Introduce RssFeedViewModel

Furnishing the RssFeed function as a single activity with fragments for
Manage and Import.

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

@@ -13,8 +13,11 @@ import org.briarproject.briar.android.blog.BlogPostFragment;
 import org.briarproject.briar.android.blog.FeedFragment;
 import org.briarproject.briar.android.blog.ReblogActivity;
 import org.briarproject.briar.android.blog.ReblogFragment;
-import org.briarproject.briar.android.blog.RssFeedImportActivity;
-import org.briarproject.briar.android.blog.RssFeedManageActivity;
+import org.briarproject.briar.android.blog.RssFeedActivity;
+import org.briarproject.briar.android.blog.RssFeedDeleteFeedDialogFragment;
+import org.briarproject.briar.android.blog.RssFeedImportFailedDialogFragment;
+import org.briarproject.briar.android.blog.RssFeedImportFragment;
+import org.briarproject.briar.android.blog.RssFeedManageFragment;
 import org.briarproject.briar.android.blog.WriteBlogPostActivity;
 import org.briarproject.briar.android.contact.ContactListFragment;
 import org.briarproject.briar.android.contact.add.nearby.AddNearbyContactActivity;
@@ -161,9 +164,7 @@ public interface ActivityComponent {
 
 	void inject(IntroductionActivity activity);
 
-	void inject(RssFeedImportActivity activity);
-
-	void inject(RssFeedManageActivity activity);
+	void inject(RssFeedActivity activity);
 
 	void inject(StartupFailureActivity activity);
 
@@ -233,4 +234,12 @@ public interface ActivityComponent {
 
 	void inject(
 			BluetoothConnecterDialogFragment bluetoothConnecterDialogFragment);
+
+	void inject(RssFeedImportFragment fragment);
+
+	void inject(RssFeedManageFragment fragment);
+
+	void inject(RssFeedImportFailedDialogFragment fragment);
+
+	void inject(RssFeedDeleteFeedDialogFragment fragment);
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/BlogModule.java

@@ -20,4 +20,8 @@ public interface BlogModule {
 	@ViewModelKey(BlogViewModel.class)
 	ViewModel bindBlogViewModel(BlogViewModel blogViewModel);
 
+	@Binds
+	@IntoMap
+	@ViewModelKey(RssFeedViewModel.class)
+	ViewModel bindRssFeedViewModel(RssFeedViewModel rssFeedViewModel);
 }

briar-android/src/main/java/org/briarproject/briar/android/blog/FeedFragment.java

@@ -131,15 +131,8 @@ public class FeedFragment extends BaseFragment
 			i.putExtra(GROUP_ID, personalBlog.getId().getBytes());
 			startActivity(i);
 			return true;
-		} else if (itemId == R.id.action_rss_feeds_import) {
-			Intent i = new Intent(getActivity(), RssFeedImportActivity.class);
-			startActivity(i);
-			return true;
-		} else if (itemId == R.id.action_rss_feeds_manage) {
-			Blog personalBlog = viewModel.getPersonalBlog().getValue();
-			if (personalBlog == null) return false;
-			Intent i = new Intent(getActivity(), RssFeedManageActivity.class);
-			i.putExtra(GROUP_ID, personalBlog.getId().getBytes());
+		} else if (itemId == R.id.action_rss_feeds) {
+			Intent i = new Intent(getActivity(), RssFeedActivity.class);
 			startActivity(i);
 			return true;
 		}

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedActivity.java

@@ -0,0 +1,69 @@
+package org.briarproject.briar.android.blog;
+
+import android.os.Bundle;
+import android.widget.Toast;
+
+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.BaseFragment.BaseFragmentListener;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.fragment.app.FragmentManager;
+import androidx.lifecycle.ViewModelProvider;
+
+import static org.briarproject.briar.android.blog.RssFeedViewModel.ImportResult.EXISTS;
+import static org.briarproject.briar.android.blog.RssFeedViewModel.ImportResult.FAILED;
+import static org.briarproject.briar.android.blog.RssFeedViewModel.ImportResult.IMPORTED;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class RssFeedActivity extends BriarActivity
+		implements BaseFragmentListener {
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+	private RssFeedViewModel viewModel;
+
+	@Override
+	public void injectActivity(ActivityComponent component) {
+		component.inject(this);
+
+		viewModel = new ViewModelProvider(this, viewModelFactory)
+				.get(RssFeedViewModel.class);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+
+		setContentView(R.layout.activity_fragment_container);
+
+		if (savedInstanceState == null) {
+			showInitialFragment(RssFeedManageFragment.newInstance());
+		}
+
+		viewModel.getImportResult().observeEvent(this, this::onImportResult);
+	}
+
+	private void onImportResult(RssFeedViewModel.ImportResult result) {
+		if (result == IMPORTED) {
+			FragmentManager fm = getSupportFragmentManager();
+			if (fm.findFragmentByTag(RssFeedImportFragment.TAG) != null) {
+				onBackPressed();
+			}
+		} else if (result == FAILED) {
+			RssFeedImportFailedDialogFragment dialog =
+					RssFeedImportFailedDialogFragment.newInstance();
+			dialog.show(getSupportFragmentManager(),
+					RssFeedImportFailedDialogFragment.TAG);
+		} else if (result == EXISTS) {
+			Toast.makeText(this, R.string.blogs_rss_feeds_import_exists,
+					Toast.LENGTH_LONG).show();
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedAdapter.java

