Move backend comms and logic out of KeyAgreementFragment

into ViewModel

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementTransport.java

@@ -34,12 +34,12 @@ class KeyAgreementTransport {
 			Logger.getLogger(KeyAgreementTransport.class.getName());
 
 	// Accept records with current protocol version, known record type
-	private static Predicate<Record> ACCEPT = r ->
+	private static final Predicate<Record> ACCEPT = r ->
 			r.getProtocolVersion() == PROTOCOL_VERSION &&
 					isKnownRecordType(r.getRecordType());
 
 	// Ignore records with current protocol version, unknown record type
-	private static Predicate<Record> IGNORE = r ->
+	private static final Predicate<Record> IGNORE = r ->
 			r.getProtocolVersion() == PROTOCOL_VERSION &&
 					!isKnownRecordType(r.getRecordType());
 

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

@@ -0,0 +1,55 @@
+package org.briarproject.briar.android.contact.add.nearby;
+
+import android.graphics.Bitmap;
+
+import androidx.annotation.Nullable;
+
+abstract class ContactAddingState {
+
+	static class KeyAgreementListening extends ContactAddingState {
+		final Bitmap qrCode;
+
+		KeyAgreementListening(Bitmap qrCode) {
+			this.qrCode = qrCode;
+		}
+	}
+
+	static class QrCodeScanned extends ContactAddingState {
+	}
+
+	static class KeyAgreementWaiting extends ContactAddingState {
+	}
+
+	static class KeyAgreementStarted extends ContactAddingState {
+	}
+
+	static class ContactExchangeStarted extends ContactAddingState {
+	}
+
+	static class ContactExchangeFinished extends ContactAddingState {
+		final ContactExchangeResult result;
+
+		ContactExchangeFinished(ContactExchangeResult result) {
+			this.result = result;
+		}
+	}
+
+	static class Failed extends ContactAddingState {
+		/**
+		 * 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;
+		}
+
+		Failed() {
+			this(null);
+		}
+	}
+
+}

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

@@ -7,14 +7,15 @@ import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.ContactExchangeFinished;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.Failed;
 
 import javax.annotation.Nullable;
 
+import androidx.appcompat.widget.Toolbar;
+
 import static android.widget.Toast.LENGTH_LONG;
 import static java.util.Objects.requireNonNull;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.ABORTED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.FAILED;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -25,15 +26,33 @@ public class ContactExchangeActivity extends KeyAgreementActivity {
 		super.onCreate(state);
 		requireNonNull(getSupportActionBar())
 				.setTitle(R.string.add_contact_title);
-		viewModel.getKeyAgreementState()
-				.observe(this, this::onKeyAgreementStateChanged);
-		viewModel.getContactExchangeResult()
-				.observe(this, this::onContactExchangeResult);
+		viewModel.getState()
+				.observe(this, this::onContactAddingStateChanged);
 	}
 
-	private void onKeyAgreementStateChanged(KeyAgreementState state) {
-		if (state == ABORTED || state == FAILED) {
-			showErrorFragment();
+	@Override
+	public void onBackPressed() {
+		if (viewModel.getState().getValue() instanceof Failed) {
+			// finish this activity when going back in failed state
+			supportFinishAfterTransition();
+		} else {
+			super.onBackPressed();
+		}
+	}
+
+	private void onContactAddingStateChanged(ContactAddingState state) {
+		if (state instanceof ContactExchangeFinished) {
+			ContactExchangeResult result =
+					((ContactExchangeFinished) state).result;
+			onContactExchangeResult(result);
+		} else if (state instanceof Failed) {
+			// Remove navigation icon, so user can't go back when failed
+			// ErrorFragment will finish or relaunch this activity
+			Toolbar toolbar = findViewById(R.id.toolbar);
+			toolbar.setNavigationIcon(null);
+
+			Boolean qrCodeTooOld = ((Failed) state).qrCodeTooOld;
+			onAddingContactFailed(qrCodeTooOld);
 		}
 	}
 
@@ -60,6 +79,22 @@ public class ContactExchangeActivity extends KeyAgreementActivity {
 		} 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,
+						getString(R.string.app_name));
+			} else {
+				msg = getString(R.string.qr_code_too_new,
+						getString(R.string.app_name));
+			}
+			showNextFragment(ContactExchangeErrorFragment.newInstance(msg));
+		}
+	}
+
 	private void showErrorFragment() {
 		showNextFragment(new ContactExchangeErrorFragment());
 	}

