Merge pull request #4323 from johnjohndoe/annotations

Add missing @NonNull and @Nullable annotations.

25 files changed, 85 insertions, 34 deletions

diff --git a/app/src/main/java/de/danoeh/antennapod/activity/DownloadAuthenticationActivity.java b/app/src/main/java/de/danoeh/antennapod/activity/DownloadAuthenticationActivity.java
index 810005d2d..1d3d9bf11 100644
--- a/app/src/main/java/de/danoeh/antennapod/activity/DownloadAuthenticationActivity.java
+++ b/app/src/main/java/de/danoeh/antennapod/activity/DownloadAuthenticationActivity.java
@@ -3,6 +3,8 @@ package de.danoeh.antennapod.activity;
 import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
+
+import androidx.annotation.NonNull;
 import androidx.appcompat.app.ActionBar;
 import androidx.appcompat.app.AppCompatActivity;
 import android.widget.Button;
@@ -86,7 +88,7 @@ public class DownloadAuthenticationActivity extends AppCompatActivity {
     }
 
     @Override
-    protected void onSaveInstanceState(Bundle outState) {
+    protected void onSaveInstanceState(@NonNull Bundle outState) {
         super.onSaveInstanceState(outState);
         outState.putString("username", etxtUsername.getText().toString());
         outState.putString("password", etxtPassword.getText().toString());
diff --git a/app/src/main/java/de/danoeh/antennapod/adapter/FeedItemlistDescriptionAdapter.java b/app/src/main/java/de/danoeh/antennapod/adapter/FeedItemlistDescriptionAdapter.java
index 690bb9e3d..6bfd34d5c 100644
--- a/app/src/main/java/de/danoeh/antennapod/adapter/FeedItemlistDescriptionAdapter.java
+++ b/app/src/main/java/de/danoeh/antennapod/adapter/FeedItemlistDescriptionAdapter.java
@@ -7,6 +7,10 @@ import android.view.ViewGroup;
 import android.widget.ArrayAdapter;
 import android.widget.Button;
 import android.widget.TextView;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 import de.danoeh.antennapod.R;
 import de.danoeh.antennapod.core.feed.MediaType;
 import de.danoeh.antennapod.core.preferences.PlaybackPreferences;
@@ -32,8 +36,9 @@ public class FeedItemlistDescriptionAdapter extends ArrayAdapter<FeedItem> {
         super(context, resource, objects);
     }
 
+    @NonNull
     @Override
-    public View getView(int position, View convertView, ViewGroup parent) {
+    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
         Holder holder;
 
         FeedItem item = getItem(position);
diff --git a/app/src/main/java/de/danoeh/antennapod/dialog/EpisodesApplyActionFragment.java b/app/src/main/java/de/danoeh/antennapod/dialog/EpisodesApplyActionFragment.java
index 6af35fa55..c3177668a 100644
--- a/app/src/main/java/de/danoeh/antennapod/dialog/EpisodesApplyActionFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/dialog/EpisodesApplyActionFragment.java
@@ -220,7 +220,7 @@ public class EpisodesApplyActionFragment extends Fragment {
     }
 
     @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
         super.onCreateOptionsMenu(menu, inflater);
         inflater.inflate(R.menu.episodes_apply_action_options, menu);
 
@@ -236,7 +236,7 @@ public class EpisodesApplyActionFragment extends Fragment {
     }
 
     @Override
-    public void onPrepareOptionsMenu(Menu menu) {
+    public void onPrepareOptionsMenu(@NonNull Menu menu) {
         // Prepare icon for select toggle button
 
         int[] icon = new int[1];
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/AddFeedFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/AddFeedFragment.java
index 546684f14..167daa08b 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/AddFeedFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/AddFeedFragment.java
@@ -12,9 +12,13 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.EditText;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.appcompat.app.AlertDialog;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.fragment.app.Fragment;
+
 import de.danoeh.antennapod.R;
 import de.danoeh.antennapod.activity.MainActivity;
 import de.danoeh.antennapod.activity.OnlineFeedViewActivity;
@@ -36,7 +40,10 @@ public class AddFeedFragment extends Fragment {
     private MainActivity activity;
 
