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POFileObserver service combined with UploadToImgur AsyncTask: service stops working after a while (NullPointer), Imgur doesn't return proper response
 

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  1. POFileObserver service combined with UploadToImgur AsyncTask: service stops working after a while (NullPointer), Imgur doesn't return proper response
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    <p>This is my first Android app, so please do go easy on me. The idea is to detect whenever user puts a photo in /mnt/sdcard and upload that to Imgur and then copy the link to system clipboard.</p> <h2>Classes in use</h2> <p>I have three classes working in my app. <code>ObserveNewImages</code> uses <code>FileObserver</code> to detect new photos in the previously stated path.</p> <p><strong>ObserveImages.java</strong> </p> <pre><code>public class ObserveNewImages extends Service { final String pathToObserve = android.os.Environment.getExternalStorageDirectory().toString(); // stores "/mnt/sdcard" final String upload_to = "https://api.imgur.com/3/upload.json"; final String API_key = "API_KEY_GOES_HERE"; public static final String TAG = "Awais"; String link; //full path to where the image is stored Intent upload; @Override public void onCreate(){ upload = new Intent(this, Imgur.class); //just initializing an intent for use later. Nothing special. super.onCreate(); } @Override public int onStartCommand(Intent intent, int flags, int startId) { Log.d(TAG, "In onStartCommand"); FileObserver observer = new FileObserver(pathToObserve){ //As soon as we detect a new file in pathToObserve //, I fire up the service for uploading image to Imgur. @Override public void onEvent(int event, String file){ if (event == FileObserver.CREATE){ Log.d(TAG, "file address: " + pathToObserve + "/" + file); link = pathToObserve + "/" + file; upload.putExtra("path",link); startService(upload); } } }; observer.startWatching(); return super.onStartCommand(intent, flags, startId); } @Override public IBinder onBind(Intent intent) { // TODO Auto-generated method stub return null; } } </code></pre> <p>Moving on to <code>Imgur.java</code> which includes two classes <code>Imgur.class</code> and a <code>ImgurTask</code> which extends <code>AsyncTask</code> so that networking tasks take place on separate thread.</p> <p><strong>Imgur.java</strong></p> <pre><code>public class Imgur extends Service{ String path; @Override public void onCreate() { // TODO Auto-generated method stub super.onCreate(); } @Override public int onStartCommand(Intent intent, int flags, int startId) { path = intent.getStringExtra("path"); new ImgurTask().execute(path); return super.onStartCommand(intent, flags, startId); } @Override public IBinder onBind(Intent intent) { // TODO Auto-generated method stub return null; } class ImgurTask extends AsyncTask&lt;String, Void, String&gt;{ final String upload_to = "https://api.imgur.com/3/upload.json"; final String API_key = "API_KEY_GOES_HERE"; public static final String TAG = "Awais"; String link; @Override protected String doInBackground(String... params) { HttpClient httpClient = new DefaultHttpClient(); HttpContext localContext = new BasicHttpContext(); HttpPost httpPost = new HttpPost(upload_to); httpPost.setHeader("Authorization", "Client-ID " + API_key); try { MultipartEntity entity = new MultipartEntity(HttpMultipartMode.BROWSER_COMPATIBLE); entity.addPart("image", new FileBody(new File(params[0]))); entity.addPart("key", new StringBody(API_key)); httpPost.setEntity(entity); HttpResponse response = httpClient.execute(httpPost, localContext); String response_string = EntityUtils.toString(response.getEntity()); Log.d(TAG, "Response from Imgur: " + response_string); JSONObject json = new JSONObject(response_string); //Parsing JSON manually since I couldn't get it work using JSONObject's built-in class functions String json_str = json.toString(); Integer indexlink = json_str.indexOf("link"); Integer colonlink = json_str.indexOf(":", indexlink); Integer secondbracket = json_str.indexOf("}", colonlink); link = json_str.substring(colonlink+2, secondbracket-1); link = link.replace("\\",""); return link; }catch (Exception e){ e.printStackTrace(); } return "error"; } @Override protected void onPostExecute(String result) { if (result != "error"){ //copying link to clipboard ClipboardManager clipboard = (ClipboardManager)getApplicationContext().getSystemService(Context.CLIPBOARD_SERVICE); ClipData clip = ClipData.newPlainText("Imgur link", result); clipboard.setPrimaryClip(clip); Toast.makeText(getApplicationContext(), "Link is ready to paste: " + result, Toast.LENGTH_SHORT).show(); } else{ Toast.makeText(getApplicationContext(), "Error: Are you connected to the Internet?", Toast.LENGTH_SHORT).show(); } super.onPostExecute(result); } } } </code></pre> <p><strong>MainActivity.java</strong></p> <p>This is only used to fire up the <code>ObserveImages</code> service.</p> <pre><code>public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //start service Intent start_observing = new Intent(this, ObserveImages.class); startService(start_observing); Toast.makeText(getApplicationContext(), "Automatic Image Uploader is now running!", Toast.LENGTH_SHORT).show(); finish(); } } </code></pre> <h2>The Problems</h2> <p>There are three problems:</p> <ul> <li><p>The services just stop working after a while. Nothing shows up the logs (which I have removed from the code here) to indicate that the app is running. To get things running again, I have to launch from app icon again. </p></li> <li><p>After a few uploads (sometimes 4-5, sometimes up to 10), Imgur's servers send a 405 Not Allowed response. Leave the app for a minute and come back again, and the servers will send back correct response.</p></li> <li><p>The app crashes after a while. FileObserver class throws a Null Pointer Exception.</p></li> </ul>
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    1. COFor point 1: the services may be dying automatically after a while. Don't know why that happens. I've even tried startForeground() but that didn't help. Point 2: This *might* be due to the fact that we are testing it by pushing one image after the other in quick succession. Imgur may have some API limitations in place, but I couldn't find it in their documentation. Point 3: No idea why it happens at all.
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      1. USAwais Imran
 

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