Move Plugin related code from activity to ViewModel

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityComponent.java

@@ -21,6 +21,11 @@ import org.briarproject.briar.android.blog.RssFeedImportActivity;
 import org.briarproject.briar.android.blog.RssFeedManageActivity;
 import org.briarproject.briar.android.blog.WriteBlogPostActivity;
 import org.briarproject.briar.android.contact.ContactListFragment;
+import org.briarproject.briar.android.contact.add.nearby.ContactExchangeActivity;
+import org.briarproject.briar.android.contact.add.nearby.ContactExchangeErrorFragment;
+import org.briarproject.briar.android.contact.add.nearby.IntroFragment;
+import org.briarproject.briar.android.contact.add.nearby.KeyAgreementActivity;
+import org.briarproject.briar.android.contact.add.nearby.KeyAgreementFragment;
 import org.briarproject.briar.android.contact.add.remote.AddContactActivity;
 import org.briarproject.briar.android.contact.add.remote.LinkExchangeFragment;
 import org.briarproject.briar.android.contact.add.remote.NicknameFragment;
@@ -36,10 +41,6 @@ import org.briarproject.briar.android.fragment.ScreenFilterDialogFragment;
 import org.briarproject.briar.android.introduction.ContactChooserFragment;
 import org.briarproject.briar.android.introduction.IntroductionActivity;
 import org.briarproject.briar.android.introduction.IntroductionMessageFragment;
-import org.briarproject.briar.android.contact.add.nearby.ContactExchangeActivity;
-import org.briarproject.briar.android.contact.add.nearby.ContactExchangeErrorFragment;
-import org.briarproject.briar.android.contact.add.nearby.KeyAgreementActivity;
-import org.briarproject.briar.android.contact.add.nearby.KeyAgreementFragment;
 import org.briarproject.briar.android.login.ChangePasswordActivity;
 import org.briarproject.briar.android.login.OpenDatabaseFragment;
 import org.briarproject.briar.android.login.PasswordFragment;
@@ -208,6 +209,8 @@ public interface ActivityComponent {
 
 	void inject(FeedFragment fragment);
 
+	void inject(IntroFragment fragment);
+	
 	void inject(KeyAgreementFragment fragment);
 
 	void inject(LinkExchangeFragment fragment);

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

@@ -1,6 +1,7 @@
 package org.briarproject.briar.android.contact.add.nearby;
 
 import android.app.Application;
+import android.bluetooth.BluetoothAdapter;
 import android.graphics.Bitmap;
 import android.util.DisplayMetrics;
 import android.widget.Toast;
@@ -30,8 +31,14 @@ 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.BluetoothConstants;
+import org.briarproject.bramble.api.plugin.LanTcpConstants;
+import org.briarproject.bramble.api.plugin.Plugin;
+import org.briarproject.bramble.api.plugin.Plugin.State;
+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.briar.R;
 import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.ContactExchangeFinished;
 import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.ContactExchangeStarted;
@@ -40,6 +47,8 @@ import org.briarproject.briar.android.contact.add.nearby.ContactAddingState.KeyA
 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 org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 
 import java.io.IOException;
 import java.nio.charset.Charset;
@@ -55,12 +64,19 @@ import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
+import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE;
 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.api.plugin.Plugin.State.ACTIVE;
+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.briar.android.contact.add.nearby.ContactExchangeViewModel.BluetoothDecision.REFUSED;
+import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.BluetoothDecision.UNKNOWN;
 
 @NotNullByDefault
 class ContactExchangeViewModel extends AndroidViewModel
@@ -69,22 +85,80 @@ class ContactExchangeViewModel extends AndroidViewModel
 	private static final Logger LOG =
 			getLogger(ContactExchangeViewModel.class.getName());
 
