//your code here... //We shall implement each portion of our code step-by-step and explain it. Let's start with captureImage. As we can see in previous section, captureImage is the onClick handler of our Take Photo button. So the method signature must follow Android specifications: MainActivity.java public class MainActivity extends ActionBarActivity { // ... public void captureImage(View view) { // ... } // ... } //To capture an image using camera we use camera intent MediaStore.ACTION_IMAGE_CAPTURE with MediaStore.EXTRA_OUTPUT as intent extras. When MediaStore.EXTRA_OUTPUT is specified the camera intent will save the captured image at our desired location for us. We need two more things to handle the request-result process i.e. a request identifier and a temporary file where we shall keep the captured image. Let's update our code accordingly and implement the camera feature. MainActivity.java public class MainActivity extends ActionBarActivity { // ... protected static final int REQUEST_IMAGE_CAPTURE = 1; File tmpfile; public void captureImage(View view) { Intent i = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); if (i.resolveActivity(getPackageManager()) != null) { try { tmpfile = File.createTempFile("Photo", ".jpg", Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)); } catch (IOException x) { // We are lost :) throw new RuntimeException(x); } i.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(tmpfile)); startActivityForResult(i, REQUEST_IMAGE_CAPTURE); } } // ... } //We don't know when the camera activity will complete and our application will resume its normal operation. So we shall wait and listen to the results in background. Android provides onActivityResult method for this purpose. We shall add it to our MainActivity class as specified in Android documentation. MainActivity.java public class MainActivity extends ActionBarActivity { // ... @Override protected void onActivityResult(int request, int result, Intent data) { if (request == REQUEST_IMAGE_CAPTURE && result == RESULT_OK) { if (tmpfile == null) { Log.e("onActivityResult", "Photo was not saved. Doing nothing"); return; } new OcrTask().execute(tmpfile); displayTextResults("Uploading photo and recognizing text. This may take a few seconds."); } } // ... } ///Here in onActivityResult we have used REQUEST_IMAGE_CAPTURE and tmpfile from captureImage. We also have used OcrTask and displayTextResults, which are our next topic. MainActivity.java public class MainActivity extends ActionBarActivity { // ... public class OcrTask extends AsyncTask<File, Void, String> { String requestUrl; String appSID = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"; String appKey = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"; @Override protected void onPreExecute() { super.onPreExecute(); // Our implementation goes here... } @Override protected String doInBackground(File... params) { // Our implementation goes here... } @Override protected void onPostExecute(String result) { super.onPostExecute(result); // Our implementation goes here... } } } //We have three methods here. onPreExecute is called before the asynchronous operation is started. It has no parameters. We perform some initial operation in here and prepare a signed request URL. A signed URL means to make sure that we are authorized to make that API call. We require appSID and appKey for this purpose which can be obtained by signing up for free at http://cloud.aspose.com/. OcrTask.onPreExecute @Override protected void onPreExecute() { super.onPreExecute(); requestUrl = "https://api.aspose.com/v1.1/ocr/recognize?appSID=" + appSID; try { Mac mac = Mac.getInstance("HmacSHA1"); mac.init(new SecretKeySpec(appKey.getBytes(), "HmacSHA1")); mac.update(requestUrl.getBytes()); String signature = Base64.encodeToString(mac.doFinal(), Base64.NO_PADDING); requestUrl += "&signature=" + signature; Log.i("onPreExecute", "Signed request URL: " + requestUrl); } catch (Exception x) { throw new RuntimeException(x); } } //The doInBackground will do the actual API call. We are using HttpUrlConnection as Http client. We shall upload our captured image file. The returned response is in JSON format and HTTP request method is POST. So we shall setup the connection parameters accordingly. OcrTask.doInBackground @Override protected String doInBackground(File... params) { File file = params[0]; HttpURLConnection connection = null; try { FileInputStream fstream = new FileInputStream(file); int fsize = fstream.available(); connection = (HttpURLConnection) new URL(requestUrl).openConnection(); connection.setRequestMethod("POST"); connection.setDoOutput(true); connection.setRequestProperty("Accept", "application/json"); connection.setRequestProperty("Content-Length", String.valueOf(fsize)); OutputStream upload = connection.getOutputStream(); byte[] buffer = new byte[10240]; int len; while ((len = fstream.read(buffer)) != -1) { upload.write(buffer, 0, len); } upload.close(); fstream.close(); InputStream i = connection.getInputStream(); String text = new Scanner(i).useDelimiter("\\A").next(); i.close(); //file.delete(); Log.i("doInBackground", text); return text; } catch (FileNotFoundException fnfx) { InputStream e = connection.getErrorStream(); String text = new Scanner(e).useDelimiter("\\A").next(); Log.i("doInBackground", text); return text; } catch (Exception x) { throw new RuntimeException(x); } } //After we have retrieved the results from Aspose.Ocr for Cloud API, we need a little bit manipulation. As the response is JSON, should now read the recognized text and also check for error, if any. We shall do the manipulation in onPostExecute method. OcrTask.onPostExecute @Override protected void onPostExecute(String result) { super.onPostExecute(result); String text = ""; try { JSONObject json = new JSONObject(result); if (json.has("Status") && json.getString("Status").equals("OK")) { text = json.getString("Text"); } else if (json.has("Message")) { text = "Error: " + json.getString("Message"); } } catch (JSONException x) { throw new RuntimeException(x); } displayTextResults(text); } //Now comes the simplest and yet important part of our application i.e. display the recognized text results. We simply change the text property of TextView that we added to our UI in the beginning. We added the id text_results and also said that we can reference it from code using R.id.text_results. Here we go: MainActivity.java public class MainActivity extends ActionBarActivity { // ... public void displayTextResults(String text) { TextView t = (TextView) findViewById(R.id.text_results); t.setText(text); } // ... }