Merge branch '1871-viewmodel-for-introduction' into 'master'

Introduce ViewModel for IntroductionActivity (and ContactChooserFragment)

See merge request briar/briar!1349

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

@@ -32,6 +32,7 @@ import org.briarproject.briar.android.account.LockManagerImpl;
 import org.briarproject.briar.android.account.SetupModule;
 import org.briarproject.briar.android.contact.ContactListModule;
 import org.briarproject.briar.android.forum.ForumModule;
+import org.briarproject.briar.android.introduction.IntroductionModule;
 import org.briarproject.briar.android.keyagreement.ContactExchangeModule;
 import org.briarproject.briar.android.logging.LoggingModule;
 import org.briarproject.briar.android.login.LoginModule;
@@ -82,6 +83,7 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 		SettingsModule.class,
 		DevReportModule.class,
 		ContactListModule.class,
+		IntroductionModule.class,
 		// below need to be within same scope as ViewModelProvider.Factory
 		ForumModule.class,
 		GroupListModule.class,

briar-android/src/main/java/org/briarproject/briar/android/contact/BaseContactListAdapter.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.contact;
 
 import android.content.Context;
-import android.view.View;
 
 import org.briarproject.briar.android.util.BriarAdapter;
 
@@ -45,8 +44,4 @@ public abstract class BaseContactListAdapter<I extends ContactItem, VH extends C
 		return true;
 	}
 
-	public interface OnContactClickListener<I> {
-		void onItemClick(View view, I item);
-	}
-
 }

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactItemViewHolder.java

@@ -7,7 +7,6 @@ import android.widget.TextView;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.contact.BaseContactListAdapter.OnContactClickListener;
 
 import javax.annotation.Nullable;
 

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactListAdapter.java

@@ -7,7 +7,6 @@ import android.view.ViewGroup;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.NullSafety;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.contact.BaseContactListAdapter.OnContactClickListener;
 
 import androidx.recyclerview.widget.DiffUtil.ItemCallback;
 import androidx.recyclerview.widget.ListAdapter;
@@ -16,9 +15,6 @@ import androidx.recyclerview.widget.ListAdapter;
 public class ContactListAdapter extends
 		ListAdapter<ContactListItem, ContactListItemViewHolder> {
 
-	// TODO: using the click listener interface from BaseContactListAdapter on
-	// purpose here because it is entangled with ContactListItemViewHolder. At
-	// some point we probably want to change that.
 	protected final OnContactClickListener<ContactListItem> listener;
 
 	public ContactListAdapter(

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactListFragment.java

@@ -15,7 +15,6 @@ 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.BaseContactListAdapter.OnContactClickListener;
 import org.briarproject.briar.android.contact.add.remote.AddContactActivity;
 import org.briarproject.briar.android.contact.add.remote.PendingContactListActivity;
 import org.briarproject.briar.android.conversation.ConversationActivity;
@@ -101,8 +100,6 @@ public class ContactListFragment extends BaseFragment
 				.observe(getViewLifecycleOwner(), result -> {
 					result.onError(this::handleException).onSuccess(items -> {
 						adapter.submitList(items);
-						// TODO remove when BriarRecyclerView was adapted
-						list.showData();
 					});
 				});
 		viewModel.getHasPendingContacts()

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactListItemViewHolder.java

@@ -5,7 +5,6 @@ import android.widget.TextView;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.contact.BaseContactListAdapter.OnContactClickListener;
 
 import java.util.Locale;
 

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactListViewModel.java

@@ -3,70 +3,41 @@ package org.briarproject.briar.android.contact;
 import android.app.Application;
 
 import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.Contact;
-import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
-import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
-import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
 import org.briarproject.bramble.api.contact.event.PendingContactAddedEvent;
 import org.briarproject.bramble.api.contact.event.PendingContactRemovedEvent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.db.TransactionManager;
 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.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
-import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
 import org.briarproject.bramble.api.system.AndroidExecutor;
-import org.briarproject.briar.android.viewmodel.DbViewModel;
-import org.briarproject.briar.android.viewmodel.LiveResult;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
-import org.briarproject.briar.api.avatar.event.AvatarUpdatedEvent;
-import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.conversation.ConversationManager;
-import org.briarproject.briar.api.conversation.ConversationMessageHeader;
-import org.briarproject.briar.api.conversation.event.ConversationMessageReceivedEvent;
-import org.briarproject.briar.api.identity.AuthorInfo;
 import org.briarproject.briar.api.identity.AuthorManager;
 
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
-import androidx.arch.core.util.Function;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
-import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.bramble.util.LogUtils.now;
 
 @NotNullByDefault
-class ContactListViewModel extends DbViewModel implements EventListener {
+class ContactListViewModel extends ContactsViewModel {
 
 	private static final Logger LOG =
 			getLogger(ContactListViewModel.class.getName());
 
-	private final ContactManager contactManager;
-	private final AuthorManager authorManager;
-	private final ConversationManager conversationManager;
-	private final ConnectionRegistry connectionRegistry;
-	private final EventBus eventBus;
 	private final AndroidNotificationManager notificationManager;
 
-	private final MutableLiveData<LiveResult<List<ContactListItem>>>
-			contactListItems = new MutableLiveData<>();
-
 	private final MutableLiveData<Boolean> hasPendingContacts =
 			new MutableLiveData<>();
 
