Implement UI for mailbox pairing error and final states

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

@@ -44,6 +44,7 @@ import org.briarproject.briar.android.hotspot.ManualHotspotFragment;
 import org.briarproject.briar.android.hotspot.QrHotspotFragment;
 import org.briarproject.briar.android.logging.CachingLogHandler;
 import org.briarproject.briar.android.login.SignInReminderReceiver;
+import org.briarproject.briar.android.mailbox.ErrorFragment;
 import org.briarproject.briar.android.mailbox.MailboxScanFragment;
 import org.briarproject.briar.android.mailbox.OfflineFragment;
 import org.briarproject.briar.android.mailbox.SetupDownloadFragment;
@@ -248,4 +249,6 @@ public interface AndroidComponent
 	void inject(MailboxScanFragment mailboxScanFragment);
 
 	void inject(OfflineFragment offlineFragment);
+
+	void inject(ErrorFragment errorFragment);
 }

briar-android/src/main/java/org/briarproject/briar/android/fragment/FinalFragment.java

@@ -63,6 +63,13 @@ public class FinalFragment extends Fragment {
 
 	private NestedScrollView scrollView;
 	protected Button buttonView;
+	protected final OnBackPressedCallback onBackPressedCallback =
+			new OnBackPressedCallback(true) {
+				@Override
+				public void handleOnBackPressed() {
+					onBackButtonPressed();
+				}
+			};
 
 	@Nullable
 	@Override
@@ -95,13 +102,8 @@ public class FinalFragment extends Fragment {
 
 		AppCompatActivity a = (AppCompatActivity) requireActivity();
 		a.setTitle(args.getInt(ARG_TITLE));
-		a.getOnBackPressedDispatcher().addCallback(
-				getViewLifecycleOwner(), new OnBackPressedCallback(true) {
-					@Override
-					public void handleOnBackPressed() {
-						onBackButtonPressed();
-					}
-				});
+		a.getOnBackPressedDispatcher()
+				.addCallback(getViewLifecycleOwner(), onBackPressedCallback);
 		return v;
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/mailbox/ErrorFragment.java

@@ -1,5 +1,6 @@
 package org.briarproject.briar.android.mailbox;
 
+import android.content.Context;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -10,8 +11,14 @@ import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.fragment.FinalFragment;
 
+import javax.inject.Inject;
+
 import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
+import androidx.fragment.app.FragmentActivity;
+import androidx.lifecycle.ViewModelProvider;
+
+import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -29,21 +36,35 @@ public class ErrorFragment extends FinalFragment {
 		return f;
 	}
 
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private MailboxViewModel viewModel;
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		FragmentActivity activity = requireActivity();
+		getAndroidComponent(activity).inject(this);
+		viewModel = new ViewModelProvider(activity, viewModelFactory)
+				.get(MailboxViewModel.class);
+	}
+
 	@Nullable
 	@Override
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
 		View v = super.onCreateView(inflater, container, savedInstanceState);
+		onBackPressedCallback.remove();
 		buttonView.setText(R.string.try_again_button);
+		buttonView.setOnClickListener(view -> {
+			getParentFragmentManager().popBackStackImmediate();
+			viewModel.tryAgainAfterError();
+		});
 		return v;
 	}
 
-	@Override
-	protected void onBackButtonPressed() {
-		requireActivity().getSupportFragmentManager().popBackStack();
-	}
-
 	@Override
 	protected boolean shouldHideActionBarBackButton() {
 		return false;

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxActivity.java

@@ -6,18 +6,19 @@ import android.widget.ProgressBar;
 import android.widget.Toast;
 
 import org.briarproject.bramble.api.mailbox.MailboxPairingState;
-import org.briarproject.bramble.api.mailbox.MailboxPairingState.Pairing;
 import org.briarproject.bramble.api.mailbox.MailboxStatus;
 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.activity.BriarActivity;
+import org.briarproject.briar.android.fragment.FinalFragment;
 