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+    @Nullable
+    public View onCreateView(@NonNull LayoutInflater inflater,
+                             @Nullable ViewGroup container,
+                             @Nullable Bundle savedInstanceState) {
         super.onCreateView(inflater, container, savedInstanceState);
         View root = inflater.inflate(R.layout.addfeed, container, false);
         activity = (MainActivity) getActivity();
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/AllEpisodesFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/AllEpisodesFragment.java
index ce2e9575c..f66032bc7 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/AllEpisodesFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/AllEpisodesFragment.java
@@ -56,7 +56,7 @@ public class AllEpisodesFragment extends EpisodesListFragment {
     }
 
     @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
         super.onCreateOptionsMenu(menu, inflater);
         menu.findItem(R.id.filter_items).setVisible(true);
         menu.findItem(R.id.mark_all_read_item).setVisible(true);
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/AudioPlayerFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/AudioPlayerFragment.java
index 9c2030c2f..7eb749681 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/AudioPlayerFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/AudioPlayerFragment.java
@@ -92,7 +92,9 @@ public class AudioPlayerFragment extends Fragment implements
     private boolean showTimeLeft;
 
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+    public View onCreateView(@NonNull LayoutInflater inflater,
+                             @Nullable ViewGroup container,
+                             @Nullable Bundle savedInstanceState) {
         super.onCreateView(inflater, container, savedInstanceState);
         View root = inflater.inflate(R.layout.audioplayer_fragment, container, false);
         toolbar = root.findViewById(R.id.toolbar);
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/CompletedDownloadsFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/CompletedDownloadsFragment.java
index 13941dd2c..3c39dc579 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/CompletedDownloadsFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/CompletedDownloadsFragment.java
@@ -104,7 +104,7 @@ public class CompletedDownloadsFragment extends Fragment {
     }
 
     @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
         super.onCreateOptionsMenu(menu, inflater);
         inflater.inflate(R.menu.downloads_completed, menu);
         menu.findItem(R.id.episode_actions).setVisible(items.size() > 0);
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/DownloadLogFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/DownloadLogFragment.java
index 1d36345ca..24f7fd85a 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/DownloadLogFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/DownloadLogFragment.java
@@ -6,6 +6,9 @@ import android.content.ClipboardManager;
 import android.content.Context;
 import android.content.res.TypedArray;
 import android.os.Bundle;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.appcompat.app.AlertDialog;
 import androidx.fragment.app.ListFragment;
 import android.util.Log;
@@ -69,7 +72,7 @@ public class DownloadLogFragment extends ListFragment {
     }
 
     @Override
-    public void onViewCreated(View view, Bundle savedInstanceState) {
+    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
         // add padding
         final ListView lv = getListView();
@@ -101,7 +104,7 @@ public class DownloadLogFragment extends ListFragment {
     }
 
     @Override
-    public void onListItemClick(ListView l, View v, int position, long id) {
+    public void onListItemClick(@NonNull ListView l, @NonNull View v, int position, long id) {
         super.onListItemClick(l, v, position, id);
 
         DownloadStatus status = adapter.getItem(position);
@@ -161,7 +164,7 @@ public class DownloadLogFragment extends ListFragment {
     }
 
     @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
         if (!isAdded()) {
             return;
         }
@@ -174,7 +177,7 @@ public class DownloadLogFragment extends ListFragment {
     }
 
     @Override
-    public void onPrepareOptionsMenu(Menu menu) {
+    public void onPrepareOptionsMenu(@NonNull Menu menu) {
         super.onPrepareOptionsMenu(menu);
         MenuItem menuItem = menu.findItem(R.id.clear_history_item);
         if (menuItem != null) {
@@ -183,7 +186,7 @@ public class DownloadLogFragment extends ListFragment {
     }
 
     @Override
-    public boolean onOptionsItemSelected(MenuItem item) {
+    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
         if (!super.onOptionsItemSelected(item)) {
             switch (item.getItemId()) {
                 case R.id.clear_history_item:
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/DownloadsFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/DownloadsFragment.java
index cf0c6db90..c173bf8ee 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/DownloadsFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/DownloadsFragment.java
@@ -8,6 +8,7 @@ import android.view.View;
 import android.view.ViewGroup;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;
 import androidx.fragment.app.Fragment;
@@ -39,7 +40,9 @@ public class DownloadsFragment extends Fragment {
     private TabLayout tabLayout;
 
