Fix null annotations, issues in various classes

app/src/main/java/acr/browser/lightning/database/BookmarkManager.java

@@ -50,15 +50,15 @@ public class BookmarkManager {
     private static final String ORDER = "order";
     private static final String FILE_BOOKMARKS = "bookmarks.dat";
 
-    private final String DEFAULT_BOOKMARK_TITLE;
+    @NonNull private final String DEFAULT_BOOKMARK_TITLE;
 
     private Map<String, HistoryItem> mBookmarksMap;
-    private String mCurrentFolder = "";
-    private final ExecutorService mExecutor;
+    @NonNull private String mCurrentFolder = "";
+    @NonNull private final ExecutorService mExecutor;
     private final File mFilesDir;
 
     @Inject
-    public BookmarkManager(Context context) {
+    public BookmarkManager(@NonNull Context context) {
         mExecutor = Executors.newSingleThreadExecutor();
         mFilesDir = context.getFilesDir();
         DEFAULT_BOOKMARK_TITLE = context.getString(R.string.untitled);
@@ -163,7 +163,7 @@ public class BookmarkManager {
                     bookmarkWriter.newLine();
                 }
                 success = true;
-            } catch (IOException | JSONException e) {
+            } catch (@NonNull IOException | JSONException e) {
                 e.printStackTrace();
             } finally {
                 Utils.close(bookmarkWriter);
@@ -196,7 +196,7 @@ public class BookmarkManager {
      */
     public synchronized boolean addBookmark(@NonNull HistoryItem item) {
         final String url = item.getUrl();
-        if (url == null || mBookmarksMap.containsKey(url)) {
+        if (mBookmarksMap.containsKey(url)) {
             return false;
         }
         mBookmarksMap.put(url, item);
@@ -209,13 +209,13 @@ public class BookmarkManager {
      *
      * @param list the list of HistoryItems to add to bookmarks
      */
-    public synchronized void addBookmarkList(List<HistoryItem> list) {
+    public synchronized void addBookmarkList(@Nullable List<HistoryItem> list) {
         if (list == null || list.isEmpty()) {
             return;
         }
         for (HistoryItem item : list) {
             final String url = item.getUrl();
-            if (url != null && !mBookmarksMap.containsKey(url)) {
+            if (!mBookmarksMap.containsKey(url)) {
                 mBookmarksMap.put(url, item);
             }
         }
@@ -228,7 +228,7 @@ public class BookmarkManager {
      *
      * @param deleteItem the bookmark item to delete
      */
-    public synchronized boolean deleteBookmark(HistoryItem deleteItem) {
+    public synchronized boolean deleteBookmark(@Nullable HistoryItem deleteItem) {
         if (deleteItem == null || deleteItem.isFolder()) {
             return false;
         }
@@ -288,7 +288,7 @@ public class BookmarkManager {
      * @param oldItem This is the old item that you wish to edit
      * @param newItem This is the new item that will overwrite the old item
      */
-    public synchronized void editBookmark(HistoryItem oldItem, HistoryItem newItem) {
+    public synchronized void editBookmark(@Nullable HistoryItem oldItem, @Nullable HistoryItem newItem) {
         if (oldItem == null || newItem == null || oldItem.isFolder()) {
             return;
         }
@@ -313,7 +313,7 @@ public class BookmarkManager {
      * This method exports the stored bookmarks to a text file in the device's
      * external download directory
      */
-    public synchronized void exportBookmarks(Activity activity) {
+    public synchronized void exportBookmarks(@NonNull Activity activity) {
         List<HistoryItem> bookmarkList = getAllBookmarks(true);
         File bookmarksExport = new File(
                 Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),
@@ -341,7 +341,7 @@ public class BookmarkManager {
