Optimize NOT NULL constraints

13 files changed, 305 insertions, 180 deletions

diff --git a/app/src/main/java/it/niedermann/owncloud/notes/edit/BaseNoteFragment.java b/app/src/main/java/it/niedermann/owncloud/notes/edit/BaseNoteFragment.java
index acfd22de..bd480a56 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/edit/BaseNoteFragment.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/edit/BaseNoteFragment.java
@@ -30,6 +30,8 @@ import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
 import com.nextcloud.android.sso.helper.SingleAccountHelper;
 import com.nextcloud.android.sso.model.SingleSignOnAccount;
 
+import java.util.Calendar;
+
 import it.niedermann.owncloud.notes.R;
 import it.niedermann.owncloud.notes.accountpicker.AccountPickerDialogFragment;
 import it.niedermann.owncloud.notes.branding.BrandedFragment;
@@ -68,7 +70,6 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
     private static final String SAVEDKEY_ORIGINAL_NOTE = "original_note";
 
     private Account localAccount;
-    private SingleSignOnAccount ssoAccount;
 
     protected NoteWithCategory note;
     // TODO do we really need this? The reference to note is currently the same
@@ -96,7 +97,7 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
     public void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         try {
-            this.ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(requireActivity().getApplicationContext());
+            SingleSignOnAccount ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(requireActivity().getApplicationContext());
             this.localAccount = db.getAccountDao().getLocalAccountByAccountName(ssoAccount.name);
 
             if (savedInstanceState == null) {
@@ -117,7 +118,7 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
                         if (content == null) {
                             throw new IllegalArgumentException(PARAM_NOTE_ID + " is not given, argument " + PARAM_NEWNOTE + " is missing and " + PARAM_CONTENT + " is missing.");
                         } else {
-                            note = new NoteWithCategory(new Note(-1, -1L, null, NoteUtil.generateNoteTitle(content), content, false, getString(R.string.category_readonly), DBStatus.VOID, -1, "", 0));
+                            note = new NoteWithCategory(new Note(-1, -1L, Calendar.getInstance(), NoteUtil.generateNoteTitle(content), content, false, getString(R.string.category_readonly), DBStatus.VOID, -1, "", 0));
                         }
                     } else {
                         final LiveData<NoteWithCategory> createLiveData = db.addNoteAndSync(localAccount, cloudNote);
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/main/MainActivity.java b/app/src/main/java/it/niedermann/owncloud/notes/main/MainActivity.java
index 8685214e..c751930f 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/main/MainActivity.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/main/MainActivity.java
@@ -80,6 +80,7 @@ import it.niedermann.owncloud.notes.shared.model.NoteClickListener;
 import it.niedermann.owncloud.notes.shared.util.NoteUtil;
 
 import static android.os.Build.VERSION.SDK_INT;
+import static android.os.Build.VERSION_CODES.LOLLIPOP;
 import static android.os.Build.VERSION_CODES.O;
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
@@ -484,7 +485,7 @@ public class MainActivity extends LockedActivity implements NoteClickListener, A
 
         binding.headerView.setBackgroundColor(mainColor);
         binding.appName.setTextColor(textColor);
-        if (SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+        if (SDK_INT >= LOLLIPOP) {
             activityBinding.progressCircular.getIndeterminateDrawable().setColorFilter(getSecondaryForegroundColorDependingOnTheme(this, mainColor), PorterDuff.Mode.SRC_IN);
         }
 
@@ -632,7 +633,7 @@ public class MainActivity extends LockedActivity implements NoteClickListener, A
     private void updateToolbars(boolean disableSearch) {
         activityBinding.homeToolbar.setVisibility(disableSearch ? VISIBLE : GONE);
         activityBinding.toolbar.setVisibility(disableSearch ? GONE : VISIBLE);
-        if (SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+        if (SDK_INT >= LOLLIPOP) {
             activityBinding.appBar.setStateListAnimator(AnimatorInflater.loadStateListAnimator(activityBinding.appBar.getContext(),
                     disableSearch ? R.animator.appbar_elevation_off : R.animator.appbar_elevation_on));
         } else {
@@ -641,7 +642,6 @@ public class MainActivity extends LockedActivity implements NoteClickListener, A
         if (disableSearch) {
             activityBinding.searchView.setQuery(null, true);
         }
-        activityBinding.searchView.setIconified(disableSearch);
     }
 
