I have a MainActivity class that needs to access an online API (thus using network resources). This requires a background thread that I've created in a separate file HttpRequestService.java.
MainActivity.java:
public class MainActivity extends Activity { public static final String API_KEY = "KEYKEYKEYKEYKEY"; public static final String CLIENT_ID = "IDIDIDIDIDIDID"; private final String BROADCAST_ACTION = "com.example.BROADCAST"; private final String EXTENDED_DATA_STATUS = "com.example.STATUS"; static final String LOGCAT_TAG = "TAGTAGTAGTAGTAG"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } @Override protected void onResume() { super.onResume(); String token = "TOKENTOKENTOKENTOKEN"; String urlString = "https://www.example.com/api?key=" + API_KEY; // Create and start intent for HttpRequestService background thread. Intent httpRequestServiceIntent = new Intent(this, HttpRequestService.class); httpRequestServiceIntent.putExtra("token", token); httpRequestServiceIntent.putExtra("urlString", urlString); httpRequestServiceIntent.putExtra("client_id", CLIENT_ID); DownloadStateReceiver downloadStateReceiver = new DownloadStateReceiver(); LocalBroadcastManager.getInstance(this).registerReceiver(downloadStateReceiver, new IntentFilter(BROADCAST_ACTION)); this.startService(httpRequestServiceIntent); } private class DownloadStateReceiver extends BroadcastReceiver { // Broadcast receiver for receiving status updates from IntentService private DownloadStateReceiver() { // prevents instantiation } @Override public void onReceive(Context context, Intent intent) { String message = intent.getStringExtra(EXTENDED_DATA_STATUS); Log.d(LOGCAT_TAG, "onReceive received message: " + message); Toast.makeText(context, "Success!: " + message, Toast.LENGTH_LONG).show(); } } HttpRequestService.java:
public final class HttpRequestService extends IntentService { public HttpRequestService(String name) { super(name); Log.e(LOGCAT_TAG, "You called the HttpRequestService directly. Don't do that. Call onHandleIntent."); } private final String LOGCAT_TAG = "HttpRequestService"; private final String BROADCAST_ACTION = "com.genda.dayplanner.BROADCAST"; private final String EXTENDED_DATA_STATUS = "com.genda.dayplanner.STATUS"; @Override protected void onHandleIntent(Intent intent) { // Gets data from the incoming Intent String token = intent.getStringExtra("token"); String urlString = intent.getStringExtra("urlString"); String client_id = intent.getStringExtra("client_id"); Boolean extraError = false; if (token == null) { Log.e(LOGCAT_TAG, "Intent didn't contain required token."); extraError = true; } if (urlString == null) { Log.e(LOGCAT_TAG, "Intent didn't contain required urlBundle."); extraError = true; } if (client_id == null) { Log.e(LOGCAT_TAG, "Intent didn't contain required client_id."); extraError = true; } if (extraError == true) { // error response } // Now do request URL url = null; try { url = new URL(urlString); } catch (MalformedURLException e) { Log.e(LOGCAT_TAG, "The URL for requesting the tasks API was malformed."); } HttpURLConnection conn = null; try { conn = (HttpURLConnection) url.openConnection(); } catch (IOException e) { Log.e(LOGCAT_TAG, "Bad connection to the API URL"); } conn.addRequestProperty("client_id", client_id); conn.setRequestProperty("Authorization", "OAuth " + token); String result = null; try { InputStream in = new BufferedInputStream(conn.getInputStream()); result = convertStreamToString(in); } catch (IOException e) { e.printStackTrace(); } finally { conn.disconnect(); } // Create new Intent with URI object Intent localIntent = new Intent(BROADCAST_ACTION); localIntent.putExtra(EXTENDED_DATA_STATUS, result); // Broadcasts intent to receivers in this app. LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent); } public static String convertStreamToString(InputStream in) { // Use BufferedReader.readLine() method. Iterate until BufferedReader returns null (no more data to read). Each line appended to StringBuilder. BufferedReader reader = new BufferedReader(new InputStreamReader(in)); StringBuilder sb = new StringBuilder(); String line = null; try { while ((line = reader.readLine()) != null) { sb.append(line + "\n"); } } catch (IOException e) { e.printStackTrace(); } finally { try { in.close(); } catch (IOException e) { e.printStackTrace(); } } return sb.toString(); } } Here's the LogCat:
09-21 17:15:28.157: D/dalvikvm(11055): newInstance failed: no <init>() 09-21 17:15:28.157: D/AndroidRuntime(11055): Shutting down VM 09-21 17:15:28.157: W/dalvikvm(11055): threadid=1: thread exiting with uncaught exception (group=0x41f3b700) 09-21 17:15:28.167: E/AndroidRuntime(11055): FATAL EXCEPTION: main 09-21 17:15:28.167: E/AndroidRuntime(11055): java.lang.RuntimeException: Unable to instantiate service com.example.HttpRequestService: java.lang.InstantiationException: can't instantiate class com.example.HttpRequestService; no empty constructor 09-21 17:15:28.167: E/AndroidRuntime(11055): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2561) 09-21 17:15:28.167: E/AndroidRuntime(11055): at android.app.ActivityThread.access$1600(ActivityThread.java:141) 09-21 17:15:28.167: E/AndroidRuntime(11055): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1338) 09-21 17:15:28.167: E/AndroidRuntime(11055): at android.os.Handler.dispatchMessage(Handler.java:99) 09-21 17:15:28.167: E/AndroidRuntime(11055): at android.os.Looper.loop(Looper.java:137) 09-21 17:15:28.167: E/AndroidRuntime(11055): at android.app.ActivityThread.main(ActivityThread.java:5103) 09-21 17:15:28.167: E/AndroidRuntime(11055): at java.lang.reflect.Method.invokeNative(Native Method) 09-21 17:15:28.167: E/AndroidRuntime(11055): at java.lang.reflect.Method.invoke(Method.java:525) 09-21 17:15:28.167: E/AndroidRuntime(11055): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 09-21 17:15:28.167: E/AndroidRuntime(11055): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 09-21 17:15:28.167: E/AndroidRuntime(11055): at dalvik.system.NativeStart.main(Native Method) 09-21 17:15:28.167: E/AndroidRuntime(11055): Caused by: java.lang.InstantiationException: can't instantiate class com.example.HttpRequestService; no empty constructor 09-21 17:15:28.167: E/AndroidRuntime(11055): at java.lang.Class.newInstanceImpl(Native Method) 09-21 17:15:28.167: E/AndroidRuntime(11055): at java.lang.Class.newInstance(Class.java:1130) 09-21 17:15:28.167: E/AndroidRuntime(11055): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2558) 09-21 17:15:28.167: E/AndroidRuntime(11055): ... 10 more The important part I think is the can't instantiate class com.example.HttpRequestService; no empty constructor. I've seen several other discussions similar to this, but they've all be able to solve the problem because their class is a subclass of their MainActivity. So they just make the subclass static and it solves the problem. Unfortunately, as a separate class HttpRequestService cannot be static. Any suggestions?