@@ -7,91 +7,54 @@ import android.view.ViewGroup;
 import android.widget.ImageButton;
 import android.widget.TextView;
 
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.util.BriarAdapter;
-import org.briarproject.briar.android.util.UiUtils;
 import org.briarproject.briar.api.feed.Feed;
 
+import androidx.recyclerview.widget.DiffUtil;
+import androidx.recyclerview.widget.ListAdapter;
 import androidx.recyclerview.widget.RecyclerView;
 
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
+import static org.briarproject.briar.android.util.UiUtils.formatDate;
 
-class RssFeedAdapter extends BriarAdapter<Feed, RssFeedAdapter.FeedViewHolder> {
+@NotNullByDefault
+class RssFeedAdapter extends ListAdapter<Feed, RssFeedAdapter.FeedViewHolder> {
 
 	private final RssFeedListener listener;
 
-	RssFeedAdapter(Context ctx, RssFeedListener listener) {
-		super(ctx, Feed.class);
+	RssFeedAdapter(RssFeedListener listener) {
+		super(new DiffUtil.ItemCallback<Feed>() {
+			@Override
+			public boolean areItemsTheSame(Feed a, Feed b) {
+				return a.getUrl().equals(b.getUrl()) &&
+						a.getBlogId().equals(b.getBlogId()) &&
+						a.getAdded() == b.getAdded();
+			}
+
+			@Override
+			public boolean areContentsTheSame(Feed a, Feed b) {
+				return a.getUpdated() == b.getUpdated();
+			}
+		});
 		this.listener = listener;
 	}
 
 	@Override
 	public FeedViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
-		View v = LayoutInflater.from(ctx).inflate(
+		View v = LayoutInflater.from(parent.getContext()).inflate(
 				R.layout.list_item_rss_feed, parent, false);
 		return new FeedViewHolder(v);
 	}
 
 	@Override
 	public void onBindViewHolder(FeedViewHolder ui, int position) {
-		Feed item = getItemAt(position);
-		if (item == null) return;
-
-		// Feed Title
-		ui.title.setText(item.getTitle());
-
-		// Delete Button
-		ui.delete.setOnClickListener(v -> listener.onDeleteClick(item));
-
-		// Author
-		if (item.getRssAuthor() != null) {
-			ui.author.setText(item.getRssAuthor());
-			ui.author.setVisibility(VISIBLE);
-			ui.authorLabel.setVisibility(VISIBLE);
-		} else {
-			ui.author.setVisibility(GONE);
-			ui.authorLabel.setVisibility(GONE);
-		}
-
-		// Imported and Last Updated
-		ui.imported.setText(UiUtils.formatDate(ctx, item.getAdded()));
-		ui.updated.setText(UiUtils.formatDate(ctx, item.getUpdated()));
-
-		// Description
-		if (item.getDescription() != null) {
-			ui.description.setText(item.getDescription());
-			ui.description.setVisibility(VISIBLE);
-		} else {
-			ui.description.setVisibility(GONE);
-		}
-
-		// Open feed's blog when clicked
-		ui.layout.setOnClickListener(v -> listener.onFeedClick(item));
+		ui.bindItem(getItem(position));
 	}
 
