Move URL retrieval to WebServerManager

and add some thread annotations

app/src/main/java/org/briarproject/hotspot/HotspotFragment.java

@@ -151,7 +151,7 @@ public class HotspotFragment extends Fragment {
 	public void onButtonClick(View view) {
 		if (hotspotStarted) {
 			button.setEnabled(false);
-			viewModel.getHotspotManager().stopWifiP2pHotspot();
+			viewModel.stopWifiP2pHotspot();
 		} else {
 			conditionManager.startConditionChecks();
 		}

app/src/main/java/org/briarproject/hotspot/HotspotManager.java

@@ -14,6 +14,7 @@ import java.util.logging.Logger;
 
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
+import androidx.annotation.UiThread;
 
 import static android.content.Context.WIFI_P2P_SERVICE;
 import static android.content.Context.WIFI_SERVICE;
@@ -75,6 +76,7 @@ class HotspotManager implements ActionListener {
 		lockTag = ctx.getPackageName() + ":app-sharing-hotspot";
 	}
 
+	@UiThread
 	void startWifiP2pHotspot() {
 		if (wifiP2pManager == null) {
 			listener.onHotspotError(ctx.getString(R.string.no_wifi_direct));

app/src/main/java/org/briarproject/hotspot/MainViewModel.java

@@ -8,23 +8,21 @@ import org.briarproject.hotspot.HotspotState.HotspotStarted;
 import org.briarproject.hotspot.HotspotState.HotspotStopped;
 import org.briarproject.hotspot.HotspotState.NetworkConfig;
 import org.briarproject.hotspot.HotspotState.StartingHotspot;
-import org.briarproject.hotspot.WebServerManager.WebServerState;
 
-import java.net.InetAddress;
 import java.util.logging.Logger;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+import androidx.annotation.WorkerThread;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
 import static android.content.Context.WIFI_SERVICE;
 import static android.os.Build.VERSION.SDK_INT;
-import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.hotspot.HotspotManager.HotspotListener;
-import static org.briarproject.hotspot.NetworkUtils.getAccessPointAddress;
 import static org.briarproject.hotspot.WebServerManager.WebServerListener;
 
 public class MainViewModel extends AndroidViewModel
@@ -63,19 +61,21 @@ public class MainViewModel extends AndroidViewModel
 		return is5GhzSupported;
 	}
 
-	HotspotManager getHotspotManager() {
-		return hotspotManager;
-	}
-
+	@UiThread
 	void startWifiP2pHotspot() {
 		hotspotManager.startWifiP2pHotspot();
 	}
 
+	@UiThread
+	void stopWifiP2pHotspot() {
+		// stop the webserver before the hotspot
+		webServerManager.stopWebServer();
+		hotspotManager.stopWifiP2pHotspot();
+	}
+
 	@Override
 	protected void onCleared() {
-		// TODO: remove from managers?
-		hotspotManager.stopWifiP2pHotspot();
-		webServerManager.stopWebServer();
+		stopWifiP2pHotspot();
 	}
 
 	@Override
@@ -86,12 +86,13 @@ public class MainViewModel extends AndroidViewModel
 	@Nullable
 	// Field to temporarily store the network config received via onHotspotStarted()
 	// in order to post it along with a HotspotStarted status
-	private NetworkConfig networkConfig;
+	private volatile NetworkConfig networkConfig;
 
 	@Override
 	public void onHotspotStarted(NetworkConfig networkConfig) {
 		this.networkConfig = networkConfig;
 		LOG.info("starting webserver");
+		// TODO: offload this to the IoExecutor
 		webServerManager.startWebServer();
 	}
 
@@ -108,32 +109,17 @@ public class MainViewModel extends AndroidViewModel
 	}
 
 	@Override
-	public void onWebServerStateChanged(WebServerState webServerStatus) {
-		switch (webServerStatus) {
-			case STARTED:
-				onWebServerStarted();
-				break;
-			case ERROR:
-				status.postValue(new HotspotError(
-						getApplication().getString(R.string.web_server_error)));
-				break;
-		}
-	}
-
-	private void onWebServerStarted() {
-		String url = "http://192.168.49.1:9999";
-		InetAddress address = getAccessPointAddress();
-		if (address == null) {
-			LOG.info(
-					"Could not find access point address, assuming 192.168.49.1");
-		} else {
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("Access point address " + address.getHostAddress());
-			}
-			url = "http://" + address.getHostAddress() + ":9999";
-		}
+	@WorkerThread
+	public void onWebServerStarted(String url) {
 		status.postValue(new HotspotStarted(networkConfig, url));
 		networkConfig = null;
 	}
 
+	@Override
+	@WorkerThread
+	public void onWebServerError() {
+		status.postValue(new HotspotError(
+				getApplication().getString(R.string.web_server_error)));
+	}
+
 }

app/src/main/java/org/briarproject/hotspot/WebServer.java

@@ -14,10 +14,12 @@ import static fi.iki.elonen.NanoHTTPD.Response.Status.OK;
 
 public class WebServer extends NanoHTTPD {
 
+	final static int PORT = 9999;
+
 	private final Context ctx;
 
 	public WebServer(Context ctx) {
-		super(9999);
+		super(PORT);
 		this.ctx = ctx;
 	}
 

app/src/main/java/org/briarproject/hotspot/WebServerManager.java

@@ -3,22 +3,26 @@ package org.briarproject.hotspot;
 import android.content.Context;
 
 import java.io.IOException;
+import java.net.InetAddress;
 import java.util.logging.Logger;
 
+import androidx.annotation.WorkerThread;
+
+import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.hotspot.LogUtils.logException;
-import static org.briarproject.hotspot.WebServerManager.WebServerState.ERROR;
-import static org.briarproject.hotspot.WebServerManager.WebServerState.STARTED;
+import static org.briarproject.hotspot.NetworkUtils.getAccessPointAddress;
+import static org.briarproject.hotspot.WebServer.PORT;
 
 class WebServerManager {
 
-	enum WebServerState {STARTED, ERROR}
-
 	interface WebServerListener {
+		@WorkerThread
+		void onWebServerStarted(String url);
 
-		void onWebServerStateChanged(WebServerState status);
-
+		@WorkerThread
+		void onWebServerError();
 	}
 
 	private static final Logger LOG =
@@ -32,17 +36,30 @@ class WebServerManager {
 		webServer = new WebServer(ctx);
 	}
 
+	@WorkerThread
 	void startWebServer() {
-		// TODO: offload this to the IoExecutor
-		new Thread(() -> {
-			try {
-				webServer.start();
-			} catch (IOException e) {
-				logException(LOG, WARNING, e);
-				listener.onWebServerStateChanged(ERROR);
+		try {
+			webServer.start();
+			onWebServerStarted();
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			listener.onWebServerError();
+		}
+	}
+
+	private void onWebServerStarted() {
+		String url = "http://192.168.49.1:" + PORT;
+		InetAddress address = getAccessPointAddress();
+		if (address == null) {
+			LOG.info(
+					"Could not find access point address, assuming 192.168.49.1");
+		} else {
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Access point address " + address.getHostAddress());
 			}
-			listener.onWebServerStateChanged(STARTED);
-		}).start();
+			url = "http://" + address.getHostAddress() + ":" + PORT;
+		}
+		listener.onWebServerStarted(url);
 	}
 
 	void stopWebServer() {