Develop Reference

How to use runOnUiThread in a class?

My code is designed to read a .txt file from a URL, and then display the text inside my textview. the problem is, I am using this code in a class. and getting this error- "cannot resolve method runOnUiThread". How do I fix this??
public class mydownloaderclass {
// this method is called from MainActivity
public static void checkForUpdates(Context context) {
new Thread() {
#Override
public void run() {
String path ="http://host.com/info.txt";
URL u = null;
try {
u = new URL(path);
HttpURLConnection c = (HttpURLConnection) u.openConnection();
c.setRequestMethod("GET");
c.connect();
InputStream in = c.getInputStream();
final ByteArrayOutputStream bo = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
in.read(buffer); // Read from Buffer.
bo.write(buffer); // Write Into Buffer.
runOnUiThread(new Runnable() {
#Override
public void run() {
TextView text = (TextView) findViewById(R.id.TextView1);
text.setText(bo.toString());
try {
bo.close();
} catch (IOException e) {
e.printStackTrace();
}
}
});
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (ProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}.start();
}
}
I tried using asynctask
public class readtextfile extends AsyncTask<String, Integer, String> {
#Override
protected String doInBackground(String... params) {
String result = "";
try {
URL url = new URL("https://www.dropbox.com/myfile.txt");
BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
String line = null;
while ((line = in.readLine()) != null) {
//get lines
result += line;
}
in.close();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
#Override
protected void onPostExecute(String result) {
Toast.makeText(context, result, Toast.LENGTH_LONG).show();
}
}

Create a Handler instead to execute statements on Main Thread like this
Handler handler = new Handler(Looper.getMainLooper());
handler.post(new Runnable() {
#Override
public void run() {
//Write your RUN on UI Runnable code here
TextView text = (TextView) findViewById(R.id.TextView1);
text.setText(bo.toString());
try {
bo.close();
} catch (IOException e) {
e.printStackTrace();
} });

Try passing a view context. It can be the activity context where the text view is defined.
The runOnUiThread runs on the main looper so it required a UI context.
For that You can define a member field in the class where the Thread is defined and set it in the constructor. Or if the thread is in the activity itself. then simply set the context field in OnCreate and use it in the thread.
Hope this helps. :)
Let me know if this fixes it.

I would suggest you to use AsyncTask, android makes this class specially for doing some task on a working thread(doInBackgroung()) and then update UI in onPostExecute() method.

ServerSocket.accept() doesn't works in second time

I'm beginer in android and i'm trying develop a connection TCP server.
I have this class:
public class JavaTCPServer {
public static void send(String aMessage) {
final String msg = aMessage;
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
Socket socket = null;
try {
ServerSocket serverSocket = GlobalSingleton.getInstance().getServerSocket();
socket = serverSocket.accept();
PrintWriter printWriter = new PrintWriter(socket.getOutputStream(), true);
printWriter.println(msg);
printWriter.flush();
printWriter.close();
} catch (IOException ex) {
ex.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
socket = null;
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}
});
thread.start();
}
}
private ServerSocket serverSocket; //Created in GlobalSingleton Class...
try {
serverSocket = new ServerSocket(Constantes.TCP_PORT);
} catch (IOException e) {
e.printStackTrace();
}
I can send message normally in the first time, but when i try to send message the second time the software remains in line: socket = serverSocket.accept(); and the message in printWriter.println(msg) is not sent.
Additional Information
When i kill the app in settings and open i can send once.
Any questions don't hesitate ask me.
Thanks for all!

Your code only accepts one connection, processes it, and then exits. It does not behave as you have described.
You need a loop.
You also need to start a separate thread to handle each connection.
And calling a method that accepts connections send() is inside out and back to front.