-	@Override
-	public int compare(Feed a, Feed b) {
-		if (a == b) return 0;
-		long aTime = a.getAdded(), bTime = b.getAdded();
-		if (aTime > bTime) return -1;
-		if (aTime < bTime) return 1;
-		return 0;
-	}
-
-	@Override
-	public boolean areContentsTheSame(Feed a, Feed b) {
-		return a.getUpdated() == b.getUpdated();
-	}
-
-	@Override
-	public boolean areItemsTheSame(Feed a, Feed b) {
-		return a.getUrl().equals(b.getUrl()) &&
-				a.getBlogId().equals(b.getBlogId()) &&
-				a.getAdded() == b.getAdded();
-	}
-
-	static class FeedViewHolder extends RecyclerView.ViewHolder {
+	class FeedViewHolder extends RecyclerView.ViewHolder {
+		private final Context ctx;
 		private final View layout;
 		private final TextView title;
 		private final ImageButton delete;
@@ -104,6 +67,7 @@ class RssFeedAdapter extends BriarAdapter<Feed, RssFeedAdapter.FeedViewHolder> {
 		private FeedViewHolder(View v) {
 			super(v);
 
+			ctx = v.getContext();
 			layout = v;
 			title = v.findViewById(R.id.titleView);
 			delete = v.findViewById(R.id.deleteButton);
@@ -113,10 +77,44 @@ class RssFeedAdapter extends BriarAdapter<Feed, RssFeedAdapter.FeedViewHolder> {
 			authorLabel = v.findViewById(R.id.author);
 			description = v.findViewById(R.id.descriptionView);
 		}
+
+		private void bindItem(Feed item) {
+			// Feed Title
+			title.setText(item.getTitle());
+
+			// Delete Button
+			delete.setOnClickListener(v -> listener.onDeleteClick(item));
+
+			// Author
+			if (item.getRssAuthor() != null) {
+				author.setText(item.getRssAuthor());
+				author.setVisibility(VISIBLE);
+				authorLabel.setVisibility(VISIBLE);
+			} else {
+				author.setVisibility(GONE);
+				authorLabel.setVisibility(GONE);
+			}
+
+			// Imported and Last Updated
+			imported.setText(formatDate(ctx, item.getAdded()));
+			updated.setText(formatDate(ctx, item.getUpdated()));
+
+			// Description
+			if (item.getDescription() != null) {
+				description.setText(item.getDescription());
+				description.setVisibility(VISIBLE);
+			} else {
+				description.setVisibility(GONE);
+			}
+
+			// Open feed's blog when clicked
+			layout.setOnClickListener(v -> listener.onFeedClick(item));
+		}
 	}
 
 	interface RssFeedListener {
 		void onFeedClick(Feed feed);
+
 		void onDeleteClick(Feed feed);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedDeleteFeedDialogFragment.java

@@ -0,0 +1,64 @@
+package org.briarproject.briar.android.blog;
+
+import android.app.Dialog;
+import android.content.Context;
+import android.os.Bundle;
+
+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.activity.BaseActivity;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.DialogFragment;
+import androidx.lifecycle.ViewModelProvider;
+
+import static java.util.Objects.requireNonNull;
+import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class RssFeedDeleteFeedDialogFragment extends DialogFragment {
+	final static String TAG = RssFeedDeleteFeedDialogFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+	private RssFeedViewModel viewModel;
+
+	static RssFeedDeleteFeedDialogFragment newInstance(GroupId groupId) {
+		Bundle args = new Bundle();
+		args.putByteArray(GROUP_ID, groupId.getBytes());
+		RssFeedDeleteFeedDialogFragment f =
+				new RssFeedDeleteFeedDialogFragment();
+		f.setArguments(args);
+		return f;
+	}
+
+	@Override
+	public void onAttach(Context ctx) {
+		super.onAttach(ctx);
+		((BaseActivity) requireActivity()).getActivityComponent().inject(this);
+
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(RssFeedViewModel.class);
+	}
+
+	@Override
+	public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
+		GroupId groupId = new GroupId(
+				requireNonNull(requireArguments().getByteArray(GROUP_ID)));
+		AlertDialog.Builder builder = new AlertDialog.Builder(requireActivity(),
+				R.style.BriarDialogTheme);
+		builder.setTitle(getString(R.string.blogs_rss_remove_feed));
+		builder.setMessage(
+				getString(R.string.blogs_rss_remove_feed_dialog_message));
+		builder.setPositiveButton(R.string.cancel, null);
+		builder.setNegativeButton(R.string.blogs_rss_remove_feed_ok,
+				(dialog, which) -> viewModel.removeFeed(groupId));
+		return builder.create();
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedImportActivity.java