+	enum BluetoothDecision {
+		/**
+		 * We haven't asked the user about Bluetooth discoverability.
+		 */
+		UNKNOWN,
+
+		/**
+		 * The device doesn't have a Bluetooth adapter.
+		 */
+		NO_ADAPTER,
+
+		/**
+		 * We're waiting for the user to accept or refuse discoverability.
+		 */
+		WAITING,
+
+		/**
+		 * The user has accepted discoverability.
+		 */
+		ACCEPTED,
+
+		/**
+		 * The user has refused discoverability.
+		 */
+		REFUSED
+	}
+
 	@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 PluginManager pluginManager;
 	private final PayloadEncoder payloadEncoder;
 	private final PayloadParser payloadParser;
 	private final Provider<KeyAgreementTask> keyAgreementTaskProvider;
 	private final ContactExchangeManager contactExchangeManager;
 	private final ConnectionManager connectionManager;
 
+	/**
+	 * Set to true when the continue button is clicked, and false when the QR
+	 * code fragment is shown. This prevents the QR code fragment from being
+	 * shown automatically before the continue button has been clicked.
+	 */
+	private final MutableLiveData<Boolean> wasContinueClicked =
+			new MutableLiveData<>(false);
+	private final MutableLiveEvent<Boolean> showQrCodeFragment =
+			new MutableLiveEvent<>();
+	private final MutableLiveEvent<TransportId> transportStateChanged =
+			new MutableLiveEvent<>();
 	private final MutableLiveData<ContactAddingState> state =
 			new MutableLiveData<>();
 
 	final QrCodeDecoder qrCodeDecoder;
 
+	@Nullable
+	private final BluetoothAdapter bt;
+	@Nullable
+	private final Plugin wifiPlugin, bluetoothPlugin;
+	// UiThread
+	BluetoothDecision bluetoothDecision = BluetoothDecision.UNKNOWN;
+
+	/**
+	 * Records whether we've enabled the wifi plugin so we don't enable it more
+	 * than once.
+	 */
+	private boolean hasEnabledWifi = false;
+
+	/**
+	 * Records whether we've enabled the Bluetooth plugin so we don't enable it
+	 * more than once.
+	 */
+	private boolean hasEnabledBluetooth = false;
+
 	@Nullable
 	private KeyAgreementTask task;
 	private volatile boolean gotLocalPayload = false, gotRemotePayload = false;
@@ -93,6 +167,7 @@ class ContactExchangeViewModel extends AndroidViewModel
 	ContactExchangeViewModel(Application app,
 			EventBus eventBus,
 			@IoExecutor Executor ioExecutor,
+			PluginManager pluginManager,
 			PayloadEncoder payloadEncoder,
 			PayloadParser payloadParser,
 			Provider<KeyAgreementTask> keyAgreementTaskProvider,
@@ -101,11 +176,15 @@ class ContactExchangeViewModel extends AndroidViewModel
 		super(app);
 		this.eventBus = eventBus;
 		this.ioExecutor = ioExecutor;
+		this.pluginManager = pluginManager;
 		this.payloadEncoder = payloadEncoder;
 		this.payloadParser = payloadParser;
 		this.keyAgreementTaskProvider = keyAgreementTaskProvider;
 		this.contactExchangeManager = contactExchangeManager;
 		this.connectionManager = connectionManager;
+		bt = BluetoothAdapter.getDefaultAdapter();
+		wifiPlugin = pluginManager.getPlugin(LanTcpConstants.ID);
+		bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
 		qrCodeDecoder = new QrCodeDecoder(ioExecutor, this);
 		eventBus.addListener(this);
 	}
@@ -117,12 +196,95 @@ class ContactExchangeViewModel extends AndroidViewModel
 		stopListening();
 	}
 
