Simplify fragment transitions for mailbox pairing UI

Now, trying again always starts before scanning, so the user needs to scan the code again.

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

@@ -49,6 +49,7 @@ import org.briarproject.briar.android.mailbox.MailboxScanFragment;
 import org.briarproject.briar.android.mailbox.MailboxStatusFragment;
 import org.briarproject.briar.android.mailbox.OfflineFragment;
 import org.briarproject.briar.android.mailbox.SetupDownloadFragment;
+import org.briarproject.briar.android.mailbox.SetupIntroFragment;
 import org.briarproject.briar.android.removabledrive.ChooserFragment;
 import org.briarproject.briar.android.removabledrive.ReceiveFragment;
 import org.briarproject.briar.android.removabledrive.SendFragment;
@@ -245,6 +246,8 @@ public interface AndroidComponent
 
 	void inject(BluetoothIntroFragment bluetoothIntroFragment);
 
+	void inject(SetupIntroFragment setupIntroFragment);
+
 	void inject(SetupDownloadFragment setupDownloadFragment);
 
 	void inject(MailboxScanFragment mailboxScanFragment);

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

@@ -59,10 +59,7 @@ public class ErrorFragment extends FinalFragment {
 		// Do not hijack back button events, but let the activity process them
 		onBackPressedCallback.remove();
 		buttonView.setText(R.string.try_again_button);
-		buttonView.setOnClickListener(view -> {
-			getParentFragmentManager().popBackStackImmediate();
-			viewModel.tryAgainAfterError();
-		});
+		buttonView.setOnClickListener(view -> viewModel.showDownloadFragment());
 		return v;
 	}
 

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

@@ -54,6 +54,8 @@ public class MailboxActivity extends BriarActivity {
 		viewModel.getState().observeEvent(this, state -> {
 			if (state instanceof MailboxState.NotSetup) {
 				onNotSetup();
+			} else if (state instanceof MailboxState.ShowDownload) {
+				onShowDownload();
 			} else if (state instanceof MailboxState.ScanningQrCode) {
 				onScanningQrCode();
 			} else if (state instanceof MailboxState.Pairing) {
@@ -62,6 +64,8 @@ public class MailboxActivity extends BriarActivity {
 				onMailboxPairingStateChanged(s);
 			} else if (state instanceof MailboxState.OfflineWhenPairing) {
 				onOffline();
+			} else if (state instanceof MailboxState.CameraError) {
+				onCameraError();
 			} else if (state instanceof MailboxState.IsPaired) {
 				onIsPaired();
 			} else {
@@ -99,32 +103,38 @@ public class MailboxActivity extends BriarActivity {
 				.commit();
 	}
 
-	private void onScanningQrCode() {
+	private void onShowDownload() {
 		FragmentManager fm = getSupportFragmentManager();
-		if (fm.findFragmentByTag(MailboxScanFragment.TAG) != null) {
-			// if the scanner is already on the back stack, pop back to it
+		if (fm.findFragmentByTag(SetupDownloadFragment.TAG) != null) {
+			// if the fragment is already on the back stack, pop back to it
 			// instead of adding it to the stack again
-			fm.popBackStackImmediate(MailboxScanFragment.TAG, 0);
+			fm.popBackStackImmediate(SetupDownloadFragment.TAG, 0);
 		} else {
-			showFragment(fm, new MailboxScanFragment(),
-					MailboxScanFragment.TAG);
+			showFragment(fm, new SetupDownloadFragment(),
+					SetupDownloadFragment.TAG);
 		}
 	}
 
+	private void onScanningQrCode() {
+		showFragment(getSupportFragmentManager(), new MailboxScanFragment(),
+				MailboxScanFragment.TAG);
+	}
+
 	private void onMailboxPairingStateChanged(MailboxPairingState s) {
 		progressBar.setVisibility(INVISIBLE);
 		FragmentManager fm = getSupportFragmentManager();
+		if (fm.getBackStackEntryCount() == 0) {
+			// We re-launched into an existing state,
+			// need to re-populate the back stack.
+			onNotSetup();
+			onShowDownload();
+		}
 		Fragment f;
 		String tag;
 		if (s instanceof MailboxPairingState.QrCodeReceived) {
-			// ignore, showing yet another progress fragment messes with back stack
-			return;
+			f = new MailboxConnectingFragment();
+			tag = MailboxConnectingFragment.TAG;
 		} 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;
 		} else if (s instanceof MailboxPairingState.InvalidQrCode) {
@@ -164,18 +174,17 @@ public class MailboxActivity extends BriarActivity {
 				OfflineFragment.TAG);
 	}
 
+	private void onCameraError() {
+		Fragment f = ErrorFragment.newInstance(
+				R.string.mailbox_setup_camera_error_title,
+				R.string.mailbox_setup_camera_error_description);
+		showFragment(getSupportFragmentManager(), f, ErrorFragment.TAG);
+	}
+
 	private void onIsPaired() {
 		progressBar.setVisibility(INVISIBLE);
 		showFragment(getSupportFragmentManager(), new MailboxStatusFragment(),
 				MailboxStatusFragment.TAG, false);
 	}
 
-	private void repopulateBackStack() {
-		FragmentManager fm = getSupportFragmentManager();
-		onNotSetup();
-		showFragment(fm, new SetupDownloadFragment(),
-				SetupDownloadFragment.TAG);
-		onScanningQrCode();
-	}
-
 }

