BaseActivity.java

public class BaseActivity extends AppCompatActivity {
    private ProgressDialog progressDialog;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        progressDialog = new ProgressDialog(this);
        progressDialog.setTitle("Title here");
        progressDialog.setMessage("Message here");
    }

    protected void showLoadingDialog() {
        hideLoadingDialog();
        progressDialog.show();
    }

    protected void hideLoadingDialog() {
        if (progressDialog != null && progressDialog.isShowing())
            progressDialog.dismiss();
    }
}

TestActivity.java

public class TestActivity extends BaseActivity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        showLoadingDialog();
    }

    @Override
    protected void onStop() {
        super.onStop();
        hideLoadingDialog();
    }
}