Merge branch '1961-connect-via-bt-ui' into 'master'

Simple version of Connect via Bluetooth UI

See merge request briar/briar!1398

bramble-api/src/main/java/org/briarproject/bramble/api/FeatureFlags.java

@@ -10,4 +10,6 @@ public interface FeatureFlags {
 	boolean shouldEnableProfilePictures();
 
 	boolean shouldEnableDisappearingMessages();
+
+	boolean shouldEnableConnectViaBluetooth();
 }

bramble-core/src/test/java/org/briarproject/bramble/test/BrambleCoreIntegrationTestModule.java

@@ -38,6 +38,11 @@ public class BrambleCoreIntegrationTestModule {
 			public boolean shouldEnableDisappearingMessages() {
 				return true;
 			}
+
+			@Override
+			public boolean shouldEnableConnectViaBluetooth() {
+				return true;
+			}
 		};
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -298,6 +298,11 @@ public class AppModule {
 			public boolean shouldEnableDisappearingMessages() {
 				return IS_DEBUG_BUILD;
 			}
+
+			@Override
+			public boolean shouldEnableConnectViaBluetooth() {
+				return IS_DEBUG_BUILD;
+			}
 		};
 	}
 }

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

@@ -28,6 +28,7 @@ import org.briarproject.briar.android.contact.add.remote.LinkExchangeFragment;
 import org.briarproject.briar.android.contact.add.remote.NicknameFragment;
 import org.briarproject.briar.android.contact.add.remote.PendingContactListActivity;
 import org.briarproject.briar.android.conversation.AliasDialogFragment;
+import org.briarproject.briar.android.conversation.BluetoothConnecterDialogFragment;
 import org.briarproject.briar.android.conversation.ConversationActivity;
 import org.briarproject.briar.android.conversation.ConversationSettingsDialog;
 import org.briarproject.briar.android.conversation.ImageActivity;
@@ -236,4 +237,6 @@ public interface ActivityComponent {
 
 	void inject(ConversationSettingsDialog dialog);
 
+	void inject(
+			BluetoothConnecterDialogFragment bluetoothConnecterDialogFragment);
 }

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

@@ -1,10 +1,6 @@
 package org.briarproject.briar.android.contact.add.nearby;
 
-import android.content.ActivityNotFoundException;
 import android.content.Context;
-import android.content.Intent;
-import android.location.LocationManager;
-import android.widget.Toast;
 
 import org.briarproject.briar.R;
 
@@ -19,11 +15,11 @@ import static android.Manifest.permission.ACCESS_FINE_LOCATION;
 import static android.Manifest.permission.CAMERA;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
 import static android.os.Build.VERSION.SDK_INT;
-import static android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS;
-import static android.widget.Toast.LENGTH_LONG;
 import static androidx.core.app.ActivityCompat.shouldShowRequestPermissionRationale;
 import static androidx.core.content.ContextCompat.checkSelfPermission;
 import static org.briarproject.briar.android.util.UiUtils.getGoToSettingsListener;
+import static org.briarproject.briar.android.util.UiUtils.isLocationEnabled;
+import static org.briarproject.briar.android.util.UiUtils.showLocationDialog;
 
 class AddNearbyContactPermissionManager {
 
@@ -51,19 +47,6 @@ class AddNearbyContactPermissionManager {
 		locationPermission = Permission.UNKNOWN;
 	}
 
-	/**
-	 * @return true if location is enabled,
-	 * or it isn't required due to this being a SDK < 28 device.
-	 */
-	static boolean isLocationEnabled(Context ctx) {
-		if (SDK_INT >= 28) {
-			LocationManager lm = ctx.getSystemService(LocationManager.class);
-			return lm.isLocationEnabled();
-		} else {
-			return true;
-		}
-	}
-
 	static boolean areEssentialPermissionsGranted(Context ctx,
 			boolean isBluetoothSupported) {
 		int ok = PERMISSION_GRANTED;
@@ -106,7 +89,7 @@ class AddNearbyContactPermissionManager {
 		} else if (locationPermission == Permission.SHOW_RATIONALE) {
 			showRationale(R.string.permission_location_title,
 					R.string.permission_location_request_body);
-		} else if (isLocationEnabled(ctx)) {
+		} else if (locationEnabled) {
 			requestPermissions();
 		} else {
 			showLocationDialog(ctx);
@@ -135,25 +118,6 @@ class AddNearbyContactPermissionManager {
 		builder.show();
 	}
 
