Null safety cleanups.

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

@@ -70,6 +70,7 @@ import static android.support.v4.app.NotificationCompat.PRIORITY_LOW;
 import static android.support.v4.app.NotificationCompat.PRIORITY_MIN;
 import static android.support.v4.app.NotificationCompat.VISIBILITY_SECRET;
 import static android.support.v4.content.ContextCompat.getColor;
+import static java.util.Objects.requireNonNull;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 import static org.briarproject.bramble.util.StringUtils.toHexString;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
@@ -119,8 +120,8 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 		this.androidExecutor = androidExecutor;
 		this.clock = clock;
 		appContext = app.getApplicationContext();
-		notificationManager = (NotificationManager)
-				appContext.getSystemService(NOTIFICATION_SERVICE);
+		notificationManager = (NotificationManager) requireNonNull(
+				appContext.getSystemService(NOTIFICATION_SERVICE));
 	}
 
 	@Override

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

@@ -30,6 +30,7 @@ import static android.content.Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS;
 import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
 import static android.content.Intent.FLAG_ACTIVITY_NO_ANIMATION;
 import static android.os.Build.VERSION.SDK_INT;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_DOZE_WHITELISTING;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PASSWORD;
@@ -177,8 +178,8 @@ public abstract class BriarActivity extends BaseActivity {
 		b.setNegativeButton(R.string.cancel,
 				(dialog, which) -> dialog.dismiss());
 		b.setOnDismissListener(dialog -> {
-			CheckBox checkBox =
-					((AlertDialog) dialog).findViewById(R.id.checkbox);
+			CheckBox checkBox = requireNonNull(
+					((AlertDialog) dialog).findViewById(R.id.checkbox));
 			if (checkBox.isChecked())
 				briarController.doNotAskAgainForDozeWhiteListing();
 		});

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

@@ -221,7 +221,6 @@ abstract class BaseControllerImpl extends DbControllerImpl
 			text = HtmlUtils.clean(blogManager.getPostText(m), ARTICLE);
 			textCache.put(m, text);
 		}
-		//noinspection ConstantConditions
 		return text;
 	}
 

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

@@ -92,13 +92,11 @@ public class BlogFragment extends BaseFragment
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
 		Bundle args = requireNonNull(getArguments());
-		byte[] b = args.getByteArray(GROUP_ID);
-		if (b == null) throw new IllegalStateException("No group ID in args");
-		groupId = new GroupId(b);
+		groupId = new GroupId(requireNonNull(args.getByteArray(GROUP_ID)));
 
 		View v = inflater.inflate(R.layout.fragment_blog, container, false);
 
-		adapter = new BlogPostAdapter(requireNonNull(getActivity()), this,
+		adapter = new BlogPostAdapter(requireActivity(), this,
 				getFragmentManager());
 		list = v.findViewById(R.id.postList);
 		list.setLayoutManager(new LinearLayoutManager(getActivity()));
@@ -269,7 +267,7 @@ public class BlogFragment extends BaseFragment
 	}
 
 	private void setToolbarTitle(Author a) {
-		getActivity().setTitle(a.getName());
+		requireActivity().setTitle(a.getName());
 	}
 
 	private void loadSharedContacts() {
@@ -311,7 +309,7 @@ public class BlogFragment extends BaseFragment
 
 	private void setToolbarSubTitle(int total, int online) {
 		ActionBar actionBar =
-				((BriarActivity) getActivity()).getSupportActionBar();
+				((BriarActivity) requireActivity()).getSupportActionBar();
 		if (actionBar != null) {
 			actionBar.setSubtitle(
 					getString(R.string.shared_with, total, online));
@@ -336,9 +334,8 @@ public class BlogFragment extends BaseFragment
 		snackbar.getView().setBackgroundResource(R.color.briar_primary);
 		if (scroll) {
 			View.OnClickListener onClick = v -> list.smoothScrollToPosition(0);
-			snackbar.setActionTextColor(ContextCompat
-					.getColor(getContext(),
-							R.color.briar_button_text_positive));
+			snackbar.setActionTextColor(ContextCompat.getColor(requireContext(),
+					R.color.briar_button_text_positive));
 			snackbar.setAction(R.string.blogs_blog_post_scroll_to, onClick);
 		}
 		snackbar.show();
@@ -347,7 +344,7 @@ public class BlogFragment extends BaseFragment
 	private void showDeleteDialog() {
 		DialogInterface.OnClickListener okListener =
 				(dialog, which) -> deleteBlog();
-		AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(),
+		AlertDialog.Builder builder = new AlertDialog.Builder(requireActivity(),
 				R.style.BriarDialogTheme);
 		builder.setTitle(getString(R.string.blogs_remove_blog));
 		builder.setMessage(
@@ -362,7 +359,7 @@ public class BlogFragment extends BaseFragment
 				new UiResultExceptionHandler<Void, DbException>(this) {
 					@Override
 					public void onResultUi(Void result) {
-						Toast.makeText(getActivity(),
+						Toast.makeText(requireActivity(),
 								R.string.blogs_blog_removed, LENGTH_SHORT)
 								.show();
 						finish();

