println("A client has connected"); // Send message to the client bufferedWriter = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())); //String s = server.nameTextField.getText() + server.serviceTextField.getText() + server.percentTextField; //bufferedWriter.write(s); // Receive message from client String data; BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream())); while((data = bufferedReader.readLine()) != null) System.out.println("Message from client " + data); System.out.println("Server has ended"); }catch(IOException e){ e.printStackTrace(); } } //Обработчик нажатия кнопки private class MyListener implements ActionListener { @Override public void actionPerformed(ActionEvent e) { String s = nameTextField.getText() + serviceTextField.getText() + percentTextField.getText(); try { bufferedWriter.write(s); bufferedWriter.newLine(); bufferedWriter.flush(); } catch (IOException e1) { e1.printStackTrace(); } } }

}

Client Code:

 public class MainActivity extends Activity { Socket socket = null; public String debuggingString = "DEBUG"; // We should use here Ethernet adapter VMware Network Adapter VMnet1: IpV4 public String hostname = "192.168.253.1"; // <-- paste your IPv4 here public int portNumber = 60123; TextView textView; BufferedReader bufferedReader; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); new Thread() { @Override public void run() { try { //connecting Log.e(debuggingString, "Attempting to connect to server"); socket = new Socket(hostname, portNumber); //Send message to server BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())); bw.write("this is a message from the client"); bw.newLine(); bw.flush(); //Receive message from server bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream())); textView = (TextView)findViewById(R.id.textView); textView.setText(bufferedReader.readLine()); } catch ( Exception e ) { Log.e(debuggingString, e.getMessage()); } } }.start(); }

    1 answer 1

    In your application, data flows are used - and all requests occur in the main UI flow, which is why jams appear.

    The error that is displayed to you says that only the main thread can access this widget.

    The problem is the following, I do not understand how threads work in Android while the application is running.

    From the above, you need to understand that you have data streams, not parallel streams.

    There are many ways to parallelize streams, read about multithreading in android

    UDP: a similar question has already been asked