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

@@ -1,7 +1,13 @@
 package org.briarproject.briar.android.contact.add.nearby;
 
 import android.app.Application;
+import android.graphics.Bitmap;
+import android.util.DisplayMetrics;
+import android.widget.Toast;
 
+import com.google.zxing.Result;
+
+import org.briarproject.bramble.api.UnsupportedVersionException;
 import org.briarproject.bramble.api.connection.ConnectionManager;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactExchangeManager;
@@ -12,95 +18,208 @@ import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementResult;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementTask;
+import org.briarproject.bramble.api.keyagreement.Payload;
+import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
+import org.briarproject.bramble.api.keyagreement.PayloadParser;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementAbortedEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFailedEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFinishedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStartedEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementWaitingEvent;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.ContactExchangeFinished;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.ContactExchangeStarted;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.KeyAgreementListening;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.KeyAgreementStarted;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.KeyAgreementWaiting;
 import org.briarproject.briar.android.contact.add.nearby.ContactExchangeResult.Error;
 import org.briarproject.briar.android.contact.add.nearby.ContactExchangeResult.Success;
 
 import java.io.IOException;
+import java.nio.charset.Charset;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import javax.inject.Inject;
+import javax.inject.Provider;
 
+import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.Objects.requireNonNull;
+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.bramble.util.LogUtils.logException;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.ABORTED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.FAILED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.FINISHED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.STARTED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.WAITING;
 
 @NotNullByDefault
 class ContactExchangeViewModel extends AndroidViewModel
-		implements EventListener {
+		implements EventListener, QrCodeDecoder.ResultCallback {
 
 	private static final Logger LOG =
 			getLogger(ContactExchangeViewModel.class.getName());
 
-	enum KeyAgreementState {
-		WAITING, STARTED, FINISHED, ABORTED, FAILED
-	}
+	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
+	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
 
 	private final EventBus eventBus;
 	private final Executor ioExecutor;
+	private final PayloadEncoder payloadEncoder;
+	private final PayloadParser payloadParser;
+	private final Provider<KeyAgreementTask> keyAgreementTaskProvider;
 	private final ContactExchangeManager contactExchangeManager;
 	private final ConnectionManager connectionManager;
-	private final MutableLiveData<KeyAgreementState> keyAgreementState =
-			new MutableLiveData<>();
-	private final MutableLiveData<ContactExchangeResult> exchangeResult =
+
+	private final MutableLiveData<ContactAddingState> state =
 			new MutableLiveData<>();
 
+	final QrCodeDecoder qrCodeDecoder;
+
+	@Nullable
+	private KeyAgreementTask task;
+	private volatile boolean gotLocalPayload = false, gotRemotePayload = false;
+
 	@Inject
 	ContactExchangeViewModel(Application app,
 			EventBus eventBus,
 			@IoExecutor Executor ioExecutor,
+			PayloadEncoder payloadEncoder,
+			PayloadParser payloadParser,
+			Provider<KeyAgreementTask> keyAgreementTaskProvider,
 			ContactExchangeManager contactExchangeManager,
 			ConnectionManager connectionManager) {
 		super(app);
 		this.eventBus = eventBus;
 		this.ioExecutor = ioExecutor;
+		this.payloadEncoder = payloadEncoder;
+		this.payloadParser = payloadParser;
+		this.keyAgreementTaskProvider = keyAgreementTaskProvider;
 		this.contactExchangeManager = contactExchangeManager;
 		this.connectionManager = connectionManager;
+		qrCodeDecoder = new QrCodeDecoder(ioExecutor, this);
+		eventBus.addListener(this);
 	}
 