     @Override
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesDatabase.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesDatabase.java
index c0a32fd4..58e7ccb3 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesDatabase.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesDatabase.java
@@ -175,16 +175,14 @@ public abstract class NotesDatabase extends RoomDatabase {
      * Inserts a note directly into the Database.
      * No Synchronisation will be triggered! Use addNoteAndSync()!
      *
-     * @param note Note to be added. Remotely created Notes must be of type CloudNote and locally created Notes must be of Type {@link Note} (with {@link DBStatus#LOCAL_EDITED})!
+     * @param note Note to be added. Locally created Notes must be of Type {@link Note} (with {@link DBStatus#LOCAL_EDITED})!
      */
     @NonNull
     @WorkerThread
     NoteWithCategory addNote(long accountId, NoteWithCategory note) {
         Note entity = new Note();
-        if (note.getId() != null) {
-            if (note.getId() > 0) {
-                entity.setId(note.getId());
-            }
+        if (note.getId() > 0) {
+            entity.setId(note.getId());
             entity.setStatus(note.getStatus());
             entity.setAccountId(note.getAccountId());
             entity.setExcerpt(note.getExcerpt());
@@ -236,9 +234,9 @@ public abstract class NotesDatabase extends RoomDatabase {
      * This method will search in the database to find out the category id in the db.
      * If there is no such category existing, this method will create it and search again.
      *
-     * @param account    The single sign on account
-     * @param noteId     The note which will be updated
-     * @param category   The category title which should be used to find the category id.
+     * @param account  The single sign on account
+     * @param noteId   The note which will be updated
+     * @param category The category title which should be used to find the category id.
      */
     @AnyThread
     public void setCategory(@NonNull Account account, long noteId, @NonNull String category) {
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Account.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Account.java
index c3598cc7..c26dd094 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Account.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Account.java
@@ -1,5 +1,7 @@
 package it.niedermann.owncloud.notes.persistence.entity;
 
+import android.graphics.Color;
+
 import androidx.annotation.ColorInt;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -21,7 +23,6 @@ import java.util.NoSuchElementException;
 import it.niedermann.owncloud.notes.persistence.NotesClient;
 import it.niedermann.owncloud.notes.shared.model.ApiVersion;
 import it.niedermann.owncloud.notes.shared.model.Capabilities;
-import it.niedermann.owncloud.notes.shared.util.ColorUtil;
 
 @Entity(
         indices = {
@@ -34,21 +35,35 @@ import it.niedermann.owncloud.notes.shared.util.ColorUtil;
 )
 public class Account {
     @PrimaryKey(autoGenerate = true)
-    private Long id;
-    private String url;
-    private String userName;
-    private String accountName;
+    private long id;
+    @NonNull
+    @ColumnInfo(defaultValue = "")
+    private String url = "";
+    @NonNull
+    @ColumnInfo(defaultValue = "")
+    private String userName = "";
+    @NonNull
+    @ColumnInfo(defaultValue = "")
+    private String accountName = "";
+    @Nullable
     private String eTag;
+    @Nullable
     private Calendar modified;
+    @Nullable
     private String apiVersion;
     @ColorInt
     @ColumnInfo(defaultValue = "-16743735")
-    private Integer color;
+    private int color = Color.parseColor("#0082C9");
     @ColorInt
     @ColumnInfo(defaultValue = "-16777216")
-    private Integer textColor;
+    private int textColor = Color.WHITE;
+    @Nullable
     private String capabilitiesETag;
 
+    @Nullable
+    @Ignore
+    private ApiVersion preferredApiVersion;
+
     public Account() {
         // Default constructor
     }
@@ -61,136 +76,130 @@ public class Account {
     }
 