+	@UiThread
+	void onContinueClicked() {
+		if (bluetoothDecision == REFUSED) {
+			bluetoothDecision = UNKNOWN; // Ask again
+		}
+		wasContinueClicked.setValue(true);
+	}
+
+	@UiThread
+	boolean isBluetoothSupported() {
+		return bt != null && bluetoothPlugin != null;
+	}
+
+	@UiThread
+	boolean isWifiReady() {
+		if (wifiPlugin == null) return true; // Continue without wifi
+		State state = wifiPlugin.getState();
+		// Wait for plugin to become enabled
+		return state == ACTIVE || state == INACTIVE;
+	}
+
+	@UiThread
+	boolean isBluetoothReady() {
+		if (bt == null || bluetoothPlugin == null) {
+			// Continue without Bluetooth
+			return true;
+		}
+		if (bluetoothDecision == BluetoothDecision.UNKNOWN ||
+				bluetoothDecision == BluetoothDecision.WAITING ||
+				bluetoothDecision == BluetoothDecision.REFUSED) {
+			// Wait for user to accept
+			return false;
+		}
+		if (bt.getScanMode() != SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
+			// Wait for adapter to become discoverable
+			return false;
+		}
+		// Wait for plugin to become active
+		return bluetoothPlugin.getState() == ACTIVE;
+	}
+
+	@UiThread
+	void enableWifiIfWeShould() {
+		if (hasEnabledWifi) return;
+		if (wifiPlugin == null) return;
+		State state = wifiPlugin.getState();
+		if (state == STARTING_STOPPING || state == DISABLED) {
+			LOG.info("Enabling wifi plugin");
+			hasEnabledWifi = true;
+			pluginManager.setPluginEnabled(LanTcpConstants.ID, true);
+		}
+	}
+
+	@UiThread
+	void enableBluetoothIfWeShould() {
+		if (bluetoothDecision != BluetoothDecision.ACCEPTED) return;
+		if (hasEnabledBluetooth) return;
+		if (bluetoothPlugin == null || !isBluetoothSupported()) return;
+		State state = bluetoothPlugin.getState();
+		if (state == STARTING_STOPPING || state == DISABLED) {
+			LOG.info("Enabling Bluetooth plugin");
+			hasEnabledBluetooth = true;
+			pluginManager.setPluginEnabled(BluetoothConstants.ID, true);
+		}
+	}
+
+	@UiThread
+	void startAddingContact() {
+		// If we return to the intro fragment, the continue button needs to be
+		// clicked again before showing the QR code fragment
+		wasContinueClicked.setValue(false);
+		// If we return to the intro fragment, ask for Bluetooth
+		// discoverability again before showing the QR code fragment
+		bluetoothDecision = UNKNOWN;
+		// If we return to the intro fragment, we may need to enable wifi and
+		// Bluetooth again
+		hasEnabledWifi = false;
+		hasEnabledBluetooth = false;
+		// start to listen with a KeyAgreementTask
+		startListening();
+		showQrCodeFragment.setEvent(true);
+	}
+
 	/**
 	 * 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() {
+	private void startListening() {
 		KeyAgreementTask oldTask = task;
 		KeyAgreementTask newTask = keyAgreementTaskProvider.get();
 		task = newTask;
@@ -142,7 +304,20 @@ class ContactExchangeViewModel extends AndroidViewModel
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof KeyAgreementListeningEvent) {
+		if (e instanceof TransportStateEvent) {
+			TransportStateEvent t = (TransportStateEvent) e;
+			if (t.getTransportId().equals(BluetoothConstants.ID)) {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Bluetooth state changed to " + t.getState());
+				}
+				transportStateChanged.setEvent(t.getTransportId());
+			} else if (t.getTransportId().equals(LanTcpConstants.ID)) {
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Wifi state changed to " + t.getState());
+				}
+				transportStateChanged.setEvent(t.getTransportId());
+			}
+		} else if (e instanceof KeyAgreementListeningEvent) {
 			LOG.info("KeyAgreementListeningEvent received");
 			KeyAgreementListeningEvent event = (KeyAgreementListeningEvent) e;
 			onLocalPayloadReceived(event.getLocalPayload());
@@ -257,6 +432,22 @@ class ContactExchangeViewModel extends AndroidViewModel
 		}
 	}
 
+	LiveData<Boolean> getWasContinueClicked() {
+		return wasContinueClicked;
+	}
+
+	/**
+	 * Receives an event when the transport state of the WiFi or Bluetooth
+	 * plugins changes.
+	 */
+	LiveEvent<TransportId> getTransportStateChanged() {
+		return transportStateChanged;
+	}
+
+	LiveEvent<Boolean> getShowQrCodeFragment() {
+		return showQrCodeFragment;
+	}
+
 	LiveData<ContactAddingState> getState() {
 		return state;
 	}

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

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.contact.add.nearby;
 