 	@Override
 	protected void onCleared() {
 		super.onCleared();
 		eventBus.removeListener(this);
+		stopListening();
+	}
+
+	/**
+	 * Call this once Bluetooth and Wi-Fi are ready to be used.
+	 * It is possible to call this more than once over the ViewModel's lifetime.
+	 */
+	@UiThread
+	void startListening() {
+		KeyAgreementTask oldTask = task;
+		KeyAgreementTask newTask = keyAgreementTaskProvider.get();
+		task = newTask;
+		ioExecutor.execute(() -> {
+			if (oldTask != null) oldTask.stopListening();
+			newTask.listen();
+		});
+	}
+
+	@UiThread
+	private void stopListening() {
+		KeyAgreementTask oldTask = task;
+		ioExecutor.execute(() -> {
+			if (oldTask != null) oldTask.stopListening();
+		});
 	}
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof KeyAgreementWaitingEvent) {
-			keyAgreementState.setValue(WAITING);
+		if (e instanceof KeyAgreementListeningEvent) {
+			LOG.info("KeyAgreementListeningEvent received");
+			KeyAgreementListeningEvent event = (KeyAgreementListeningEvent) e;
+			onLocalPayloadReceived(event.getLocalPayload());
+		} else if (e instanceof KeyAgreementWaitingEvent) {
+			LOG.info("KeyAgreementWaitingEvent received");
+			state.setValue(new KeyAgreementWaiting());
 		} else if (e instanceof KeyAgreementStartedEvent) {
-			keyAgreementState.setValue(STARTED);
-		} else if (e instanceof KeyAgreementAbortedEvent) {
-			keyAgreementState.setValue(ABORTED);
+			LOG.info("KeyAgreementStartedEvent received");
+			state.setValue(new KeyAgreementStarted());
 		} else if (e instanceof KeyAgreementFinishedEvent) {
-			keyAgreementState.setValue(FINISHED);
+			LOG.info("KeyAgreementFinishedEvent received");
 			KeyAgreementResult result =
 					((KeyAgreementFinishedEvent) e).getResult();
 			startContactExchange(result);
+			state.setValue(new ContactExchangeStarted());
+		} else if (e instanceof KeyAgreementAbortedEvent) {
+			LOG.info("KeyAgreementAbortedEvent received");
+			resetPayloadFlags();
+			state.setValue(new ContactAddingState.Failed());
 		} else if (e instanceof KeyAgreementFailedEvent) {
-			keyAgreementState.setValue(FAILED);
+			LOG.info("KeyAgreementFailedEvent received");
+			resetPayloadFlags();
+			state.setValue(new ContactAddingState.Failed());
 		}
 	}
 
+	/**
+	 * This sets the QR code by setting the state to KeyAgreementListening.
+	 */
+	private void onLocalPayloadReceived(Payload localPayload) {
+		if (gotLocalPayload) return;
+		DisplayMetrics dm = getApplication().getResources().getDisplayMetrics();
+		ioExecutor.execute(() -> {
+			byte[] payloadBytes = payloadEncoder.encode(localPayload);
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Local payload is " + payloadBytes.length
+						+ " bytes");
+			}
+			// Use ISO 8859-1 to encode bytes directly as a string
+			String content = new String(payloadBytes, ISO_8859_1);
+			Bitmap qrCode = QrCodeUtils.createQrCode(dm, content);
+			gotLocalPayload = true;
+			state.postValue(new KeyAgreementListening(qrCode));
+		});
+	}
+
+	@Override
+	@IoExecutor
+	public void onQrCodeDecoded(Result result) {
+		LOG.info("Got result from decoder");
+		// Ignore results until the KeyAgreementTask is ready
+		if (!gotLocalPayload || gotRemotePayload) 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);
+			gotRemotePayload = true;
+			requireNonNull(task).connectAndRunProtocol(remotePayload);
+			state.postValue(new ContactAddingState.QrCodeScanned());
+		} catch (UnsupportedVersionException e) {
+			resetPayloadFlags();
+			state.postValue(new ContactAddingState.Failed(e.isTooOld()));
+		} catch (IOException | IllegalArgumentException e) {
+			LOG.log(WARNING, "QR Code Invalid", e);
+			Toast.makeText(getApplication(), R.string.qr_code_invalid,
+					LENGTH_LONG).show();
+			resetPayloadFlags();
+			state.postValue(new ContactAddingState.Failed());
+		}
+	}
+
+	private void resetPayloadFlags() {
+		gotRemotePayload = false;
+		gotLocalPayload = false;
+	}
+
 	@UiThread
 	private void startContactExchange(KeyAgreementResult result) {
 		TransportId t = result.getTransportId();
@@ -114,14 +233,17 @@ class ContactExchangeViewModel extends AndroidViewModel
 				// Reuse the connection as a transport connection
 				connectionManager
 						.manageOutgoingConnection(contact.getId(), t, conn);
-				exchangeResult.postValue(new Success(contact.getAuthor()));
+				Success success = new Success(contact.getAuthor());
+				state.postValue(new ContactExchangeFinished(success));
 			} catch (ContactExistsException e) {
 				tryToClose(conn);
-				exchangeResult.postValue(new Error(e.getRemoteAuthor()));
+				Error error = new Error(e.getRemoteAuthor());
+				state.postValue(new ContactExchangeFinished(error));
 			} catch (DbException | IOException e) {
 				tryToClose(conn);
 				logException(LOG, WARNING, e);
-				exchangeResult.postValue(new Error(null));
+				Error error = new Error(null);
+				state.postValue(new ContactExchangeFinished(error));
 			}
 		});
 	}
@@ -135,11 +257,8 @@ class ContactExchangeViewModel extends AndroidViewModel
 		}
 	}
 
