Don't start hotspot while running and use proper ErrorFragment

briar-android/src/main/java/org/briarproject/briar/android/fragment/ErrorFragment.java

@@ -17,7 +17,7 @@ import androidx.annotation.Nullable;
 @ParametersNotNullByDefault
 public class ErrorFragment extends BaseFragment {
 
-	private static final String TAG = ErrorFragment.class.getName();
+	public static final String TAG = ErrorFragment.class.getName();
 
 	private static final String ERROR_MSG = "errorMessage";
 

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotActivity.java

@@ -3,13 +3,13 @@ package org.briarproject.briar.android.hotspot;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.MenuItem;
-import android.widget.Toast;
 
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
+import org.briarproject.briar.android.fragment.ErrorFragment;
 import org.briarproject.briar.android.hotspot.HotspotState.HotspotError;
 import org.briarproject.briar.android.hotspot.HotspotState.HotspotStarted;
 
@@ -17,10 +17,10 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import androidx.appcompat.app.ActionBar;
+import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
 import androidx.lifecycle.ViewModelProvider;
 
-import static android.widget.Toast.LENGTH_LONG;
 import static org.briarproject.briar.android.util.UiUtils.showFragment;
 import static org.briarproject.briar.api.android.AndroidNotificationManager.ACTION_STOP_HOTSPOT;
 
@@ -60,9 +60,9 @@ public class HotspotActivity extends BriarActivity {
 					showFragment(fm, new HotspotFragment(), tag);
 				}
 			} else if (hotspotState instanceof HotspotError) {
-				// TODO ErrorFragment
 				String error = ((HotspotError) hotspotState).getError();
-				Toast.makeText(this, error, LENGTH_LONG).show();
+				Fragment f = ErrorFragment.newInstance(error);
+				showFragment(getSupportFragmentManager(), f, ErrorFragment.TAG);
 			}
 		});
 

briar-android/src/main/java/org/briarproject/briar/android/hotspot/HotspotViewModel.java

@@ -72,8 +72,15 @@ class HotspotViewModel extends DbViewModel
 
 	@UiThread
 	void startHotspot() {
-		hotspotManager.startWifiP2pHotspot();
+		HotspotState s = state.getValue();
-		notificationManager.showHotspotNotification();
+		if (s instanceof HotspotStarted) {
+			// Don't try to start again, if already started, just re-set value.
+			// This can happen if the user navigates back to intro fragment.
+			state.setValue(s);
+		} else {
+			hotspotManager.startWifiP2pHotspot();
+			notificationManager.showHotspotNotification();
+		}
 	}
 
 	@UiThread

briar-android/src/main/java/org/briarproject/briar/android/hotspot/WebServer.java

@@ -65,7 +65,7 @@ public class WebServer extends NanoHTTPD {
 		} catch (Exception e) {
 			logException(LOG, WARNING, e);
 			res = newFixedLengthResponse(INTERNAL_ERROR, MIME_PLAINTEXT,
-					INTERNAL_ERROR.getDescription());
+					ctx.getString(R.string.hotspot_error_web_server_serve));
 		}
 		return res;
 	}
@@ -123,7 +123,7 @@ public class WebServer extends NanoHTTPD {
 		} catch (FileNotFoundException e) {
 			logException(LOG, WARNING, e);
 			res = newFixedLengthResponse(NOT_FOUND, MIME_PLAINTEXT,
-					"Error 404, file not found.");
+					ctx.getString(R.string.hotspot_error_web_server_serve));
 		}
 		return res;
 	}

briar-android/src/main/res/values/strings.xml

@@ -713,7 +713,8 @@
 	<string name="hotspot_error_start_callback_failed_unknown">Hotspot failed to start with an unknown error, reason %d</string>
 	<string name="hotspot_error_start_callback_no_group_info">Hotspot failed to start: no group info</string>
 	<string name="hotspot_error_web_server_start">Error starting web server!</string>
-	<string name="hotspot_flag_test">Warning: This is a debug app that can NOT be installed on another device</string>
+	<string name="hotspot_error_web_server_serve">Error presenting website.\n\nPlease send feedback (with anonymous data) via the Briar app if the issue persists.</string>
+	<string name="hotspot_flag_test">Warning: This app was installed with Android Studio and can NOT be installed on another device.</string>
 
 	<string name="hotspot_tab_manual">Manual</string>
 	<string name="hotspot_manual_wifi">To download the app on another phone, please connect to this Wi-Fi network:</string>