-import android.content.Context;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -10,9 +9,13 @@ import android.widget.ScrollView;
 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.fragment.BaseFragment;
 
 import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.lifecycle.ViewModelProvider;
 
 import static android.view.View.FOCUS_DOWN;
 
@@ -20,33 +23,27 @@ import static android.view.View.FOCUS_DOWN;
 @ParametersNotNullByDefault
 public class IntroFragment extends BaseFragment {
 
-	interface IntroScreenSeenListener {
-		void showNextScreen();
-	}
-
 	public static final String TAG = IntroFragment.class.getName();
 
-	private IntroScreenSeenListener screenSeenListener;
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private ContactExchangeViewModel viewModel;
+
 	private ScrollView scrollView;
 
 	public static IntroFragment newInstance() {
-
 		Bundle args = new Bundle();
-
 		IntroFragment fragment = new IntroFragment();
 		fragment.setArguments(args);
 		return fragment;
 	}
 
 	@Override
-	public void onAttach(Context context) {
-		super.onAttach(context);
-		screenSeenListener = (IntroScreenSeenListener) context;
-	}
-
-	@Override
-	public String getUniqueTag() {
-		return TAG;
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(ContactExchangeViewModel.class);
 	}
 
 	@Nullable
@@ -59,7 +56,7 @@ public class IntroFragment extends BaseFragment {
 				false);
 		scrollView = v.findViewById(R.id.scrollView);
 		View button = v.findViewById(R.id.continueButton);
-		button.setOnClickListener(view -> screenSeenListener.showNextScreen());
+		button.setOnClickListener(view -> viewModel.onContinueClicked());
 		return v;
 	}
 
@@ -69,4 +66,9 @@ public class IntroFragment extends BaseFragment {
 		scrollView.post(() -> scrollView.fullScroll(FOCUS_DOWN));
 	}
 
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
 }

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

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.contact.add.nearby;
 
-import android.bluetooth.BluetoothAdapter;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
@@ -8,21 +7,12 @@ import android.content.IntentFilter;
 import android.os.Bundle;
 import android.view.MenuItem;
 
-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.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.plugin.BluetoothConstants;
-import org.briarproject.bramble.api.plugin.LanTcpConstants;
-import org.briarproject.bramble.api.plugin.Plugin;
-import org.briarproject.bramble.api.plugin.Plugin.State;
-import org.briarproject.bramble.api.plugin.PluginManager;
-import org.briarproject.bramble.api.plugin.event.TransportStateEvent;
 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.IntroFragment.IntroScreenSeenListener;
+import org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.BluetoothDecision;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
 
@@ -43,51 +33,21 @@ import static android.Manifest.permission.ACCESS_FINE_LOCATION;
 import static android.Manifest.permission.CAMERA;
 import static android.bluetooth.BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE;
 import static android.bluetooth.BluetoothAdapter.ACTION_SCAN_MODE_CHANGED;
-import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
 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.bramble.api.nullsafety.NullSafety.requireNonNull;
-import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
-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.briar.android.activity.RequestCodes.REQUEST_BLUETOOTH_DISCOVERABLE;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PERMISSION_CAMERA_LOCATION;
+import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.BluetoothDecision.ACCEPTED;
+import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.BluetoothDecision.REFUSED;
+import static org.briarproject.briar.android.contact.add.nearby.ContactExchangeViewModel.BluetoothDecision.UNKNOWN;
 import static org.briarproject.briar.android.util.UiUtils.getGoToSettingsListener;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public abstract class KeyAgreementActivity extends BriarActivity implements
-		BaseFragmentListener, IntroScreenSeenListener, EventListener {
-
-	private enum BluetoothDecision {
-		/**
-		 * We haven't asked the user about Bluetooth discoverability.
-		 */
-		UNKNOWN,
-
-		/**
-		 * The device doesn't have a Bluetooth adapter.
-		 */
-		NO_ADAPTER,
-
-		/**
-		 * We're waiting for the user to accept or refuse discoverability.
-		 */
-		WAITING,
-
-		/**
-		 * The user has accepted discoverability.
-		 */
-		ACCEPTED,
-
-		/**
-		 * The user has refused discoverability.
-		 */
-		REFUSED
-	}
+public abstract class KeyAgreementActivity extends BriarActivity
+		implements BaseFragmentListener {
 
 	private enum Permission {
 		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
@@ -96,16 +56,9 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	private static final Logger LOG =
 			getLogger(KeyAgreementActivity.class.getName());
 