-	LiveData<KeyAgreementState> getKeyAgreementState() {
-		return keyAgreementState;
+	LiveData<ContactAddingState> getState() {
+		return state;
 	}
 
-	LiveData<ContactExchangeResult> getContactExchangeResult() {
-		return exchangeResult;
-	}
 }

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

@@ -205,6 +205,7 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		if (isResumed && continueClicked && areEssentialPermissionsGranted()) {
 			if (isWifiReady() && isBluetoothReady()) {
 				LOG.info("Wifi and Bluetooth are ready");
+				viewModel.startListening();
 				showQrCodeFragment();
 			} else {
 				if (shouldEnableWifi()) {

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

@@ -1,9 +1,7 @@
 package org.briarproject.briar.android.contact.add.nearby;
 
-import android.content.Context;
 import android.graphics.Bitmap;
 import android.os.Bundle;
-import android.util.DisplayMetrics;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
@@ -12,36 +10,24 @@ import android.widget.LinearLayout.LayoutParams;
 import android.widget.TextView;
 import android.widget.Toast;
 
-import com.google.zxing.Result;
-
-import org.briarproject.bramble.api.UnsupportedVersionException;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventBus;
-import org.briarproject.bramble.api.keyagreement.KeyAgreementTask;
-import org.briarproject.bramble.api.keyagreement.Payload;
-import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
-import org.briarproject.bramble.api.keyagreement.PayloadParser;
-import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
 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.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState;
-import org.briarproject.briar.android.fragment.BaseEventFragment;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.ContactExchangeStarted;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.Failed;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.KeyAgreementStarted;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.KeyAgreementWaiting;
+import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.QrCodeScanned;
+import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.QrCodeView;
 
-import java.io.IOException;
-import java.nio.charset.Charset;
-import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 import javax.inject.Inject;
-import javax.inject.Provider;
 
 import androidx.annotation.UiThread;
-import androidx.lifecycle.LifecycleOwner;
 import androidx.lifecycle.ViewModelProvider;
 
 import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_NOSENSOR;
@@ -50,39 +36,20 @@ import static android.view.View.VISIBLE;
 import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
 import static android.widget.LinearLayout.HORIZONTAL;
 import static android.widget.Toast.LENGTH_LONG;
-import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.ABORTED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.FAILED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.FINISHED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.STARTED;
-import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.KeyAgreementState.WAITING;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public class KeyAgreementFragment extends BaseEventFragment
-		implements QrCodeDecoder.ResultCallback, QrCodeView.FullscreenListener {
+public class KeyAgreementFragment extends BaseFragment
+		implements QrCodeView.FullscreenListener {
 
 	static final String TAG = KeyAgreementFragment.class.getName();
 
 	private static final Logger LOG = Logger.getLogger(TAG);
-	@SuppressWarnings("CharsetObjectCanBeUsed") // Requires minSdkVersion >= 19
-	private static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
-	@Inject
-	Provider<KeyAgreementTask> keyAgreementTaskProvider;
-	@Inject
-	PayloadEncoder payloadEncoder;
-	@Inject
-	PayloadParser payloadParser;
-	@Inject
-	@IoExecutor
-	Executor ioExecutor;
-	@Inject
-	EventBus eventBus;
 
 	private ContactExchangeViewModel viewModel;
 	private CameraView cameraView;
@@ -91,10 +58,6 @@ public class KeyAgreementFragment extends BaseEventFragment
 	private QrCodeView qrCodeView;
 	private TextView status;
 