     @Override
-    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+    public View onCreateView(@NonNull LayoutInflater inflater,
+                             @Nullable ViewGroup container,
+                             @Nullable Bundle savedInstanceState) {
         super.onCreateView(inflater, container, savedInstanceState);
         View root = inflater.inflate(R.layout.pager_fragment, container, false);
         Toolbar toolbar = root.findViewById(R.id.toolbar);
@@ -76,7 +79,7 @@ public class DownloadsFragment extends Fragment {
     }
 
     @Override
-    public void onViewCreated(View view, Bundle savedInstanceState) {
+    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
         super.onViewCreated(view, savedInstanceState);
         if (getArguments() != null) {
             int tab = getArguments().getInt(ARG_SELECTED_TAB);
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/EpisodesListFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/EpisodesListFragment.java
index 29b6a1b16..44f6c8827 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/EpisodesListFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/EpisodesListFragment.java
@@ -120,7 +120,7 @@ public abstract class EpisodesListFragment extends Fragment {
     }
 
     @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
         if (!isAdded()) {
             return;
         }
@@ -131,7 +131,7 @@ public abstract class EpisodesListFragment extends Fragment {
     }
 
     @Override
-    public boolean onOptionsItemSelected(MenuItem item) {
+    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
         if (!super.onOptionsItemSelected(item)) {
             switch (item.getItemId()) {
                 case R.id.refresh_item:
@@ -176,7 +176,7 @@ public abstract class EpisodesListFragment extends Fragment {
     }
 
     @Override
-    public boolean onContextItemSelected(MenuItem item) {
+    public boolean onContextItemSelected(@NonNull MenuItem item) {
         Log.d(TAG, "onContextItemSelected() called with: " + "item = [" + item + "]");
         if (!getUserVisibleHint()) {
             return false;
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/FavoriteEpisodesFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/FavoriteEpisodesFragment.java
index 4f8b4f00c..d50be88c5 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/FavoriteEpisodesFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/FavoriteEpisodesFragment.java
@@ -53,12 +53,14 @@ public class FavoriteEpisodesFragment extends EpisodesListFragment {
         ItemTouchHelper.SimpleCallback simpleItemTouchCallback = new ItemTouchHelper.SimpleCallback(0,
                 ItemTouchHelper.LEFT) {
             @Override
-            public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
+            public boolean onMove(@NonNull RecyclerView recyclerView,
+                                  @NonNull RecyclerView.ViewHolder viewHolder,
+                                  @NonNull RecyclerView.ViewHolder target) {
                 return false;
             }
 
             @Override
-            public void onSwiped(RecyclerView.ViewHolder viewHolder, int swipeDir) {
+            public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int swipeDir) {
                 EpisodeItemViewHolder holder = (EpisodeItemViewHolder) viewHolder;
                 Log.d(TAG, String.format("remove(%s)", holder.getFeedItem().getId()));
 
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/FeedInfoFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/FeedInfoFragment.java
index 071fa9f54..ae03b5032 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/FeedInfoFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/FeedInfoFragment.java
@@ -162,7 +162,7 @@ public class FeedInfoFragment extends Fragment {
     }
 
     @Override
-    public void onConfigurationChanged(Configuration newConfig) {
+    public void onConfigurationChanged(@NonNull Configuration newConfig) {
         super.onConfigurationChanged(newConfig);
         int horizontalSpacing = (int) getResources().getDimension(R.dimen.additional_horizontal_spacing);
         header.setPadding(horizontalSpacing, header.getPaddingTop(), horizontalSpacing, header.getPaddingBottom());
@@ -227,7 +227,7 @@ public class FeedInfoFragment extends Fragment {
     }
 
     @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
         super.onCreateOptionsMenu(menu, inflater);
         inflater.inflate(R.menu.feedinfo, menu);
         optionsMenu = menu;
@@ -235,7 +235,7 @@ public class FeedInfoFragment extends Fragment {
     }
 
