Android app crashes when class is called that uses a new thread to connect to server

Question

This is the class in question

public class ServerLink {

private static Context context;
private Socket sock;
private String IP;
private int Port;
private InputStream is;
private OutputStream out;
private String temp;
private boolean bTemp;

public ServerLink(Context contxt){
    this(contxt,"18.220.103.72",2267);
}

public ServerLink(Context contxt,String inIP, int inPort){
    context = contxt;
    IP = inIP;
    Port = inPort;
}

public boolean sendLoginToServer(final String pass, final String username){
    Thread t1 = new Thread(new Runnable() {
        public void run()
        {
            try{
                bTemp = false;
                sock = new Socket(IP,Port);
                out = sock.getOutputStream();
                is = sock.getInputStream();

                sendToServer("Login");
                sendToServer(username.length() + ";" + username + ";" + pass);

                temp = "";
                String serverAnswer = Listener();

                if(serverAnswer.equals("")){
                    Toast.makeText(context,"WTF",Toast.LENGTH_LONG).show();
                }
                else if(serverAnswer.equals("login")){
                    Toast.makeText(context,"Yay",Toast.LENGTH_LONG).show();
                    bTemp = true;
                }
                else if(serverAnswer.equals("nigol")){
                    Toast.makeText(context,"Nay",Toast.LENGTH_LONG).show();
                }
            }
            catch (java.io.IOException e){
                Toast.makeText(context,e.getMessage().toString(),Toast.LENGTH_LONG).show();
            }
        }});
    t1.start();
    return bTemp;
}

public void sendToServer(String input){
    try{

        String toSend = input;
        byte[] toSendBytes = toSend.getBytes();
        int toSendLen = toSendBytes.length;
        byte[] toSendLenBytes = new byte[4];
        toSendLenBytes[0] = (byte)(toSendLen & 0xff);
        toSendLenBytes[1] = (byte)((toSendLen >> 8) & 0xff);
        toSendLenBytes[2] = (byte)((toSendLen >> 16) & 0xff);
        toSendLenBytes[3] = (byte)((toSendLen >> 24) & 0xff);
        out.write(toSendLenBytes);
        out.write(toSendBytes);

    }
    catch (java.io.IOException e){
        Toast.makeText(context,e.getMessage().toString(),Toast.LENGTH_LONG).show();
    }
}

public String Listener(){
    try {
        byte[] lenBytes = new byte[4];
        is.read(lenBytes, 0, 4);
        int len = (((lenBytes[3] & 0xff) << 24) | ((lenBytes[2] & 0xff) << 16) |
                ((lenBytes[1] & 0xff) << 8) | (lenBytes[0] & 0xff));
        byte[] receivedBytes = new byte[len];
        is.read(receivedBytes, 0, len);
        String message = new String(receivedBytes, 0, len);
        return message;
    }
    catch (java.io.IOException e){
        Toast.makeText(context,e.getMessage().toString(),Toast.LENGTH_LONG).show();
        return  e.getMessage().toString();
    }
}
}

It crashes my app when called. I tried using a new thread for each, and this code does work, I've tried using it as methods, but it is a group project so I want a class everyone can easily use, but doesn't work currently. It should connect to a server that returns login if successful, nigol if unsuccessful, the server does work, we've tested it with other platforms, but I cannot seem to get this class correct

score 1 · Accepted Answer · answered Aug 18 '17 at 08:02

You can not show toast message from any thread other than UI. I recommend using an AsyncTask or use this:

MyActivity.this.runOnUiThread(new Runnable() {
    public void run() {
        Toast.makeText(activity, "Hello", Toast.LENGTH_SHORT).show();
    }
});

Android app crashes when class is called that uses a new thread to connect to server

1 Answers1