-	private boolean gotRemotePayload;
-	private volatile boolean gotLocalPayload;
-	private KeyAgreementTask task;
-
 	public static KeyAgreementFragment newInstance() {
 		Bundle args = new Bundle();
 		KeyAgreementFragment fragment = new KeyAgreementFragment();
@@ -109,11 +72,6 @@ public class KeyAgreementFragment extends BaseEventFragment
 				.get(ContactExchangeViewModel.class);
 	}
 
-	@Override
-	public String getUniqueTag() {
-		return TAG;
-	}
-
 	@Nullable
 	@Override
 	public View onCreateView(LayoutInflater inflater,
@@ -133,16 +91,15 @@ public class KeyAgreementFragment extends BaseEventFragment
 		qrCodeView = view.findViewById(R.id.qr_code_view);
 		qrCodeView.setFullscreenListener(this);
 
-		LifecycleOwner lifecycleOwner = getViewLifecycleOwner();
-		viewModel.getKeyAgreementState()
-				.observe(lifecycleOwner, this::onKeyAgreementStateChanged);
+		viewModel.getState().observe(getViewLifecycleOwner(),
+				this::onContactAddingStateChanged);
 	}
 
 	@Override
 	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
 		super.onActivityCreated(savedInstanceState);
 		requireActivity().setRequestedOrientation(SCREEN_ORIENTATION_NOSENSOR);
-		cameraView.setPreviewConsumer(new QrCodeDecoder(this));
+		cameraView.setPreviewConsumer(viewModel.qrCodeDecoder);
 	}
 
 	@Override
@@ -153,7 +110,16 @@ public class KeyAgreementFragment extends BaseEventFragment
 		} catch (CameraException e) {
 			logCameraExceptionAndFinish(e);
 		}
-		startListening();
+	}
+
+	@Override
+	public void onStop() {
+		super.onStop();
+		try {
+			cameraView.stop();
+		} catch (CameraException e) {
+			logCameraExceptionAndFinish(e);
+		}
 	}
 
 	@Override
@@ -178,17 +144,42 @@ public class KeyAgreementFragment extends BaseEventFragment
 		cameraOverlay.invalidate();
 	}
 
-	@Override
-	public void onStop() {
-		super.onStop();
-		stopListening();
-		try {
-			cameraView.stop();
-		} catch (CameraException e) {
-			logCameraExceptionAndFinish(e);
+	@UiThread
+	private void onContactAddingStateChanged(ContactAddingState state) {
+		if (state instanceof ContactAddingState.KeyAgreementListening) {
+			Bitmap qrCode =
+					((ContactAddingState.KeyAgreementListening) state).qrCode;
+			qrCodeView.setQrCode(qrCode);
+		} else if (state instanceof QrCodeScanned) {
+			try {
+				cameraView.stop();
+			} catch (CameraException e) {
+				logCameraExceptionAndFinish(e);
+			}
+			cameraView.setVisibility(INVISIBLE);
+			statusView.setVisibility(VISIBLE);
+			status.setText(R.string.connecting_to_device);
+		} else if (state instanceof KeyAgreementWaiting) {
+			status.setText(R.string.waiting_for_contact_to_scan);
+		} else if (state instanceof KeyAgreementStarted) {
+			qrCodeView.setVisibility(INVISIBLE);
+			statusView.setVisibility(VISIBLE);
+			status.setText(R.string.authenticating_with_device);
+		} else if (state instanceof ContactExchangeStarted) {
+			statusView.setVisibility(VISIBLE);
+			status.setText(R.string.exchanging_contact_details);
+		} else if (state instanceof Failed) {
+			// the activity will replace this fragment with an error fragment
+			statusView.setVisibility(INVISIBLE);
+			cameraView.setVisibility(INVISIBLE);
 		}
 	}
 