     @Override
-    public void onPrepareOptionsMenu(Menu menu) {
+    public void onPrepareOptionsMenu(@NonNull Menu menu) {
         super.onPrepareOptionsMenu(menu);
         menu.findItem(R.id.share_link_item).setVisible(feed != null && feed.getLink() != null);
         menu.findItem(R.id.visit_website_item).setVisible(feed != null && feed.getLink() != null
@@ -243,7 +243,7 @@ public class FeedInfoFragment extends Fragment {
     }
 
     @Override
-    public boolean onOptionsItemSelected(MenuItem item) {
+    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
         if (feed == null) {
             ((MainActivity) getActivity()).showSnackbarAbovePlayer(
                     R.string.please_wait_for_data, Toast.LENGTH_LONG);
diff --git a/app/src/main/java/de/danoeh/antennapod/fragment/FeedItemlistFragment.java b/app/src/main/java/de/danoeh/antennapod/fragment/FeedItemlistFragment.java
index 950fb47c6..02df1c969 100644
--- a/app/src/main/java/de/danoeh/antennapod/fragment/FeedItemlistFragment.java
+++ b/app/src/main/java/de/danoeh/antennapod/fragment/FeedItemlistFragment.java
@@ -228,7 +228,7 @@ public class FeedItemlistFragment extends Fragment implements AdapterView.OnItem
     };
 
     @Override
-    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
+    public void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
         if (!isAdded()) {
             return;
         }
@@ -246,21 +246,21 @@ public class FeedItemlistFragment extends Fragment implements AdapterView.OnItem
     }
 
     @Override
-    public void onPrepareOptionsMenu(Menu menu) {
+    public void onPrepareOptionsMenu(@NonNull Menu menu) {
         if (feed != null) {
             FeedMenuHandler.onPrepareOptionsMenu(menu, feed);
         }
     }
 
     @Override
-    public void onConfigurationChanged(Configuration newConfig) {
+    public void onConfigurationChanged(@NonNull Configuration newConfig) {
         super.onConfigurationChanged(newConfig);
         int horizontalSpacing = (int) getResources().getDimension(R.dimen.additional_horizontal_spacing);
         header.setPadding(horizontalSpacing, header.getPaddingTop(), horizontalSpacing, header.getPaddingBottom());
     }
 
     @Override
-    public boolean onOptionsItemSelected(MenuItem item) {
+    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
         if (!super.onOptionsItemSelected(item)) {
             if (feed == null) {
                 ((MainActivity) getActivity()).showSnackbarAbovePlayer(
diff --git a/core/src/main/java/de/danoeh/antennapod/core/event/DownloadEvent.java b/core/src/main/java/de/danoeh/antennapod/core/event/DownloadEvent.java
index 24a71ec96..efd53ab9d 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/event/DownloadEvent.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/event/DownloadEvent.java
@@ -1,5 +1,7 @@
 package de.danoeh.antennapod.core.event;
 
+import androidx.annotation.NonNull;
+
 import java.util.ArrayList;
 import java.util.List;
 
@@ -19,6 +21,7 @@ public class DownloadEvent {
         return new DownloadEvent(update);
     }
 
+    @NonNull
     @Override
     public String toString() {
         return "DownloadEvent{" +
diff --git a/core/src/main/java/de/danoeh/antennapod/core/event/DownloadLogEvent.java b/core/src/main/java/de/danoeh/antennapod/core/event/DownloadLogEvent.java
index 7428c5b00..5ab5decf9 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/event/DownloadLogEvent.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/event/DownloadLogEvent.java
@@ -1,5 +1,7 @@
 package de.danoeh.antennapod.core.event;
 
+import androidx.annotation.NonNull;
+
 public class DownloadLogEvent {
 
     private DownloadLogEvent() {
@@ -9,6 +11,7 @@ public class DownloadLogEvent {
         return new DownloadLogEvent();
     }
 
+    @NonNull
     @Override
     public String toString() {
         return "DownloadLogEvent";
diff --git a/core/src/main/java/de/danoeh/antennapod/core/event/DownloaderUpdate.java b/core/src/main/java/de/danoeh/antennapod/core/event/DownloaderUpdate.java
index f549940b7..10992408d 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/event/DownloaderUpdate.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/event/DownloaderUpdate.java
@@ -46,6 +46,7 @@ public class DownloaderUpdate {
         this.mediaIds = mediaIds1.toArray();
     }
 