@@ -1,170 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import android.os.Bundle;
-import android.text.Editable;
-import android.text.TextWatcher;
-import android.util.Patterns;
-import android.view.Menu;
-import android.view.MenuItem;
-import android.widget.Button;
-import android.widget.EditText;
-import android.widget.ProgressBar;
-
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.briar.R;
-import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.activity.BriarActivity;
-import org.briarproject.briar.api.feed.FeedManager;
-
-import java.io.IOException;
-import java.net.MalformedURLException;
-import java.net.URL;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.inject.Inject;
-
-import androidx.appcompat.app.AlertDialog;
-
-import static android.view.View.GONE;
-import static android.view.View.VISIBLE;
-import static android.view.inputmethod.EditorInfo.IME_ACTION_DONE;
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-import static org.briarproject.briar.android.util.UiUtils.hideSoftKeyboard;
-
-public class RssFeedImportActivity extends BriarActivity {
-
-	private static final Logger LOG =
-			Logger.getLogger(RssFeedImportActivity.class.getName());
-
-	private EditText urlInput;
-	private Button importButton;
-	private ProgressBar progressBar;
-
-	@Inject
-	@IoExecutor
-	Executor ioExecutor;
-
-	@Inject
-	@SuppressWarnings("WeakerAccess")
-	volatile FeedManager feedManager;
-
-	@Override
-	public void onCreate(Bundle savedInstanceState) {
-		super.onCreate(savedInstanceState);
-
-		setContentView(R.layout.activity_rss_feed_import);
-
-		urlInput = findViewById(R.id.urlInput);
-		urlInput.addTextChangedListener(new TextWatcher() {
-			@Override
-			public void beforeTextChanged(CharSequence s, int start, int count,
-					int after) {
-			}
-
-			@Override
-			public void onTextChanged(CharSequence s, int start, int before,
-					int count) {
-			}
-
-			@Override
-			public void afterTextChanged(Editable s) {
-				enableOrDisableImportButton();
-			}
-		});
-		urlInput.setOnEditorActionListener((v, actionId, event) -> {
-			if (actionId == IME_ACTION_DONE && importButton.isEnabled() &&
-					importButton.getVisibility() == VISIBLE) {
-				publish();
-				return true;
-			}
-			return false;
-		});
-
-		importButton = findViewById(R.id.importButton);
-		importButton.setOnClickListener(v -> publish());
-
-		progressBar = findViewById(R.id.progressBar);
-	}
-
-	@Override
-	public boolean onCreateOptionsMenu(Menu menu) {
-		return super.onCreateOptionsMenu(menu);
-	}
-
-	@Override
-	public boolean onOptionsItemSelected(MenuItem item) {
-		return super.onOptionsItemSelected(item);
-	}
-
-	@Override
-	public void injectActivity(ActivityComponent component) {
-		component.inject(this);
-	}
-
-	private void enableOrDisableImportButton() {
-		String url = urlInput.getText().toString();
-		importButton.setEnabled(validateAndNormaliseUrl(url) != null);
-	}
-
-	@Nullable
-	private String validateAndNormaliseUrl(String url) {
-		if (!Patterns.WEB_URL.matcher(url).matches()) return null;
-		try {
-			return new URL(url).toString();
-		} catch (MalformedURLException e) {
-			return null;
-		}
-	}
-
-	private void publish() {
-		// hide import button, show progress bar
-		importButton.setVisibility(GONE);
-		progressBar.setVisibility(VISIBLE);
-		hideSoftKeyboard(urlInput);
-
-		String url = validateAndNormaliseUrl(urlInput.getText().toString());
-		if (url == null) throw new AssertionError();
-		importFeed(url);
-	}
-
-	private void importFeed(String url) {
-		ioExecutor.execute(() -> {
-			try {
-				feedManager.addFeed(url);
-				feedImported();
-			} catch (DbException | IOException e) {
-				logException(LOG, WARNING, e);
-				importFailed();
-			}
-		});
-	}
-
-	private void feedImported() {
-		runOnUiThreadUnlessDestroyed(this::supportFinishAfterTransition);
-	}
-
-	private void importFailed() {
-		runOnUiThreadUnlessDestroyed(() -> {
-			// hide progress bar, show publish button
-			progressBar.setVisibility(GONE);
-			importButton.setVisibility(VISIBLE);
-
-			// show error dialog
-			AlertDialog.Builder builder =
-					new AlertDialog.Builder(RssFeedImportActivity.this,
-							R.style.BriarDialogTheme);
-			builder.setMessage(R.string.blogs_rss_feeds_import_error);
-			builder.setNegativeButton(R.string.cancel, null);
-			builder.setPositiveButton(R.string.try_again_button,
-					(dialog, which) -> publish());
-			AlertDialog dialog = builder.create();
-			dialog.show();
-		});
-	}
-
-}
-