             }
             Utils.showSnackbar(activity, activity.getString(R.string.bookmark_export_path)
                     + ' ' + bookmarksExport.getPath());
-        } catch (IOException | JSONException e) {
+        } catch (@NonNull IOException | JSONException e) {
             e.printStackTrace();
         } finally {
             Utils.close(bookmarkWriter);
@@ -357,6 +357,7 @@ public class BookmarkManager {
      * @param sort force to sort the returned bookmarkList
      * @return returns a list of bookmarks that can be sorted
      */
+    @NonNull
     public synchronized List<HistoryItem> getAllBookmarks(boolean sort) {
         final List<HistoryItem> bookmarks = new ArrayList<>(mBookmarksMap.values());
         if (sort) {
@@ -374,7 +375,8 @@ public class BookmarkManager {
      * @param folder the name of the folder to retrieve bookmarks from
      * @return a list of bookmarks found in that folder
      */
-    public synchronized List<HistoryItem> getBookmarksFromFolder(String folder, boolean sort) {
+    @NonNull
+    public synchronized List<HistoryItem> getBookmarksFromFolder(@Nullable String folder, boolean sort) {
         List<HistoryItem> bookmarks = new ArrayList<>();
         if (folder == null || folder.isEmpty()) {
             bookmarks.addAll(getFolders(sort));
@@ -405,6 +407,7 @@ public class BookmarkManager {
      *
      * @return the current folder
      */
+    @Nullable
     public String getCurrentFolder() {
         return mCurrentFolder;
     }
@@ -416,11 +419,12 @@ public class BookmarkManager {
      *
      * @return a list of all folders
      */
+    @NonNull
     private synchronized List<HistoryItem> getFolders(boolean sort) {
         final HashMap<String, HistoryItem> folders = new HashMap<>();
         for (HistoryItem item : mBookmarksMap.values()) {
             final String folderName = item.getFolder();
-            if (folderName != null && !folderName.isEmpty() && !folders.containsKey(folderName)) {
+            if (!folderName.isEmpty() && !folders.containsKey(folderName)) {
                 final HistoryItem folder = new HistoryItem();
                 folder.setIsFolder(true);
                 folder.setTitle(folderName);
@@ -442,11 +446,12 @@ public class BookmarkManager {
      *
      * @return a list of folder title strings
      */
+    @NonNull
     public synchronized List<String> getFolderTitles() {
         final Set<String> folders = new HashSet<>();
         for (HistoryItem item : mBookmarksMap.values()) {
             final String folderName = item.getFolder();
-            if (folderName != null && !folderName.isEmpty()) {
+            if (!folderName.isEmpty()) {
                 folders.add(folderName);
             }
         }
@@ -459,7 +464,7 @@ public class BookmarkManager {
      *
      * @param file the file to attempt to import bookmarks from
      */
-    public synchronized void importBookmarksFromFile(File file, Activity activity) {
+    public synchronized void importBookmarksFromFile(@Nullable File file, @NonNull Activity activity) {
         if (file == null) {
             return;
         }
@@ -483,7 +488,7 @@ public class BookmarkManager {
             addBookmarkList(list);
             String message = activity.getResources().getString(R.string.message_import);
             Utils.showSnackbar(activity, number + " " + message);
-        } catch (IOException | JSONException e) {
+        } catch (@NonNull IOException | JSONException e) {
             e.printStackTrace();
             Utils.createInformativeDialog(activity, R.string.title_error, R.string.import_bookmark_error);
         } finally {
@@ -496,8 +501,8 @@ public class BookmarkManager {
      */
     private static class SortIgnoreCase implements Comparator<HistoryItem> {
 