     @Nullable
-    @Ignore
-    private ApiVersion preferredApiVersion;
+    public ApiVersion getPreferredApiVersion() {
+        return preferredApiVersion;
+    }
+
+    /**
+     * @param availableApiVersions <code>["0.2", "1.0", ...]</code>
+     */
+    public void setPreferredApiVersion(@Nullable String availableApiVersions) {
+        // TODO move this logic to NotesClient?
+        try {
+            if (availableApiVersions == null) {
+                this.preferredApiVersion = null;
+                return;
+            }
+            final JSONArray versionsArray = new JSONArray(availableApiVersions);
+            final Collection<ApiVersion> supportedApiVersions = new HashSet<>(versionsArray.length());
+            for (int i = 0; i < versionsArray.length(); i++) {
+                final ApiVersion parsedApiVersion = ApiVersion.of(versionsArray.getString(i));
+                for (ApiVersion temp : NotesClient.SUPPORTED_API_VERSIONS) {
+                    if (temp.compareTo(parsedApiVersion) == 0) {
+                        supportedApiVersions.add(parsedApiVersion);
+                        break;
+                    }
+                }
+            }
+            this.preferredApiVersion = Collections.max(supportedApiVersions);
+        } catch (JSONException | NoSuchElementException e) {
+            e.printStackTrace();
+            this.preferredApiVersion = null;
+        }
+    }
+
+    public void setCapabilities(@NonNull Capabilities capabilities) {
+        capabilitiesETag = capabilities.getETag();
+        apiVersion = capabilities.getApiVersion();
+        setColor(capabilities.getColor());
+        setTextColor(capabilities.getTextColor());
+    }
 
-    public Long getId() {
+    public long getId() {
         return id;
     }
 
-    public void setId(Long id) {
+    public void setId(long id) {
         this.id = id;
     }
 
+    @NonNull
     public String getUrl() {
         return url;
     }
 
-    public void setUrl(String url) {
+    public void setUrl(@NonNull String url) {
         this.url = url;
     }
 
+    @NonNull
     public String getUserName() {
         return userName;
     }
 
-    public void setUserName(String userName) {
+    public void setUserName(@NonNull String userName) {
         this.userName = userName;
     }
 
+    @NonNull
     public String getAccountName() {
         return accountName;
     }
 
-    public void setAccountName(String accountName) {
+    public void setAccountName(@NonNull String accountName) {
         this.accountName = accountName;
     }
 
+    @Nullable
     public String getETag() {
         return eTag;
     }
 
-    public void setETag(String eTag) {
+    public void setETag(@Nullable String eTag) {
         this.eTag = eTag;
     }
 
+    @Nullable
     public Calendar getModified() {
         return modified;
     }
 
-    public void setModified(Calendar modified) {
+    public void setModified(@Nullable Calendar modified) {
         this.modified = modified;
     }
 
+    @Nullable
     public String getApiVersion() {
         return apiVersion;
     }
 
-    public void setApiVersion(String apiVersion) {
+    public void setApiVersion(@Nullable String apiVersion) {
         this.apiVersion = apiVersion;
-        setPreferredApiVersion(apiVersion);
     }
 
-    public String getCapabilitiesETag() {
-        return capabilitiesETag;
-    }
-
-    public void setCapabilitiesETag(String capabilitiesETag) {
-        this.capabilitiesETag = capabilitiesETag;
-    }
-
-    public void setCapabilities(@NonNull Capabilities capabilities) {
-        capabilitiesETag = capabilities.getETag();
-        apiVersion = capabilities.getApiVersion();
-        setColor(capabilities.getColor());
-        setTextColor(capabilities.getTextColor());
-    }
-
-    @Nullable
-    public ApiVersion getPreferredApiVersion() {
-        return preferredApiVersion;
-    }
-
-    /**
-     * @param availableApiVersions <code>["0.2", "1.0", ...]</code>
-     */
-    public void setPreferredApiVersion(@Nullable String availableApiVersions) {
-        // TODO move this logic to NotesClient?
-        try {
-            if (availableApiVersions == null) {
-                this.preferredApiVersion = null;
-                return;
-            }
-            JSONArray versionsArray = new JSONArray(availableApiVersions);
-            Collection<ApiVersion> supportedApiVersions = new HashSet<>(versionsArray.length());
-            for (int i = 0; i < versionsArray.length(); i++) {
-                ApiVersion parsedApiVersion = ApiVersion.of(versionsArray.getString(i));
-                for (ApiVersion temp : NotesClient.SUPPORTED_API_VERSIONS) {
-                    if (temp.compareTo(parsedApiVersion) == 0) {
-                        supportedApiVersions.add(parsedApiVersion);
-                        break;
-                    }
-                }
-            }
-            this.preferredApiVersion = Collections.max(supportedApiVersions);
-        } catch (JSONException | NoSuchElementException e) {
-            e.printStackTrace();
-            this.preferredApiVersion = null;
-        }
-    }
-
-    public Integer getColor() {
+    public int getColor() {
         return color;
     }
 
