public class MainActivity extends AppCompatActivity {

private Boolean  statusKeyboard = false;
private EditText mTextoEditor1;
private Button mBotonSend;
private TextView mDumpTextView;
private MiTareaAsincrona tarea1;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate( savedInstanceState );
    setContentView( R.layout.activity_main );
    Toolbar toolbar = (Toolbar) findViewById( R.id.toolbar );
    setSupportActionBar( toolbar );

    mBotonSend = findViewById(R.id.bt2_SendButton);
    mDumpTextView = (TextView) findViewById(R.id.tv1_ReadValues);
    mTextoEditor1 = (EditText) findViewById(R.id.et1_WriteValues);

    mBotonSend.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            String message = mTextoEditor1.getText().toString();
            if (mTextoEditor1.getText().toString().trim().equals("")) {
                Toast.makeText(MainActivity.this, "Por favar Ingresar al texto...", Toast.LENGTH_SHORT).show();
            } else {
                mDumpTextView.append( message + "rn" );
            }
            mTextoEditor1.setText("");
        }
    });

    tarea1 = new MiTareaAsincrona();
    tarea1.execute();
}

private class MiTareaAsincrona extends AsyncTask<Void, Integer, Boolean> {
    @Override
    protected Boolean doInBackground(Void... params) {
        setupTimer(20);
        return true;
    }

    @Override
    protected void onPostExecute(Boolean result) {
        if(result)
            Toast.makeText(MainActivity.this, "Timer finalizado!", Toast.LENGTH_SHORT).show();
    }

    @Override
    protected void onCancelled() { }
}

private void setupTimer(Integer milisegundos) {
    new CountDownTimer( milisegundos, 1000 ) {
        public void onTick(long millisUntilFinished) {
            //mDumpTextView.setText( "seconds: " + millisUntilFinished / 1000 );
        }

        public void onFinish() {
            mDumpTextView.setText( "done!" );
            start();
        }
    }.start();
  }
}