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

@@ -35,7 +35,6 @@ import javax.inject.Inject;
 import static android.app.Activity.RESULT_OK;
 import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TOP;
 import static android.support.design.widget.Snackbar.LENGTH_LONG;
-import static java.util.Objects.requireNonNull;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_WRITE_BLOG_POST;
@@ -78,14 +77,14 @@ public class FeedFragment extends BaseFragment implements
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-		requireNonNull(getActivity()).setTitle(R.string.blogs_button);
+		requireActivity().setTitle(R.string.blogs_button);
 
 		View v = inflater.inflate(R.layout.fragment_blog, container, false);
 
-		adapter =
-				new BlogPostAdapter(getActivity(), this, getFragmentManager());
+		adapter = new BlogPostAdapter(requireActivity(), this,
+				getFragmentManager());
 
-		layoutManager = new LinearLayoutManager(getActivity());
+		layoutManager = new LinearLayoutManager(requireActivity());
 		list = v.findViewById(R.id.postList);
 		list.setLayoutManager(layoutManager);
 		list.setAdapter(adapter);
@@ -176,19 +175,19 @@ public class FeedFragment extends BaseFragment implements
 		if (personalBlog == null) return false;
 		switch (item.getItemId()) {
 			case R.id.action_write_blog_post:
-				Intent i1 =
-						new Intent(getActivity(), WriteBlogPostActivity.class);
+				Intent i1 = new Intent(requireActivity(),
+								WriteBlogPostActivity.class);
 				i1.putExtra(GROUP_ID, personalBlog.getId().getBytes());
 				startActivityForResult(i1, REQUEST_WRITE_BLOG_POST);
 				return true;
 			case R.id.action_rss_feeds_import:
-				Intent i2 =
-						new Intent(getActivity(), RssFeedImportActivity.class);
+				Intent i2 = new Intent(requireActivity(),
+						RssFeedImportActivity.class);
 				startActivity(i2);
 				return true;
 			case R.id.action_rss_feeds_manage:
-				Intent i3 =
-						new Intent(getActivity(), RssFeedManageActivity.class);
+				Intent i3 = new Intent(requireActivity(),
+						RssFeedManageActivity.class);
 				i3.putExtra(GROUP_ID, personalBlog.getId().getBytes());
 				startActivity(i3);
 				return true;
@@ -230,10 +229,11 @@ public class FeedFragment extends BaseFragment implements
 
 	@Override
 	public void onAuthorClick(BlogPostItem post) {
+		if (getContext() == null) return;
 		Intent i = new Intent(getContext(), BlogActivity.class);
 		i.putExtra(GROUP_ID, post.getGroupId().getBytes());
 		i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
-		getContext().startActivity(i);
+		requireContext().startActivity(i);
 	}
 
 	@Override
@@ -252,9 +252,8 @@ public class FeedFragment extends BaseFragment implements
 		s.getView().setBackgroundResource(R.color.briar_primary);
 		if (scroll) {
 			OnClickListener onClick = v -> list.smoothScrollToPosition(0);
-			s.setActionTextColor(ContextCompat
-					.getColor(getContext(),
-							R.color.briar_button_text_positive));
+			s.setActionTextColor(ContextCompat.getColor(requireContext(),
+					R.color.briar_button_text_positive));
 			s.setAction(R.string.blogs_blog_post_scroll_to, onClick);
 		}
 		s.show();

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

@@ -2,8 +2,11 @@ package org.briarproject.briar.android.blog;
 
 import android.content.Intent;
 import android.os.Bundle;
+import android.support.annotation.Nullable;
 import android.view.MenuItem;
 