@@ -79,99 +50,25 @@ class ContactListViewModel extends DbViewModel implements EventListener {
 			ConversationManager conversationManager,
 			ConnectionRegistry connectionRegistry, EventBus eventBus,
 			AndroidNotificationManager notificationManager) {
-		super(application, dbExecutor, lifecycleManager, db, androidExecutor);
+		super(application, dbExecutor, lifecycleManager, db, androidExecutor,
-		this.contactManager = contactManager;
+				contactManager, authorManager, conversationManager,
-		this.authorManager = authorManager;
+				connectionRegistry, eventBus);
-		this.conversationManager = conversationManager;
-		this.connectionRegistry = connectionRegistry;
-		this.eventBus = eventBus;
 		this.notificationManager = notificationManager;
-		this.eventBus.addListener(this);
-	}
-
-	@Override
-	protected void onCleared() {
-		super.onCleared();
-		eventBus.removeListener(this);
-	}
-
-	void loadContacts() {
-		loadList(this::loadContacts, contactListItems::setValue);
-	}
-
-	private List<ContactListItem> loadContacts(Transaction txn)
-			throws DbException {
-		long start = now();
-		List<ContactListItem> contacts = new ArrayList<>();
-		for (Contact c : contactManager.getContacts(txn)) {
-			ContactId id = c.getId();
-			AuthorInfo authorInfo = authorManager.getAuthorInfo(txn, c);
-			MessageTracker.GroupCount count =
-					conversationManager.getGroupCount(txn, id);
-			boolean connected = connectionRegistry.isConnected(c.getId());
-			contacts.add(new ContactListItem(c, authorInfo, connected, count));
-		}
-		Collections.sort(contacts);
-		logDuration(LOG, "Full load", start);
-		return contacts;
 	}
 
 	@Override
 	public void eventOccurred(Event e) {
-		if (e instanceof ContactAddedEvent) {
+		super.eventOccurred(e);
-			LOG.info("Contact added, reloading");
+		if (e instanceof PendingContactAddedEvent ||
-			loadContacts();
-		} else if (e instanceof ContactConnectedEvent) {
-			updateItem(((ContactConnectedEvent) e).getContactId(),
-					item -> new ContactListItem(item, true), false);
-		} else if (e instanceof ContactDisconnectedEvent) {
-			updateItem(((ContactDisconnectedEvent) e).getContactId(),
-					item -> new ContactListItem(item, false), false);
-		} else if (e instanceof ContactRemovedEvent) {
-			LOG.info("Contact removed, removing item");
-			removeItem(((ContactRemovedEvent) e).getContactId());
-		} else if (e instanceof ConversationMessageReceivedEvent) {
-			LOG.info("Conversation message received, updating item");
-			ConversationMessageReceivedEvent<?> p =
-					(ConversationMessageReceivedEvent<?>) e;
-			ConversationMessageHeader h = p.getMessageHeader();
-			updateItem(p.getContactId(), item -> new ContactListItem(item, h),
-					true);
-		} else if (e instanceof PendingContactAddedEvent ||
 				e instanceof PendingContactRemovedEvent) {
 			checkForPendingContacts();
-		} else if (e instanceof AvatarUpdatedEvent) {
-			AvatarUpdatedEvent a = (AvatarUpdatedEvent) e;
-			updateItem(a.getContactId(), item -> new ContactListItem(item,
-					a.getAttachmentHeader()), false);
 		}
 	}
 
-	LiveData<LiveResult<List<ContactListItem>>> getContactListItems() {
-		return contactListItems;
-	}
-
 	LiveData<Boolean> getHasPendingContacts() {
 		return hasPendingContacts;
 	}
 
-	private void updateItem(ContactId c,
-			Function<ContactListItem, ContactListItem> replacer, boolean sort) {
-		List<ContactListItem> list = updateListItems(contactListItems,
-				itemToTest -> itemToTest.getContact().getId().equals(c),
-				replacer);
-		if (list == null) return;
-		if (sort) Collections.sort(list);
-		contactListItems.setValue(new LiveResult<>(list));
-	}
-
-	private void removeItem(ContactId c) {
-		List<ContactListItem> list = removeListItems(contactListItems,
-				itemToTest -> itemToTest.getContact().getId().equals(c));
-		if (list == null) return;
-		contactListItems.setValue(new LiveResult<>(list));
-	}
-
 	void checkForPendingContacts() {
 		runOnDbThread(() -> {
 			try {