-	private static void showLocationDialog(Context ctx) {
-		AlertDialog.Builder builder =
-				new AlertDialog.Builder(ctx, R.style.BriarDialogTheme);
-		builder.setTitle(R.string.permission_location_setting_title);
-		builder.setMessage(R.string.permission_location_setting_body);
-		builder.setNegativeButton(R.string.cancel, null);
-		builder.setPositiveButton(R.string.permission_location_setting_button,
-				(dialog, which) -> {
-					Intent i = new Intent(ACTION_LOCATION_SOURCE_SETTINGS);
-					try {
-						ctx.startActivity(i);
-					} catch (ActivityNotFoundException e) {
-						Toast.makeText(ctx, R.string.error_start_activity,
-								LENGTH_LONG).show();
-					}
-				});
-		builder.show();
-	}
-
 	private void requestPermissions() {
 		String[] permissions;
 		if (isBluetoothSupported) {

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

@@ -82,11 +82,11 @@ 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.AddNearbyContactPermissionManager.areEssentialPermissionsGranted;
-import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactPermissionManager.isLocationEnabled;
 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;
 import static org.briarproject.briar.android.contact.add.nearby.AddNearbyContactViewModel.BluetoothDecision.UNKNOWN;
 import static org.briarproject.briar.android.util.UiUtils.handleException;
+import static org.briarproject.briar.android.util.UiUtils.isLocationEnabled;
 
 @NotNullByDefault
 class AddNearbyContactViewModel extends AndroidViewModel

briar-android/src/main/java/org/briarproject/briar/android/conversation/BluetoothConnecter.java

