Merge branch '2397-wrong-type-of-qr-code' into 'master'

Show appropriate error message if user scans wrong kind of QR code

Closes #2397

See merge request briar/briar!1748

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddContactState.java

@@ -3,12 +3,14 @@ package org.briarproject.briar.android.contact.add.nearby;
 import android.graphics.Bitmap;
 
 import org.briarproject.bramble.api.identity.Author;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType;
 
 import androidx.annotation.Nullable;
 
 abstract class AddContactState {
 
 	static class KeyAgreementListening extends AddContactState {
+
 		final Bitmap qrCode;
 
 		KeyAgreementListening(Bitmap qrCode) {
@@ -29,6 +31,7 @@ abstract class AddContactState {
 	}
 
 	static class ContactExchangeFinished extends AddContactState {
+
 		final ContactExchangeResult result;
 
 		ContactExchangeFinished(ContactExchangeResult result) {
@@ -37,25 +40,34 @@ abstract class AddContactState {
 	}
 
 	static class Failed extends AddContactState {
-		/**
-		 * Non-null if failed due to the scanned QR code version.
-		 * True if the app producing the code is too old.
-		 * False if the scanning app is too old.
-		 */
-		@Nullable
-		final Boolean qrCodeTooOld;
 
-		Failed(@Nullable Boolean qrCodeTooOld) {
-			this.qrCodeTooOld = qrCodeTooOld;
+		static class WrongQrCodeType extends Failed {
+
+			final QrCodeType qrCodeType;
+
+			WrongQrCodeType(QrCodeType qrCodeType) {
+				this.qrCodeType = qrCodeType;
+			}
 		}
 
-		Failed() {
-			this(null);
+		static class WrongQrCodeVersion extends Failed {
+
+			/**
+			 * True if the app producing the code is too old.
+			 * False if the scanning app is too old.
+			 */
+			final boolean qrCodeTooOld;
+
+			WrongQrCodeVersion(boolean qrCodeTooOld) {
+				this.qrCodeTooOld = qrCodeTooOld;
+			}
 		}
 	}
 
 	abstract static class ContactExchangeResult {
+
 		static class Success extends ContactExchangeResult {
+
 			final Author remoteAuthor;
 
 			Success(Author remoteAuthor) {
@@ -64,6 +76,7 @@ abstract class AddContactState {
 		}
 
 		static class Error extends ContactExchangeResult {
+
 			@Nullable
 			final Author duplicateAuthor;
 

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactActivity.java

@@ -6,12 +6,15 @@ import android.view.MenuItem;
 import android.widget.Toast;
 
 import org.briarproject.bramble.api.identity.Author;
+import org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeFinished;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeResult;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.Failed;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.Failed.WrongQrCodeType;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.Failed.WrongQrCodeVersion;
 import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
@@ -34,6 +37,7 @@ import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
 import static android.widget.Toast.LENGTH_LONG;
 import static java.util.Objects.requireNonNull;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.MAILBOX;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.ACCEPTED;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.REFUSED;
 
@@ -141,9 +145,15 @@ public class AddNearbyContactActivity extends BriarActivity
 			ContactExchangeResult result =
 					((ContactExchangeFinished) state).result;
 			onContactExchangeResult(result);
+		} else if (state instanceof WrongQrCodeType) {
+			QrCodeType qrCodeType = ((WrongQrCodeType) state).qrCodeType;
+			if (qrCodeType == MAILBOX) onMailboxQrCodeScanned();
+			else onWrongQrCodeType();
+		} else if (state instanceof WrongQrCodeVersion) {
+			boolean qrCodeTooOld = ((WrongQrCodeVersion) state).qrCodeTooOld;
+			onWrongQrCodeVersion(qrCodeTooOld);
 		} else if (state instanceof Failed) {
-			Boolean qrCodeTooOld = ((Failed) state).qrCodeTooOld;
-			onAddingContactFailed(qrCodeTooOld);
+			showErrorFragment();
 		}
 	}
 