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.R;
@@ -13,11 +16,13 @@ import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener
 
 import static org.briarproject.briar.android.blog.BasePostFragment.POST_ID;
 
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
 public class ReblogActivity extends BriarActivity implements
 		BaseFragmentListener {
 
 	@Override
-	public void onCreate(Bundle savedInstanceState) {
+	public void onCreate(@Nullable Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
 		Intent intent = getIntent();

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

@@ -51,7 +51,6 @@ import javax.inject.Inject;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.support.v4.app.ActivityOptionsCompat.makeSceneTransitionAnimation;
 import static android.support.v4.view.ViewCompat.getTransitionName;
-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.logDuration;
@@ -106,13 +105,13 @@ public class ContactListFragment extends BaseFragment implements EventListener {
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-		requireNonNull(getActivity()).setTitle(R.string.contact_list_button);
+		requireActivity().setTitle(R.string.contact_list_button);
 
 		View contentView = inflater.inflate(R.layout.list, container, false);
 
 		OnContactClickListener<ContactListItem> onContactClickListener =
 				(view, item) -> {
-					Intent i = new Intent(getActivity(),
+					Intent i = new Intent(requireActivity(),
 							ConversationActivity.class);
 					ContactId contactId = item.getContact().getId();
 					i.putExtra(CONTACT_ID, contactId.getInt());
@@ -130,16 +129,17 @@ public class ContactListFragment extends BaseFragment implements EventListener {
 								Pair.create(holder.bulb,
 										getTransitionName(holder.bulb));
 						ActivityOptionsCompat options =
-								makeSceneTransitionAnimation(getActivity(),
+								makeSceneTransitionAnimation(requireActivity(),
 										avatar, bulb);
-						ActivityCompat.startActivity(getActivity(), i,
+						ActivityCompat.startActivity(requireActivity(), i,
 								options.toBundle());
 					} else {
 						// work-around for android bug #224270
 						startActivity(i);
 					}
 				};
-		adapter = new ContactListAdapter(getContext(), onContactClickListener);
+		adapter = new ContactListAdapter(requireContext(),
+				onContactClickListener);
 		list = contentView.findViewById(R.id.list);
 		list.setLayoutManager(new LinearLayoutManager(getContext()));
 		list.setAdapter(adapter);
@@ -161,8 +161,8 @@ public class ContactListFragment extends BaseFragment implements EventListener {
 		// Handle presses on the action bar items
 		switch (item.getItemId()) {
 			case R.id.action_add_contact:
-				Intent intent =
-						new Intent(getContext(), ContactExchangeActivity.class);
+				Intent intent = new Intent(requireContext(),
+						ContactExchangeActivity.class);
 				startActivity(intent);
 				return true;
 			default:

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

@@ -69,11 +69,11 @@ public abstract class BaseContactSelectorFragment<I extends SelectableContactIte
 		View contentView = inflater.inflate(R.layout.list, container, false);
 
 		list = contentView.findViewById(R.id.list);
-		list.setLayoutManager(new LinearLayoutManager(getActivity()));
+		list.setLayoutManager(new LinearLayoutManager(requireActivity()));
 		list.setEmptyImage(R.drawable.ic_empty_state_contact_list);
 		list.setEmptyText(getString(R.string.no_contacts_selector));
 		list.setEmptyAction(getString(R.string.no_contacts_selector_action));
-		adapter = getAdapter(requireNonNull(getContext()), this);
+		adapter = getAdapter(requireContext(), this);
 		list.setAdapter(adapter);
 
 		// restore selected contacts if available

briar-android/src/main/java/org/briarproject/briar/android/conversation/AliasDialogFragment.java

@@ -39,9 +39,8 @@ public class AliasDialogFragment extends AppCompatDialogFragment {
 
 		setStyle(STYLE_NO_TITLE, R.style.BriarDialogTheme);
 
-		BriarActivity a = (BriarActivity) requireNonNull(getActivity());
-		a.getActivityComponent().inject(this);
-		viewModel = ViewModelProviders.of(getActivity(), viewModelFactory)
+		((BriarActivity) requireActivity()).getActivityComponent().inject(this);
+		viewModel = ViewModelProviders.of(requireActivity(), viewModelFactory)
 				.get(ConversationViewModel.class);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -502,7 +502,6 @@ public class ConversationActivity extends BriarActivity
 	 * <p>
 	 * Attention: Call this only after contactName has been initialized.
 	 */
-	@SuppressWarnings("ConstantConditions")
 	private List<ConversationItem> createItems(
 			Collection<ConversationMessageHeader> headers) {
 		List<ConversationItem> items = new ArrayList<>(headers.size());