@@ -0,0 +1,182 @@
+package org.briarproject.briar.android.conversation;
+
+import android.app.Activity;
+import android.app.Application;
+import android.bluetooth.BluetoothAdapter;
+import android.content.Context;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.connection.ConnectionRegistry;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.plugin.BluetoothConstants;
+import org.briarproject.bramble.api.plugin.Plugin;
+import org.briarproject.bramble.api.plugin.PluginManager;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.contact.ContactItem;
+
+import java.util.Random;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.annotation.Nullable;
+import androidx.annotation.StringRes;
+import androidx.annotation.UiThread;
+import androidx.appcompat.app.AlertDialog;
+
+import static android.Manifest.permission.ACCESS_FINE_LOCATION;
+import static android.os.Build.VERSION.SDK_INT;
+import static androidx.core.app.ActivityCompat.shouldShowRequestPermissionRationale;
+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.util.UiUtils.getGoToSettingsListener;
+import static org.briarproject.briar.android.util.UiUtils.isLocationEnabled;
+import static org.briarproject.briar.android.util.UiUtils.showLocationDialog;
+
+class BluetoothConnecter {
+
+	private final Logger LOG = getLogger(BluetoothConnecter.class.getName());
+
+	private enum Permission {
+		UNKNOWN, GRANTED, SHOW_RATIONALE, PERMANENTLY_DENIED
+	}
+
+	private final Application app;
+	private final PluginManager pluginManager;
+	private final Executor ioExecutor;
+	private final AndroidExecutor androidExecutor;
+	private final ConnectionRegistry connectionRegistry;
+	private final BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
+
+	private volatile Plugin bluetoothPlugin;
+
+	private Permission locationPermission = Permission.UNKNOWN;
+
+	@Inject
+	BluetoothConnecter(Application app,
+			PluginManager pluginManager,
+			@IoExecutor Executor ioExecutor,
+			AndroidExecutor androidExecutor,
+			ConnectionRegistry connectionRegistry) {
+		this.app = app;
+		this.pluginManager = pluginManager;
+		this.ioExecutor = ioExecutor;
+		this.androidExecutor = androidExecutor;
+		this.bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
+		this.connectionRegistry = connectionRegistry;
+	}
+
+	boolean isConnectedViaBluetooth(ContactId contactId) {
+		return connectionRegistry.isConnected(contactId, BluetoothConstants.ID);
+	}
+
+	boolean isDiscovering() {
+		// TODO bluetoothPlugin.isDiscovering()
+		return false;
+	}
+
+	/**
+	 * Call this when the using activity or fragment starts,
+	 * because permissions might have changed while it was stopped.
+	 */
+	void reset() {
+		locationPermission = Permission.UNKNOWN;
+		// When this class is instantiated before we are logged in
+		// (like when returning to a killed activity), bluetoothPlugin would be
+		// null and we consider bluetooth not supported. So reset here.
+		bluetoothPlugin = pluginManager.getPlugin(BluetoothConstants.ID);
+	}
+
+	@UiThread
+	void onLocationPermissionResult(Activity activity,
+			@Nullable Boolean result) {
+		if (result != null && result) {
+			locationPermission = Permission.GRANTED;
+		} else if (shouldShowRequestPermissionRationale(activity,
+				ACCESS_FINE_LOCATION)) {
+			locationPermission = Permission.SHOW_RATIONALE;
+		} else {
+			locationPermission = Permission.PERMANENTLY_DENIED;
+		}
+	}
+
+	boolean isBluetoothNotSupported() {
+		return bt == null || bluetoothPlugin == null;
+	}
+
+	boolean areRequirementsFulfilled(Context ctx,
+			ActivityResultLauncher<String> permissionRequest,
+			Runnable onLocationDenied) {
+		boolean permissionGranted =
+				SDK_INT < 23 || locationPermission == Permission.GRANTED;
+		boolean locationEnabled = isLocationEnabled(ctx);
+		if (permissionGranted && locationEnabled) return true;
+
+		if (locationPermission == Permission.PERMANENTLY_DENIED) {
+			showDenialDialog(ctx, onLocationDenied);
+		} else if (locationPermission == Permission.SHOW_RATIONALE) {
+			showRationale(ctx, permissionRequest);
+		} else if (!locationEnabled) {
+			showLocationDialog(ctx);
+		}
+		return false;
+	}
+
+	private void showDenialDialog(Context ctx, Runnable onLocationDenied) {
+		new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
+				.setTitle(R.string.permission_location_title)
+				.setMessage(R.string.permission_location_denied_body)
+				.setPositiveButton(R.string.ok, getGoToSettingsListener(ctx))
+				.setNegativeButton(R.string.cancel, (v, d) ->
+						onLocationDenied.run())
+				.show();
+	}
+
+	private void showRationale(Context ctx,
+			ActivityResultLauncher<String> permissionRequest) {
+		new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
+				.setTitle(R.string.permission_location_title)
+				.setMessage(R.string.permission_location_request_body)
+				.setPositiveButton(R.string.ok, (dialog, which) ->
+						permissionRequest.launch(ACCESS_FINE_LOCATION))
+				.show();
+	}
+
+	@UiThread
+	void onBluetoothDiscoverable(ContactItem contact) {
+		connect(contact.getContact().getId());
+	}
+
+	private void connect(ContactId contactId) {
+		// TODO
+		//  * enable bluetooth connections setting, if not enabled
+		//  * wait for plugin to become active
+		ioExecutor.execute(() -> {
+			Random r = new Random();
+			try {
+				showToast(R.string.toast_connect_via_bluetooth_start);
+				// TODO do real work here
+				Thread.sleep(r.nextInt(3000) + 3000);
+				if (r.nextBoolean()) {
+					showToast(R.string.toast_connect_via_bluetooth_success);
+				} else {
+					showToast(R.string.toast_connect_via_bluetooth_error);
+				}
+			} catch (InterruptedException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	private void showToast(@StringRes int res) {
+		androidExecutor.runOnUiThread(() ->
+				Toast.makeText(app, res, Toast.LENGTH_LONG).show()
+		);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/BluetoothConnecterDialogFragment.java