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
 	@UiThread
 	private void logCameraExceptionAndFinish(CameraException e) {
 		logException(LOG, WARNING, e);
@@ -197,130 +188,6 @@ public class KeyAgreementFragment extends BaseEventFragment
 		finish();
 	}
 
-	@UiThread
-	private void startListening() {
-		KeyAgreementTask oldTask = task;
-		KeyAgreementTask newTask = keyAgreementTaskProvider.get();
-		task = newTask;
-		ioExecutor.execute(() -> {
-			if (oldTask != null) oldTask.stopListening();
-			newTask.listen();
-		});
-	}
-
-	@UiThread
-	private void stopListening() {
-		KeyAgreementTask oldTask = task;
-		ioExecutor.execute(() -> {
-			if (oldTask != null) oldTask.stopListening();
-		});
-	}
-
-	@UiThread
-	private void reset() {
-		// If we've stopped the camera view, restart it
-		if (gotRemotePayload) {
-			try {
-				cameraView.start();
-			} catch (CameraException e) {
-				logCameraExceptionAndFinish(e);
-				return;
-			}
-		}
-		statusView.setVisibility(INVISIBLE);
-		cameraView.setVisibility(VISIBLE);
-		gotRemotePayload = false;
-		gotLocalPayload = false;
-		startListening();
-	}
-
-	@UiThread
-	private void qrCodeScanned(String content) {
-		try {
-			byte[] payloadBytes = content.getBytes(ISO_8859_1);
-			if (LOG.isLoggable(INFO))
-				LOG.info("Remote payload is " + payloadBytes.length + " bytes");
-			Payload remotePayload = payloadParser.parse(payloadBytes);
-			gotRemotePayload = true;
-			cameraView.stop();
-			cameraView.setVisibility(INVISIBLE);
-			statusView.setVisibility(VISIBLE);
-			status.setText(R.string.connecting_to_device);
-			task.connectAndRunProtocol(remotePayload);
-		} catch (UnsupportedVersionException e) {
-			reset();
-			String msg;
-			if (e.isTooOld()) {
-				msg = getString(R.string.qr_code_too_old,
-						getString(R.string.app_name));
-			} else {
-				msg = getString(R.string.qr_code_too_new,
-						getString(R.string.app_name));
-			}
-			showNextFragment(ContactExchangeErrorFragment.newInstance(msg));
-		} catch (CameraException e) {
-			logCameraExceptionAndFinish(e);
-		} catch (IOException | IllegalArgumentException e) {
-			LOG.log(WARNING, "QR Code Invalid", e);
-			reset();
-			Toast.makeText(getActivity(), R.string.qr_code_invalid,
-					LENGTH_LONG).show();
-		}
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof KeyAgreementListeningEvent) {
-			KeyAgreementListeningEvent event = (KeyAgreementListeningEvent) e;
-			gotLocalPayload = true;
-			setQrCode(event.getLocalPayload());
-		}
-	}
-
-	@UiThread
-	private void onKeyAgreementStateChanged(KeyAgreementState state) {
-		if (state == WAITING) {
-			status.setText(R.string.waiting_for_contact_to_scan);
-		} else if (state == STARTED) {
-			qrCodeView.setVisibility(INVISIBLE);
-			statusView.setVisibility(VISIBLE);
-			status.setText(R.string.authenticating_with_device);
-		} else if (state == FINISHED) {
-			statusView.setVisibility(VISIBLE);
-			status.setText(R.string.exchanging_contact_details);
-		} else if (state == ABORTED || state == FAILED) {
-			reset();
-		}
-	}
-
-	private void setQrCode(Payload localPayload) {
-		Context context = getContext();
-		if (context == null) return;
-		DisplayMetrics dm = context.getResources().getDisplayMetrics();
-		ioExecutor.execute(() -> {
-			byte[] payloadBytes = payloadEncoder.encode(localPayload);
-			if (LOG.isLoggable(INFO)) {
-				LOG.info("Local payload is " + payloadBytes.length
-						+ " bytes");
-			}
-			// Use ISO 8859-1 to encode bytes directly as a string
-			String content = new String(payloadBytes, ISO_8859_1);
-			Bitmap qrCode = QrCodeUtils.createQrCode(dm, content);
-			runOnUiThreadUnlessDestroyed(
-					() -> qrCodeView.setQrCode(qrCode));
-		});
-	}
-
-	@Override
-	public void handleResult(Result result) {
-		runOnUiThreadUnlessDestroyed(() -> {
-			LOG.info("Got result from decoder");
-			// Ignore results until the KeyAgreementTask is ready
-			if (!gotLocalPayload) return;
-			if (!gotRemotePayload) qrCodeScanned(result.getText());
-		});
-	}
-
 	@Override
 	protected void finish() {
 		requireActivity().getSupportFragmentManager().popBackStack();