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedImportFailedDialogFragment.java

@@ -0,0 +1,53 @@
+package org.briarproject.briar.android.blog;
+
+import android.app.Dialog;
+import android.content.Context;
+import android.os.Bundle;
+
+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 javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.appcompat.app.AlertDialog;
+import androidx.fragment.app.DialogFragment;
+import androidx.lifecycle.ViewModelProvider;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class RssFeedImportFailedDialogFragment extends DialogFragment {
+	final static String TAG = RssFeedImportFailedDialogFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+	private RssFeedViewModel viewModel;
+
+	static RssFeedImportFailedDialogFragment newInstance() {
+		return new RssFeedImportFailedDialogFragment();
+	}
+
+	@Override
+	public void onAttach(Context ctx) {
+		super.onAttach(ctx);
+		((BaseActivity) requireActivity()).getActivityComponent().inject(this);
+
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(RssFeedViewModel.class);
+	}
+
+	@Override
+	public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
+		AlertDialog.Builder builder =
+				new AlertDialog.Builder(requireActivity(),
+						R.style.BriarDialogTheme);
+		builder.setMessage(R.string.blogs_rss_feeds_import_error);
+		builder.setNegativeButton(R.string.cancel, null);
+		builder.setPositiveButton(R.string.try_again_button,
+				(dialog, which) -> viewModel.retryImportFeed());
+
+		return builder.create();
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedImportFragment.java

@@ -0,0 +1,124 @@
+package org.briarproject.briar.android.blog;
+
+import android.os.Bundle;
+import android.text.Editable;
+import android.text.TextWatcher;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.ProgressBar;
+
+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.fragment.BaseFragment;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.lifecycle.ViewModelProvider;
+
+import static android.view.View.GONE;
+import static android.view.View.VISIBLE;
+import static android.view.inputmethod.EditorInfo.IME_ACTION_DONE;
+import static org.briarproject.briar.android.util.UiUtils.hideSoftKeyboard;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class RssFeedImportFragment extends BaseFragment {
+	public static final String TAG = RssFeedImportFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+	private RssFeedViewModel viewModel;
+
+	private EditText urlInput;
+	private Button importButton;
+	private ProgressBar progressBar;
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(RssFeedViewModel.class);
+	}
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		requireActivity().setTitle(getString(R.string.blogs_rss_feeds_import));
+		View v = inflater.inflate(R.layout.fragment_rss_feed_import,
+				container, false);
+
+		urlInput = v.findViewById(R.id.urlInput);
+		urlInput.addTextChangedListener(new TextWatcher() {
+			@Override
+			public void beforeTextChanged(CharSequence s, int start, int count,
+					int after) {
+			}
+
+			@Override
+			public void onTextChanged(CharSequence s, int start, int before,
+					int count) {
+			}
+
+			@Override
+			public void afterTextChanged(Editable s) {
+				enableOrDisableImportButton();
+			}
+		});
+		urlInput.setOnEditorActionListener((view, actionId, event) -> {
+			if (actionId == IME_ACTION_DONE && importButton.isEnabled() &&
+					importButton.getVisibility() == VISIBLE) {
+				publish();
+				return true;
+			}
+			return false;
+		});
+
+		importButton = v.findViewById(R.id.importButton);
+		importButton.setOnClickListener(view -> publish());
+
+		progressBar = v.findViewById(R.id.progressBar);
+
+		viewModel.getIsImporting().observe(getViewLifecycleOwner(),
+				this::onIsImporting);
+
+		return v;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	private void enableOrDisableImportButton() {
+		String url = urlInput.getText().toString();
+		importButton.setEnabled(viewModel.validateAndNormaliseUrl(url) != null);
+	}
+
+	private void publish() {
+		String url = viewModel
+				.validateAndNormaliseUrl(urlInput.getText().toString());
+		if (url == null) throw new AssertionError();
+		viewModel.importFeed(url);
+	}
+
+	private void onIsImporting(Boolean importing) {
+		if (importing) {
+			// show progress bar, hide import button
+			importButton.setVisibility(GONE);
+			progressBar.setVisibility(VISIBLE);
+			hideSoftKeyboard(urlInput);
+		} else {
+			// show publish button, hide progress bar
+			importButton.setVisibility(VISIBLE);
+			progressBar.setVisibility(GONE);
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedManageActivity.java