@@ -0,0 +1,151 @@
+package org.briarproject.briar.android.conversation;
+
+import android.app.Activity;
+import android.app.Dialog;
+import android.content.Context;
+import android.os.Bundle;
+import android.view.View;
+import android.widget.Button;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.contact.ContactId;
+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.BaseActivity;
+import org.briarproject.briar.android.contact.ContactItem;
+import org.briarproject.briar.android.util.RequestBluetoothDiscoverable;
+
+import javax.inject.Inject;
+
+import androidx.activity.result.ActivityResultLauncher;
+import androidx.activity.result.contract.ActivityResultContracts.RequestPermission;
+import androidx.annotation.Nullable;
+import androidx.annotation.StringRes;
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.DialogFragment;
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.Manifest.permission.ACCESS_FINE_LOCATION;
+import static android.content.DialogInterface.BUTTON_POSITIVE;
+import static android.widget.Toast.LENGTH_LONG;
+import static java.util.Objects.requireNonNull;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class BluetoothConnecterDialogFragment extends DialogFragment {
+
+	final static String TAG = BluetoothConnecterDialogFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private ConversationViewModel viewModel;
+	private BluetoothConnecter bluetoothConnecter;
+
+	private final ActivityResultLauncher<Integer> bluetoothDiscoverableRequest =
+			registerForActivityResult(new RequestBluetoothDiscoverable(),
+					this::onBluetoothDiscoverable);
+	private final ActivityResultLauncher<String> permissionRequest =
+			registerForActivityResult(new RequestPermission(),
+					this::onPermissionRequestResult);
+
+	@Override
+	public void onAttach(Context ctx) {
+		super.onAttach(ctx);
+		((BaseActivity) requireActivity()).getActivityComponent().inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(ConversationViewModel.class);
+		bluetoothConnecter = viewModel.getBluetoothConnecter();
+	}
+
+	@Override
+	public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
+		Context ctx = requireContext();
+		return new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
+				.setTitle(R.string.dialog_title_connect_via_bluetooth)
+				.setMessage(R.string.dialog_message_connect_via_bluetooth)
+				// actual listener gets set in onResume()
+				.setPositiveButton(R.string.start, null)
+				.setNegativeButton(R.string.cancel, null)
+				.setCancelable(false) // keep it open until dismissed
+				.create();
+	}
+
+	@Override
+	public void onStart() {
+		super.onStart();
+		bluetoothConnecter.reset();
+		if (bluetoothConnecter.isBluetoothNotSupported()) {
+			showToast(R.string.toast_connect_via_bluetooth_error);
+			dismiss();
+			return;
+		}
+		// MenuItem only gets enabled after contactItem has loaded
+		ContactItem contact =
+				requireNonNull(viewModel.getContactItem().getValue());
+		ContactId contactId = contact.getContact().getId();
+		if (bluetoothConnecter.isConnectedViaBluetooth(contactId)) {
+			showToast(R.string.toast_connect_via_bluetooth_success);
+			dismiss();
+			return;
+		}
+		if (bluetoothConnecter.isDiscovering()) {
+			// TODO showToast(R.string.toast_connect_via_bluetooth_discovering);
+			dismiss();
+		}
+	}
+
+	@Override
+	public void onResume() {
+		super.onResume();
+		// Set the click listener for the START button here
+		// to prevent it from automatically dismissing the dialog.
+		// The dialog is shown in onStart(), so we set the listener here later.
+		AlertDialog dialog = (AlertDialog) getDialog();
+		Button positiveButton = dialog.getButton(BUTTON_POSITIVE);
+		positiveButton.setOnClickListener(this::onStartClicked);
+	}
+
+	private void onStartClicked(View v) {
+		// The dialog starts a permission request which comes back as true
+		// if the permission is already granted.
+		// So we can use the request as a generic entry point to the whole flow.
+		permissionRequest.launch(ACCESS_FINE_LOCATION);
+	}
+
+	private void onPermissionRequestResult(@Nullable Boolean result) {
+		Activity a = requireActivity();
+		// update permission result in BluetoothConnecter
+		bluetoothConnecter.onLocationPermissionResult(a, result);
+		// what to do when the user denies granting the location permission
+		Runnable onLocationPermissionDenied = () -> {
+			Toast.makeText(requireContext(),
+					R.string.toast_connect_via_bluetooth_no_location_permission,
+					LENGTH_LONG).show();
+			dismiss();
+		};
+		// if requirements are fulfilled, request Bluetooth discoverability
+		if (bluetoothConnecter.areRequirementsFulfilled(a, permissionRequest,
+				onLocationPermissionDenied)) {
+			bluetoothDiscoverableRequest.launch(120); // for 2min
+		}
+	}
+
+	private void onBluetoothDiscoverable(@Nullable Boolean result) {
+		if (result != null && result) {
+			// MenuItem only gets enabled after contactItem has loaded
+			ContactItem contact =
+					requireNonNull(viewModel.getContactItem().getValue());
+			bluetoothConnecter.onBluetoothDiscoverable(contact);
+			dismiss();
+		} else {
+			showToast(R.string.toast_connect_via_bluetooth_not_discoverable);
+		}
+	}
+
+	private void showToast(@StringRes int stringRes) {
+		Toast.makeText(requireContext(), stringRes, LENGTH_LONG).show();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -99,6 +99,7 @@ import androidx.appcompat.widget.Toolbar;
 import androidx.core.app.ActivityCompat;
 import androidx.core.app.ActivityOptionsCompat;
 import androidx.core.content.ContextCompat;
+import androidx.fragment.app.FragmentManager;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.Observer;
 import androidx.lifecycle.ViewModelProvider;
@@ -370,9 +371,14 @@ public class ConversationActivity extends BriarActivity
 						this::showIntroductionOnboarding);
 			}
 		});
-		// enable alias action if available
-		observeOnce(viewModel.getContactItem(), this, contact ->
-				menu.findItem(R.id.action_set_alias).setEnabled(true));
+		if (!featureFlags.shouldEnableConnectViaBluetooth()) {
+			menu.findItem(R.id.action_connect_via_bluetooth).setVisible(false);
+		}
+		// enable alias and bluetooth action once available
+		observeOnce(viewModel.getContactItem(), this, contact -> {
+			menu.findItem(R.id.action_set_alias).setEnabled(true);
+			menu.findItem(R.id.action_connect_via_bluetooth).setEnabled(true);
+		});
 		// Show auto-delete menu item if feature is enabled
 		if (featureFlags.shouldEnableDisappearingMessages()) {
 			MenuItem item = menu.findItem(R.id.action_conversation_settings);
@@ -381,40 +387,41 @@ public class ConversationActivity extends BriarActivity
 			viewModel.getPrivateMessageFormat().observe(this, format ->
 					item.setEnabled(format == TEXT_IMAGES_AUTO_DELETE));
 		}
-
 		return super.onCreateOptionsMenu(menu);
 	}
 
