Move background work into view model.

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

@@ -33,6 +33,7 @@ import org.briarproject.bramble.plugin.tor.CircumventionProvider;
 import org.briarproject.bramble.util.AndroidUtils;
 import org.briarproject.bramble.util.StringUtils;
 import org.briarproject.briar.android.account.LockManagerImpl;
+import org.briarproject.briar.android.keyagreement.ContactExchangeModule;
 import org.briarproject.briar.android.viewmodel.ViewModelModule;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.android.DozeWatchdog;
@@ -59,7 +60,7 @@ import static java.util.Collections.emptyList;
 import static org.briarproject.bramble.api.reporting.ReportingConstants.DEV_ONION_ADDRESS;
 import static org.briarproject.bramble.api.reporting.ReportingConstants.DEV_PUBLIC_KEY_HEX;
 
-@Module(includes = ViewModelModule.class)
+@Module(includes = {ContactExchangeModule.class, ViewModelModule.class})
 public class AppModule {
 
 	static class EagerSingletons {

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/ContactExchangeActivity.java

@@ -1,24 +1,18 @@
 package org.briarproject.briar.android.keyagreement;
 
+import android.arch.lifecycle.ViewModelProvider;
+import android.arch.lifecycle.ViewModelProviders;
 import android.os.Bundle;
 import android.support.annotation.UiThread;
 import android.widget.Toast;
 
-import org.briarproject.bramble.api.contact.ContactExchangeManager;
-import org.briarproject.bramble.api.contact.event.ContactExchangeFailedEvent;
-import org.briarproject.bramble.api.contact.event.ContactExchangeSucceededEvent;
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementResult;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 
-import java.util.concurrent.Executor;
-
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
@@ -27,16 +21,12 @@ import static java.util.Objects.requireNonNull;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-public class ContactExchangeActivity extends KeyAgreementActivity implements
-		EventListener {
+public class ContactExchangeActivity extends KeyAgreementActivity {
 
 	@Inject
-	@IoExecutor
-	Executor ioExecutor;
+	ViewModelProvider.Factory viewModelFactory;
 
-	// Fields that are accessed from background threads must be volatile
-	@Inject
-	volatile ContactExchangeManager contactExchangeManager;
+	private ContactExchangeViewModel viewModel;
 
 	@Override
 	public void injectActivity(ActivityComponent component) {
@@ -46,45 +36,27 @@ public class ContactExchangeActivity extends KeyAgreementActivity implements
 	@Override
 	public void onCreate(@Nullable Bundle state) {
 		super.onCreate(state);
-		getSupportActionBar().setTitle(R.string.add_contact_title);
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		// Listen to updates from ContactExchangeManager
-		eventBus.addListener(this);
-	}
-
-	@Override
-	protected void onStop() {
-		super.onStop();
-		// Stop listening to updates from ContactExchangeManager
-		eventBus.addListener(this);
+		requireNonNull(getSupportActionBar())
+				.setTitle(R.string.add_contact_title);
+		viewModel = ViewModelProviders.of(this, viewModelFactory)
+				.get(ContactExchangeViewModel.class);
 	}
 
 	private void startContactExchange(KeyAgreementResult result) {
-		ioExecutor.execute(() -> {
-			// Exchange contact details
-			contactExchangeManager.exchangeContacts(result.getTransportId(),
-					result.getConnection(), result.getMasterKey(),
-					result.wasAlice());
-		});
-	}
-
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof ContactExchangeSucceededEvent) {
-			ContactExchangeSucceededEvent c = (ContactExchangeSucceededEvent) e;
-			contactExchangeSucceeded(c.getRemoteAuthor());
-		} else if (e instanceof ContactExchangeFailedEvent) {
-			ContactExchangeFailedEvent c = (ContactExchangeFailedEvent) e;
-			if (c.wasDuplicateContact()) {
-				duplicateContact(requireNonNull(c.getDuplicateRemoteAuthor()));
+		viewModel.getSucceeded().observe(this, succeeded -> {
+			if (succeeded == null) return;
+			if (succeeded) {
+				Author remote = requireNonNull(viewModel.getRemoteAuthor());
+				contactExchangeSucceeded(remote);
 			} else {
-				contactExchangeFailed();
+				Author duplicate = viewModel.getDuplicateAuthor();
+				if (duplicate == null) contactExchangeFailed();
+				else duplicateContact(duplicate);
 			}
-		}
+		});
+		viewModel.startContactExchange(result.getTransportId(),
+				result.getConnection(), result.getMasterKey(),
+				result.wasAlice());
 	}
 