I solved my own problem.
I wrote my class as the follow bellow code:
public class JavaTCPServer {
private ServerSocket serverSocket;
private String message;
private Handler updateConversationHandler;
private Thread serverThread = null;
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public ServerSocket getServerSocket() {
return serverSocket;
}
public void setServerSocket(ServerSocket serverSocket) {
this.serverSocket = serverSocket;
}
public JavaTCPServer() {
setUpdateConversationHandler(new Handler());
this.serverThread = new Thread(new ServerThread());
this.serverThread.start();
}
public Handler getUpdateConversationHandler() {
return updateConversationHandler;
}
public void setUpdateConversationHandler(Handler updateConversationHandler) {
this.updateConversationHandler = updateConversationHandler;
}
class ServerThread implements Runnable {
public void run() {
Socket socket = null;
try {
serverSocket = new ServerSocket(Constantes.TCP_PORT);
} catch (IOException e) {
e.printStackTrace();
}
while (!Thread.currentThread().isInterrupted()) {
try {
socket = serverSocket.accept();
CommunicationThread commThread = new CommunicationThread(
socket);
new Thread(commThread).start();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
class CommunicationThread implements Runnable {
private Socket clientSocket;
private BufferedReader input;
private String messageSend;
public CommunicationThread(Socket clientSocket) {
this.clientSocket = clientSocket;
try {
this.setInput(new BufferedReader(new InputStreamReader(
this.clientSocket.getInputStream())));
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
while (!Thread.currentThread().isInterrupted()) {
Central central = GlobalSingleton.getInstance()
.get_current_central();
if (central != null) {
if ((central.getStep() <= central.getObjetivo()) &&
(central.getStep() == 99)){
try {
messageSend = getMessage();
PrintWriter printWriter = new PrintWriter(
clientSocket.getOutputStream(), true);
printWriter.println(messageSend);
printWriter.flush();
try {
Thread.sleep(1500);
} catch (InterruptedException e) {
e.printStackTrace();
}
printWriter.println(Constantes.EXIT_CONFIG);
printWriter.flush();
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
} catch (IOException e) {
e.printStackTrace();
}
central.setStep(central.getStep() + 1);
}
}
/*
* try { String read = input.readLine();
* updateConversationHandler.post(new updateUIThread(read)); }
* catch (IOException e) { e.printStackTrace(); }
*/
}
}
public BufferedReader getInput() {
return input;
}
public void setInput(BufferedReader input) {
this.input = input;
}
}
}
With this class you can send and receive tcp messages all the time.
Thanks for all help!

Serversocket.accept() function is for accepting a new client and connecting with the client, for messages you need to use DataInputStream() and DataOutputStream() after connecting with the server. This happens because for the first time server accepts the new client and process further but after this it does not get a new connection and it waits for new connection at serversocket.accept().

Why DataOutputStream loses a character?

I have a simple connection activity:
package com.example.conn08;
import ...;
public class MainActivity extends Activity
{
public static Socket clientSocket;
public static DataOutputStream outToServer;
public static PrintWriter outTest;
public static BufferedReader inToServer;
With PrintWriter outTest I test server's availability:
If the user has no Internet, or the server doesn't work, I put Thread on a pause with Boolean shouldContinue.
private Thread mThread;
private final Object lock = new Object();
private Boolean shouldContinue = true;
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mThread = new Thread(new Runnable()
{
public void run()
{
while (true)
{
synchronized(lock)
{
try
{
lock.wait(); // lock the Thread
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
while (shouldContinue)
{
try
{
final String data = inToServer.readLine();
if (data != null)
{
Log.v("data", data);
runOnUiThread(new Runnable()
{
#Override
public void run()
{
String put[] = data.split("#");
//Data parsing
}
});
}
}
catch (IOException e)
{
e.printStackTrace();
}
Check on availability of the server:
try {
if(clientSocket.getInputStream().read() == -1)
{
Log.v("Connection: ", "lost");
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
});
mThread.start();
Connect();
}
public void Connect()
{
shouldContinue = true;
try
{
clientSocket = new Socket();
clientSocket.connect(new InetSocketAddress("localhost", 15780), 30000);
outToServer = new DataOutputStream(clientSocket.getOutputStream());
inToServer = new BufferedReader(
new InputStreamReader(clientSocket.getInputStream()));
outTest = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(clientSocket.getOutputStream())), true);
synchronized(lock)
{
lock.notify();
}
sendUTF("3#kokoko"); //send the message!
}
catch (IOException e)
{
e.printStackTrace();
}
}
public static void sendUTF(String str)
{
try
{
byte[] buf = str.getBytes("UTF-8");
outToServer.write(buf, 0, buf.length);
outToServer.writeBytes("\n");
outToServer.flush();
}
catch (IOException e)
{
e.printStackTrace();
outServ.setText("Нет соединения!");
}
}
}
Problem in that when I don't use the
if(clientSocket.getInputStream().read() == -1)
And send data to server like here:
sendUTF("3#kokoko");
All is fine, but if I use it, on server I see this message like
"#kokoko" - I lose the first character of the message and my socket is crushed! Help me please

How to create asyncTask to prevent networkOnMainThreadException

I'm new to android application development. I tried to develop an android server client chat
for my first project. This is the code for the client side. When the client press btnJoin,
it will connect to the server and send a string. I've read many example and many of them
looks like this. I got a networkOnMainThreadException. How do I make an asyncTask to prevent
this problem? Any help would be much appreciated.
btnJoin = (Button) findViewById(R.id.buttonJoin);
btnJoin.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Socket socket = null;
DataOutputStream dataOutputStream = null;
DataInputStream dataInputStream = null;
try {
socket = new Socket("192.168.1.4", 9092);
dataOutputStream = new DataOutputStream(socket.getOutputStream());
dataInputStream = new DataInputStream(socket.getInputStream());
dataOutputStream.writeUTF("Hello server!");
txtIP.append(dataInputStream.readUTF() + "\n");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataOutputStream != null) {
try {
dataOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataInputStream != null) {
try {
dataInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
});