-
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
 
-	@Inject
-	EventBus eventBus;
-
-	@Inject
-	PluginManager pluginManager;
-
 	protected ContactExchangeViewModel viewModel;
 
 	/**
@@ -116,31 +69,9 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	 */
 	private boolean isResumed = false;
 
-	/**
-	 * Set to true when the continue button is clicked, and false when the QR
-	 * code fragment is shown. This prevents the QR code fragment from being
-	 * shown automatically before the continue button has been clicked.
-	 */
-	private boolean continueClicked = false;
-
-	/**
-	 * Records whether we've enabled the wifi plugin so we don't enable it more
-	 * than once.
-	 */
-	private boolean hasEnabledWifi = false;
-
-	/**
-	 * Records whether we've enabled the Bluetooth plugin so we don't enable it
-	 * more than once.
-	 */
-	private boolean hasEnabledBluetooth = false;
-
 	private Permission cameraPermission = Permission.UNKNOWN;
 	private Permission locationPermission = Permission.UNKNOWN;
-	private BluetoothDecision bluetoothDecision = BluetoothDecision.UNKNOWN;
 	private BroadcastReceiver bluetoothReceiver = null;
-	private Plugin wifiPlugin = null, bluetoothPlugin = null;
-	private BluetoothAdapter bt = null;
 
 	@Override
 	public void injectActivity(ActivityComponent component) {
@@ -162,9 +93,42 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		IntentFilter filter = new IntentFilter(ACTION_SCAN_MODE_CHANGED);
 		bluetoothReceiver = new BluetoothStateReceiver();
 		registerReceiver(bluetoothReceiver, filter);
-		wifiPlugin = pluginManager.getPlugin(LanTcpConstants.ID);
-		bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
-		bt = BluetoothAdapter.getDefaultAdapter();
+		viewModel.getWasContinueClicked().observe(this, clicked -> {
+			if (clicked && checkPermissions()) showQrCodeFragmentIfAllowed();
+		});
+		viewModel.getTransportStateChanged().observeEvent(this,
+				t -> showQrCodeFragmentIfAllowed());
+		viewModel.getShowQrCodeFragment().observeEvent(this, show -> {
+			if (show) showQrCodeFragment();
+		});
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		// Permissions may have been granted manually while we were stopped
+		cameraPermission = Permission.UNKNOWN;
+		locationPermission = Permission.UNKNOWN;
+	}
+
+	@Override
+	protected void onPostResume() {
+		super.onPostResume();
+		isResumed = true;
+		// Workaround for
+		// https://code.google.com/p/android/issues/detail?id=190966
+		showQrCodeFragmentIfAllowed();
+	}
+
+	@Override
+	protected void onPause() {
+		super.onPause();
+		isResumed = false;
+	}
+
+	@Override
+	protected void onStop() {
+		super.onStop();
 	}
 
 	@Override
@@ -182,45 +146,22 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		return super.onOptionsItemSelected(item);
 	}
 