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactsViewModel.java

@@ -0,0 +1,170 @@
+package org.briarproject.briar.android.contact;
+
+import android.app.Application;
+
+import org.briarproject.bramble.api.connection.ConnectionRegistry;
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.ContactManager;
+import org.briarproject.bramble.api.contact.event.ContactAddedEvent;
+import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.db.TransactionManager;
+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.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.event.ContactConnectedEvent;
+import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.android.viewmodel.DbViewModel;
+import org.briarproject.briar.android.viewmodel.LiveResult;
+import org.briarproject.briar.api.avatar.event.AvatarUpdatedEvent;
+import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.conversation.ConversationManager;
+import org.briarproject.briar.api.conversation.ConversationMessageHeader;
+import org.briarproject.briar.api.conversation.event.ConversationMessageReceivedEvent;
+import org.briarproject.briar.api.identity.AuthorInfo;
+import org.briarproject.briar.api.identity.AuthorManager;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.UiThread;
+import androidx.arch.core.util.Function;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.now;
+
+@NotNullByDefault
+public class ContactsViewModel extends DbViewModel implements EventListener {
+
+	private static final Logger LOG =
+			getLogger(ContactsViewModel.class.getName());
+
+	protected final ContactManager contactManager;
+	private final AuthorManager authorManager;
+	private final ConversationManager conversationManager;
+	private final ConnectionRegistry connectionRegistry;
+	private final EventBus eventBus;
+
+	private final MutableLiveData<LiveResult<List<ContactListItem>>>
+			contactListItems = new MutableLiveData<>();
+
+	@Inject
+	public ContactsViewModel(Application application,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager, TransactionManager db,
+			AndroidExecutor androidExecutor, ContactManager contactManager,
+			AuthorManager authorManager,
+			ConversationManager conversationManager,
+			ConnectionRegistry connectionRegistry, EventBus eventBus) {
+		super(application, dbExecutor, lifecycleManager, db, androidExecutor);
+		this.contactManager = contactManager;
+		this.authorManager = authorManager;
+		this.conversationManager = conversationManager;
+		this.connectionRegistry = connectionRegistry;
+		this.eventBus = eventBus;
+		this.eventBus.addListener(this);
+	}
+
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		eventBus.removeListener(this);
+	}
+
+	protected void loadContacts() {
+		loadList(this::loadContacts, contactListItems::setValue);
+	}
+
+	private List<ContactListItem> loadContacts(Transaction txn)
+			throws DbException {
+		long start = now();
+		List<ContactListItem> contacts = new ArrayList<>();
+		for (Contact c : contactManager.getContacts(txn)) {
+			ContactId id = c.getId();
+			if (!displayContact(id)) {
+				continue;
+			}
+			AuthorInfo authorInfo = authorManager.getAuthorInfo(txn, c);
+			MessageTracker.GroupCount count =
+					conversationManager.getGroupCount(txn, id);
+			boolean connected = connectionRegistry.isConnected(c.getId());
+			contacts.add(new ContactListItem(c, authorInfo, connected, count));
+		}
+		Collections.sort(contacts);
+		logDuration(LOG, "Full load", start);
+		return contacts;
+	}
+
+	/**
+	 * Override this method to display only a subset of contacts.
+	 */
+	protected boolean displayContact(ContactId contactId) {
+		return true;
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof ContactAddedEvent) {
+			LOG.info("Contact added, reloading");
+			loadContacts();
+		} else if (e instanceof ContactConnectedEvent) {
+			updateItem(((ContactConnectedEvent) e).getContactId(),
+					item -> new ContactListItem(item, true), false);
+		} else if (e instanceof ContactDisconnectedEvent) {
+			updateItem(((ContactDisconnectedEvent) e).getContactId(),
+					item -> new ContactListItem(item, false), false);
+		} else if (e instanceof ContactRemovedEvent) {
+			LOG.info("Contact removed, removing item");
+			removeItem(((ContactRemovedEvent) e).getContactId());
+		} else if (e instanceof ConversationMessageReceivedEvent) {
+			LOG.info("Conversation message received, updating item");
+			ConversationMessageReceivedEvent<?> p =
+					(ConversationMessageReceivedEvent<?>) e;
+			ConversationMessageHeader h = p.getMessageHeader();
+			updateItem(p.getContactId(), item -> new ContactListItem(item, h),
+					true);
+		} else if (e instanceof AvatarUpdatedEvent) {
+			AvatarUpdatedEvent a = (AvatarUpdatedEvent) e;
+			updateItem(a.getContactId(), item -> new ContactListItem(item,
+					a.getAttachmentHeader()), false);
+		}
+	}
+
+	public LiveData<LiveResult<List<ContactListItem>>> getContactListItems() {
+		return contactListItems;
+	}
+
+	@UiThread
+	private void updateItem(ContactId c,
+			Function<ContactListItem, ContactListItem> replacer, boolean sort) {
+		List<ContactListItem> list = updateListItems(contactListItems,
+				itemToTest -> itemToTest.getContact().getId().equals(c),
+				replacer);
+		if (list == null) return;
+		if (sort) Collections.sort(list);
+		contactListItems.setValue(new LiveResult<>(list));
+	}
+
+	@UiThread
+	private void removeItem(ContactId c) {
+		List<ContactListItem> list = removeListItems(contactListItems,
+				itemToTest -> itemToTest.getContact().getId().equals(c));
+		if (list == null) return;
+		contactListItems.setValue(new LiveResult<>(list));
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contact/LegacyContactListAdapter.java

@@ -1,50 +0,0 @@
-package org.briarproject.briar.android.contact;
-
-import android.content.Context;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.briar.R;
-
-@NotNullByDefault
-public class LegacyContactListAdapter extends
-		BaseContactListAdapter<ContactListItem, ContactListItemViewHolder> {
-
-	public LegacyContactListAdapter(Context context,
-			OnContactClickListener<ContactListItem> listener) {
-		super(context, ContactListItem.class, listener);
-	}
-
-	@Override
-	public ContactListItemViewHolder onCreateViewHolder(ViewGroup viewGroup,
-			int i) {
-		View v = LayoutInflater.from(viewGroup.getContext()).inflate(
-				R.layout.list_item_contact, viewGroup, false);
-
-		return new ContactListItemViewHolder(v);
-	}
-
-	@Override
-	public boolean areContentsTheSame(ContactListItem c1, ContactListItem c2) {
-		// check for all properties that influence visual
-		// representation of contact
-		if (c1.isEmpty() != c2.isEmpty()) {
-			return false;
-		}
-		if (c1.getUnreadCount() != c2.getUnreadCount()) {
-			return false;
-		}
-		if (c1.getTimestamp() != c2.getTimestamp()) {
-			return false;
-		}
-		return c1.isConnected() == c2.isConnected();
-	}
-
-	@Override
-	public int compare(ContactListItem c1, ContactListItem c2) {
-		return Long.compare(c2.getTimestamp(), c1.getTimestamp());
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/contact/OnContactClickListener.java

@@ -0,0 +1,9 @@
+package org.briarproject.briar.android.contact;
+
+import android.view.View;
+
+public interface OnContactClickListener<I> {
+
+	void onItemClick(View view, I item);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/contactselection/BaseContactSelectorAdapter.java