-        public int compare(HistoryItem o1, HistoryItem o2) {
-            if (o1 == null || o2 == null || o1.getTitle() == null || o2.getTitle() == null) {
+        public int compare(@Nullable HistoryItem o1, @Nullable HistoryItem o2) {
+            if (o1 == null || o2 == null) {
                 return 0;
             }
             if (o1.isFolder() == o2.isFolder()) {

app/src/main/java/acr/browser/lightning/database/HistoryDatabase.java

@@ -38,17 +38,17 @@ public class HistoryDatabase extends SQLiteOpenHelper {
     private static final String KEY_TITLE = "title";
     private static final String KEY_TIME_VISITED = "time";
 
-    private SQLiteDatabase mDatabase;
+    @Nullable private SQLiteDatabase mDatabase;
 
     @Inject
-    public HistoryDatabase(Context context) {
+    public HistoryDatabase(@NonNull Context context) {
         super(context.getApplicationContext(), DATABASE_NAME, null, DATABASE_VERSION);
         mDatabase = this.getWritableDatabase();
     }
 
     // Creating Tables
     @Override
-    public void onCreate(SQLiteDatabase db) {
+    public void onCreate(@NonNull SQLiteDatabase db) {
         String CREATE_HISTORY_TABLE = "CREATE TABLE " + TABLE_HISTORY + '(' + KEY_ID
                 + " INTEGER PRIMARY KEY," + KEY_URL + " TEXT," + KEY_TITLE + " TEXT,"
                 + KEY_TIME_VISITED + " INTEGER" + ')';
@@ -57,7 +57,7 @@ public class HistoryDatabase extends SQLiteOpenHelper {
 
     // Upgrading database
     @Override
-    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+    public void onUpgrade(@NonNull SQLiteDatabase db, int oldVersion, int newVersion) {
         // Drop older table if it exists
         db.execSQL("DROP TABLE IF EXISTS " + TABLE_HISTORY);
         // Create tables again
@@ -65,15 +65,12 @@ public class HistoryDatabase extends SQLiteOpenHelper {
     }
 
     public synchronized void deleteHistory() {
+        mDatabase = openIfNecessary();
         mDatabase.delete(TABLE_HISTORY, null, null);
         mDatabase.close();
         mDatabase = this.getWritableDatabase();
     }
 
-    private synchronized boolean isClosed() {
-        return mDatabase == null || !mDatabase.isOpen();
-    }
-
     @Override
     public synchronized void close() {
         if (mDatabase != null) {
@@ -83,19 +80,21 @@ public class HistoryDatabase extends SQLiteOpenHelper {
         super.close();
     }
 
-    private void openIfNecessary() {
-        if (isClosed()) {
+    @NonNull
+    private SQLiteDatabase openIfNecessary() {
+        if (mDatabase == null || !mDatabase.isOpen()) {
             mDatabase = this.getWritableDatabase();
         }
+        return mDatabase;
     }
 
     public synchronized void deleteHistoryItem(@NonNull String url) {
-        openIfNecessary();
+        mDatabase = openIfNecessary();
         mDatabase.delete(TABLE_HISTORY, KEY_URL + " = ?", new String[]{url});
     }
 
     public synchronized void visitHistoryItem(@NonNull String url, @Nullable String title) {
-        openIfNecessary();
+        mDatabase = openIfNecessary();
         ContentValues values = new ContentValues();
         values.put(KEY_TITLE, title == null ? "" : title);
         values.put(KEY_TIME_VISITED, System.currentTimeMillis());
@@ -110,7 +109,7 @@ public class HistoryDatabase extends SQLiteOpenHelper {
     }
 
     private synchronized void addHistoryItem(@NonNull HistoryItem item) {
-        openIfNecessary();
+        mDatabase = openIfNecessary();
         ContentValues values = new ContentValues();
         values.put(KEY_URL, item.getUrl());
         values.put(KEY_TITLE, item.getTitle());
@@ -118,8 +117,9 @@ public class HistoryDatabase extends SQLiteOpenHelper {
         mDatabase.insert(TABLE_HISTORY, null, values);
     }
 
+    @Nullable
     synchronized String getHistoryItem(@NonNull String url) {
-        openIfNecessary();
+        mDatabase = openIfNecessary();
         Cursor cursor = mDatabase.query(TABLE_HISTORY, new String[]{KEY_ID, KEY_URL, KEY_TITLE},
                 KEY_URL + " = ?", new String[]{url}, null, null, null, null);
         String m = null;
@@ -132,8 +132,9 @@ public class HistoryDatabase extends SQLiteOpenHelper {
         return m;
     }
 
+    @NonNull
     public synchronized List<HistoryItem> findItemsContaining(@Nullable String search) {
-        openIfNecessary();
+        mDatabase = openIfNecessary();
         List<HistoryItem> itemList = new ArrayList<>(5);
         if (search == null) {
             return itemList;
@@ -160,7 +161,7 @@ public class HistoryDatabase extends SQLiteOpenHelper {
 
     @NonNull
     public synchronized List<HistoryItem> getLastHundredItems() {
-        openIfNecessary();
+        mDatabase = openIfNecessary();
         List<HistoryItem> itemList = new ArrayList<>(100);
         String selectQuery = "SELECT * FROM " + TABLE_HISTORY + " ORDER BY " + KEY_TIME_VISITED
                 + " DESC";
@@ -183,7 +184,7 @@ public class HistoryDatabase extends SQLiteOpenHelper {
 