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item) {
-		// Handle presses on the action bar items
-		switch (item.getItemId()) {
-			case android.R.id.home:
-				onBackPressed();
-				return true;
-			case R.id.action_introduction:
-				if (contactId == null) return false;
-				Intent intent = new Intent(this, IntroductionActivity.class);
-				intent.putExtra(CONTACT_ID, contactId.getInt());
-				startActivityForResult(intent, REQUEST_INTRODUCTION);
-				return true;
-			case R.id.action_set_alias:
-				AliasDialogFragment.newInstance().show(
-						getSupportFragmentManager(), AliasDialogFragment.TAG);
-				return true;
-			case R.id.action_conversation_settings:
-				if (contactId == null) return false;
-				onAutoDeleteTimerNoticeClicked();
-				return true;
-			case R.id.action_delete_all_messages:
-				askToDeleteAllMessages();
-				return true;
-			case R.id.action_social_remove_person:
-				askToRemoveContact();
-				return true;
-			default:
-				return super.onOptionsItemSelected(item);
+		// contactId gets set before in onCreate()
+		int itemId = item.getItemId();
+		if (itemId == android.R.id.home) {
+			onBackPressed();
+			return true;
+		} else if (itemId == R.id.action_introduction) {
+			Intent intent = new Intent(this, IntroductionActivity.class);
+			intent.putExtra(CONTACT_ID, contactId.getInt());
+			startActivityForResult(intent, REQUEST_INTRODUCTION);
+			return true;
+		} else if (itemId == R.id.action_set_alias) {
+			AliasDialogFragment.newInstance().show(
+					getSupportFragmentManager(), AliasDialogFragment.TAG);
+			return true;
+		} else if (itemId == R.id.action_conversation_settings) {
+			onAutoDeleteTimerNoticeClicked();
+			return true;
+		} else if (itemId == R.id.action_connect_via_bluetooth) {
+			FragmentManager fm = getSupportFragmentManager();
+			new BluetoothConnecterDialogFragment().show(fm,
+					BluetoothConnecterDialogFragment.TAG);
+			return true;
+		} else if (itemId == R.id.action_delete_all_messages) {
+			askToDeleteAllMessages();
+			return true;
+		} else if (itemId == R.id.action_social_remove_person) {
+			askToRemoveContact();
+			return true;
 		}
+		return super.onOptionsItemSelected(item);
 	}
 