+    @NonNull
     @Override
     public String toString() {
         return "DownloaderUpdate{" +
diff --git a/core/src/main/java/de/danoeh/antennapod/core/event/FavoritesEvent.java b/core/src/main/java/de/danoeh/antennapod/core/event/FavoritesEvent.java
index 578007561..d3be8fac0 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/event/FavoritesEvent.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/event/FavoritesEvent.java
@@ -1,5 +1,7 @@
 package de.danoeh.antennapod.core.event;
 
+import androidx.annotation.NonNull;
+
 import org.apache.commons.lang3.builder.ToStringBuilder;
 import org.apache.commons.lang3.builder.ToStringStyle;
 
@@ -27,6 +29,7 @@ public class FavoritesEvent {
         return new FavoritesEvent(Action.REMOVED, item);
     }
 
+    @NonNull
     @Override
     public String toString() {
         return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
diff --git a/core/src/main/java/de/danoeh/antennapod/core/event/FeedItemEvent.java b/core/src/main/java/de/danoeh/antennapod/core/event/FeedItemEvent.java
index 4b14a72d2..02559b2f5 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/event/FeedItemEvent.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/event/FeedItemEvent.java
@@ -21,7 +21,7 @@ public class FeedItemEvent {
     private final Action action;
     @NonNull public final List<FeedItem> items;
 
-    private FeedItemEvent(Action action, List<FeedItem> items) {
+    private FeedItemEvent(@NonNull Action action, @NonNull List<FeedItem> items) {
         this.action = action;
         this.items = items;
     }
@@ -42,6 +42,7 @@ public class FeedItemEvent {
         return updated(Arrays.asList(items));
     }
 
+    @NonNull
     @Override
     public String toString() {
         return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
diff --git a/core/src/main/java/de/danoeh/antennapod/core/feed/FeedEvent.java b/core/src/main/java/de/danoeh/antennapod/core/feed/FeedEvent.java
index 15cdf92dc..044554451 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/feed/FeedEvent.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/feed/FeedEvent.java
@@ -1,5 +1,7 @@
 package de.danoeh.antennapod.core.feed;
 
+import androidx.annotation.NonNull;
+
 import org.apache.commons.lang3.builder.ToStringBuilder;
 import org.apache.commons.lang3.builder.ToStringStyle;
 
@@ -18,6 +20,7 @@ public class FeedEvent {
         this.feedId = feedId;
     }
 
+    @NonNull
     @Override
     public String toString() {
         return new ToStringBuilder(this, ToStringStyle.SHORT_PREFIX_STYLE)
diff --git a/core/src/main/java/de/danoeh/antennapod/core/feed/FeedItem.java b/core/src/main/java/de/danoeh/antennapod/core/feed/FeedItem.java
index 60ebe6965..b681c21d1 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/feed/FeedItem.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/feed/FeedItem.java
@@ -1,6 +1,8 @@
 package de.danoeh.antennapod.core.feed;
 
 import android.database.Cursor;
+
+import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import android.text.TextUtils;
 
@@ -482,6 +484,7 @@ public class FeedItem extends FeedComponent implements ShownotesProvider, ImageR
      */
     public void removeTag(String tag) { tags.remove(tag); }
 
+    @NonNull
     @Override
     public String toString() {
         return ToStringBuilder.reflectionToString(this, ToStringStyle.SHORT_PREFIX_STYLE);
diff --git a/core/src/main/java/de/danoeh/antennapod/core/glide/ChapterImageModelLoader.java b/core/src/main/java/de/danoeh/antennapod/core/glide/ChapterImageModelLoader.java
index 36da11eca..35a9d987b 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/glide/ChapterImageModelLoader.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/glide/ChapterImageModelLoader.java
@@ -28,8 +28,9 @@ import org.apache.commons.io.IOUtils;
 public final class ChapterImageModelLoader implements ModelLoader<EmbeddedChapterImage, ByteBuffer> {
 
     public static class Factory implements ModelLoaderFactory<EmbeddedChapterImage, ByteBuffer> {
+        @NonNull
         @Override
-        public ModelLoader<EmbeddedChapterImage, ByteBuffer> build(MultiModelLoaderFactory unused) {
+        public ModelLoader<EmbeddedChapterImage, ByteBuffer> build(@NonNull MultiModelLoaderFactory unused) {
             return new ChapterImageModelLoader();
         }
 
