问题
I want to transfer data from Android device to the java desktop server. I have a text and button. As I press the button on the device, the text should be displayed on the java desktop server. I also have added AsyncTask in the client. The error code has also been added. The port i have used is 4444 and the ip address I used is of my local host address.
I am doing a very silly mistake. Can you please guide me.
I run the server code, it first gives me : Server started. Listening to the port 4444.
Now, I run the client code and write something on my mobile. As I press my button, it gives me error. And the app crashes and closes. I am a new one. Thanks in advance.
Client Code :
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
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
try {
client = new Socket("134.190.162.165", 4444); //connect to 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();
}
}
});
}
public class Asynctask extends AsyncTask<View, Integer, Socket>
{
private static final String IP_ADDRESS = "134.190.162.165"; // Toshiba laptop
// private static final String IP_ADDRESS = "10.0.0.2"; // Toshiba laptop
private static final int DEST_PORT = 4444;
private EditText mTextField;
/**
* Store provided views (used later in onPostExecute(...)).
*
* Create socket to communicate with server (blocking call).
*/
protected Socket doInBackground(View... params)
{
// Store provided views.
if (params.length != 1)
throw new IllegalArgumentException();
mTextField = (EditText) params[0];
// Create socket.
Socket client = null;
try
{
client = new Socket(IP_ADDRESS, DEST_PORT); // connect to server
} catch (UnknownHostException e)
{
e.printStackTrace();
} catch (IOException e)
{
e.printStackTrace();
}
return client;
}
/**
* Write to server.
*/
protected void onPostExecute(Socket client)
{
try
{
PrintWriter printwriter;
String messsage;
messsage = mTextField.getText().toString(); // get the text message on the text field
mTextField.setText(""); // Reset the text field to blank
printwriter = new PrintWriter(client.getOutputStream(), true);
printwriter.write(messsage); // write the message to output stream
printwriter.flush();
printwriter.close();
client.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
Server Code:
public class server {
private static ServerSocket serverSocket;
private static Socket clientSocket;
private static InputStreamReader inputStreamReader;
private static BufferedReader bufferedReader;
private static String message;
public static void main(String[] args) {
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");
}
}
}
}
The error which I get is:
FATAL EXCEPTION: main
android.os.NetworkOnMainThreadException
android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099)
libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
libcore.io.IoBridge.connectErrno(IoBridge.java:127)
libcore.io.IoBridge.connect(IoBridge.java:112)
java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
java.net.Socket.startupSocket(Socket.java:572)
java.net.Socket.tryAllAddresses(Socket.java:127)
java.net.Socket.<init>(Socket.java:177)
java.net.Socket.<init>(Socket.java:149)
com.example.client.MainActivity$1.onClick(MainActivity.java:42)
android.view.View.performClick(View.java:3567)
In the manifest file, I have added all the requirements. It does not give any compile time error.
I checked from many websites but the code which is working is this only. But I dont know where I am making mistake in running it or somewhere else.
If any other option is there, please suggest me, i am scratching my head since long
Thanks
回答1:
Your code seems very confusing. The client seems to have code for doing the network connection and I/O both on the main thread (in the OnClickListener attached to button) and in the AsyncTask (which is never created). Try this for an OnClickListener:
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
message = textField.getText().toString(); //get the text message on the text field
textField.setText(""); //Reset the text field to blank
new Asynctask().execute(message);
}
});
But you have another problem: while your AsyncTask is (correctly) making the socket connection in doInBackground, it is incorrectly doing the network I/O in onPostExecute. The network I/O also needs to be done in the background. Try this for an AsyncTask:
public class Asynctask extends AsyncTask<String, Void, Void> {
private static final String IP_ADDRESS = "134.190.162.165"; // Toshiba laptop
// private static final String IP_ADDRESS = "10.0.0.2"; // Toshiba laptop
private static final int DEST_PORT = 4444;
private EditText mTextField;
/**
* Store provided views (used later in onPostExecute(...)).
*
* Create socket to communicate with server (blocking call).
*/
protected Void doInBackground(String... messages) {
if (messages.length != 1) { return null; }
String message = messages[0];
// Create socket.
Socket client = null;
try {
client = new Socket(IP_ADDRESS, DEST_PORT); // connect to server
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
// Write to server.
try {
printwriter = new PrintWriter(client.getOutputStream(), true);
printwriter.write(messsage); // write the message to output stream
printwriter.flush();
printwriter.close();
}
catch (IOException e) {
e.printStackTrace();
} finally {
try {
client.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
The above is entirely untested, so it may not be exactly right. I also didn't look at your server code; this answer just addresses the NetworkOnMainThreadException problem.
来源：https://stackoverflow.com/questions/21818076/data-from-android-mobile-to-java-application-through-socket