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

@@ -4,7 +4,6 @@ import android.hardware.Camera;
 import android.hardware.Camera.CameraInfo;
 import android.hardware.Camera.PreviewCallback;
 import android.hardware.Camera.Size;
-import android.os.AsyncTask;
 
 import com.google.zxing.BinaryBitmap;
 import com.google.zxing.LuminanceSource;
@@ -15,10 +14,12 @@ import com.google.zxing.Result;
 import com.google.zxing.common.HybridBinarizer;
 import com.google.zxing.qrcode.QRCodeReader;
 
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 
+import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import androidx.annotation.UiThread;
@@ -26,22 +27,23 @@ import androidx.annotation.UiThread;
 import static com.google.zxing.DecodeHintType.CHARACTER_SET;
 import static java.util.Collections.singletonMap;
 import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 
-@SuppressWarnings("deprecation")
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 
-	private static final Logger LOG =
-			Logger.getLogger(QrCodeDecoder.class.getName());
+	private static final Logger LOG = getLogger(QrCodeDecoder.class.getName());
 
+	private final Executor ioExecutor;
 	private final Reader reader = new QRCodeReader();
 	private final ResultCallback callback;
 
 	private Camera camera = null;
 	private int cameraIndex = 0;
 
-	QrCodeDecoder(ResultCallback callback) {
+	QrCodeDecoder(@IoExecutor Executor ioExecutor, ResultCallback callback) {
+		this.ioExecutor = ioExecutor;
 		this.callback = callback;
 	}
 
@@ -74,8 +76,7 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 				if (data.length == size.width * size.height * 3 / 2) {
 					CameraInfo info = new CameraInfo();
 					Camera.getCameraInfo(cameraIndex, info);
-					new DecoderTask(data, size.width, size.height,
-							info.orientation).execute();
+					decode(data, size.width, size.height, info.orientation);
 				} else {
 					// Camera parameters have changed - ask for a new preview
 					LOG.info("Preview size does not match camera parameters");
@@ -89,43 +90,23 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 		}
 	}
 
-	private class DecoderTask extends AsyncTask<Void, Void, Void> {
-
-		private final byte[] data;
-		private final int width, height, orientation;
-
-		private DecoderTask(byte[] data, int width, int height,
-				int orientation) {
-			this.data = data;
-			this.width = width;
-			this.height = height;
-			this.orientation = orientation;
-		}
-
-		@Override
-		protected Void doInBackground(Void... params) {
+	private void decode(byte[] data, int width, int height, int orientation) {
+		ioExecutor.execute(() -> {
 			BinaryBitmap bitmap = binarize(data, width, height, orientation);
 			Result result;
 			try {
 				result = reader.decode(bitmap,
 						singletonMap(CHARACTER_SET, "ISO8859_1"));
+				callback.onQrCodeDecoded(result);
 			} catch (ReaderException e) {
 				// No barcode found
-				return null;
 			} catch (RuntimeException e) {
 				LOG.warning("Invalid preview frame");
-				return null;
 			} finally {
 				reader.reset();
 			}
-			callback.handleResult(result);
-			return null;
-		}
-
-		@Override
-		protected void onPostExecute(Void result) {
-			askForPreviewFrame();
-		}
+		});
+		askForPreviewFrame();
 	}
 
 	private static BinaryBitmap binarize(byte[] data, int width, int height,
@@ -143,7 +124,7 @@ class QrCodeDecoder implements PreviewConsumer, PreviewCallback {
 
 	@NotNullByDefault
 	interface ResultCallback {
-
-		void handleResult(Result result);
+		@IoExecutor
+		void onQrCodeDecoded(Result result);
 	}
 }