Printing the output from a Bufferedreader to a TextView

Question

i am currently programming an app that manly works as a console for receiving and sending messages to my socket server.

I want to output the messages that the server sent me to a textview.

My problem is that i am getting the following exception when changing the textview

W/System.err: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

My code:

public class SocketListener implements Runnable {

public static BufferedReader r;



public void run() {

    try {
        MainActivity.ausgabe.setText("Reading socket");

        String message;
        Boolean run = true;
        while (run) {
            if(r != null) {
                MainActivity.ausgabe.setText("Reading line");
                message = r.readLine();
                MainActivity.ausgabe.setText("Line read");
                if(message != null){
                    MainActivity.ausgabe.setText(message);
                }

            }
        }


    } catch (Exception e) {
        e.printStackTrace();

    }
}

}

As far as i have tested, the problem is in this line:

 message = r.readLine();

because changing the textview before this line works perfekt, but after this line doesnt work (It prints the "reading line" but runs into the error when printing "line read")

I hope you can help me cause i couldnt find anything on the internet

Undead

The error message seems pretty clear. – Mena Jan 16 '18 at 14:11 — Mena, Jan 16 '18 at 14:11

score 1 · Accepted Answer · answered Jan 16 '18 at 14:38

When implementing interaction between Thread and Activity you should use Handler (info) or runOnUiThread (info).

I think the error throw is somehow delayed (because of multithreading) so you are seeing it after the view has actually changed. Probably there is another thread that checks for correct view manipulation and throws this error when discovers validation (I was unable to find exact info in Android docs).

Printing the output from a Bufferedreader to a TextView

1 Answers1