@@ -170,15 +180,27 @@ public class AddNearbyContactActivity extends BriarActivity
 		} else throw new AssertionError();
 	}
 
-	private void onAddingContactFailed(@Nullable Boolean qrCodeTooOld) {
-		if (qrCodeTooOld == null) {
-			showErrorFragment();
-		} else {
-			String msg;
-			if (qrCodeTooOld) msg = getString(R.string.qr_code_too_old_1);
-			else msg = getString(R.string.qr_code_too_new_1);
-			showNextFragment(AddNearbyContactErrorFragment.newInstance(msg));
-		}
+	private void onMailboxQrCodeScanned() {
+		String title = getString(R.string.qr_code_invalid);
+		String msg = getString(R.string.mailbox_qr_code_for_contact);
+		showNextFragment(
+				AddNearbyContactErrorFragment.newInstance(title, msg, false));
+	}
+
+	private void onWrongQrCodeType() {
+		String title = getString(R.string.qr_code_invalid);
+		String msg = getString(R.string.qr_code_format_unknown);
+		showNextFragment(
+				AddNearbyContactErrorFragment.newInstance(title, msg, false));
+	}
+
+	private void onWrongQrCodeVersion(boolean qrCodeTooOld) {
+		String title = getString(R.string.qr_code_invalid);
+		String msg;
+		if (qrCodeTooOld) msg = getString(R.string.qr_code_too_old_1);
+		else msg = getString(R.string.qr_code_too_new_1);
+		showNextFragment(
+				AddNearbyContactErrorFragment.newInstance(title, msg, false));
 	}
 
 	private void showErrorFragment() {

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactErrorFragment.java

@@ -22,6 +22,7 @@ import androidx.fragment.app.FragmentActivity;
 import androidx.lifecycle.ViewModelProvider;
 
 import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static android.view.View.GONE;
 import static org.briarproject.briar.android.util.UiUtils.hideViewOnSmallScreen;
 import static org.briarproject.briar.android.util.UiUtils.onSingleLinkClick;
 
@@ -31,17 +32,22 @@ public class AddNearbyContactErrorFragment extends BaseFragment {
 
 	public static final String TAG =
 			AddNearbyContactErrorFragment.class.getName();
-	private static final String ERROR_MSG = "errorMessage";
+	private static final String ARG_TITLE = "title";
+	private static final String ARG_ERROR_MSG = "message";
+	private static final String ARG_FEEDBACK = "feedback";
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
 
 	private AddNearbyContactViewModel viewModel;
 
-	public static AddNearbyContactErrorFragment newInstance(String errorMsg) {
+	public static AddNearbyContactErrorFragment newInstance(String title,
+			String errorMessage, boolean feedback) {
 		AddNearbyContactErrorFragment f = new AddNearbyContactErrorFragment();
 		Bundle args = new Bundle();
-		args.putString(ERROR_MSG, errorMsg);
+		args.putString(ARG_TITLE, title);
+		args.putString(ARG_ERROR_MSG, errorMessage);
+		args.putBoolean(ARG_FEEDBACK, feedback);
 		f.setArguments(args);
 		return f;
 	}
@@ -66,19 +72,32 @@ public class AddNearbyContactErrorFragment extends BaseFragment {
 		View v = inflater.inflate(R.layout.fragment_error_contact_exchange,
 				container, false);
 
-		// set optional error message
-		TextView explanation = v.findViewById(R.id.errorMessage);
+		String title = null, errorMessage = null;
+		boolean feedback = true;
 		Bundle args = getArguments();
-		String errorMessage = args == null ? null : args.getString(ERROR_MSG);
-		if (errorMessage == null) {
-			explanation.setText(getString(R.string.add_contact_error_two_way));
-		} else {
-			explanation.setText(args.getString(ERROR_MSG));
+		if (args != null) {
+			title = args.getString(ARG_TITLE);
+			errorMessage = args.getString(ARG_ERROR_MSG);
+			feedback = args.getBoolean(ARG_FEEDBACK, true);
+		}
+
+		if (title != null) {
+			TextView titleView = v.findViewById(R.id.errorTitle);
+			titleView.setText(title);
+		}
+
+		if (errorMessage != null) {
+			TextView messageView = v.findViewById(R.id.errorMessage);
+			messageView.setText(errorMessage);
 		}
 