 	@Override

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationViewModel.java

@@ -101,6 +101,7 @@ public class ConversationViewModel extends DbViewModel
 	private final AttachmentCreator attachmentCreator;
 	private final AutoDeleteManager autoDeleteManager;
 	private final ConversationManager conversationManager;
+	private final BluetoothConnecter bluetoothConnecter;
 
 	@Nullable
 	private ContactId contactId = null;
@@ -139,7 +140,8 @@ public class ConversationViewModel extends DbViewModel
 			AttachmentRetriever attachmentRetriever,
 			AttachmentCreator attachmentCreator,
 			AutoDeleteManager autoDeleteManager,
-			ConversationManager conversationManager) {
+			ConversationManager conversationManager,
+			BluetoothConnecter bluetoothConnecter) {
 		super(application, dbExecutor, lifecycleManager, db, androidExecutor);
 		this.db = db;
 		this.eventBus = eventBus;
@@ -152,6 +154,7 @@ public class ConversationViewModel extends DbViewModel
 		this.attachmentCreator = attachmentCreator;
 		this.autoDeleteManager = autoDeleteManager;
 		this.conversationManager = conversationManager;
+		this.bluetoothConnecter = bluetoothConnecter;
 		messagingGroupId = map(contactItem, c ->
 				messagingManager.getContactGroup(c.getContact()).getId());
 		eventBus.addListener(this);
@@ -411,6 +414,10 @@ public class ConversationViewModel extends DbViewModel
 		return attachmentRetriever;
 	}
 
+	BluetoothConnecter getBluetoothConnecter() {
+		return bluetoothConnecter;
+	}
+
 	LiveData<ContactItem> getContactItem() {
 		return contactItem;
 	}

briar-android/src/main/java/org/briarproject/briar/android/util/UiUtils.java

@@ -3,11 +3,13 @@ package org.briarproject.briar.android.util;
 import android.annotation.SuppressLint;
 import android.annotation.TargetApi;
 import android.app.KeyguardManager;
+import android.content.ActivityNotFoundException;
 import android.content.Context;
 import android.content.DialogInterface.OnClickListener;
 import android.content.Intent;
 import android.content.res.Resources;
 import android.graphics.drawable.Drawable;
+import android.location.LocationManager;
 import android.net.Uri;
 import android.os.PowerManager;
 import android.text.Spannable;
@@ -72,6 +74,7 @@ import static android.content.Intent.EXTRA_MIME_TYPES;
 import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
 import static android.os.Build.MANUFACTURER;
 import static android.os.Build.VERSION.SDK_INT;
+import static android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS;
 import static android.provider.Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS;
 import static android.text.format.DateUtils.DAY_IN_MILLIS;
 import static android.text.format.DateUtils.FORMAT_ABBREV_ALL;
@@ -331,6 +334,19 @@ public class UiUtils {
 		return i;
 	}
 
+	/**
+	 * @return true if location is enabled,
+	 * or it isn't required due to this being a SDK < 28 device.
+	 */
+	public static boolean isLocationEnabled(Context ctx) {
+		if (SDK_INT >= 28) {
+			LocationManager lm = ctx.getSystemService(LocationManager.class);
+			return lm.isLocationEnabled();
+		} else {
+			return true;
+		}
+	}
+
 	public static boolean isSamsung7() {
 		return (SDK_INT == 24 || SDK_INT == 25) &&
 				MANUFACTURER.equalsIgnoreCase("Samsung");
@@ -474,6 +490,25 @@ public class UiUtils {
 		return isoCode;
 	}
 