 	@UiThread

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/ContactExchangeModule.java

@@ -0,0 +1,20 @@
+package org.briarproject.briar.android.keyagreement;
+
+import android.arch.lifecycle.ViewModel;
+
+import org.briarproject.briar.android.viewmodel.ViewModelKey;
+
+import dagger.Binds;
+import dagger.Module;
+import dagger.multibindings.IntoMap;
+
+@Module
+public abstract class ContactExchangeModule {
+
+	@Binds
+	@IntoMap
+	@ViewModelKey(ContactExchangeViewModel.class)
+	abstract ViewModel bindContactExchangeViewModel(
+			ContactExchangeViewModel contactExchangeViewModel);
+
+}

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/ContactExchangeViewModel.java

@@ -0,0 +1,93 @@
+package org.briarproject.briar.android.keyagreement;
+
+import android.app.Application;
+import android.arch.lifecycle.AndroidViewModel;
+import android.arch.lifecycle.LiveData;
+import android.arch.lifecycle.MutableLiveData;
+import android.support.annotation.UiThread;
+
+import org.briarproject.bramble.api.contact.ContactExchangeManager;
+import org.briarproject.bramble.api.contact.event.ContactExchangeFailedEvent;
+import org.briarproject.bramble.api.contact.event.ContactExchangeSucceededEvent;
+import org.briarproject.bramble.api.crypto.SecretKey;
+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.identity.Author;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+
+import java.util.concurrent.Executor;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import static java.util.Objects.requireNonNull;
+
+@NotNullByDefault
+class ContactExchangeViewModel extends AndroidViewModel
+		implements EventListener {
+
+	private final Executor ioExecutor;
+	private final ContactExchangeManager contactExchangeManager;
+	private final EventBus eventBus;
+	private final MutableLiveData<Boolean> succeeded = new MutableLiveData<>();
+
+	@Nullable
+	private Author remoteAuthor, duplicateAuthor;
+
+	@Inject
+	ContactExchangeViewModel(Application app, @IoExecutor Executor ioExecutor,
+			ContactExchangeManager contactExchangeManager, EventBus eventBus) {
+		super(app);
+		this.ioExecutor = ioExecutor;
+		this.contactExchangeManager = contactExchangeManager;
+		this.eventBus = eventBus;
+		eventBus.addListener(this);
+	}
+
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		eventBus.removeListener(this);
+	}
+
+	@UiThread
+	void startContactExchange(TransportId t, DuplexTransportConnection conn,
+			SecretKey masterKey, boolean alice) {
+		ioExecutor.execute(() -> contactExchangeManager.exchangeContacts(t,
+				conn, masterKey, alice));
+	}
+
+	@UiThread
+	@Nullable
+	Author getRemoteAuthor() {
+		return remoteAuthor;
+	}
+
+	@UiThread
+	@Nullable
+	Author getDuplicateAuthor() {
+		return duplicateAuthor;
+	}
+
+	LiveData<Boolean> getSucceeded() {
+		return succeeded;
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof ContactExchangeSucceededEvent) {
+			ContactExchangeSucceededEvent c = (ContactExchangeSucceededEvent) e;
+			remoteAuthor = c.getRemoteAuthor();
+			succeeded.setValue(true);
+		} else if (e instanceof ContactExchangeFailedEvent) {
+			ContactExchangeFailedEvent c = (ContactExchangeFailedEvent) e;
+			if (c.wasDuplicateContact())
+				duplicateAuthor = requireNonNull(c.getDuplicateRemoteAuthor());
+			succeeded.setValue(false);
+		}
+	}
+}

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

@@ -14,6 +14,6 @@ import dagger.MapKey;
 @Target({ElementType.METHOD})
 @Retention(RetentionPolicy.RUNTIME)
 @MapKey
-@interface ViewModelKey {
+public @interface ViewModelKey {
 	Class<? extends ViewModel> value();
 }