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentManager;
 import androidx.lifecycle.ViewModelProvider;
 
 import static android.view.View.INVISIBLE;
@@ -84,9 +85,9 @@ public class MailboxActivity extends BriarActivity {
 	@Override
 	public void onBackPressed() {
 		MailboxState s = viewModel.getState().getLastValue();
-		if (s instanceof MailboxState.Pairing &&
-				((MailboxState.Pairing) s).pairingState instanceof Pairing) {
-			// don't go back in flow if we are already pairing with the mailbox
+		if (s instanceof MailboxState.Pairing) {
+			// don't go back in the flow if we are already pairing
+			// with the mailbox. We provide a try-again button instead.
 			supportFinishAfterTransition();
 		} else {
 			super.onBackPressed();
@@ -102,47 +103,63 @@ public class MailboxActivity extends BriarActivity {
 	}
 
 	private void onScanningQrCode() {
-		showFragment(getSupportFragmentManager(), new MailboxScanFragment(),
-				MailboxScanFragment.TAG);
+		FragmentManager fm = getSupportFragmentManager();
+		if (fm.findFragmentByTag(MailboxScanFragment.TAG) != null) {
+			// if the scanner is already on the back stack, pop back to it
+			// instead of adding it to the stack again
+			fm.popBackStackImmediate(MailboxScanFragment.TAG, 0);
+		} else {
+			showFragment(fm, new MailboxScanFragment(),
+					MailboxScanFragment.TAG);
+		}
 	}
 
 	private void onMailboxPairingStateChanged(MailboxPairingState s) {
 		progressBar.setVisibility(INVISIBLE);
+		FragmentManager fm = getSupportFragmentManager();
 		Fragment f;
 		String tag;
-		boolean addToBackStack = true;
 		if (s instanceof MailboxPairingState.QrCodeReceived) {
 			// ignore, showing yet another progress fragment messes with back stack
 			return;
 		} else if (s instanceof MailboxPairingState.Pairing) {
+			if (fm.getBackStackEntryCount() == 0) {
+				// We re-launched into an existing state,
+				// need to re-populate the back stack.
+				repopulateBackStack();
+			}
 			f = new MailboxConnectingFragment();
 			tag = MailboxConnectingFragment.TAG;
-			addToBackStack = false;
 		} else if (s instanceof MailboxPairingState.InvalidQrCode) {
 			f = ErrorFragment.newInstance(
 					R.string.mailbox_setup_qr_code_wrong_title,
 					R.string.mailbox_setup_qr_code_wrong_description);
 			tag = ErrorFragment.TAG;
 		} else if (s instanceof MailboxPairingState.MailboxAlreadyPaired) {
-			// TODO
-			Toast.makeText(this, "MailboxAlreadyPaired", LENGTH_LONG).show();
-			return;
+			f = ErrorFragment.newInstance(
+					R.string.mailbox_setup_already_paired_title,
+					R.string.mailbox_setup_already_paired_description);
+			tag = ErrorFragment.TAG;
 		} else if (s instanceof MailboxPairingState.ConnectionError) {
-			// TODO
-			Toast.makeText(this, "Connection Error", LENGTH_LONG).show();
-			return;
-		} else if (s instanceof MailboxPairingState.AssertionError) {
-			// TODO
-			Toast.makeText(this, "Connection Error", LENGTH_LONG).show();
-			return;
+			f = ErrorFragment.newInstance(
+					R.string.mailbox_setup_io_error_title,
+					R.string.mailbox_setup_io_error_description);
+			tag = ErrorFragment.TAG;
+		} else if (s instanceof MailboxPairingState.UnexpectedError) {
+			f = ErrorFragment.newInstance(
+					R.string.mailbox_setup_assertion_error_title,
+					R.string.mailbox_setup_assertion_error_description);
+			tag = ErrorFragment.TAG;
 		} else if (s instanceof MailboxPairingState.Paired) {
-			// TODO
-			Toast.makeText(this, "Connection Error", LENGTH_LONG).show();
-			return;
+			f = FinalFragment.newInstance(R.string.mailbox_setup_paired_title,
+					R.drawable.ic_check_circle_outline,
+					R.color.briar_brand_green,
+					R.string.mailbox_setup_paired_description);
+			tag = FinalFragment.TAG;
 		} else {
 			throw new IllegalStateException("Unhandled state: " + s.getClass());
 		}
-		showFragment(getSupportFragmentManager(), f, tag, addToBackStack);
+		showFragment(fm, f, tag);
 	}
 