@@ -6,6 +6,7 @@ import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.android.contact.BaseContactListAdapter;
 import org.briarproject.briar.android.contact.ContactItemViewHolder;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 
 import java.util.ArrayList;
 import java.util.Collection;

briar-android/src/main/java/org/briarproject/briar/android/contactselection/BaseContactSelectorFragment.java

@@ -12,8 +12,8 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.contact.BaseContactListAdapter.OnContactClickListener;
 import org.briarproject.briar.android.contact.ContactItemViewHolder;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 import org.briarproject.briar.android.controller.handler.UiResultExceptionHandler;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.BriarRecyclerView;

briar-android/src/main/java/org/briarproject/briar/android/contactselection/BaseSelectableContactHolder.java

@@ -6,8 +6,8 @@ import android.widget.TextView;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.contact.BaseContactListAdapter.OnContactClickListener;
 import org.briarproject.briar.android.contact.ContactItemViewHolder;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 
 import javax.annotation.Nullable;
 

briar-android/src/main/java/org/briarproject/briar/android/contactselection/ContactSelectorAdapter.java

@@ -7,6 +7,7 @@ import android.view.ViewGroup;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 
 @NotNullByDefault
 class ContactSelectorAdapter extends

briar-android/src/main/java/org/briarproject/briar/android/contactselection/ContactSelectorFragment.java

@@ -8,7 +8,7 @@ import android.view.MenuItem;
 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.BaseContactListAdapter.OnContactClickListener;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault

briar-android/src/main/java/org/briarproject/briar/android/contactselection/SelectableContactHolder.java

@@ -3,7 +3,7 @@ package org.briarproject.briar.android.contactselection;
 import android.view.View;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.briar.android.contact.BaseContactListAdapter.OnContactClickListener;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 
 import javax.annotation.Nullable;
 

briar-android/src/main/java/org/briarproject/briar/android/introduction/ContactChooserFragment.java

@@ -5,74 +5,41 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 
-import org.briarproject.bramble.api.connection.ConnectionRegistry;
-import org.briarproject.bramble.api.contact.Contact;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.contact.ContactManager;
-import org.briarproject.bramble.api.db.DbException;
 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.BaseContactListAdapter.OnContactClickListener;
+import org.briarproject.briar.android.contact.ContactListAdapter;
 import org.briarproject.briar.android.contact.ContactListItem;
-import org.briarproject.briar.android.contact.LegacyContactListAdapter;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.BriarRecyclerView;
-import org.briarproject.briar.api.client.MessageTracker.GroupCount;
-import org.briarproject.briar.api.conversation.ConversationManager;
-import org.briarproject.briar.api.identity.AuthorInfo;
-import org.briarproject.briar.api.identity.AuthorManager;
-
-import java.util.ArrayList;
-import java.util.List;
-import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
-import androidx.annotation.UiThread;
+import androidx.lifecycle.ViewModelProvider;
 import androidx.recyclerview.widget.LinearLayoutManager;
 
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
-
-@UiThread
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public class ContactChooserFragment extends BaseFragment {
+public class ContactChooserFragment extends BaseFragment
+		implements OnContactClickListener<ContactListItem> {
 
-	public static final String TAG = ContactChooserFragment.class.getName();
+	private static final String TAG = ContactChooserFragment.class.getName();
-	private static final Logger LOG = Logger.getLogger(TAG);
 
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private IntroductionViewModel viewModel;
+	private final ContactListAdapter adapter = new ContactListAdapter(this);
 	private BriarRecyclerView list;
-	private LegacyContactListAdapter adapter;
-	private ContactId contactId;
-
-	// Fields that are accessed from background threads must be volatile
-	private volatile Contact c1;
-	@Inject
-	volatile ContactManager contactManager;
-	@Inject
-	volatile AuthorManager authorManager;
-	@Inject
-	volatile ConversationManager conversationManager;
-	@Inject
-	volatile ConnectionRegistry connectionRegistry;
-
-	public static ContactChooserFragment newInstance(ContactId id) {
-		Bundle args = new Bundle();
-
-		ContactChooserFragment fragment = new ContactChooserFragment();
-		args.putInt(CONTACT_ID, id.getInt());
-		fragment.setArguments(args);
-		return fragment;
-	}
 
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(IntroductionViewModel.class);
 	}
 
 	@Override
@@ -80,23 +47,20 @@ public class ContactChooserFragment extends BaseFragment {
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
 
-		View contentView = inflater.inflate(R.layout.list, container, false);
+		// change toolbar text (relevant when navigating back to this fragment)
+		requireActivity().setTitle(R.string.introduction_activity_title);
 
-		OnContactClickListener<ContactListItem> onContactClickListener =
+		View contentView = inflater.inflate(R.layout.list, container, false);
-				(view, item) -> {
-					if (c1 == null) throw new IllegalStateException();
-					Contact c2 = item.getContact();
-					showMessageScreen(c1, c2);
-				};
-		adapter = new LegacyContactListAdapter(requireActivity(),
-				onContactClickListener);
 
 		list = contentView.findViewById(R.id.list);
 		list.setLayoutManager(new LinearLayoutManager(getActivity()));
 		list.setAdapter(adapter);
 		list.setEmptyText(R.string.no_contacts);
 
-		contactId = new ContactId(requireArguments().getInt(CONTACT_ID));
+		viewModel.getContactListItems().observe(getViewLifecycleOwner(),
+				result -> result.onError(this::handleException)
+						.onSuccess(adapter::submitList)
+		);
 
 		return contentView;
 	}
@@ -104,14 +68,13 @@ public class ContactChooserFragment extends BaseFragment {
 	@Override
 	public void onStart() {
 		super.onStart();
-		loadContacts();
+		list.startPeriodicUpdate();
 	}
 