     @NonNull
     public synchronized List<HistoryItem> getAllHistoryItems() {
-        openIfNecessary();
+        mDatabase = openIfNecessary();
         List<HistoryItem> itemList = new ArrayList<>();
         String selectQuery = "SELECT  * FROM " + TABLE_HISTORY + " ORDER BY " + KEY_TIME_VISITED
                 + " DESC";
@@ -204,7 +205,7 @@ public class HistoryDatabase extends SQLiteOpenHelper {
     }
 
     public synchronized int getHistoryItemsCount() {
-        openIfNecessary();
+        mDatabase = openIfNecessary();
         String countQuery = "SELECT * FROM " + TABLE_HISTORY;
         Cursor cursor = mDatabase.rawQuery(countQuery, null);
         int n = cursor.getCount();

app/src/main/java/acr/browser/lightning/database/HistoryItem.java

@@ -7,6 +7,8 @@ import android.graphics.Bitmap;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 
+import acr.browser.lightning.utils.Preconditions;
+
 public class HistoryItem implements Comparable<HistoryItem> {
 
     // private variables
@@ -26,7 +28,6 @@ public class HistoryItem implements Comparable<HistoryItem> {
     private int mOrder = 0;
     private boolean mIsFolder = false;
 
-    // Empty constructor
     public HistoryItem() {}
 
     public HistoryItem(@NonNull HistoryItem item) {
@@ -37,15 +38,17 @@ public class HistoryItem implements Comparable<HistoryItem> {
         this.mIsFolder = item.mIsFolder;
     }
 
-    // constructor
     public HistoryItem(@NonNull String url, @NonNull String title) {
+        Preconditions.checkNonNull(url);
+        Preconditions.checkNonNull(title);
         this.mUrl = url;
         this.mTitle = title;
         this.mBitmap = null;
     }
 
-    // constructor
     public HistoryItem(@NonNull String url, @NonNull String title, int imageId) {
+        Preconditions.checkNonNull(url);
+        Preconditions.checkNonNull(title);
         this.mUrl = url;
         this.mTitle = title;
         this.mBitmap = null;
@@ -86,24 +89,20 @@ public class HistoryItem implements Comparable<HistoryItem> {
         return mBitmap;
     }
 
-    // getting name
     @NonNull
     public String getUrl() {
         return this.mUrl;
     }
 
-    // setting name
     public void setUrl(@Nullable String url) {
         this.mUrl = (url == null) ? "" : url;
     }
 
-    // getting phone number
     @NonNull
     public String getTitle() {
         return this.mTitle;
     }
 
-    // setting phone number
     public void setTitle(@Nullable String title) {
         this.mTitle = (title == null) ? "" : title;
     }

app/src/main/java/acr/browser/lightning/object/SearchAdapter.java

@@ -7,6 +7,8 @@ import android.graphics.drawable.Drawable;
 import android.net.ConnectivityManager;
 import android.net.NetworkInfo;
 import android.os.AsyncTask;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -59,7 +61,7 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
     private final List<HistoryItem> mFilteredList = new ArrayList<>(5);
     private final List<HistoryItem> mAllBookmarks = new ArrayList<>(5);
     private final Object mLock = new Object();
-    private final Context mContext;
+    @NonNull private final Context mContext;
     private boolean mUseGoogle = true;
     private boolean mIsExecuting = false;
     private final boolean mDarkTheme;
@@ -70,11 +72,11 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
     private static final long INTERVAL_DAY = 86400000;
     private static final int MAX_SUGGESTIONS = 5;
     private static final SuggestionsComparator mComparator = new SuggestionsComparator();
-    private final String mSearchSubtitle;
+    @NonNull private final String mSearchSubtitle;
     private SearchFilter mFilter;
-    private final Drawable mSearchDrawable;
-    private final Drawable mHistoryDrawable;
-    private final Drawable mBookmarkDrawable;
+    @NonNull private final Drawable mSearchDrawable;
+    @NonNull private final Drawable mHistoryDrawable;
+    @NonNull private final Drawable mBookmarkDrawable;
     private String mLanguage;
 