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageFragment.java

@@ -57,8 +57,7 @@ public class ImageFragment extends Fragment {
 	@Override
 	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
 		super.onActivityCreated(savedInstanceState);
-		BaseActivity a = (BaseActivity) requireNonNull(getActivity());
-		a.getActivityComponent().inject(this);
+		((BaseActivity) requireActivity()).getActivityComponent().inject(this);
 	}
 
 	@Override
@@ -78,8 +77,8 @@ public class ImageFragment extends Fragment {
 		View v = inflater.inflate(R.layout.fragment_image, container,
 				false);
 
-		viewModel = ViewModelProviders.of(requireNonNull(getActivity()),
-				viewModelFactory).get(ImageViewModel.class);
+		viewModel = ViewModelProviders.of(requireActivity(), viewModelFactory)
+				.get(ImageViewModel.class);
 
 		photoView = v.findViewById(R.id.photoView);
 		photoView.setScaleLevels(1, 2, 4);

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumListFragment.java

@@ -44,7 +44,6 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 import static android.support.design.widget.Snackbar.LENGTH_INDEFINITE;
-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.logDuration;
@@ -93,24 +92,23 @@ public class ForumListFragment extends BaseEventFragment implements
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-
-		requireNonNull(getActivity()).setTitle(R.string.forums_button);
+		requireActivity().setTitle(R.string.forums_button);
 
 		View contentView =
 				inflater.inflate(R.layout.fragment_forum_list, container,
 						false);
 
-		adapter = new ForumListAdapter(getActivity());
+		adapter = new ForumListAdapter(requireActivity());
 
 		list = contentView.findViewById(R.id.forumList);
-		list.setLayoutManager(new LinearLayoutManager(getActivity()));
+		list.setLayoutManager(new LinearLayoutManager(requireActivity()));
 		list.setAdapter(adapter);
 
 		snackbar = Snackbar.make(list, "", LENGTH_INDEFINITE);
 		snackbar.getView().setBackgroundResource(R.color.briar_primary);
 		snackbar.setAction(R.string.show, this);
-		snackbar.setActionTextColor(ContextCompat
-				.getColor(getActivity(), R.color.briar_button_text_positive));
+		snackbar.setActionTextColor(ContextCompat.getColor(requireContext(),
+						R.color.briar_button_text_positive));
 
 		return contentView;
 	}
@@ -148,8 +146,8 @@ public class ForumListFragment extends BaseEventFragment implements
 		// Handle presses on the action bar items
 		switch (item.getItemId()) {
 			case R.id.action_create_forum:
-				Intent intent =
-						new Intent(getContext(), CreateForumActivity.class);
+				Intent intent = new Intent(requireContext(),
+						CreateForumActivity.class);
 				startActivity(intent);
 				return true;
 			default:
@@ -270,7 +268,7 @@ public class ForumListFragment extends BaseEventFragment implements
 	@Override
 	public void onClick(View view) {
 		// snackbar click
-		Intent i = new Intent(getContext(), ForumInvitationActivity.class);
+		Intent i = new Intent(requireContext(), ForumInvitationActivity.class);
 		startActivity(i);
 	}
 }

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

 package org.briarproject.briar.android.fragment;
 
 import android.annotation.SuppressLint;
-import android.app.Activity;
 import android.app.Dialog;
 import android.content.DialogInterface;
 import android.os.Bundle;
@@ -26,6 +25,8 @@ import java.util.Collection;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
+import static java.util.Objects.requireNonNull;
+
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class ScreenFilterDialogFragment extends DialogFragment {
@@ -58,26 +59,20 @@ public class ScreenFilterDialogFragment extends DialogFragment {
 	@Override
 	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
 		super.onActivityCreated(savedInstanceState);
-		Activity activity = getActivity();
-		if (activity == null) throw new IllegalStateException();
-		((BaseActivity) activity).getActivityComponent().inject(this);
+		((BaseActivity) requireActivity()).getActivityComponent().inject(this);
 	}
 