@@ -1,178 +0,0 @@
-package org.briarproject.briar.android.blog;
-
-import android.content.DialogInterface;
-import android.content.Intent;
-import android.os.Bundle;
-import android.view.Menu;
-import android.view.MenuInflater;
-import android.view.MenuItem;
-
-import com.google.android.material.snackbar.Snackbar;
-
-import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.briar.R;
-import org.briarproject.briar.android.activity.ActivityComponent;
-import org.briarproject.briar.android.activity.BriarActivity;
-import org.briarproject.briar.android.blog.RssFeedAdapter.RssFeedListener;
-import org.briarproject.briar.android.view.BriarRecyclerView;
-import org.briarproject.briar.api.feed.Feed;
-import org.briarproject.briar.api.feed.FeedManager;
-
-import java.util.List;
-import java.util.logging.Logger;
-
-import javax.inject.Inject;
-
-import androidx.appcompat.app.AlertDialog;
-import androidx.recyclerview.widget.LinearLayoutManager;
-
-import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
-import static com.google.android.material.snackbar.Snackbar.LENGTH_LONG;
-import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.util.LogUtils.logException;
-
-public class RssFeedManageActivity extends BriarActivity
-		implements RssFeedListener {
-
-	private static final Logger LOG =
-			Logger.getLogger(RssFeedManageActivity.class.getName());
-
-	private BriarRecyclerView list;
-	private RssFeedAdapter adapter;
-
-	@Inject
-	@SuppressWarnings("WeakerAccess")
-	volatile FeedManager feedManager;
-
-	@Override
-	public void onCreate(Bundle savedInstanceState) {
-		super.onCreate(savedInstanceState);
-
-		setContentView(R.layout.activity_rss_feed_manage);
-
-		adapter = new RssFeedAdapter(this, this);
-
-		list = findViewById(R.id.feedList);
-		list.setLayoutManager(new LinearLayoutManager(this));
-		list.setAdapter(adapter);
-	}
-
-	@Override
-	public void onStart() {
-		super.onStart();
-		loadFeeds();
-	}
-
-	@Override
-	public void onStop() {
-		super.onStop();
-		adapter.clear();
-		list.showProgressBar();
-	}
-
-	@Override
-	public boolean onCreateOptionsMenu(Menu menu) {
-		MenuInflater inflater = getMenuInflater();
-		inflater.inflate(R.menu.rss_feed_manage_actions, menu);
-		return super.onCreateOptionsMenu(menu);
-	}
-
-	@Override
-	public boolean onOptionsItemSelected(MenuItem item) {
-		if (item.getItemId() == android.R.id.home) {
-			onBackPressed();
-			return true;
-		} else if (item.getItemId() == R.id.action_rss_feeds_import) {
-			Intent i = new Intent(this, RssFeedImportActivity.class);
-			startActivity(i);
-			return true;
-		}
-		return super.onOptionsItemSelected(item);
-	}
-
-	@Override
-	public void injectActivity(ActivityComponent component) {
-		component.inject(this);
-	}
-
-	@Override
-	public void onFeedClick(Feed feed) {
-		Intent i = new Intent(this, BlogActivity.class);
-		i.putExtra(GROUP_ID, feed.getBlogId().getBytes());
-		i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
-		startActivity(i);
-	}
-
-	@Override
-	public void onDeleteClick(Feed feed) {
-		DialogInterface.OnClickListener okListener =
-				(dialog, which) -> deleteFeed(feed);
-		AlertDialog.Builder builder = new AlertDialog.Builder(this,
-				R.style.BriarDialogTheme);
-		builder.setTitle(getString(R.string.blogs_rss_remove_feed));
-		builder.setMessage(
-				getString(R.string.blogs_rss_remove_feed_dialog_message));
-		builder.setPositiveButton(R.string.cancel, null);
-		builder.setNegativeButton(R.string.blogs_rss_remove_feed_ok,
-				okListener);
-		builder.show();
-	}
-
-	private void loadFeeds() {
-		int revision = adapter.getRevision();
-		runOnDbThread(() -> {
-			try {
-				displayFeeds(revision, feedManager.getFeeds());
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				onLoadError();
-			}
-		});
-	}
-
-	private void displayFeeds(int revision, List<Feed> feeds) {
-		runOnUiThreadUnlessDestroyed(() -> {
-			if (revision == adapter.getRevision()) {
-				adapter.incrementRevision();
-				if (feeds.isEmpty()) list.showData();
-				else adapter.addAll(feeds);
-			} else {
-				LOG.info("Concurrent update, reloading");
-				loadFeeds();
-			}
-		});
-	}
-
-	private void deleteFeed(Feed feed) {
-		runOnDbThread(() -> {
-			try {
-				feedManager.removeFeed(feed);
-				onFeedDeleted(feed);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-				onDeleteError();
-			}
-		});
-	}
-
-	private void onLoadError() {
-		runOnUiThreadUnlessDestroyed(() -> {
-			list.setEmptyText(R.string.blogs_rss_feeds_manage_error);
-			list.showData();
-		});
-	}
-
-	private void onFeedDeleted(Feed feed) {
-		runOnUiThreadUnlessDestroyed(() -> {
-			adapter.incrementRevision();
-			adapter.remove(feed);
-		});
-	}
-
-	private void onDeleteError() {
-		runOnUiThreadUnlessDestroyed(() -> Snackbar.make(list,
-				R.string.blogs_rss_feeds_manage_delete_error,
-				LENGTH_LONG).show());
-	}
-}
-