-		// make feedback link clickable
 		TextView sendFeedback = v.findViewById(R.id.sendFeedback);
-		onSingleLinkClick(sendFeedback, this::triggerFeedback);
+		if (feedback) {
+			// make feedback link clickable
+			onSingleLinkClick(sendFeedback, this::triggerFeedback);
+		} else {
+			sendFeedback.setVisibility(GONE);
+		}
 
 		// buttons
 		Button tryAgain = v.findViewById(R.id.tryAgainButton);

briar-android/src/main/java/org/briarproject/briar/android/contact/add/nearby/AddNearbyContactViewModel.java

@@ -43,6 +43,7 @@ import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
+import org.briarproject.bramble.api.qrcode.WrongQrCodeTypeException;
 import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.bramble.plugin.bluetooth.BluetoothPlugin;
 import org.briarproject.briar.R;
@@ -50,9 +51,13 @@ import org.briarproject.briar.android.contact.add.nearby.AddContactState.Contact
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeResult.Error;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeResult.Success;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.ContactExchangeStarted;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.Failed;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.Failed.WrongQrCodeType;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.Failed.WrongQrCodeVersion;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementListening;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementStarted;
 import org.briarproject.briar.android.contact.add.nearby.AddContactState.KeyAgreementWaiting;
+import org.briarproject.briar.android.contact.add.nearby.AddContactState.QrCodeScanned;
 import org.briarproject.briar.android.qrcode.QrCodeDecoder;
 import org.briarproject.briar.android.qrcode.QrCodeUtils;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
@@ -60,7 +65,6 @@ import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.nullsafety.NotNullByDefault;
 
 import java.io.IOException;
-import java.nio.charset.Charset;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -85,6 +89,7 @@ import static org.briarproject.bramble.api.plugin.Plugin.State.DISABLED;
 import static org.briarproject.bramble.api.plugin.Plugin.State.INACTIVE;
 import static org.briarproject.bramble.api.plugin.Plugin.State.STARTING_STOPPING;
 import static org.briarproject.bramble.util.LogUtils.logException;
+import static org.briarproject.bramble.util.StringUtils.ISO_8859_1;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactPermissionManager.areEssentialPermissionsGranted;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.NO_ADAPTER;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.REFUSED;
@@ -126,9 +131,6 @@ class AddNearbyContactViewModel extends AndroidViewModel
 		REFUSED
 	}
 
-	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
-	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
-
 	private final EventBus eventBus;
 	private final AndroidExecutor androidExecutor;
 	private final Executor ioExecutor;
@@ -376,11 +378,11 @@ class AddNearbyContactViewModel extends AndroidViewModel
 		} else if (e instanceof KeyAgreementAbortedEvent) {
 			LOG.info("KeyAgreementAbortedEvent received");
 			resetPayloadFlags();
-			state.setValue(new AddContactState.Failed());
+			state.setValue(new Failed());
 		} else if (e instanceof KeyAgreementFailedEvent) {
 			LOG.info("KeyAgreementFailedEvent received");
 			resetPayloadFlags();
-			state.setValue(new AddContactState.Failed());
+			state.setValue(new Failed());
 		}
 	}
 