 	private void onOffline() {
@@ -156,4 +173,12 @@ public class MailboxActivity extends BriarActivity {
 		Toast.makeText(this, "NOT IMPLEMENTED", LENGTH_LONG).show();
 	}
 
+	private void repopulateBackStack() {
+		FragmentManager fm = getSupportFragmentManager();
+		onNotSetup();
+		showFragment(fm, new SetupDownloadFragment(),
+				SetupDownloadFragment.TAG);
+		onScanningQrCode();
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxState.java

@@ -19,6 +19,11 @@ class MailboxState {
 		Pairing(MailboxPairingState pairingState) {
 			this.pairingState = pairingState;
 		}
+
+		@Nullable
+		String getQrCodePayload() {
+			return pairingState.qrCodePayload;
+		}
 	}
 
 	static class OfflineWhenPairing extends MailboxState {

briar-android/src/main/java/org/briarproject/briar/android/mailbox/MailboxViewModel.java

@@ -34,6 +34,7 @@ import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
 
 import static java.util.Objects.requireNonNull;
+import static java.util.logging.Level.INFO;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.plugin.Plugin.State.ACTIVE;
 
@@ -129,6 +130,10 @@ class MailboxViewModel extends DbViewModel
 	@UiThread
 	@Override
 	public void accept(MailboxPairingState mailboxPairingState) {
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("New pairing state: " +
+					mailboxPairingState.getClass().getSimpleName());
+		}
 		state.setEvent(new MailboxState.Pairing(mailboxPairingState));
 	}
 
@@ -149,6 +154,17 @@ class MailboxViewModel extends DbViewModel
 		}
 	}
 
+	@UiThread
+	void tryAgainAfterError() {
+		MailboxState.Pairing pairing = (MailboxState.Pairing)
+				requireNonNull(state.getLastValue());
+		if (pairing.getQrCodePayload() == null) {
+			onScanButtonClicked();
+		} else {
+			onQrCodePayloadReceived(pairing.getQrCodePayload());
+		}
+	}
+
 	@UiThread
 	QrCodeDecoder getQrCodeDecoder() {
 		return qrCodeDecoder;

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

@@ -625,6 +625,15 @@
 	<string name="mailbox_setup_connecting">Connecting…</string>
 	<string name="mailbox_setup_qr_code_wrong_title">Wrong QR code</string>
 	<string name="mailbox_setup_qr_code_wrong_description">The scanned code is invalid. Please open the Briar Mailbox app on your mailbox device and scan the QR code it presents.</string>
+	<string name="mailbox_setup_already_paired_title">Mailbox already linked</string>
+	<string name="mailbox_setup_already_paired_description">Unlink the mailbox on your other device and try again.</string>
+	<string name="mailbox_setup_io_error_title">Could not connect</string>
+	<string name="mailbox_setup_io_error_description">Ensure that both devices are connected to the internet and try again.</string>
+	<string name="mailbox_setup_assertion_error_title">Mailbox Error</string>
+	<string name="mailbox_setup_assertion_error_description">Please send feedback (with anonymous data) via the Briar app if the issue persists.</string>
+	<string name="mailbox_setup_paired_title">Connected</string>
+	<string name="mailbox_setup_paired_description">The mailbox has been successfully linked.\n
+	\nFor ideal message delivery, keep the mailbox device connected to a charger and online.</string>
 	<string name="tor_offline_title">Offline</string>
 	<string name="tor_offline_description">Ensure that this device is online and connections to the internet are allowed.\n\nAfterwards, wait for the globe icon in connection settings to turn green.</string>
 	<string name="tor_offline_button_check">Check connection settings</string>