-	@Override
-	public void onStart() {
-		super.onStart();
-		eventBus.addListener(this);
-		// Permissions may have been granted manually while we were stopped
-		cameraPermission = Permission.UNKNOWN;
-		locationPermission = Permission.UNKNOWN;
-	}
-
-	@Override
-	protected void onPostResume() {
-		super.onPostResume();
-		isResumed = true;
-		// Workaround for
-		// https://code.google.com/p/android/issues/detail?id=190966
-		showQrCodeFragmentIfAllowed();
-	}
-
 	@SuppressWarnings("StatementWithEmptyBody")
 	private void showQrCodeFragmentIfAllowed() {
+		boolean continueClicked = // never set to null
+				requireNonNull(viewModel.getWasContinueClicked().getValue());
 		if (isResumed && continueClicked && areEssentialPermissionsGranted()) {
-			if (isWifiReady() && isBluetoothReady()) {
+			if (viewModel.isWifiReady() && viewModel.isBluetoothReady()) {
 				LOG.info("Wifi and Bluetooth are ready");
-				viewModel.startListening();
-				showQrCodeFragment();
+				viewModel.startAddingContact();
 			} else {
-				if (shouldEnableWifi()) {
-					LOG.info("Enabling wifi plugin");
-					hasEnabledWifi = true;
-					pluginManager.setPluginEnabled(LanTcpConstants.ID, true);
-				}
-				if (bluetoothDecision == BluetoothDecision.UNKNOWN) {
+				viewModel.enableWifiIfWeShould();
+				if (viewModel.bluetoothDecision == UNKNOWN) {
 					requestBluetoothDiscoverable();
-				} else if (bluetoothDecision == BluetoothDecision.REFUSED) {
+				} else if (viewModel.bluetoothDecision == REFUSED) {
 					// Ask again when the user clicks "continue"
-				} else if (shouldEnableBluetooth()) {
-					LOG.info("Enabling Bluetooth plugin");
-					hasEnabledBluetooth = true;
-					pluginManager.setPluginEnabled(BluetoothConstants.ID, true);
+				} else {
+					viewModel.enableBluetoothIfWeShould();
 				}
 			}
 		}
@@ -229,119 +170,42 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	private boolean areEssentialPermissionsGranted() {
 		return cameraPermission == Permission.GRANTED &&
 				(SDK_INT < 23 || locationPermission == Permission.GRANTED ||
-						!isBluetoothSupported());
-	}
-
-	private boolean isBluetoothSupported() {
-		return bt != null && bluetoothPlugin != null;
-	}
-
-	private boolean isWifiReady() {
-		if (wifiPlugin == null) return true; // Continue without wifi
-		State state = wifiPlugin.getState();
-		// Wait for plugin to become enabled
-		return state == ACTIVE || state == INACTIVE;
-	}
-
-	private boolean isBluetoothReady() {
-		if (!isBluetoothSupported()) {
-			// Continue without Bluetooth
-			return true;
-		}
-		if (bluetoothDecision == BluetoothDecision.UNKNOWN ||
-				bluetoothDecision == BluetoothDecision.WAITING ||
-				bluetoothDecision == BluetoothDecision.REFUSED) {
-			// Wait for user to accept
-			return false;
-		}
-		if (bt.getScanMode() != SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
-			// Wait for adapter to become discoverable
-			return false;
-		}
-		// Wait for plugin to become active
-		return bluetoothPlugin.getState() == ACTIVE;
-	}
-
-	private boolean shouldEnableWifi() {
-		if (hasEnabledWifi) return false;
-		if (wifiPlugin == null) return false;
-		State state = wifiPlugin.getState();
-		return state == STARTING_STOPPING || state == DISABLED;
+						!viewModel.isBluetoothSupported());
 	}
 
 	private void requestBluetoothDiscoverable() {
-		if (!isBluetoothSupported()) {
-			bluetoothDecision = BluetoothDecision.NO_ADAPTER;
+		if (!viewModel.isBluetoothSupported()) {
+			viewModel.bluetoothDecision = BluetoothDecision.NO_ADAPTER;
 			showQrCodeFragmentIfAllowed();
 		} else {
 			Intent i = new Intent(ACTION_REQUEST_DISCOVERABLE);
 			if (i.resolveActivity(getPackageManager()) != null) {
 				LOG.info("Asking for Bluetooth discoverability");
-				bluetoothDecision = BluetoothDecision.WAITING;
+				viewModel.bluetoothDecision = BluetoothDecision.WAITING;
 				startActivityForResult(i, REQUEST_BLUETOOTH_DISCOVERABLE);
 			} else {
-				bluetoothDecision = BluetoothDecision.NO_ADAPTER;
+				viewModel.bluetoothDecision = BluetoothDecision.NO_ADAPTER;
 				showQrCodeFragmentIfAllowed();
 			}
 		}
 	}
 
