Improved polling for web gui (fixes #7).

src/main/java/com/nutomic/syncthingandroid/WebGuiActivity.java

@@ -8,7 +8,6 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.ServiceConnection;
 import android.os.Bundle;
-import android.os.Handler;
 import android.os.IBinder;
 import android.util.Log;
 import android.view.Menu;
@@ -30,7 +29,7 @@ import java.io.InputStream;
 /**
  * Holds a WebView that shows the web ui of the local syncthing instance.
  */
-public class WebGuiActivity extends Activity {
+public class WebGuiActivity extends Activity implements SyncthingService.OnWebGuiAvailableListener {
 
 	private static final String TAG = "WebGuiActivity";
 
@@ -54,6 +53,7 @@ public class WebGuiActivity extends Activity {
 		public void onServiceConnected(ComponentName className, IBinder service) {
 			SyncthingServiceBinder binder = (SyncthingServiceBinder) service;
 			mSyncthingService = binder.getService();
+			mSyncthingService.registerOnWebGuiAvailableListener(WebGuiActivity.this);
 		}
 
 		public void onServiceDisconnected(ComponentName className) {
@@ -62,32 +62,14 @@ public class WebGuiActivity extends Activity {
 	};
 
 	/**
-	 * Retries loading every second until the web UI becomes available.
+	 * Hides the loading screen and shows the WebView once it is fully loaded.
 	 */
 	private WebViewClient mWebViewClient = new WebViewClient() {
 
-		private int mError = 0;
-
-		@Override
-		public void onReceivedError(WebView view, int errorCode, String description,
-				String failingUrl) {
-			mError = errorCode;
-			new Handler().postDelayed(new Runnable() {
-				@Override
-				public void run() {
-					mError = 0;
-					mWebView.loadUrl(SyncthingService.SYNCTHING_URL);
-				}
-			}, 1000);
-
-		}
-
 		@Override
 		public void onPageFinished(WebView view, String url) {
-			if (mError == 0) {
+			mWebView.setVisibility(View.VISIBLE);
-				mWebView.setVisibility(View.VISIBLE);
+			mLoadingView.setVisibility(View.GONE);
-				mLoadingView.setVisibility(View.GONE);
-			}
 		}
 	};
 
@@ -100,11 +82,6 @@ public class WebGuiActivity extends Activity {
 	@SuppressLint("SetJavaScriptEnabled")
 	public void onCreate(Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
-		getApplicationContext().startService(
-				new Intent(this, SyncthingService.class));
-		getApplicationContext().bindService(
-				new Intent(this, SyncthingService.class),
-				mSyncthingServiceConnection, Context.BIND_AUTO_CREATE);
 
 		setContentView(R.layout.main);
 
@@ -115,7 +92,6 @@ public class WebGuiActivity extends Activity {
 		mWebView = (WebView) findViewById(R.id.webview);
 		mWebView.getSettings().setJavaScriptEnabled(true);
 		mWebView.setWebViewClient(mWebViewClient);
-		mWebView.loadUrl(SyncthingService.SYNCTHING_URL);
 
 		// Handle first start.
 		File config = new File(getApplicationInfo().dataDir, CONFIG_FILE);
@@ -130,8 +106,23 @@ public class WebGuiActivity extends Activity {
 					.setNeutralButton(android.R.string.ok, null)
 					.show();
 		}
+
+		getApplicationContext().startService(
+				new Intent(this, SyncthingService.class));
+		getApplicationContext().bindService(
+				new Intent(this, SyncthingService.class),
+				mSyncthingServiceConnection, Context.BIND_AUTO_CREATE);
 	}
 
+	/**
+	 * Loads and shows WebView, hides loading view.
+	 */
+	@Override
+	public void onWebGuiAvailable() {
+		mWebView.loadUrl(SyncthingService.SYNCTHING_URL);
+	}
+
+
 	@Override
 	public void onDestroy() {
 		super.onDestroy();

src/main/java/com/nutomic/syncthingandroid/service/SyncthingService.java

@@ -4,6 +4,7 @@ import android.app.Notification;
 import android.app.PendingIntent;
 import android.app.Service;
 import android.content.Intent;
+import android.os.AsyncTask;
 import android.os.IBinder;
 import android.support.v4.app.NotificationCompat;
 import android.util.Log;
@@ -11,10 +12,21 @@ import android.util.Log;
 import com.nutomic.syncthingandroid.R;
 import com.nutomic.syncthingandroid.WebGuiActivity;
 
