Android 应用程序未从套接字输入读取 stream

Question

My android application is not receiving any data from my server, for some reason. Strangely enough, a different socket client I wrote (which runs on my computer rather than an AVD) receives and prints all server-sent messages without fault. It uses similar code to what is held within the doInBackground method.

public class Client extends AsyncTask<Void, Void, Void>  {

    int port;
    Socket s;

    @Override
    protected Void doInBackground(Void... voids) {
        try {
            port = 1818;
            s = new Socket("xx.xx.xx.xx", port);
            if (!s.isConnected()) {
                s.close();
            }

            BufferedReader re = new BufferedReader(new InputStreamReader(s.getInputStream()));
            String temp = null;

            while ((temp = re.readLine()) != null)
            {
                MainActivity.changeT(temp); // This will replace the TextView's text with temp.
            }

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

I am thinking a possible solution would be to place the while loop into a separate thread, but I am not sure. Any suggestions are welcome: :-)

Answer 1

While the application was accessing the server appropriately, MainActivity.changeT(temp); is attempting to access the UI thread from a background thread, which is not appropriate.

I solved this by passing an instance of the MainActivity to this Client class, and I used the runnable method runOnUiThread(...) .

public class Client extends AsyncTask<Void, Void, Void> {

    int port;
    Socket s;
    MainActivity instance;

    Client(MainActivity instance)
    {
        this.instance = instance;
    }

    @Override
    protected Void doInBackground(Void... voids) {
        try {
            port = 1818;
            s = new Socket("xx.xx.xx.xx", port);
            if (!s.isConnected()) {
                s.close();
                return null;
            }

            BufferedReader re = new BufferedReader(new InputStreamReader(s.getInputStream()));
            String temp = null;
            TextView t = instance.getT(); // Accesses a getter method that returns the TextView.

            while ((temp = re.readLine()) != null)
            {
                setText(t, temp); // Accesses the UI Thread and changes the TextView.
            }

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

    private void setText(final TextView text,final String value){
        instance.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                text.setText(value); // This is equivalent to writing the code in the UI thread itself.
            }
        });
    }