 	@Override
 	public void onStop() {
 		super.onStop();
-		adapter.clear();
+		list.stopPeriodicUpdate();
-		list.showProgressBar();
 	}
 
 	@Override
@@ -119,43 +82,9 @@ public class ContactChooserFragment extends BaseFragment {
 		return TAG;
 	}
 
-	private void loadContacts() {
+	@Override
-		listener.runOnDbThread(() -> {
+	public void onItemClick(View view, ContactListItem item) {
-			try {
+		viewModel.setSecondContactId(item.getContact().getId());
-				List<ContactListItem> contacts = new ArrayList<>();
+		viewModel.triggerContactSelected();
-				for (Contact c : contactManager.getContacts()) {
-					if (c.getId().equals(contactId)) {
-						c1 = c;
-					} else {
-						AuthorInfo authorInfo = authorManager.getAuthorInfo(c);
-						ContactId id = c.getId();
-						GroupCount count =
-								conversationManager.getGroupCount(id);
-						boolean connected =
-								connectionRegistry.isConnected(c.getId());
-						contacts.add(new ContactListItem(c, authorInfo,
-								connected, count));
-					}
-				}
-				displayContacts(contacts);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
 	}
-
-	private void displayContacts(List<ContactListItem> contacts) {
-		runOnUiThreadUnlessDestroyed(() -> {
-			if (contacts.isEmpty()) list.showData();
-			else adapter.addAll(contacts);
-		});
-	}
-
-	private void showMessageScreen(Contact c1, Contact c2) {
-		IntroductionMessageFragment messageFragment =
-				IntroductionMessageFragment
-						.newInstance(c1.getId().getInt(), c2.getId().getInt());
-		showNextFragment(messageFragment);
-	}
-
 }

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionActivity.java

@@ -9,30 +9,67 @@ import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
 import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
 
+import javax.inject.Inject;
+
+import androidx.annotation.NonNull;
+import androidx.lifecycle.ViewModelProvider;
+
 import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
 
 public class IntroductionActivity extends BriarActivity
 		implements BaseFragmentListener {
 
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private IntroductionViewModel viewModel;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(IntroductionViewModel.class);
+	}
+
+	private static final String BUNDLE_CONTACT2 = "contact2";
+
 	@Override
 	public void onCreate(Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
 		Intent intent = getIntent();
-		int id = intent.getIntExtra(CONTACT_ID, -1);
+		int contactId1 = intent.getIntExtra(CONTACT_ID, -1);
-		if (id == -1) throw new IllegalStateException("No ContactId");
+		if (contactId1 == -1)
-		ContactId contactId = new ContactId(id);
+			throw new IllegalStateException("No ContactId");
+		ContactId firstContactId = new ContactId(contactId1);
+
+		viewModel.setFirstContactId(firstContactId);
 
 		setContentView(R.layout.activity_fragment_container);
 
 		if (savedInstanceState == null) {
-			showInitialFragment(ContactChooserFragment.newInstance(contactId));
+			showInitialFragment(new ContactChooserFragment());
+		} else {
+			int contactId2 = savedInstanceState.getInt(BUNDLE_CONTACT2);
+			ContactId secondContactId = new ContactId(contactId2);
+			viewModel.setSecondContactId(secondContactId);
 		}
+
+		viewModel.getSecondContactSelected().observeEvent(this, e -> {
+			IntroductionMessageFragment fragment =
+					new IntroductionMessageFragment();
+			showNextFragment(fragment);
+		});
 	}
 
 	@Override
-	public void injectActivity(ActivityComponent component) {
+	public void onSaveInstanceState(@NonNull Bundle outState) {
-		component.inject(this);
+		super.onSaveInstanceState(outState);
+
+		ContactId secondContactId = viewModel.getSecondContactId();
+		if (secondContactId != null) {
+			outState.putInt(BUNDLE_CONTACT2, secondContactId.getInt());
+		}
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionInfo.java

@@ -0,0 +1,28 @@
+package org.briarproject.briar.android.introduction;
+
+import org.briarproject.briar.android.contact.ContactItem;
+
+class IntroductionInfo {
+	private final ContactItem c1;
+	private final ContactItem c2;
+	private final boolean possible;
+
+	IntroductionInfo(ContactItem c1, ContactItem c2,
+			boolean possible) {
+		this.c1 = c1;
+		this.c2 = c2;
+		this.possible = possible;
+	}
+
+	ContactItem getContact1() {
+		return c1;
+	}
+
+	ContactItem getContact2() {
+		return c2;
+	}
+
+	boolean isPossible() {
+		return possible;
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionMessageFragment.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.introduction;
 
-import android.content.Context;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.MenuItem;
@@ -8,12 +7,7 @@ import android.view.View;
 import android.view.ViewGroup;
 import android.widget.ProgressBar;
 import android.widget.TextView;
-import android.widget.Toast;
 
-import org.briarproject.bramble.api.contact.Contact;
-import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.contact.ContactManager;
-import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
@@ -24,25 +18,19 @@ import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
 import org.briarproject.briar.api.attachment.AttachmentHeader;
-import org.briarproject.briar.api.identity.AuthorInfo;
-import org.briarproject.briar.api.identity.AuthorManager;
-import org.briarproject.briar.api.introduction.IntroductionManager;
 
 import java.util.List;
-import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
-import androidx.appcompat.app.ActionBar;
+import androidx.fragment.app.FragmentActivity;
+import androidx.lifecycle.ViewModelProvider;
 import de.hdodenhof.circleimageview.CircleImageView;
 
 import static android.app.Activity.RESULT_OK;
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
-import static android.widget.Toast.LENGTH_SHORT;
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.briar.android.util.UiUtils.getContactDisplayName;
 import static org.briarproject.briar.android.util.UiUtils.hideSoftKeyboard;
 import static org.briarproject.briar.android.view.AuthorView.setAvatar;
@@ -53,45 +41,21 @@ import static org.briarproject.briar.api.introduction.IntroductionConstants.MAX_
 public class IntroductionMessageFragment extends BaseFragment
 		implements SendListener {
 