@@ -446,22 +448,22 @@ class AddNearbyContactViewModel extends AndroidViewModel
 		// Ignore results until the KeyAgreementTask is ready
 		if (!gotLocalPayload || gotRemotePayload || currentTask == null) return;
 		try {
-			byte[] payloadBytes = result.getText().getBytes(ISO_8859_1);
-			if (LOG.isLoggable(INFO))
-				LOG.info("Remote payload is " + payloadBytes.length + " bytes");
-			Payload remotePayload = payloadParser.parse(payloadBytes);
+			Payload remotePayload = payloadParser.parse(result.getText());
 			gotRemotePayload = true;
 			currentTask.connectAndRunProtocol(remotePayload);
-			state.postValue(new AddContactState.QrCodeScanned());
+			state.postValue(new QrCodeScanned());
+		} catch (WrongQrCodeTypeException e) {
+			resetPayloadFlags();
+			state.postValue(new WrongQrCodeType(e.getQrCodeType()));
 		} catch (UnsupportedVersionException e) {
 			resetPayloadFlags();
-			state.postValue(new AddContactState.Failed(e.isTooOld()));
+			state.postValue(new WrongQrCodeVersion(e.isTooOld()));
 		} catch (IOException | IllegalArgumentException e) {
 			LOG.log(WARNING, "QR Code Invalid", e);
 			androidExecutor.runOnUiThread(() -> Toast.makeText(getApplication(),
 					R.string.qr_code_invalid, LENGTH_LONG).show());
 			resetPayloadFlags();
-			state.postValue(new AddContactState.Failed());
+			state.postValue(new Failed());
 		}
 	}
 

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

@@ -436,7 +436,7 @@ class HotspotManager {
 	}
 
 	private static String createWifiLoginString(String ssid, String password) {
-		// https://en.wikipedia.org/wiki/QR_code#WiFi_network_login
+		// https://en.wikipedia.org/wiki/QR_code#Joining_a_Wi%E2%80%91Fi_network
 		// do not remove the dangling ';', it can cause problems to omit it
 		return "WIFI:S:" + ssid + ";T:WPA;P:" + password + ";;";
 	}

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxActivity.java

@@ -6,10 +6,24 @@ import android.widget.ProgressBar;
 import android.widget.Toast;
 
 import org.briarproject.bramble.api.mailbox.MailboxPairingState;
+import org.briarproject.bramble.api.mailbox.MailboxPairingState.ConnectionError;
+import org.briarproject.bramble.api.mailbox.MailboxPairingState.InvalidQrCode;
+import org.briarproject.bramble.api.mailbox.MailboxPairingState.MailboxAlreadyPaired;
+import org.briarproject.bramble.api.mailbox.MailboxPairingState.Paired;
+import org.briarproject.bramble.api.mailbox.MailboxPairingState.Pending;
+import org.briarproject.bramble.api.mailbox.MailboxPairingState.UnexpectedError;
 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.FinalFragment;
+import org.briarproject.briar.android.mailbox.MailboxState.CameraError;
+import org.briarproject.briar.android.mailbox.MailboxState.IsPaired;
+import org.briarproject.briar.android.mailbox.MailboxState.NotSetup;
+import org.briarproject.briar.android.mailbox.MailboxState.OfflineWhenPairing;
+import org.briarproject.briar.android.mailbox.MailboxState.Pairing;
+import org.briarproject.briar.android.mailbox.MailboxState.ScanningQrCode;
+import org.briarproject.briar.android.mailbox.MailboxState.ShowDownload;
+import org.briarproject.briar.android.mailbox.MailboxState.WasUnpaired;
 import org.briarproject.briar.android.view.BlankFragment;
 import org.briarproject.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.nullsafety.ParametersNotNullByDefault;
@@ -25,6 +39,9 @@ import androidx.lifecycle.ViewModelProvider;
 import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
 import static android.widget.Toast.LENGTH_LONG;
+import static org.briarproject.bramble.api.mailbox.MailboxConstants.QR_FORMAT_VERSION;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.BQP;
+import static org.briarproject.bramble.api.qrcode.QrCodeClassifier.QrCodeType.MAILBOX;
 import static org.briarproject.briar.android.util.UiUtils.showFragment;
 