 	@Override
 	public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
-		Activity activity = getActivity();
-		if (activity == null) throw new IllegalStateException();
-		AlertDialog.Builder builder = new AlertDialog.Builder(activity,
+		AlertDialog.Builder builder = new AlertDialog.Builder(requireActivity(),
 				R.style.BriarDialogThemeNoFilter);
 		builder.setTitle(R.string.screen_filter_title);
-		Bundle args = getArguments();
-		if (args == null) throw new IllegalStateException();
-		ArrayList<String> appNames = args.getStringArrayList("appNames");
+		Bundle args = requireNonNull(getArguments());
+		ArrayList<String> appNames =
+				requireNonNull(args.getStringArrayList("appNames"));
 		ArrayList<String> packageNames =
-				args.getStringArrayList("packageNames");
-		if (appNames == null || packageNames == null)
-			throw new IllegalStateException();
-		LayoutInflater inflater = activity.getLayoutInflater();
+				requireNonNull(args.getStringArrayList("packageNames"));
+		LayoutInflater inflater = requireActivity().getLayoutInflater();
 		// See https://stackoverflow.com/a/24720976/6314875
 		@SuppressLint("InflateParams")
 		View dialogView = inflater.inflate(R.layout.dialog_screen_filter, null);

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

@@ -76,7 +76,6 @@ public class ContactChooserFragment extends BaseFragment {
 	@Override
 	public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-
 		View contentView = inflater.inflate(R.layout.list, container, false);
 
 		OnContactClickListener<ContactListItem> onContactClickListener =
@@ -85,11 +84,11 @@ public class ContactChooserFragment extends BaseFragment {
 					Contact c2 = item.getContact();
 					showMessageScreen(c1, c2);
 				};
-		adapter = new ContactListAdapter(requireNonNull(getActivity()),
+		adapter = new ContactListAdapter(requireActivity(),
 				onContactClickListener);
 
 		list = contentView.findViewById(R.id.list);
-		list.setLayoutManager(new LinearLayoutManager(getActivity()));
+		list.setLayoutManager(new LinearLayoutManager(requireActivity()));
 		list.setAdapter(adapter);
 		list.setEmptyText(R.string.no_contacts);
 

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

@@ -36,6 +36,7 @@ import static android.hardware.Camera.Parameters.FOCUS_MODE_MACRO;
 import static android.hardware.Camera.Parameters.SCENE_MODE_AUTO;
 import static android.hardware.Camera.Parameters.SCENE_MODE_BARCODE;
 import static android.os.Build.VERSION.SDK_INT;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -127,7 +128,7 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 		}
 		setDisplayOrientation(getScreenRotationDegrees());
 		// Use barcode scene mode if it's available
-		Parameters params = camera.getParameters();
+		Parameters params = requireNonNull(camera).getParameters();
 		params = setSceneMode(camera, params);
 		if (SCENE_MODE_BARCODE.equals(params.getSceneMode())) {
 			// If the scene mode enabled the flash, try to disable it
@@ -164,8 +165,9 @@ public class CameraView extends SurfaceView implements SurfaceHolder.Callback,
 	 * See {@link Camera#setDisplayOrientation(int)}.
 	 */
 	private int getScreenRotationDegrees() {
-		WindowManager wm =
-				(WindowManager) getContext().getSystemService(WINDOW_SERVICE);
+		WindowManager wm = (WindowManager)
+				getContext().getSystemService(WINDOW_SERVICE);
+		if (wm == null) return 0;
 		Display d = wm.getDefaultDisplay();
 		switch (d.getRotation()) {
 			case Surface.ROTATION_0:

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

@@ -71,9 +71,7 @@ public class ContactExchangeErrorFragment extends BaseFragment {
 
 		// buttons
 		Button tryAgain = v.findViewById(R.id.tryAgainButton);
-		tryAgain.setOnClickListener(view -> {
-			if (getActivity() != null) getActivity().onBackPressed();
-		});
+		tryAgain.setOnClickListener(view -> requireActivity().onBackPressed());
 		Button cancel = v.findViewById(R.id.cancelButton);
 		cancel.setOnClickListener(view -> finish());
 		return v;

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

@@ -42,6 +42,7 @@ import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE;
 import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE;
 import static android.bluetooth.BluetoothAdapter.STATE_ON;
 import static android.content.pm.PackageManager.PERMISSION_GRANTED;
+import static java.util.Objects.requireNonNull;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_BLUETOOTH_DISCOVERABLE;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_PERMISSION_CAMERA_LOCATION;
@@ -96,14 +97,13 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 		component.inject(this);
 	}
 