@@ -41,12 +42,15 @@ public final class ChapterImageModelLoader implements ModelLoader<EmbeddedChapte
 
     @Nullable
     @Override
-    public LoadData<ByteBuffer> buildLoadData(EmbeddedChapterImage model, int width, int height, Options options) {
+    public LoadData<ByteBuffer> buildLoadData(@NonNull EmbeddedChapterImage model,
+                                              int width,
+                                              int height,
+                                              @NonNull Options options) {
         return new LoadData<>(new ObjectKey(model), new EmbeddedImageFetcher(model));
     }
 
     @Override
-    public boolean handles(EmbeddedChapterImage model) {
+    public boolean handles(@NonNull EmbeddedChapterImage model) {
         return true;
     }
 
diff --git a/core/src/main/java/de/danoeh/antennapod/core/glide/FastBlurTransformation.java b/core/src/main/java/de/danoeh/antennapod/core/glide/FastBlurTransformation.java
index d0301db2f..1f8ae5ad9 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/glide/FastBlurTransformation.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/glide/FastBlurTransformation.java
@@ -21,7 +21,10 @@ public class FastBlurTransformation extends BitmapTransformation {
     }
 
     @Override
-    protected Bitmap transform(BitmapPool pool, Bitmap source, int outWidth, int outHeight) {
+    protected Bitmap transform(@NonNull BitmapPool pool,
+                               @NonNull Bitmap source,
+                               int outWidth,
+                               int outHeight) {
         int targetWidth = outWidth / 3;
         int targetHeight = (int) (1.0 * outHeight * targetWidth / outWidth);
         Bitmap resized = ThumbnailUtils.extractThumbnail(source, targetWidth, targetHeight);
diff --git a/core/src/main/java/de/danoeh/antennapod/core/storage/DownloadRequester.java b/core/src/main/java/de/danoeh/antennapod/core/storage/DownloadRequester.java
index f10dde65f..e3121caa2 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/storage/DownloadRequester.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/storage/DownloadRequester.java
@@ -340,7 +340,7 @@ public class DownloadRequester implements DownloadStateProvider {
     /**
      * Checks if feedfile is in the downloads list
      */
-    public synchronized boolean isDownloadingFile(FeedFile item) {
+    public synchronized boolean isDownloadingFile(@NonNull FeedFile item) {
         return item.getDownload_url() != null && downloads.containsKey(item.getDownload_url());
     }
 
diff --git a/core/src/main/java/de/danoeh/antennapod/core/sync/model/EpisodeAction.java b/core/src/main/java/de/danoeh/antennapod/core/sync/model/EpisodeAction.java
index 6154ccc84..798be8d96 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/sync/model/EpisodeAction.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/sync/model/EpisodeAction.java
@@ -3,6 +3,7 @@ package de.danoeh.antennapod.core.sync.model;
 import android.text.TextUtils;
 import android.util.Log;
 
+import androidx.annotation.NonNull;
 import androidx.core.util.ObjectsCompat;
 import de.danoeh.antennapod.core.feed.FeedItem;
 import de.danoeh.antennapod.core.util.DateUtils;
@@ -179,6 +180,7 @@ public class EpisodeAction {
         return obj;
     }
 
+    @NonNull
     @Override
     public String toString() {
         return "EpisodeAction{"
diff --git a/core/src/main/java/de/danoeh/antennapod/core/sync/model/EpisodeActionChanges.java b/core/src/main/java/de/danoeh/antennapod/core/sync/model/EpisodeActionChanges.java
index 77942ffa0..90af585af 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/sync/model/EpisodeActionChanges.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/sync/model/EpisodeActionChanges.java
@@ -23,6 +23,7 @@ public class EpisodeActionChanges {
         return this.timestamp;
     }
 
+    @NonNull
     @Override
     public String toString() {
         return "EpisodeActionGetResponse{"