 @MethodsNotNullByDefault
@@ -56,24 +73,23 @@ public class MailboxActivity extends BriarActivity {
 		}
 
 		viewModel.getPairingState().observeEvent(this, state -> {
-			if (state instanceof MailboxState.NotSetup) {
+			if (state instanceof NotSetup) {
 				onNotSetup();
-			} else if (state instanceof MailboxState.ShowDownload) {
+			} else if (state instanceof ShowDownload) {
 				onShowDownload();
-			} else if (state instanceof MailboxState.ScanningQrCode) {
+			} else if (state instanceof ScanningQrCode) {
 				onScanningQrCode();
-			} else if (state instanceof MailboxState.Pairing) {
-				MailboxPairingState s =
-						((MailboxState.Pairing) state).pairingState;
+			} else if (state instanceof Pairing) {
+				MailboxPairingState s = ((Pairing) state).pairingState;
 				onMailboxPairingStateChanged(s);
-			} else if (state instanceof MailboxState.OfflineWhenPairing) {
+			} else if (state instanceof OfflineWhenPairing) {
 				onOffline();
-			} else if (state instanceof MailboxState.CameraError) {
+			} else if (state instanceof CameraError) {
 				onCameraError();
-			} else if (state instanceof MailboxState.IsPaired) {
-				onIsPaired(((MailboxState.IsPaired) state).isOnline);
-			} else if (state instanceof MailboxState.WasUnpaired) {
-				MailboxState.WasUnpaired s = (MailboxState.WasUnpaired) state;
+			} else if (state instanceof IsPaired) {
+				onIsPaired(((IsPaired) state).isOnline);
+			} else if (state instanceof WasUnpaired) {
+				WasUnpaired s = (WasUnpaired) state;
 				onUnPaired(s.tellUserToWipeMailbox);
 			} else {
 				throw new AssertionError("Unknown state: " + state);
@@ -104,7 +120,7 @@ public class MailboxActivity extends BriarActivity {
 	@Override
 	public void onBackPressed() {
 		MailboxState s = viewModel.getPairingState().getLastValue();
-		if (s instanceof MailboxState.Pairing) {
+		if (s instanceof Pairing) {
 			// don't go back in the flow if we are already pairing
 			// with the mailbox. We provide a try-again button instead.
 			supportFinishAfterTransition();
@@ -158,31 +174,44 @@ public class MailboxActivity extends BriarActivity {
 		}
 		Fragment f;
 		String tag;
-		if (s instanceof MailboxPairingState.Pending) {
-			long timeStarted = ((MailboxPairingState.Pending) s).timeStarted;
+		if (s instanceof Pending) {
+			long timeStarted = ((Pending) s).timeStarted;
 			f = MailboxConnectingFragment.newInstance(timeStarted);
 			tag = MailboxConnectingFragment.TAG;
-		} else if (s instanceof MailboxPairingState.InvalidQrCode) {
-			f = ErrorFragment.newInstance(
-					R.string.mailbox_setup_qr_code_wrong_title,
-					R.string.mailbox_setup_qr_code_wrong_description);
+		} else if (s instanceof InvalidQrCode) {
+			InvalidQrCode i = (InvalidQrCode) s;
+			int errorRes;
+			if (i.qrCodeType == MAILBOX) {
+				if (i.formatVersion < QR_FORMAT_VERSION) {
+					errorRes = R.string.mailbox_qr_code_too_old;
+				} else if (i.formatVersion > QR_FORMAT_VERSION) {
+					errorRes = R.string.mailbox_qr_code_too_new;
+				} else {
+					errorRes = R.string.mailbox_setup_qr_code_wrong_description;
+				}
+			} else if (i.qrCodeType == BQP) {
+				errorRes = R.string.contact_qr_code_for_mailbox;
+			} else {
+				errorRes = R.string.mailbox_setup_qr_code_wrong_description;
+			}
+			f = ErrorFragment.newInstance(R.string.qr_code_invalid, errorRes);
 			tag = ErrorFragment.TAG;
-		} else if (s instanceof MailboxPairingState.MailboxAlreadyPaired) {
+		} else if (s instanceof MailboxAlreadyPaired) {
 			f = ErrorFragment.newInstance(
 					R.string.mailbox_setup_already_paired_title,
 					R.string.mailbox_setup_already_paired_description);
 			tag = ErrorFragment.TAG;
-		} else if (s instanceof MailboxPairingState.ConnectionError) {
+		} else if (s instanceof ConnectionError) {
 			f = ErrorFragment.newInstance(
 					R.string.mailbox_setup_io_error_title,
 					R.string.mailbox_setup_io_error_description);
 			tag = ErrorFragment.TAG;
-		} else if (s instanceof MailboxPairingState.UnexpectedError) {
+		} else if (s instanceof UnexpectedError) {
 			f = ErrorFragment.newInstance(
 					R.string.mailbox_setup_assertion_error_title,
 					R.string.mailbox_setup_assertion_error_description);
 			tag = ErrorFragment.TAG;
-		} else if (s instanceof MailboxPairingState.Paired) {
+		} else if (s instanceof Paired) {
 			f = FinalFragment.newInstance(R.string.mailbox_setup_paired_title,
 					R.drawable.ic_check_circle_outline,
 					R.color.briar_brand_green,