-    public void setColor(Integer color) {
+    public void setColor(int color) {
         this.color = color;
     }
 
-    public Integer getTextColor() {
+    public int getTextColor() {
         return textColor;
     }
 
-    public void setTextColor(Integer textColor) {
+    public void setTextColor(int textColor) {
         this.textColor = textColor;
     }
 
-    @NonNull
-    @Override
-    public String toString() {
-        return "Account{" +
-                "accountName='" + accountName + '\'' +
-                '}';
+    @Nullable
+    public String getCapabilitiesETag() {
+        return capabilitiesETag;
+    }
+
+    public void setCapabilitiesETag(@Nullable String capabilitiesETag) {
+        this.capabilitiesETag = capabilitiesETag;
     }
 
     @Override
@@ -200,20 +209,17 @@ public class Account {
 
         Account account = (Account) o;
 
-        if (id != null ? !id.equals(account.id) : account.id != null) return false;
-        if (url != null ? !url.equals(account.url) : account.url != null) return false;
-        if (userName != null ? !userName.equals(account.userName) : account.userName != null)
-            return false;
-        if (accountName != null ? !accountName.equals(account.accountName) : account.accountName != null)
-            return false;
+        if (id != account.id) return false;
+        if (color != account.color) return false;
+        if (textColor != account.textColor) return false;
+        if (!url.equals(account.url)) return false;
+        if (!userName.equals(account.userName)) return false;
+        if (!accountName.equals(account.accountName)) return false;
         if (eTag != null ? !eTag.equals(account.eTag) : account.eTag != null) return false;
         if (modified != null ? !modified.equals(account.modified) : account.modified != null)
             return false;
         if (apiVersion != null ? !apiVersion.equals(account.apiVersion) : account.apiVersion != null)
             return false;
-        if (color != null ? !color.equals(account.color) : account.color != null) return false;
-        if (textColor != null ? !textColor.equals(account.textColor) : account.textColor != null)
-            return false;
         if (capabilitiesETag != null ? !capabilitiesETag.equals(account.capabilitiesETag) : account.capabilitiesETag != null)
             return false;
         return preferredApiVersion != null ? preferredApiVersion.equals(account.preferredApiVersion) : account.preferredApiVersion == null;
@@ -221,17 +227,34 @@ public class Account {
 
     @Override
     public int hashCode() {
-        int result = id != null ? id.hashCode() : 0;
-        result = 31 * result + (url != null ? url.hashCode() : 0);
-        result = 31 * result + (userName != null ? userName.hashCode() : 0);
-        result = 31 * result + (accountName != null ? accountName.hashCode() : 0);
+        int result = (int) (id ^ (id >>> 32));
+        result = 31 * result + url.hashCode();
+        result = 31 * result + userName.hashCode();
+        result = 31 * result + accountName.hashCode();
         result = 31 * result + (eTag != null ? eTag.hashCode() : 0);
         result = 31 * result + (modified != null ? modified.hashCode() : 0);
         result = 31 * result + (apiVersion != null ? apiVersion.hashCode() : 0);
-        result = 31 * result + (color != null ? color.hashCode() : 0);
-        result = 31 * result + (textColor != null ? textColor.hashCode() : 0);
+        result = 31 * result + color;
+        result = 31 * result + textColor;
         result = 31 * result + (capabilitiesETag != null ? capabilitiesETag.hashCode() : 0);
         result = 31 * result + (preferredApiVersion != null ? preferredApiVersion.hashCode() : 0);
         return result;
     }
+
+    @Override
+    public String toString() {
+        return "Account{" +
+                "id=" + id +
+                ", url='" + url + '\'' +
+                ", userName='" + userName + '\'' +
+                ", accountName='" + accountName + '\'' +
+                ", eTag='" + eTag + '\'' +
+                ", modified=" + modified +
+                ", apiVersion='" + apiVersion + '\'' +
+                ", color=" + color +
+                ", textColor=" + textColor +
+                ", capabilitiesETag='" + capabilitiesETag + '\'' +
+                ", preferredApiVersion=" + preferredApiVersion +
+                '}';
+    }
 }
\ No newline at end of file
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Category.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Category.java
index 0205e07e..b87b8ea3 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Category.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Category.java
@@ -1,5 +1,8 @@
 package it.niedermann.owncloud.notes.persistence.entity;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.room.ColumnInfo;
 import androidx.room.Entity;
 import androidx.room.ForeignKey;
 import androidx.room.Index;
@@ -30,7 +33,10 @@ public class Category implements Serializable {
     @PrimaryKey(autoGenerate = true)
     private long id;
     private long accountId;
-    private String title;
+    @NonNull
+    @ColumnInfo(defaultValue = "")
+    private String title = "";
+    @Nullable
     private CategorySortingMethod sortingMethod;
 
     public long getId() {
@@ -49,19 +55,43 @@ public class Category implements Serializable {
         this.accountId = accountId;
     }
 