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedManageFragment.java

@@ -0,0 +1,123 @@
+package org.briarproject.briar.android.blog;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.Menu;
+import android.view.MenuInflater;
+import android.view.MenuItem;
+import android.view.View;
+import android.view.ViewGroup;
+
+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.fragment.BaseFragment;
+import org.briarproject.briar.android.view.BriarRecyclerView;
+import org.briarproject.briar.api.feed.Feed;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import androidx.annotation.NonNull;
+import androidx.lifecycle.ViewModelProvider;
+import androidx.recyclerview.widget.LinearLayoutManager;
+
+import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
+import static org.briarproject.briar.android.blog.RssFeedAdapter.RssFeedListener;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class RssFeedManageFragment extends BaseFragment
+		implements RssFeedListener {
+	public static final String TAG = RssFeedManageFragment.class.getName();
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+	private RssFeedViewModel viewModel;
+
+	private BriarRecyclerView list;
+	private final RssFeedAdapter adapter = new RssFeedAdapter(this);
+
+	public static RssFeedManageFragment newInstance() {
+		return new RssFeedManageFragment();
+	}
+
+	@Override
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(RssFeedViewModel.class);
+	}
+
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		requireActivity().setTitle(R.string.blogs_rss_feeds);
+		View v = inflater.inflate(R.layout.fragment_rss_feed_manage,
+				container, false);
+
+		list = v.findViewById(R.id.feedList);
+		list.setLayoutManager(new LinearLayoutManager(getActivity()));
+		list.setAdapter(adapter);
+
+		viewModel.getFeeds().observe(getViewLifecycleOwner(), result -> result
+				.onError(e -> {
+					list.setEmptyText(R.string.blogs_rss_feeds_manage_error);
+					list.showData();
+				})
+				.onSuccess(feeds -> {
+					adapter.submitList(feeds);
+					if (requireNonNull(feeds).size() == 0) {
+						list.showData();
+					}
+				})
+		);
+
+		return v;
+	}
+
+	@Override
+	public String getUniqueTag() {
+		return TAG;
+	}
+
+	@Override
+	public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+		inflater.inflate(R.menu.rss_feed_manage_actions, menu);
+		super.onCreateOptionsMenu(menu, inflater);
+	}
+
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		if (item.getItemId() == android.R.id.home) {
+			requireActivity().onBackPressed();
+			return true;
+		} else if (item.getItemId() == R.id.action_rss_feeds_import) {
+			showNextFragment(new RssFeedImportFragment());
+			return true;
+		}
+		return super.onOptionsItemSelected(item);
+	}
+
+	@Override
+	public void onFeedClick(Feed feed) {
+		Intent i = new Intent(getActivity(), BlogActivity.class);
+		i.putExtra(GROUP_ID, feed.getBlogId().getBytes());
+		i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+		startActivity(i);
+	}
+
+	@Override
+	public void onDeleteClick(Feed feed) {
+		RssFeedDeleteFeedDialogFragment dialog =
+				RssFeedDeleteFeedDialogFragment.newInstance(feed.getBlogId());
+		dialog.show(getParentFragmentManager(),
+				RssFeedDeleteFeedDialogFragment.TAG);
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/blog/RssFeedViewModel.java