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxViewModel.java

@@ -15,6 +15,7 @@ import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.mailbox.MailboxManager;
 import org.briarproject.bramble.api.mailbox.MailboxPairingState;
+import org.briarproject.bramble.api.mailbox.MailboxPairingState.Paired;
 import org.briarproject.bramble.api.mailbox.MailboxPairingTask;
 import org.briarproject.bramble.api.mailbox.MailboxStatus;
 import org.briarproject.bramble.api.mailbox.event.OwnMailboxConnectionStatusEvent;
@@ -24,7 +25,14 @@ import org.briarproject.bramble.api.plugin.TorConstants;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.event.TransportInactiveEvent;
 import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.android.mailbox.MailboxState.CameraError;
+import org.briarproject.briar.android.mailbox.MailboxState.IsPaired;
 import org.briarproject.briar.android.mailbox.MailboxState.NotSetup;
+import org.briarproject.briar.android.mailbox.MailboxState.OfflineWhenPairing;
+import org.briarproject.briar.android.mailbox.MailboxState.Pairing;
+import org.briarproject.briar.android.mailbox.MailboxState.ScanningQrCode;
+import org.briarproject.briar.android.mailbox.MailboxState.ShowDownload;
+import org.briarproject.briar.android.mailbox.MailboxState.WasUnpaired;
 import org.briarproject.briar.android.qrcode.QrCodeDecoder;
 import org.briarproject.briar.android.viewmodel.DbViewModel;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
@@ -113,7 +121,7 @@ class MailboxViewModel extends DbViewModel
 					MailboxStatus mailboxStatus =
 							mailboxManager.getMailboxStatus(txn);
 					boolean isOnline = isTorActive();
-					pairingState.postEvent(new MailboxState.IsPaired(isOnline));
+					pairingState.postEvent(new IsPaired(isOnline));
 					status.postValue(mailboxStatus);
 				} else {
 					pairingState.postEvent(new NotSetup());
@@ -142,14 +150,14 @@ class MailboxViewModel extends DbViewModel
 	@UiThread
 	private void onTorInactive() {
 		MailboxState lastState = pairingState.getLastValue();
-		if (lastState instanceof MailboxState.IsPaired) {
+		if (lastState instanceof IsPaired) {
 			// we are already paired, so use IsPaired state
-			pairingState.setEvent(new MailboxState.IsPaired(false));
-		} else if (lastState instanceof MailboxState.Pairing) {
-			MailboxState.Pairing p = (MailboxState.Pairing) lastState;
+			pairingState.setEvent(new IsPaired(false));
+		} else if (lastState instanceof Pairing) {
+			Pairing p = (Pairing) lastState;
 			// check that we not just finished pairing (showing success screen)
-			if (!(p.pairingState instanceof MailboxPairingState.Paired)) {
-				pairingState.setEvent(new MailboxState.OfflineWhenPairing());
+			if (!(p.pairingState instanceof Paired)) {
+				pairingState.setEvent(new OfflineWhenPairing());
 			}
 			// else ignore offline event as user will be leaving UI flow anyway
 		}
@@ -158,15 +166,15 @@ class MailboxViewModel extends DbViewModel
 	@UiThread
 	void onScanButtonClicked() {
 		if (isTorActive()) {
-			pairingState.setEvent(new MailboxState.ScanningQrCode());
+			pairingState.setEvent(new ScanningQrCode());
 		} else {
-			pairingState.setEvent(new MailboxState.OfflineWhenPairing());
+			pairingState.setEvent(new OfflineWhenPairing());
 		}
 	}
 