+    @NonNull
     public String getTitle() {
         return title;
     }
 
-    public void setTitle(String title) {
+    public void setTitle(@NonNull String title) {
         this.title = title;
     }
 
+    @Nullable
     public CategorySortingMethod getSortingMethod() {
         return sortingMethod;
     }
 
-    public void setSortingMethod(CategorySortingMethod sortingMethod) {
+    public void setSortingMethod(@Nullable CategorySortingMethod sortingMethod) {
         this.sortingMethod = sortingMethod;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof Category)) return false;
+
+        Category category = (Category) o;
+
+        if (id != category.id) return false;
+        if (accountId != category.accountId) return false;
+        if (!title.equals(category.title)) return false;
+        return sortingMethod == category.sortingMethod;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = (int) (id ^ (id >>> 32));
+        result = 31 * result + (int) (accountId ^ (accountId >>> 32));
+        result = 31 * result + title.hashCode();
+        result = 31 * result + (sortingMethod != null ? sortingMethod.hashCode() : 0);
+        return result;
+    }
 }
\ No newline at end of file
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Note.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Note.java
index b336b4a9..0dada540 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Note.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/Note.java
@@ -1,7 +1,7 @@
 package it.niedermann.owncloud.notes.persistence.entity;
 
 import androidx.annotation.NonNull;
-import androidx.annotation.RestrictTo;
+import androidx.annotation.Nullable;
 import androidx.room.ColumnInfo;
 import androidx.room.Entity;
 import androidx.room.ForeignKey;
@@ -13,7 +13,6 @@ import java.io.Serializable;
 import java.util.Calendar;
 
 import it.niedermann.owncloud.notes.shared.model.DBStatus;
-import it.niedermann.owncloud.notes.shared.model.Item;
 
 @Entity(
         foreignKeys = {
@@ -40,30 +39,38 @@ import it.niedermann.owncloud.notes.shared.model.Item;
 )
 public class Note implements Serializable {
     @PrimaryKey(autoGenerate = true)
-    private Long id;
+    private long id;
+    @Nullable
     private Long remoteId;
-    private Long accountId;
+    private long accountId;
+    @NonNull
     private DBStatus status = DBStatus.VOID;
-    private String title;
-    @ColumnInfo(defaultValue = "0")
+    @NonNull
+    @ColumnInfo(defaultValue = "")
+    private String title = "";
+    @Nullable
     private Calendar modified;
-    private String content;
+    @NonNull
+    @ColumnInfo(defaultValue = "")
+    private String content = "";
     @ColumnInfo(defaultValue = "0")
-    private Boolean favorite;
+    private boolean favorite = false;
+    @Nullable
     private Long categoryId;
+    @Nullable
     private String eTag;
     @NonNull
     @ColumnInfo(defaultValue = "")
     private String excerpt = "";
     @ColumnInfo(defaultValue = "0")
-    private Integer scrollY = 0;
+    private int scrollY = 0;
 
     public Note() {
         super();
     }
 
     @Ignore
-    public Note(Long remoteId, Calendar modified, String title, String content, Boolean favorite, String eTag) {
+    public Note(@Nullable Long remoteId, @Nullable Calendar modified, @NonNull String title, @NonNull String content, boolean favorite, @Nullable String eTag) {
         this.remoteId = remoteId;
         this.title = title;
         this.modified = modified;
@@ -73,7 +80,7 @@ public class Note implements Serializable {
     }
 
     @Ignore
-    public Note(long id, Long remoteId, Calendar modified, String title, String content, boolean favorite, String etag, DBStatus status, long accountId, @NonNull String excerpt, Integer scrollY) {
+    public Note(long id, @Nullable Long remoteId, @Nullable Calendar modified, @NonNull String title, @NonNull String content, boolean favorite, @Nullable String etag, @NonNull DBStatus status, long accountId, @NonNull String excerpt, int scrollY) {
         this(remoteId, modified, title, content, favorite, etag);
         this.id = id;
         this.status = status;
@@ -82,84 +89,90 @@ public class Note implements Serializable {
         this.scrollY = scrollY;
     }
 