-	public static final String TAG =
+	private static final String TAG =
 			IntroductionMessageFragment.class.getName();
-	private static final Logger LOG = Logger.getLogger(TAG);
 
-	private final static String CONTACT_ID_1 = "contact1";
+	@Inject
-	private final static String CONTACT_ID_2 = "contact2";
+	ViewModelProvider.Factory viewModelFactory;
+
+	private IntroductionViewModel viewModel;
 
-	private IntroductionActivity introductionActivity;
 	private ViewHolder ui;
-	private Contact contact1, contact2;
-
-	// Fields that are accessed from background threads must be volatile
-	@Inject
-	protected volatile ContactManager contactManager;
-	@Inject
-	protected volatile AuthorManager authorManager;
-	@Inject
-	protected volatile IntroductionManager introductionManager;
-
-	public static IntroductionMessageFragment newInstance(int contactId1,
-			int contactId2) {
-		Bundle args = new Bundle();
-		args.putInt(CONTACT_ID_1, contactId1);
-		args.putInt(CONTACT_ID_2, contactId2);
-		IntroductionMessageFragment fragment =
-				new IntroductionMessageFragment();
-		fragment.setArguments(args);
-		return fragment;
-	}
-
-	@Override
-	public void onAttach(Context context) {
-		super.onAttach(context);
-		introductionActivity = (IntroductionActivity) context;
-	}
 
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(IntroductionViewModel.class);
 	}
 
 	@Override
@@ -100,18 +64,7 @@ public class IntroductionMessageFragment extends BaseFragment
 			@Nullable Bundle savedInstanceState) {
 
 		// change toolbar text
-		ActionBar actionBar = introductionActivity.getSupportActionBar();
+		requireActivity().setTitle(R.string.introduction_message_title);
-		if (actionBar != null) {
-			actionBar.setTitle(R.string.introduction_message_title);
-		}
-
-		// get contact IDs from fragment arguments
-		Bundle args = requireArguments();
-		int contactId1 = args.getInt(CONTACT_ID_1, -1);
-		int contactId2 = args.getInt(CONTACT_ID_2, -1);
-		if (contactId1 == -1 || contactId2 == -1) {
-			throw new AssertionError("Use newInstance() to instantiate");
-		}
 
 		// inflate view
 		View v = inflater.inflate(R.layout.introduction_message, container,
@@ -123,69 +76,44 @@ public class IntroductionMessageFragment extends BaseFragment
 		ui.message.setMaxTextLength(MAX_INTRODUCTION_TEXT_LENGTH);
 		ui.message.setReady(false);
 
-		// get contacts and then show view
+		viewModel.getIntroductionInfo().observe(getViewLifecycleOwner(), ii -> {
-		prepareToSetUpViews(contactId1, contactId2);
+			if (ii == null) {
+				return;
+			}
+			setUpViews(ii.getContact1(), ii.getContact2(),
+					ii.isPossible());
+		});
 
 		return v;
 	}
 
-	@Override
-	public void onStart() {
-		super.onStart();
-	}
-
 	@Override
 	public String getUniqueTag() {
 		return TAG;
 	}
 
-	private void prepareToSetUpViews(int contactId1, int contactId2) {
-		introductionActivity.runOnDbThread(() -> {
-			try {
-				Contact contact1 =
-						contactManager.getContact(new ContactId(contactId1));
-				Contact contact2 =
-						contactManager.getContact(new ContactId(contactId2));
-				AuthorInfo a1 = authorManager.getAuthorInfo(contact1);
-				AuthorInfo a2 = authorManager.getAuthorInfo(contact2);
-				boolean possible =
-						introductionManager.canIntroduce(contact1, contact2);
-				ContactItem c1 = new ContactItem(contact1, a1);
-				ContactItem c2 = new ContactItem(contact2, a2);
-				setUpViews(c1, c2, possible);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
-	}
-
 	private void setUpViews(ContactItem c1, ContactItem c2, boolean possible) {
-		introductionActivity.runOnUiThreadUnlessDestroyed(() -> {
+		// set avatars
-			contact1 = c1.getContact();
+		setAvatar(ui.avatar1, c1);
-			contact2 = c2.getContact();
+		setAvatar(ui.avatar2, c2);
 
-			// set avatars
+		// set contact names
-			setAvatar(ui.avatar1, c1);
+		ui.contactName1.setText(getContactDisplayName(c1.getContact()));
-			setAvatar(ui.avatar2, c2);
+		ui.contactName2.setText(getContactDisplayName(c2.getContact()));
 
-			// set contact names
+		// hide progress bar
-			ui.contactName1.setText(getContactDisplayName(c1.getContact()));
+		ui.progressBar.setVisibility(GONE);
-			ui.contactName2.setText(getContactDisplayName(c2.getContact()));
 
