okHTTP-callback.java

public void requestWeb() throws Exception {
        url = "http://google.com";
        Request request = new Request.Builder().url(url).build();

        client.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Request request, IOException e) {
                Log.e("onFailure", "onFailure exception happened");
                e.printStackTrace();
            }

            @Override
            public void onResponse(final Response response) throws IOException {
                if(response.isSuccessful() == false)
                    resultStr = "unexpected code: " + response;
                else
                    resultStr = response.body().string();

                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        responseTxt.setText(resultStr);
                    }
                });
            }
        });
    }