Change your code as:
btnJoin.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View view){
new LongOperation().execute("");
}
}
private class LongOperation extends AsyncTask<String, Void, String> {
Socket socket = null;
String strresult="";
DataOutputStream dataOutputStream = null;
DataInputStream dataInputStream = null;
#Override
protected String doInBackground(String... params) {
try {
socket = new Socket("192.168.1.4", 9092);
dataOutputStream = new DataOutputStream(socket.getOutputStream());
dataInputStream = new DataInputStream(socket.getInputStream());
dataOutputStream.writeUTF("Hello server!");
strresult.append(dataInputStream.readUTF() + "\n");
// txtIP.append(dataInputStream.readUTF() + "\n");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataOutputStream != null) {
try {
dataOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataInputStream != null) {
try {
dataInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return strresult;
}
#Override
protected void onPostExecute(String result) {
TextView txtIP= (TextView) findViewById(R.id.txtIP);
// txtIP.append(result + "\n");
txtIP.setText(result + "\n");
}
#Override
protected void onPreExecute() {
}
}

Use AsyncTask like this :
First have it nested in your class, it should look similar to :
private class Communicator extends AsyncTask<Void, Void, Boolean> {
String tmp;
String err;
#Override
protected Boolean doInBackground() {
try {
socket = new Socket("192.168.1.4", 9092);
dataOutputStream = new DataOutputStream(socket.getOutputStream());
dataInputStream = new DataInputStream(socket.getInputStream());
dataOutputStream.writeUTF("Hello server!");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataOutputStream != null) {
try {
dataOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dataInputStream != null) {
try {
dataInputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return true;
}
#Override
protected void onPreExecute() {
}
#Override
protected void onPostExecute(Boolean result) {
txtIP.append(dataInputStream.readUTF() + "\n");
}
}
When you have AsyncTask,you can start it like this :
...
#Override
public void onClick(View v) {
Communicator c=new Communicator();
c.execute();
}
....

try to implement this code in your app
private class LongOperation extends AsyncTask<Object, Integer, Object> {
#Override
protected void onPreExecute() {
super.onPreExecute();
}
#Override
protected Object doInBackground(Object... params) {
//do hard work here
return params;
}
#Override
protected void onProgressUpdate(Integer... values) {
}
#Override
protected void onPostExecute(Object result) {
super.onPostExecute(result);
}
}

AsyncTask must be subclassed to be used. The subclass will override at least one method (doInBackground(Params...)), and most often will override a second one (onPostExecute(Result).)
Here is an example of subclassing:
private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
protected Long doInBackground(URL... urls) {
int count = urls.length;
long totalSize = 0;
for (int i = 0; i < count; i++) {
totalSize += Downloader.downloadFile(urls[i]);
publishProgress((int) ((i / (float) count) * 100));
// Escape early if cancel() is called
if (isCancelled()) break;
}
return totalSize;
}
protected void onProgressUpdate(Integer... progress) {
setProgressPercent(progress[0]);
}
protected void onPostExecute(Long result) {
showDialog("Downloaded " + result + " bytes");
}
}
Once created, a task is executed very simply:
new DownloadFilesTask().execute(url1, url2, url3);
for more details refer below links...
http://www.vogella.com/articles/AndroidPerformance/article.html
http://developer.android.com/reference/android/os/AsyncTask.html

Functioning Socket read no longer works when called in AsyncTask

I'm making an app that sends a string to a server over a socket and then reads the output after the server has processed that data. It worked perfectly when it was my foreground task, but I have since used AsyncTask to show a process dialog while the socket communication runs in the background, and things start breaking after I read the output from the server and then try to close the socket.
private class Progressor extends AsyncTask<String, Void, Void> {
ProgressDialog dialog;
protected void onPreExecute() {
dialog = ProgressDialog.show(ClearTalkInputActivity.this, "Loading..", "Analyzing Text", true, false);
}
protected Void doInBackground(String... strings) {
String language = strings[0].toLowerCase();
String the_text = strings[1];
Socket socket = null;
DataOutputStream dos = null;
DataInputStream dis = null;
try {
socket = new Socket(my_ip, port);
dos = new DataOutputStream(socket.getOutputStream());
dis = new DataInputStream(socket.getInputStream());
dos.writeUTF(language+"****"+the_text);
String in = "";
while (in.indexOf("</content>") < 0) {
in += dis.readUTF();
}
socket.close();
save_str(OUTPUT_KEY, in);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
if (dos != null) {
try {
dos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (dis != null) {
try {
dis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
protected void onPostExecute() {
if (dialog.isShowing())
dialog.dismiss();
startActivity(new Intent (output_intent));
}
}

The recommended way in Android is to use one of the two included HttpClients:
Apache HTTP Client
HttpURLConnection
There is no need to use sockets directly. These clients do a lot to improve your experience.
Here is a blog article by the Android developers, that explain the basics: http://android-developers.blogspot.de/2011/09/androids-http-clients.html