     @Inject
@@ -86,7 +88,7 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
     @Inject
     PreferenceManager mPreferenceManager;
 
-    public SearchAdapter(Context context, boolean dark, boolean incognito) {
+    public SearchAdapter(@NonNull Context context, boolean dark, boolean incognito) {
         BrowserApp.getAppComponent().inject(this);
         mAllBookmarks.addAll(mBookmarkManager.getAllBookmarks(true));
         mUseGoogle = mPreferenceManager.getGoogleSearchSuggestionsEnabled();
@@ -109,7 +111,7 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
     private static class NameFilter implements FilenameFilter {
 
         @Override
-        public boolean accept(File dir, String filename) {
+        public boolean accept(File dir, @NonNull String filename) {
             return filename.endsWith(CACHE_FILE_TYPE);
         }
 
@@ -146,8 +148,9 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
         return 0;
     }
 
+    @Nullable
     @Override
-    public View getView(int position, View convertView, ViewGroup parent) {
+    public View getView(int position, @Nullable View convertView, ViewGroup parent) {
         SuggestionHolder holder;
 
         if (convertView == null) {
@@ -232,8 +235,9 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
 
     private class SearchFilter extends Filter {
 
+        @NonNull
         @Override
-        protected FilterResults performFiltering(CharSequence constraint) {
+        protected FilterResults performFiltering(@Nullable CharSequence constraint) {
             FilterResults results = new FilterResults();
             if (constraint == null) {
                 return results;
@@ -273,7 +277,7 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
         }
 
         @Override
-        public CharSequence convertResultToString(Object resultValue) {
+        public CharSequence convertResultToString(@NonNull Object resultValue) {
             return ((HistoryItem) resultValue).getUrl();
         }
 
@@ -301,6 +305,7 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
         private XmlPullParserFactory mFactory;
         private XmlPullParser mXpp;
 
+        @NonNull
         @Override
         protected List<HistoryItem> doInBackground(String... arg0) {
             mIsExecuting = true;
@@ -351,7 +356,7 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
         }
 
         @Override
-        protected void onPostExecute(List<HistoryItem> result) {
+        protected void onPostExecute(@NonNull List<HistoryItem> result) {
             mIsExecuting = false;
             synchronized (mSuggestions) {
                 mSuggestions.clear();
@@ -375,7 +380,8 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
      * @param query the query to get suggestions for
      * @return the cache file containing the suggestions
      */
-    private static File downloadSuggestionsForQuery(String query, String language, Application app) {
+    @NonNull
+    private static File downloadSuggestionsForQuery(@NonNull String query, String language, @NonNull Application app) {
         File cacheFile = new File(app.getCacheDir(), query.hashCode() + CACHE_FILE_TYPE);
         if (System.currentTimeMillis() - INTERVAL_DAY < cacheFile.lastModified()) {
             return cacheFile;
@@ -419,12 +425,12 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
         return cacheFile;
     }
 
-    private static boolean isNetworkConnected(Context context) {
+    private static boolean isNetworkConnected(@NonNull Context context) {
         NetworkInfo networkInfo = getActiveNetworkInfo(context);
         return networkInfo != null && networkInfo.isConnected();
     }
 
-    private static NetworkInfo getActiveNetworkInfo(Context context) {
+    private static NetworkInfo getActiveNetworkInfo(@NonNull Context context) {
         ConnectivityManager connectivity = (ConnectivityManager) context
                 .getSystemService(Context.CONNECTIVITY_SERVICE);
         if (connectivity == null) {
@@ -433,6 +439,7 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
         return connectivity.getActiveNetworkInfo();
     }
 
+    @NonNull
     private synchronized List<HistoryItem> getFilteredList() {
         List<HistoryItem> list = new ArrayList<>(5);
         synchronized (mBookmarks) {
@@ -464,7 +471,7 @@ public class SearchAdapter extends BaseAdapter implements Filterable {
     private static class SuggestionsComparator implements Comparator<HistoryItem> {
 