+import org.apache.http.HttpEntity;
+import org.apache.http.HttpResponse;
+import org.apache.http.HttpStatus;
+import org.apache.http.client.HttpClient;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.client.methods.HttpHead;
+import org.apache.http.conn.HttpHostConnectException;
+import org.apache.http.impl.client.DefaultHttpClient;
+
 import java.io.BufferedReader;
 import java.io.DataOutputStream;
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.util.LinkedList;
 
 /**
  * Holds the native syncthing instance and provides an API to access it.
@@ -35,8 +47,26 @@ public class SyncthingService extends Service {
 	 */
 	public static final String SYNCTHING_URL = "http://127.0.0.1:8080";
 
+	/**
+	 * Interval in ms, at which connections to the web gui are performed on first start
+	 * to find out if it's online.
+	 */
+	private static final long WEB_GUI_POLL_INTERVAL = 100;
+
 	private final SyncthingServiceBinder mBinder = new SyncthingServiceBinder(this);
 
+	/**
+	 * Callback for when the Syncthing web interface becomes first available after service start.
+	 */
+	public interface OnWebGuiAvailableListener {
+		public void onWebGuiAvailable();
+	}
+
+	private LinkedList<OnWebGuiAvailableListener> mOnWebGuiAvailableListeners =
+			new LinkedList<OnWebGuiAvailableListener>();
+
+	private boolean mIsWebGuiAvailable = false;
+
 	@Override
 	public int onStartCommand(Intent intent, int flags, int startId) {
 		return START_STICKY;
@@ -100,6 +130,48 @@ public class SyncthingService extends Service {
 			}
 		}
 	}
+
+	/**
+	 * Polls SYNCTHING_URL until it returns HTTP status OK, then calls all listeners
+	 * in mOnWebGuiAvailableListeners and clears it.
+	 */
+	private class PollWebGuiAvailableTask extends AsyncTask<Void, Void, Void> {
+		@Override
+		protected Void doInBackground(Void... voids) {
+			int status = 0;
+			HttpClient httpclient = new DefaultHttpClient();
+			HttpHead head = new HttpHead(SYNCTHING_URL);
+			do {
+				try {
+					Thread.sleep(WEB_GUI_POLL_INTERVAL);
+					HttpResponse response = httpclient.execute(head);
+					// NOTE: status is not really needed, as HttpHostConnectException is thrown
+					// earlier.
+					status = response.getStatusLine().getStatusCode();
+				}
+				catch (HttpHostConnectException e) {
+					// We catch this in every call, as long as the service is not online,
+					// so we ignore and continue.
+				}
+				catch (IOException e) {
+					Log.d(TAG, "Failed to poll for web interface", e);
+				}
+				catch (InterruptedException e) {
+					Log.d(TAG, "Failed to poll for web interface", e);
+				}
+			} while(status != HttpStatus.SC_OK);
+			return null;
+		}
+
+		@Override
+		protected void onPostExecute(Void aVoid) {
+			mIsWebGuiAvailable = true;
+			for (OnWebGuiAvailableListener listener : mOnWebGuiAvailableListeners) {
+				listener.onWebGuiAvailable();
+			}
+			mOnWebGuiAvailableListeners.clear();
+		}
+	}
 	
 	/**
 	 * Creates notification, starts native binary.
@@ -118,6 +190,8 @@ public class SyncthingService extends Service {
 		startForeground(NOTIFICATION_ID, n);
 
 		new Thread(new NativeSyncthingRunnable()).start();
+
+		new PollWebGuiAvailableTask().execute();
 	}
 
 	@Override
@@ -134,4 +208,19 @@ public class SyncthingService extends Service {
 		new PostTask().execute(PostTask.URI_SHUTDOWN);
 	}
 
+	/**
+	 * Register a listener for the web gui becoming available..
+	 *
+	 * If the web gui is already available, listener will be called immediately.
+	 * Listeners are unregistered automatically after being called.
+	 */
+	public void registerOnWebGuiAvailableListener(OnWebGuiAvailableListener listener) {
+		if (mIsWebGuiAvailable) {
+			listener.onWebGuiAvailable();
+		}
+		else {
+			mOnWebGuiAvailableListeners.addLast(listener);
+		}
+	}
+
 }