button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            new Thread(new Runnable() {
                @Override
                public void run() {

                    FormBody.Builder builder1 = new FormBody.Builder();
                    builder1.add("user", login.getText().toString());
                    builder1.add("password", pass.getText().toString());
                    RequestBody postBody = builder1
                            .build();
                    Request.Builder builder = new Request.Builder();
                    builder.url(urlUsers);
                    builder.post(postBody);
                    Request request = builder
                            .build();
                    OkHttpClient client = new OkHttpClient();
                    Call call = client.newCall(request);
                    Response response;
                    try {
                        response = call.execute();
                        assert response.body() != null;
                        String serverResponse = response.body().string();
                        
                        if (serverResponse.equals("success")){
                            show.setText(serverResponse);
                        }
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }

                }
            }).start();

Method show.setText(serverResponse) does set text, but without IF.
With IF it’s code no works. How resolve this issue?

Here for resolve my issue about android app with authorisation