How to change value of TextView from non-activity class

Question

I am making a bluetooth communication application. My MainActivity calls the loop in BluetoothConnection class (script to establish Bluetooth connection, send and receive messages), which Logs every message that it receives. I want to display this message in TextView.

I tried making TextView variable inside MainActivity, and setting its value from BluetoothConnection class but it ended with error

MainActivity:

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemClickListener{
    static TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        textView = (TextView) findViewById(R.id.textView);
    }
}

BluetoothConnection:

            while(true)
            {
                try
                {
                    bytes = mmInStream.read(buffer);
                    String incomingMessage = new String(buffer, 0, bytes);
                    Log.d(TAG, "InputStream: " + incomingMessage);

                    MainActivity.textView.setText(incomingMessage);
                }
                catch (IOException e)
                {
                    Log.e(TAG,"write: Error reading inputStream. " + e.getMessage());
                    break;
                }
            }

I expect the TextView to change, but application crashes with error: 'android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.'

what is BluetoothConnection class? Is it Service? – Dmitriy Pavlukhin Aug 16 '19 at 17:32 — Dmitriy Pavlukhin, Aug 16 '19 at 17:32

score 0 · Answer 1 · answered Aug 16 '19 at 17:32

0

You need to pass the MainActivity's context to the BluetoothConnection.class

After that you can do:

    TextView txtView = (TextView) ((MainActivity)context).findViewById(R.id.your_tv);
    txtView.setText("Hello");

answered Aug 16 '19 at 17:32

Yash

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This is not a good solution. Better to have a presenter that handles this interaction. – JakeB Aug 16 '19 at 19:54

How to change value of TextView from non-activity class

1 Answers1