-			// hide progress bar
+		if (possible) {
-			ui.progressBar.setVisibility(GONE);
+			// show views
-
+			ui.notPossible.setVisibility(GONE);
-			if (possible) {
+			ui.message.setVisibility(VISIBLE);
-				// show views
+			ui.message.setReady(true);
-				ui.notPossible.setVisibility(GONE);
+			ui.message.showSoftKeyboard();
-				ui.message.setVisibility(VISIBLE);
+		} else {
-				ui.message.setReady(true);
+			ui.notPossible.setVisibility(VISIBLE);
-				ui.message.showSoftKeyboard();
+			ui.message.setVisibility(GONE);
-			} else {
+		}
-				ui.notPossible.setVisibility(VISIBLE);
-				ui.message.setVisibility(GONE);
-			}
-		});
 	}
 
 	@Override
@@ -193,7 +121,7 @@ public class IntroductionMessageFragment extends BaseFragment
 		switch (item.getItemId()) {
 			case android.R.id.home:
 				hideSoftKeyboard(ui.message);
-				introductionActivity.onBackPressed();
+				requireActivity().onBackPressed();
 				return true;
 			default:
 				return super.onOptionsItemSelected(item);
@@ -206,32 +134,13 @@ public class IntroductionMessageFragment extends BaseFragment
 		// disable button to prevent accidental double invitations
 		ui.message.setReady(false);
 
-		makeIntroduction(contact1, contact2, text);
+		viewModel.makeIntroduction(text);
 
 		// don't wait for the introduction to be made before finishing activity
 		hideSoftKeyboard(ui.message);
-		introductionActivity.setResult(RESULT_OK);
+		FragmentActivity activity = requireActivity();
-		introductionActivity.supportFinishAfterTransition();
+		activity.setResult(RESULT_OK);
-	}
+		activity.supportFinishAfterTransition();
-
-	private void makeIntroduction(Contact c1, Contact c2,
-			@Nullable String text) {
-		introductionActivity.runOnDbThread(() -> {
-			// actually make the introduction
-			try {
-				long timestamp = System.currentTimeMillis();
-				introductionManager.makeIntroduction(c1, c2, text, timestamp);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				introductionError();
-			}
-		});
-	}
-
-	private void introductionError() {
-		introductionActivity.runOnUiThreadUnlessDestroyed(
-				() -> Toast.makeText(introductionActivity,
-						R.string.introduction_error, LENGTH_SHORT).show());
 	}
 
 	private static class ViewHolder {

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionModule.java

@@ -0,0 +1,19 @@
+package org.briarproject.briar.android.introduction;
+
+import org.briarproject.briar.android.viewmodel.ViewModelKey;
+
+import androidx.lifecycle.ViewModel;
+import dagger.Binds;
+import dagger.Module;
+import dagger.multibindings.IntoMap;
+
+@Module
+public abstract class IntroductionModule {
+
+	@Binds
+	@IntoMap
+	@ViewModelKey(IntroductionViewModel.class)
+	abstract ViewModel bindIntroductionViewModel(
+			IntroductionViewModel introductionViewModel);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionViewModel.java

@@ -0,0 +1,181 @@
+package org.briarproject.briar.android.introduction;
+
+import android.app.Application;
+import android.widget.Toast;
+
+import org.briarproject.bramble.api.connection.ConnectionRegistry;
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.ContactManager;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.TransactionManager;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.contact.ContactItem;
+import org.briarproject.briar.android.contact.ContactsViewModel;
+import org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
+import org.briarproject.briar.api.conversation.ConversationManager;
+import org.briarproject.briar.api.identity.AuthorInfo;
+import org.briarproject.briar.api.identity.AuthorManager;
+import org.briarproject.briar.api.introduction.IntroductionManager;
+
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import static android.widget.Toast.LENGTH_SHORT;
+import static java.util.Objects.requireNonNull;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@NotNullByDefault
+class IntroductionViewModel extends ContactsViewModel {
+
+	private static final Logger LOG =
+			getLogger(IntroductionViewModel.class.getName());
+
+	private final ContactManager contactManager;
+	private final AuthorManager authorManager;
+	private final IntroductionManager introductionManager;
+
+	@Inject
+	IntroductionViewModel(Application application,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager, TransactionManager db,
+			AndroidExecutor androidExecutor, ContactManager contactManager,
+			AuthorManager authorManager,
+			ConversationManager conversationManager,
+			ConnectionRegistry connectionRegistry, EventBus eventBus,
+			IntroductionManager introductionManager) {
+		super(application, dbExecutor, lifecycleManager, db, androidExecutor,
+				contactManager, authorManager, conversationManager,
+				connectionRegistry, eventBus);
+		this.contactManager = contactManager;
+		this.authorManager = authorManager;
+		this.introductionManager = introductionManager;
+	}
+
+	/*
+	 * This is the contact from whose conversation we started the introduction
+	 * using the menu item.
+	 */
+	@Nullable
+	private ContactId firstContactId;
+	/*
+	 * This is the contact we selected from the list of contacts as a second
+	 * contact for the introduction.
+	 */
+	@Nullable
+	private ContactId secondContactId;
+
+	private final MutableLiveEvent<Boolean> secondContactSelected =
+			new MutableLiveEvent<>();
+
+	private final MutableLiveData<IntroductionInfo> introductionInfo =
+			new MutableLiveData<>();
+
+	void setFirstContactId(ContactId contactId) {
+		this.firstContactId = contactId;
+		loadContacts();
+	}
+
+	@Nullable
+	ContactId getSecondContactId() {
+		return secondContactId;
+	}
+
+	void setSecondContactId(ContactId contactId) {
+		secondContactId = contactId;
+		// Setting this to null here so that IntroductionMessageFragment can
+		// tell whether the correct value has been loaded from the database when
+		// selecting a second contact repeatedly.
+		introductionInfo.setValue(null);
+		loadIntroductionInfo();
+	}
+
+	/**
+	 * Trigger the event that the second contact has been selected from the
+	 * contact list by the user.
+	 */
+	void triggerContactSelected() {
+		secondContactSelected.setEvent(true);
+	}
+
+	/**
+	 * This event will be triggered once the second contact has been selected
+	 * from the list of contacts displayed. It is not fired when the second
+	 * contact gets restored from the saved instance state.
+	 */
+	LiveEvent<Boolean> getSecondContactSelected() {
+		return secondContactSelected;
+	}
+
+	/**
+	 * Holder for the introduction info object with data about both contacts
+	 * and whether the introduction is possible. May wrap null if the data
+	 * is not available yet. This happens when it is reset by selecting a
+	 * contact with the same view model instance more than once.
+	 */
+	LiveData<IntroductionInfo> getIntroductionInfo() {
+		return introductionInfo;
+	}
+
+	@Override
+	protected boolean displayContact(ContactId contactId) {
+		return !requireNonNull(firstContactId).equals(contactId);
+	}
+
+	private void loadIntroductionInfo() {
+		final ContactId firstContactId = requireNonNull(this.firstContactId);
+		final ContactId secondContactId = requireNonNull(this.secondContactId);
+		runOnDbThread(() -> {
+			try {
+				Contact firstContact =
+						contactManager.getContact(firstContactId);
+				Contact secondContact =
+						contactManager.getContact(secondContactId);
+				AuthorInfo a1 = authorManager.getAuthorInfo(firstContact);
+				AuthorInfo a2 = authorManager.getAuthorInfo(secondContact);
+				boolean possible = introductionManager
+						.canIntroduce(firstContact, secondContact);
+				ContactItem c1 = new ContactItem(firstContact, a1);
+				ContactItem c2 = new ContactItem(secondContact, a2);
+				introductionInfo.postValue(
+						new IntroductionInfo(c1, c2, possible));
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	void makeIntroduction(@Nullable String text) {
+		final IntroductionInfo info =
+				requireNonNull(introductionInfo.getValue());
+		runOnDbThread(() -> {
+			// actually make the introduction
+			try {
+				long timestamp = System.currentTimeMillis();
+				introductionManager.makeIntroduction(
+						info.getContact1().getContact(),
+						info.getContact2().getContact(), text, timestamp);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				androidExecutor.runOnUiThread(() -> Toast.makeText(
+						getApplication(), R.string.introduction_error,
+						LENGTH_SHORT).show());
+			}
+		});
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/privategroup/reveal/RevealContactsFragment.java