-	private boolean shouldEnableBluetooth() {
-		if (bluetoothDecision != BluetoothDecision.ACCEPTED) return false;
-		if (hasEnabledBluetooth) return false;
-		if (!isBluetoothSupported()) return false;
-		State state = bluetoothPlugin.getState();
-		return state == STARTING_STOPPING || state == DISABLED;
-	}
-
-	@Override
-	protected void onPause() {
-		super.onPause();
-		isResumed = false;
-	}
-
-	@Override
-	protected void onStop() {
-		super.onStop();
-		eventBus.removeListener(this);
-	}
-
-	@Override
-	public void showNextScreen() {
-		continueClicked = true;
-		if (bluetoothDecision == BluetoothDecision.REFUSED) {
-			bluetoothDecision = BluetoothDecision.UNKNOWN; // Ask again
-		}
-		if (checkPermissions()) showQrCodeFragmentIfAllowed();
-	}
-
 	@Override
 	public void onActivityResult(int request, int result,
 			@Nullable Intent data) {
 		if (request == REQUEST_BLUETOOTH_DISCOVERABLE) {
 			if (result == RESULT_CANCELED) {
 				LOG.info("Bluetooth discoverability was refused");
-				bluetoothDecision = BluetoothDecision.REFUSED;
+				viewModel.bluetoothDecision = REFUSED;
 			} else {
 				LOG.info("Bluetooth discoverability was accepted");
-				bluetoothDecision = BluetoothDecision.ACCEPTED;
+				viewModel.bluetoothDecision = ACCEPTED;
 			}
 			showQrCodeFragmentIfAllowed();
 		} else super.onActivityResult(request, result, data);
 	}
 
 	private void showQrCodeFragment() {
-		// If we return to the intro fragment, the continue button needs to be
-		// clicked again before showing the QR code fragment
-		continueClicked = false;
-		// If we return to the intro fragment, ask for Bluetooth
-		// discoverability again before showing the QR code fragment
-		bluetoothDecision = BluetoothDecision.UNKNOWN;
-		// If we return to the intro fragment, we may need to enable wifi and
-		// Bluetooth again
-		hasEnabledWifi = false;
-		hasEnabledBluetooth = false;
-
 		// FIXME #824
 		FragmentManager fm = getSupportFragmentManager();
 		if (fm.findFragmentByTag(KeyAgreementFragment.TAG) == null) {
@@ -362,7 +226,7 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 					R.string.permission_camera_denied_body);
 			return false;
 		}
-		if (isBluetoothSupported() &&
+		if (viewModel.isBluetoothSupported() &&
 				locationPermission == Permission.PERMANENTLY_DENIED) {
 			showDenialDialog(R.string.permission_location_title,
 					R.string.permission_location_denied_body);
@@ -406,7 +270,7 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 
 	private void requestPermissions() {
 		String[] permissions;
-		if (isBluetoothSupported()) {
+		if (viewModel.isBluetoothSupported()) {
 			permissions = new String[] {CAMERA, ACCESS_FINE_LOCATION};
 		} else {
 			permissions = new String[] {CAMERA};
@@ -430,7 +294,7 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		} else {
 			cameraPermission = Permission.PERMANENTLY_DENIED;
 		}
-		if (isBluetoothSupported()) {
+		if (viewModel.isBluetoothSupported()) {
 			if (gotPermission(ACCESS_FINE_LOCATION, permissions,
 					grantResults)) {
 				locationPermission = Permission.GRANTED;
@@ -463,24 +327,6 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 				permission);
 	}
 
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof TransportStateEvent) {
-			TransportStateEvent t = (TransportStateEvent) e;
-			if (t.getTransportId().equals(BluetoothConstants.ID)) {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info("Bluetooth state changed to " + t.getState());
-				}
-				showQrCodeFragmentIfAllowed();
-			} else if (t.getTransportId().equals(LanTcpConstants.ID)) {
-				if (LOG.isLoggable(INFO)) {
-					LOG.info("Wifi state changed to " + t.getState());
-				}
-				showQrCodeFragmentIfAllowed();
-			}
-		}
-	}
-
 	private class BluetoothStateReceiver extends BroadcastReceiver {
 
 		@Override