+	public static void showLocationDialog(Context ctx) {
+		AlertDialog.Builder builder =
+				new AlertDialog.Builder(ctx, R.style.BriarDialogTheme);
+		builder.setTitle(R.string.permission_location_setting_title);
+		builder.setMessage(R.string.permission_location_setting_body);
+		builder.setNegativeButton(R.string.cancel, null);
+		builder.setPositiveButton(R.string.permission_location_setting_button,
+				(dialog, which) -> {
+					Intent i = new Intent(ACTION_LOCATION_SOURCE_SETTINGS);
+					try {
+						ctx.startActivity(i);
+					} catch (ActivityNotFoundException e) {
+						Toast.makeText(ctx, R.string.error_start_activity,
+								LENGTH_LONG).show();
+					}
+				});
+		builder.show();
+	}
+
 	public static Drawable getDialogIcon(Context ctx, @DrawableRes int resId) {
 		Drawable icon =
 				VectorDrawableCompat.create(ctx.getResources(), resId, null);

briar-android/src/main/res/menu/conversation_actions.xml

@@ -23,6 +23,12 @@
 		app:showAsAction="never"
 		tools:visible="true" />
 
+	<item
+		android:id="@+id/action_connect_via_bluetooth"
+		android:enabled="false"
+		android:title="@string/menu_item_connect_via_bluetooth"
+		app:showAsAction="never" />
+
 	<item
 		android:id="@+id/action_delete_all_messages"
 		android:title="@string/delete_all_messages"

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

@@ -142,6 +142,7 @@
 	<string name="allow">Allow</string>
 	<string name="open">Open</string>
 	<string name="change">Change</string>
+	<string name="start">Start</string>
 	<string name="no_data">No data</string>
 	<string name="ellipsis">…</string>
 	<string name="text_too_long">The entered text is too long</string>
@@ -168,6 +169,14 @@
 	<string name="set_contact_alias">Change contact name</string>
 	<string name="set_contact_alias_hint">Contact name</string>
 	<string name="menu_item_disappearing_messages">Disappearing messages</string>
+	<string name="menu_item_connect_via_bluetooth">Connect via Bluetooth</string>
+	<string name="dialog_title_connect_via_bluetooth">Connect via Bluetooth</string>
+	<string name="dialog_message_connect_via_bluetooth">Your contact needs to be nearby for this to work.\n\nYou and your contact should both press \"Start\" at the same time.</string>
+	<string name="toast_connect_via_bluetooth_not_discoverable">Cannot continue without Bluetooth</string>
+	<string name="toast_connect_via_bluetooth_no_location_permission">Cannot continue without location permission</string>
+	<string name="toast_connect_via_bluetooth_start">Connecting via Bluetooth…</string>
+	<string name="toast_connect_via_bluetooth_success">Successfully connected via Bluetooth</string>
+	<string name="toast_connect_via_bluetooth_error">Could not connect via Bluetooth</string>
 	<!-- The first placeholder will show a duration like "7 days". The second placeholder at the end will add "Tap to learn more." -->
 	<string name="auto_delete_msg_you_enabled">Your messages will disappear after %1$s. %2$s</string>
 	<!-- The placeholder at the end will add "Tap to learn more." -->

briar-headless/src/main/java/org/briarproject/briar/headless/HeadlessModule.kt

@@ -94,5 +94,6 @@ internal class HeadlessModule(private val appDir: File) {
         override fun shouldEnableImageAttachments() = false
         override fun shouldEnableProfilePictures() = false
         override fun shouldEnableDisappearingMessages() = false
+        override fun shouldEnableConnectViaBluetooth() = false
     }
 }

briar-headless/src/test/java/org/briarproject/briar/headless/HeadlessTestModule.kt

@@ -82,6 +82,7 @@ internal class HeadlessTestModule(private val appDir: File) {
         override fun shouldEnableImageAttachments() = false
         override fun shouldEnableProfilePictures() = false
         override fun shouldEnableDisappearingMessages() = false
+        override fun shouldEnableConnectViaBluetooth() = false
     }
 
     @Provides