         @Override
-        public int compare(HistoryItem lhs, HistoryItem rhs) {
+        public int compare(@NonNull HistoryItem lhs, @NonNull HistoryItem rhs) {
             if (lhs.getImageId() == rhs.getImageId()) return 0;
             if (lhs.getImageId() == R.drawable.ic_bookmark) return -1;
             if (rhs.getImageId() == R.drawable.ic_bookmark) return 1;

app/src/main/java/acr/browser/lightning/preference/PreferenceManager.java

@@ -2,6 +2,8 @@ package acr.browser.lightning.preference;
 
 import android.content.Context;
 import android.content.SharedPreferences;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 
 import javax.inject.Inject;
 import javax.inject.Singleton;
@@ -66,7 +68,7 @@ public class PreferenceManager {
     private static final String PREFERENCES = "settings";
 
     @Inject
-    PreferenceManager(final Context context) {
+    PreferenceManager(@NonNull final Context context) {
         mPrefs = context.getSharedPreferences(PREFERENCES, 0);
     }
 
@@ -114,6 +116,7 @@ public class PreferenceManager {
         return mPrefs.getBoolean(Name.COOKIES, true);
     }
 
+    @NonNull
     public String getDownloadDirectory() {
         return mPrefs.getString(Name.DOWNLOAD_DIRECTORY, DownloadHandler.DEFAULT_DOWNLOAD_PATH);
     }
@@ -134,6 +137,7 @@ public class PreferenceManager {
         return mPrefs.getBoolean(Name.HIDE_STATUS_BAR, false);
     }
 
+    @NonNull
     public String getHomepage() {
         return mPrefs.getString(Name.HOMEPAGE, Constants.HOMEPAGE);
     }
@@ -162,6 +166,7 @@ public class PreferenceManager {
         return mPrefs.getBoolean(Name.POPUPS, true);
     }
 
+    @NonNull
     public String getProxyHost() {
         return mPrefs.getString(Name.USE_PROXY_HOST, "localhost");
     }
@@ -182,6 +187,7 @@ public class PreferenceManager {
         return mPrefs.getBoolean(Name.RESTORE_LOST_TABS, true);
     }
 
+    @Nullable
     public String getSavedUrl() {
         return mPrefs.getString(Name.SAVE_URL, null);
     }
@@ -194,6 +200,7 @@ public class PreferenceManager {
         return mPrefs.getInt(Name.SEARCH, 1);
     }
 
+    @NonNull
     public String getSearchUrl() {
         return mPrefs.getString(Name.SEARCH_URL, Constants.GOOGLE_SEARCH);
     }
@@ -226,7 +233,8 @@ public class PreferenceManager {
         return mPrefs.getInt(Name.USER_AGENT, 1);
     }
 
-    public String getUserAgentString(String def) {
+    @Nullable
+    public String getUserAgentString(@Nullable String def) {
         return mPrefs.getString(Name.USER_AGENT_STRING, def);
     }
 
@@ -234,6 +242,7 @@ public class PreferenceManager {
         return mPrefs.getBoolean(Name.USE_WIDE_VIEWPORT, true);
     }
 
+    @NonNull
     public String getTextEncoding() {
         return mPrefs.getString(Name.TEXT_ENCODING, Constants.DEFAULT_ENCODING);
     }
@@ -250,15 +259,15 @@ public class PreferenceManager {
         return mPrefs.getBoolean(Name.IDENTIFYING_HEADERS, false);
     }
 
-    private void putBoolean(String name, boolean value) {
+    private void putBoolean(@NonNull String name, boolean value) {
         mPrefs.edit().putBoolean(name, value).apply();
     }
 
-    private void putInt(String name, int value) {
+    private void putInt(@NonNull String name, int value) {
         mPrefs.edit().putInt(name, value).apply();
     }
 
-    private void putString(String name, String value) {
+    private void putString(@NonNull String name, @Nullable String value) {
         mPrefs.edit().putString(name, value).apply();
     }
 
@@ -274,7 +283,7 @@ public class PreferenceManager {
         putBoolean(Name.SHOW_TABS_IN_DRAWER, show);
     }
 
-    public void setTextEncoding(String encoding) {
+    public void setTextEncoding(@NonNull String encoding) {
         putString(Name.TEXT_ENCODING, encoding);
     }
 