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

@@ -94,7 +94,7 @@ public class MailboxScanFragment extends Fragment {
 		logException(LOG, WARNING, e);
 		Toast.makeText(requireContext(), R.string.camera_error,
 				LENGTH_LONG).show();
-		requireActivity().getSupportFragmentManager().popBackStack();
+		viewModel.onCameraError();
 	}
 
 }

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

@@ -3,13 +3,14 @@ package org.briarproject.briar.android.mailbox;
 import org.briarproject.bramble.api.mailbox.MailboxPairingState;
 import org.briarproject.bramble.api.mailbox.MailboxStatus;
 
-import androidx.annotation.Nullable;
-
 class MailboxState {
 
 	static class NotSetup extends MailboxState {
 	}
 
+	static class ShowDownload extends MailboxState {
+	}
+
 	static class ScanningQrCode extends MailboxState {
 	}
 
@@ -19,24 +20,12 @@ class MailboxState {
 		Pairing(MailboxPairingState pairingState) {
 			this.pairingState = pairingState;
 		}
-
-		@Nullable
-		String getQrCodePayload() {
-			return pairingState.qrCodePayload;
-		}
 	}
 
 	static class OfflineWhenPairing extends MailboxState {
-		@Nullable
-		final String qrCodePayload;
+	}
 
-		OfflineWhenPairing(@Nullable String qrCodePayload) {
-			this.qrCodePayload = qrCodePayload;
-		}
-
-		OfflineWhenPairing() {
-			this(null);
-		}
+	static class CameraError extends MailboxState {
 	}
 
 	static class IsPaired extends MailboxState {

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

@@ -33,7 +33,6 @@ import androidx.annotation.AnyThread;
 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;
@@ -110,6 +109,11 @@ class MailboxViewModel extends DbViewModel
 		}
 	}
 
+	@UiThread
+	void onCameraError() {
+		state.setEvent(new MailboxState.CameraError());
+	}
+
 	@Override
 	@IoExecutor
 	public void onQrCodeDecoded(Result result) {
@@ -123,7 +127,7 @@ class MailboxViewModel extends DbViewModel
 			pairingTask = mailboxManager.startPairingTask(qrCodePayload);
 			pairingTask.addObserver(this);
 		} else {
-			state.postEvent(new MailboxState.OfflineWhenPairing(qrCodePayload));
+			state.postEvent(new MailboxState.OfflineWhenPairing());
 		}
 	}
 
@@ -143,26 +147,8 @@ class MailboxViewModel extends DbViewModel
 	}
 
 	@UiThread
-	void tryAgainWhenOffline() {
-		MailboxState.OfflineWhenPairing offline =
-				(MailboxState.OfflineWhenPairing) requireNonNull(
-						state.getLastValue());
-		if (offline.qrCodePayload == null) {
-			onScanButtonClicked();
-		} else {
-			onQrCodePayloadReceived(offline.qrCodePayload);
-		}
-	}
-
-	@UiThread
-	void tryAgainAfterError() {
-		MailboxState.Pairing pairing = (MailboxState.Pairing)
-				requireNonNull(state.getLastValue());
-		if (pairing.getQrCodePayload() == null) {
-			onScanButtonClicked();
-		} else {
-			onQrCodePayloadReceived(pairing.getQrCodePayload());
-		}
+	void showDownloadFragment() {
+		state.setEvent(new MailboxState.ShowDownload());
 	}
 
 	@UiThread

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

@@ -62,10 +62,7 @@ public class OfflineFragment extends Fragment {
 			startActivity(i);
 		});
 		buttonView = v.findViewById(R.id.button);
-		buttonView.setOnClickListener(view -> {
-			getParentFragmentManager().popBackStackImmediate();
-			viewModel.tryAgainWhenOffline();
-		});
+		buttonView.setOnClickListener(view -> viewModel.showDownloadFragment());
 
 		return v;
 	}

briar-android/src/main/java/org/briarproject/briar/android/mailbox/SetupIntroFragment.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;
@@ -11,12 +12,15 @@ import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.R;
 
+import javax.inject.Inject;
+
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
-import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentActivity;
+import androidx.lifecycle.ViewModelProvider;
 
 import static android.view.View.FOCUS_DOWN;
-import static org.briarproject.briar.android.util.UiUtils.showFragment;
+import static org.briarproject.briar.android.AppModule.getAndroidComponent;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -24,8 +28,22 @@ public class SetupIntroFragment extends Fragment {
 
 	static final String TAG = SetupIntroFragment.class.getName();
 
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private MailboxViewModel viewModel;
+
 	private ScrollView scrollView;
 
+	@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,
@@ -35,11 +53,7 @@ public class SetupIntroFragment extends Fragment {
 				container, false);
 		scrollView = v.findViewById(R.id.scrollView);
 		Button button = v.findViewById(R.id.continueButton);
-		button.setOnClickListener(view -> {
-			FragmentManager fm = getParentFragmentManager();
-			Fragment f = new SetupDownloadFragment();
-			showFragment(fm, f, SetupDownloadFragment.TAG);
-		});
+		button.setOnClickListener(view -> viewModel.showDownloadFragment());
 		return v;
 	}
 

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

@@ -631,6 +631,8 @@
 	<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_camera_error_title" translatable="false">@string/camera_error</string>
+	<string name="mailbox_setup_camera_error_description">Could not access camera. Try again, maybe after rebooting device.</string>
 	<string name="mailbox_setup_paired_title">Connected</string>
 	<string name="mailbox_setup_paired_description">Your Mailbox has been successfully linked with Briar.\n
 		\nKeep your Mailbox connected to power and Wi-Fi so it\'s always online.</string>