 	@UiThread
 	void onCameraError() {
-		pairingState.setEvent(new MailboxState.CameraError());
+		pairingState.setEvent(new CameraError());
 	}
 
 	@Override
@@ -182,7 +190,7 @@ class MailboxViewModel extends DbViewModel
 			pairingTask = mailboxManager.startPairingTask(qrCodePayload);
 			pairingTask.addObserver(this);
 		} else {
-			pairingState.postEvent(new MailboxState.OfflineWhenPairing());
+			pairingState.postEvent(new OfflineWhenPairing());
 		}
 	}
 
@@ -193,7 +201,7 @@ class MailboxViewModel extends DbViewModel
 			LOG.info("New pairing state: " +
 					mailboxPairingState.getClass().getSimpleName());
 		}
-		pairingState.setEvent(new MailboxState.Pairing(mailboxPairingState));
+		pairingState.setEvent(new Pairing(mailboxPairingState));
 	}
 
 	private boolean isTorActive() {
@@ -203,7 +211,7 @@ class MailboxViewModel extends DbViewModel
 
 	@UiThread
 	void showDownloadFragment() {
-		pairingState.setEvent(new MailboxState.ShowDownload());
+		pairingState.setEvent(new ShowDownload());
 	}
 
 	@UiThread
@@ -214,7 +222,7 @@ class MailboxViewModel extends DbViewModel
 	@UiThread
 	void checkIfOnlineWhenPaired() {
 		boolean isOnline = isTorActive();
-		pairingState.setEvent(new MailboxState.IsPaired(isOnline));
+		pairingState.setEvent(new IsPaired(isOnline));
 	}
 
 	LiveData<Boolean> checkConnection() {
@@ -227,7 +235,7 @@ class MailboxViewModel extends DbViewModel
 		checkConnection(success -> {
 			boolean isOnline = isTorActive();
 			// make UI move back to status fragment by changing pairingState
-			pairingState.postEvent(new MailboxState.IsPaired(isOnline));
+			pairingState.postEvent(new IsPaired(isOnline));
 		});
 	}
 
@@ -246,7 +254,7 @@ class MailboxViewModel extends DbViewModel
 		ioExecutor.execute(() -> {
 			try {
 				boolean wasWiped = mailboxManager.unPair();
-				pairingState.postEvent(new MailboxState.WasUnpaired(!wasWiped));
+				pairingState.postEvent(new WasUnpaired(!wasWiped));
 			} catch (DbException e) {
 				handleException(e);
 			}

briar-android/src/main/java/org/briarproject/briar/android/qrcode/QrCodeDecoder.java

@@ -41,7 +41,6 @@ public class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	private final ResultCallback callback;
 
 	private Camera camera = null;
-	private int cameraIndex = 0;
 
 	public QrCodeDecoder(AndroidExecutor androidExecutor,
 			@IoExecutor Executor ioExecutor, ResultCallback callback) {
@@ -53,14 +52,12 @@ public class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 	@Override
 	public void start(Camera camera, int cameraIndex) {
 		this.camera = camera;
-		this.cameraIndex = cameraIndex;
 		askForPreviewFrame();
 	}
 