@@ -382,7 +391,7 @@ public class PreferenceManager {
         putBoolean(Name.RESTORE_LOST_TABS, enable);
     }
 
-    public void setSavedUrl(String url) {
+    public void setSavedUrl(@NonNull String url) {
         putString(Name.SAVE_URL, url);
     }
 
@@ -394,7 +403,7 @@ public class PreferenceManager {
         putInt(Name.SEARCH, choice);
     }
 
-    public void setSearchUrl(String url) {
+    public void setSearchUrl(@NonNull String url) {
         putString(Name.SEARCH_URL, url);
     }
 

app/src/main/java/acr/browser/lightning/utils/IntentUtils.java

@@ -8,6 +8,8 @@ import android.content.pm.PackageManager;
 import android.content.pm.ResolveInfo;
 import android.net.Uri;
 import android.os.Build;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.util.Log;
 import android.webkit.WebView;
 
@@ -31,7 +33,7 @@ public class IntentUtils {
         mActivity = activity;
     }
 
-    public boolean startActivityForUrl(WebView tab, String url) {
+    public boolean startActivityForUrl(@Nullable WebView tab, @NonNull String url) {
         Intent intent;
         try {
             intent = Intent.parseUri(url, Intent.URI_INTENT_SCHEME);

app/src/main/java/acr/browser/lightning/utils/ThemeUtils.java

@@ -74,12 +74,10 @@ public class ThemeUtils {
         return resultBitmap;
     }
 
-    @Nullable
+    @NonNull
     public static Drawable getThemedDrawable(@NonNull Context context, @DrawableRes int res, boolean dark) {
         int color = dark ? getIconDarkThemeColor(context) : getIconLightThemeColor(context);
         final Drawable drawable = ContextCompat.getDrawable(context, res);
-        if (drawable == null)
-            return null;
         drawable.mutate();
         drawable.setColorFilter(color, PorterDuff.Mode.SRC_IN);
         return drawable;

app/src/main/java/acr/browser/lightning/utils/UrlUtils.java

@@ -15,6 +15,8 @@
  */
 package acr.browser.lightning.utils;
 
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.util.Patterns;
 import android.webkit.URLUtil;
 
@@ -58,7 +60,8 @@ public class UrlUtils {
      * @return a stripped url like "www.google.com", or the original string if it could
      * not be stripped
      */
-    public static String stripUrl(String url) {
+    @Nullable
+    public static String stripUrl(@Nullable String url) {
         if (url == null) return null;
         Matcher m = STRIP_URL_PATTERN.matcher(url);
         if (m.matches()) {
@@ -79,7 +82,7 @@ public class UrlUtils {
      *                    URL. If false, invalid URLs will return null
      * @return Original or modified URL
      */
-    public static String smartUrlFilter(String url, boolean canBeSearch, String searchUrl) {
+    public static String smartUrlFilter(@NonNull String url, boolean canBeSearch, String searchUrl) {
         String inUrl = url.trim();
         boolean hasSpace = inUrl.indexOf(' ') != -1;
         Matcher matcher = ACCEPTED_URI_SCHEMA.matcher(inUrl);
@@ -108,7 +111,8 @@ public class UrlUtils {
     }
 
     /* package */
-    static String fixUrl(String inUrl) {
+    @NonNull
+    static String fixUrl(@NonNull String inUrl) {
         // FIXME: Converting the url to lower case
         // duplicates functionality in smartUrlFilter().
         // However, changing all current callers of fixUrl to
@@ -140,7 +144,8 @@ public class UrlUtils {
 
     // Returns the filtered URL. Cannot return null, but can return an empty string
     /* package */
-    static String filteredUrl(String inUrl) {
+    @Nullable
+    static String filteredUrl(@Nullable String inUrl) {
         if (inUrl == null) {
             return "";
         }
@@ -154,7 +159,7 @@ public class UrlUtils {
     /**
      * Returns whether the given url is the bookmarks/history page or a normal website
      */
-    public static boolean isSpecialUrl(String url) {
+    public static boolean isSpecialUrl(@Nullable String url) {
         return url != null && url.startsWith(Constants.FILE) &&
                 (url.endsWith(BookmarkPage.FILENAME) ||
                         url.endsWith(HistoryPage.FILENAME) ||