Resume activity in Android

in order to get back to previous Activity you have to finish the visible one, use this:

finish();

If the activity was started for a result, you should give a result then, like this:

Intent intent = new Intent();
intent.putExtra(KEY_RESPONSE, responseData);
setResult(RESULT_OK, intent);
finish();

And you should catch the result on the caller Activity using:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

  switch (requestCode) {
    // Test for the code you have used to start the Activity
  }
}

Hope it helps, Regards

If your Activity is still running, this code will bring it to the front without entering onCreate

Intent openMainActivity = new Intent(TerceraActiviry.this, Main.class);
openMainActivity.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivityIfNeeded(openMainActivity, 0);