-	@SuppressWarnings("ConstantConditions")
 	@Override
 	public void onCreate(@Nullable Bundle state) {
 		super.onCreate(state);
 		setContentView(R.layout.activity_fragment_container_toolbar);
 		Toolbar toolbar = findViewById(R.id.toolbar);
 		setSupportActionBar(toolbar);
-		getSupportActionBar().setDisplayHomeAsUpEnabled(true);
+		requireNonNull(getSupportActionBar()).setDisplayHomeAsUpEnabled(true);
 		if (state == null) {
 			showInitialFragment(IntroFragment.newInstance());
 		}
@@ -202,7 +202,8 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	}
 
 	@Override
-	public void onActivityResult(int request, int result, Intent data) {
+	public void onActivityResult(int request, int result,
+			@Nullable Intent data) {
 		if (request == REQUEST_BLUETOOTH_DISCOVERABLE) {
 			if (result == RESULT_CANCELED) {
 				setBluetoothState(BluetoothState.REFUSED);

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

@@ -53,7 +53,6 @@ import static android.view.View.VISIBLE;
 import static android.view.ViewGroup.LayoutParams.MATCH_PARENT;
 import static android.widget.LinearLayout.HORIZONTAL;
 import static android.widget.Toast.LENGTH_LONG;
-import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
@@ -139,8 +138,7 @@ public class KeyAgreementFragment extends BaseEventFragment
 	@Override
 	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
 		super.onActivityCreated(savedInstanceState);
-		requireNonNull(getActivity())
-				.setRequestedOrientation(SCREEN_ORIENTATION_NOSENSOR);
+		requireActivity().setRequestedOrientation(SCREEN_ORIENTATION_NOSENSOR);
 		cameraView.setPreviewConsumer(new QrCodeDecoder(this));
 	}
 
@@ -191,7 +189,7 @@ public class KeyAgreementFragment extends BaseEventFragment
 	@UiThread
 	private void logCameraExceptionAndFinish(CameraException e) {
 		logException(LOG, WARNING, e);
-		Toast.makeText(getActivity(), R.string.camera_error,
+		Toast.makeText(requireActivity(), R.string.camera_error,
 				LENGTH_LONG).show();
 		finish();
 	}
@@ -262,7 +260,7 @@ public class KeyAgreementFragment extends BaseEventFragment
 		} catch (IOException | IllegalArgumentException e) {
 			LOG.log(WARNING, "QR Code Invalid", e);
 			reset();
-			Toast.makeText(getActivity(), R.string.qr_code_invalid,
+			Toast.makeText(requireActivity(), R.string.qr_code_invalid,
 					LENGTH_LONG).show();
 		}
 	}
@@ -353,7 +351,7 @@ public class KeyAgreementFragment extends BaseEventFragment
 
 	@Override
 	protected void finish() {
-		getActivity().getSupportFragmentManager().popBackStack();
+		requireActivity().getSupportFragmentManager().popBackStack();
 	}
 
 	@NotNullByDefault

briar-android/src/main/java/org/briarproject/briar/android/login/AuthorNameFragment.java

@@ -17,7 +17,6 @@ import javax.annotation.Nullable;
 
 import static android.view.inputmethod.EditorInfo.IME_ACTION_NEXT;
 import static android.view.inputmethod.EditorInfo.IME_ACTION_NONE;
-import static java.util.Objects.requireNonNull;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.util.StringUtils.toUtf8;
 import static org.briarproject.briar.android.util.UiUtils.setError;
@@ -45,7 +44,7 @@ public class AuthorNameFragment extends SetupFragment {
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-		requireNonNull(getActivity()).setTitle(getString(R.string.setup_title));
+		requireActivity().setTitle(getString(R.string.setup_title));
 		View v = inflater.inflate(R.layout.fragment_setup_author_name,
 				container, false);
 		authorNameWrapper = v.findViewById(R.id.nickname_entry_wrapper);

briar-android/src/main/java/org/briarproject/briar/android/login/DozeFragment.java

@@ -18,7 +18,6 @@ import org.briarproject.briar.android.login.PowerView.OnCheckedChangedListener;
 
 import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
-import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_DOZE_WHITELISTING;
 import static org.briarproject.briar.android.util.UiUtils.getDozeWhitelistingIntent;