 	@Override
 	public void stop() {
 		camera = null;
-		cameraIndex = 0;
 	}
 
 	@UiThread

briar-android/src/main/res/layout/fragment_error_contact_exchange.xml

@@ -51,12 +51,12 @@
 				android:layout_width="0dp"
 				android:layout_height="wrap_content"
 				android:layout_marginTop="@dimen/margin_xlarge"
+				android:text="@string/add_contact_error_two_way"
 				android:textAppearance="@style/TextAppearance.MaterialComponents.Body1"
 				app:layout_constraintBottom_toTopOf="@+id/sendFeedback"
 				app:layout_constraintEnd_toEndOf="parent"
 				app:layout_constraintStart_toStartOf="parent"
-				app:layout_constraintTop_toBottomOf="@+id/errorTitle"
-				tools:text="error explanation" />
+				app:layout_constraintTop_toBottomOf="@+id/errorTitle" />
 
 			<TextView
 				android:id="@+id/sendFeedback"

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

@@ -252,6 +252,8 @@
 	<string name="qr_code_invalid">The QR code is invalid</string>
 	<string name="qr_code_too_old_1">The QR code you have scanned comes from an older version of Briar.\n\nPlease ask your contact to upgrade to the latest version and then try again.</string>
 	<string name="qr_code_too_new_1">The QR code you have scanned comes from a newer version of Briar.\n\nPlease upgrade to the latest version and then try again.</string>
+	<string name="mailbox_qr_code_for_contact">The QR code you have scanned comes from Briar Mailbox.\n\nIf you want to link a Mailbox, please choose Settings > Mailbox from the Briar menu.</string>
+	<string name="qr_code_format_unknown">The QR code you have scanned does not come from Briar.\n\nPlease scan the QR code shown on your contact\'s screen.</string>
 	<string name="camera_error">Camera error</string>
 	<string name="connecting_to_device">Connecting to device\u2026</string>
 	<string name="authenticating_with_device">Authenticating with device\u2026</string>
@@ -636,8 +638,10 @@
 	<string name="mailbox_setup_connecting">Connecting to Mailbox…</string>
 	<!-- This string is shown when connecting to a Mailbox for the first time. The placeholder will be replaced with a duration, e.g. "2 minutes". -->
 	<string name="mailbox_setup_connecting_info">This may take up to %1s</string>
-	<string name="mailbox_setup_qr_code_wrong_title">Wrong QR code</string>
-	<string name="mailbox_setup_qr_code_wrong_description">The scanned code is invalid. Please open the Briar Mailbox app on your Mailbox device and scan the QR code it presents.</string>
+	<string name="mailbox_qr_code_too_old">The QR code you have scanned comes from an older version of Briar Mailbox.\n\nPlease upgrade Briar Mailbox to the latest version and then try again.</string>
+	<string name="mailbox_qr_code_too_new">The QR code you have scanned comes from a newer version of Briar Mailbox.\n\nPlease upgrade Briar to the latest version and then try again.</string>
+	<string name="contact_qr_code_for_mailbox">The QR code you have scanned is for adding a Briar contact.\n\nIf you want to add a contact, please go to the contact list and tap the + icon.</string>
+	<string name="mailbox_setup_qr_code_wrong_description">The QR code you have scanned does not come from Briar Mailbox.\n\nPlease open the Briar Mailbox app on your Mailbox device and scan the QR code it presents.</string>
 	<string name="mailbox_setup_already_paired_title">Mailbox already linked</string>
 	<string name="mailbox_setup_already_paired_description">Unlink the Mailbox on your other device and try again.</string>
 	<string name="mailbox_setup_io_error_title">Could not connect</string>