@@ -8,7 +8,7 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.contact.BaseContactListAdapter.OnContactClickListener;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 import org.briarproject.briar.android.contactselection.BaseContactSelectorFragment;
 import org.briarproject.briar.android.contactselection.ContactSelectorController;
 

briar-android/src/main/java/org/briarproject/briar/android/privategroup/reveal/RevealableContactAdapter.java

@@ -8,6 +8,7 @@ import android.view.ViewGroup;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 import org.briarproject.briar.android.contactselection.BaseContactSelectorAdapter;
 
 import java.util.ArrayList;

briar-android/src/main/java/org/briarproject/briar/android/privategroup/reveal/RevealableContactViewHolder.java

@@ -5,7 +5,7 @@ import android.widget.ImageView;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.contact.BaseContactListAdapter.OnContactClickListener;
+import org.briarproject.briar.android.contact.OnContactClickListener;
 import org.briarproject.briar.android.contactselection.BaseSelectableContactHolder;
 
 import javax.annotation.Nullable;

briar-android/src/main/java/org/briarproject/briar/android/view/BriarRecyclerView.java

@@ -52,7 +52,8 @@ public class BriarRecyclerView extends FrameLayout {
 				R.styleable.BriarRecyclerView);
 		isScrollingToEnd = attributes
 				.getBoolean(R.styleable.BriarRecyclerView_scrollToEnd, true);
-		int drawableRes = attributes.getResourceId(R.styleable.BriarRecyclerView_emptyImage, -1);
+		int drawableRes = attributes
+				.getResourceId(R.styleable.BriarRecyclerView_emptyImage, -1);
 		if (drawableRes != -1) setEmptyImage(drawableRes);
 		String emtpyText =
 				attributes.getString(R.styleable.BriarRecyclerView_emptyText);
@@ -87,10 +88,30 @@ public class BriarRecyclerView extends FrameLayout {
 		}
 
 		emptyObserver = new RecyclerView.AdapterDataObserver() {
+
+			@Override
+			public void onChanged() {
+				super.onChanged();
+				showData();
+			}
+
+			@Override
+			public void onItemRangeChanged(int positionStart, int itemCount) {
+				super.onItemRangeChanged(positionStart, itemCount);
+				if (itemCount > 0) showData();
+			}
+
+			@Override
+			public void onItemRangeMoved(int fromPosition, int toPosition,
+					int itemCount) {
+				super.onItemRangeMoved(fromPosition, toPosition, itemCount);
+				if (itemCount > 0) showData();
+			}
+
 			@Override
 			public void onItemRangeInserted(int positionStart, int itemCount) {
 				super.onItemRangeInserted(positionStart, itemCount);
-				if (itemCount > 0) showData();
+				showData();
 			}
 
 			@Override

briar-android/src/main/java/org/briarproject/briar/android/viewmodel/DbViewModel.java

@@ -43,7 +43,7 @@ public abstract class DbViewModel extends AndroidViewModel {
 	private final Executor dbExecutor;
 	private final LifecycleManager lifecycleManager;
 	private final TransactionManager db;
-	private final AndroidExecutor androidExecutor;
+	protected final AndroidExecutor androidExecutor;
 
 	public DbViewModel(
 			@NonNull Application application,