@@ -0,0 +1,180 @@
+package org.briarproject.briar.android.blog;
+
+import android.app.Application;
+import android.util.Patterns;
+
+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.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.briar.android.viewmodel.DbViewModel;
+import org.briarproject.briar.android.viewmodel.LiveEvent;
+import org.briarproject.briar.android.viewmodel.LiveResult;
+import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
+import org.briarproject.briar.api.feed.Feed;
+import org.briarproject.briar.api.feed.FeedManager;
+
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URL;
+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.Nullable;
+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;
+import static org.briarproject.briar.android.blog.RssFeedViewModel.ImportResult.EXISTS;
+import static org.briarproject.briar.android.blog.RssFeedViewModel.ImportResult.FAILED;
+import static org.briarproject.briar.android.blog.RssFeedViewModel.ImportResult.IMPORTED;
+
+@NotNullByDefault
+class RssFeedViewModel extends DbViewModel {
+	enum ImportResult {IMPORTED, FAILED, EXISTS}
+
+	private static final Logger LOG =
+			getLogger(RssFeedViewModel.class.getName());
+
+	private final FeedManager feedManager;
+	private final Executor ioExecutor;
+	private final Executor dbExecutor;
+
+	private final MutableLiveData<LiveResult<List<Feed>>> feeds =
+			new MutableLiveData<>();
+
+	@Nullable
+	private volatile String urlFailedImport = null;
+	private final MutableLiveData<Boolean> isImporting =
+			new MutableLiveData<>(false);
+	private final MutableLiveEvent<ImportResult> importResult =
+			new MutableLiveEvent<>();
+
+	@Inject
+	RssFeedViewModel(Application app,
+			FeedManager feedManager,
+			@IoExecutor Executor ioExecutor,
+			@DatabaseExecutor Executor dbExecutor,
+			LifecycleManager lifecycleManager,
+			TransactionManager db,
+			AndroidExecutor androidExecutor) {
+		super(app, dbExecutor, lifecycleManager, db, androidExecutor);
+		this.feedManager = feedManager;
+		this.ioExecutor = ioExecutor;
+		this.dbExecutor = dbExecutor;
+
+		loadFeeds();
+	}
+
+	@Nullable
+	String validateAndNormaliseUrl(String url) {
+		if (!Patterns.WEB_URL.matcher(url).matches()) return null;
+		try {
+			return new URL(url).toString();
+		} catch (MalformedURLException e) {
+			return null;
+		}
+	}
+
+	LiveData<LiveResult<List<Feed>>> getFeeds() {
+		return feeds;
+	}
+
+	private void loadFeeds() {
+		loadFromDb(this::loadFeeds, feeds::setValue);
+	}
+
+	@DatabaseExecutor
+	private List<Feed> loadFeeds(Transaction txn) throws DbException {
+		long start = now();
+		List<Feed> feeds = feedManager.getFeeds(txn);
+		Collections.sort(feeds);
+		logDuration(LOG, "Loading feeds", start);
+		return feeds;
+	}
+
+	void removeFeed(GroupId groupId) {
+		dbExecutor.execute(() -> {
+			List<Feed> updated = removeListItems(getList(feeds), feed -> {
+				if (feed.getBlogId().equals(groupId)) {
+					try {
+						feedManager.removeFeed(feed);
+						return true;
+					} catch (DbException e) {
+						handleException(e);
+					}
+				}
+				return false;
+			});
+			if (updated != null) {
+				feeds.postValue(new LiveResult<>(updated));
+			}
+		});
+	}
+
+	LiveEvent<ImportResult> getImportResult() {
+		return importResult;
+	}
+
+	LiveData<Boolean> getIsImporting() {
+		return isImporting;
+	}
+
+	void importFeed(String url) {
+		isImporting.setValue(true);
+		urlFailedImport = null;
+		ioExecutor.execute(() -> {
+			try {
+				if (exists(url)) {
+					importResult.postEvent(EXISTS);
+					return;
+				}
+				Feed feed = feedManager.addFeed(url);
+				List<Feed> updated = addListItem(getList(feeds), feed);
+				if (updated != null) {
+					Collections.sort(updated);
+					feeds.postValue(new LiveResult<>(updated));
+				}
+				importResult.postEvent(IMPORTED);
+			} catch (DbException | IOException e) {
+				logException(LOG, WARNING, e);
+				urlFailedImport = url;
+				importResult.postEvent(FAILED);
+			} finally {
+				isImporting.postValue(false);
+			}
+		});
+	}
+
+	void retryImportFeed() {
+		if (urlFailedImport == null) {
+			throw new AssertionError();
+		}
+		importFeed(urlFailedImport);
+	}
+
+	private boolean exists(String url) {
+		List<Feed> list = getList(feeds);
+		if (list != null) {
+			for (Feed feed : list) {
+				if (url.equals(feed.getUrl())) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+}