-    public Long getId() {
+    public long getId() {
         return id;
     }
 
-    public void setId(Long id) {
+    public void setId(long id) {
         this.id = id;
     }
 
+    @Nullable
     public Long getRemoteId() {
         return remoteId;
     }
 
-    public void setRemoteId(Long remoteId) {
+    public void setRemoteId(@Nullable Long remoteId) {
         this.remoteId = remoteId;
     }
 
-    public Long getAccountId() {
+    public long getAccountId() {
         return accountId;
     }
 
-    public void setAccountId(Long accountId) {
+    public void setAccountId(long accountId) {
         this.accountId = accountId;
     }
 
-    @RestrictTo(RestrictTo.Scope.TESTS)
-    public Long getCategoryId() {
-        return categoryId;
-    }
-
-    public void setCategoryId(Long categoryId) {
-        this.categoryId = categoryId;
-    }
-
+    @NonNull
     public DBStatus getStatus() {
         return status;
     }
 
-    public void setStatus(DBStatus status) {
+    public void setStatus(@NonNull DBStatus status) {
         this.status = status;
     }
 
+    @NonNull
     public String getTitle() {
         return title;
     }
 
-    public void setTitle(String title) {
+    public void setTitle(@NonNull String title) {
         this.title = title;
     }
 
+    @Nullable
     public Calendar getModified() {
         return modified;
     }
 
-    public void setModified(Calendar modified) {
+    public void setModified(@Nullable Calendar modified) {
         this.modified = modified;
     }
 
+    @NonNull
     public String getContent() {
         return content;
     }
 
-    public void setContent(String content) {
+    public void setContent(@NonNull String content) {
         this.content = content;
     }
 
-    public Boolean getFavorite() {
+    public boolean getFavorite() {
         return favorite;
     }
 
-    public void setFavorite(Boolean favorite) {
+    public void setFavorite(boolean favorite) {
         this.favorite = favorite;
     }
 
+    @Nullable
+    public Long getCategoryId() {
+        return categoryId;
+    }
+
+    public void setCategoryId(@Nullable Long categoryId) {
+        this.categoryId = categoryId;
+    }
+
+    @Nullable
     public String getETag() {
         return eTag;
     }
 
-    public void setETag(String eTag) {
+    public void setETag(@Nullable String eTag) {
         this.eTag = eTag;
     }
 
@@ -172,11 +185,11 @@ public class Note implements Serializable {
         this.excerpt = excerpt;
     }
 
-    public Integer getScrollY() {
+    public int getScrollY() {
         return scrollY;
     }
 
-    public void setScrollY(Integer scrollY) {
+    public void setScrollY(int scrollY) {
         this.scrollY = scrollY;
     }
 
@@ -187,39 +200,37 @@ public class Note implements Serializable {
 
         Note note = (Note) o;
 
-        if (id != null ? !id.equals(note.id) : note.id != null) return false;
+        if (id != note.id) return false;
+        if (accountId != note.accountId) return false;
+        if (favorite != note.favorite) return false;
+        if (scrollY != note.scrollY) return false;
         if (remoteId != null ? !remoteId.equals(note.remoteId) : note.remoteId != null)
             return false;
-        if (accountId != null ? !accountId.equals(note.accountId) : note.accountId != null)
-            return false;
         if (status != note.status) return false;
-        if (title != null ? !title.equals(note.title) : note.title != null) return false;
+        if (!title.equals(note.title)) return false;
         if (modified != null ? !modified.equals(note.modified) : note.modified != null)
             return false;
-        if (content != null ? !content.equals(note.content) : note.content != null) return false;
-        if (favorite != null ? !favorite.equals(note.favorite) : note.favorite != null)
-            return false;
+        if (!content.equals(note.content)) return false;
         if (categoryId != null ? !categoryId.equals(note.categoryId) : note.categoryId != null)
             return false;
         if (eTag != null ? !eTag.equals(note.eTag) : note.eTag != null) return false;
-        if (!excerpt.equals(note.excerpt)) return false;
-        return scrollY != null ? scrollY.equals(note.scrollY) : note.scrollY == null;
+        return excerpt.equals(note.excerpt);
     }
 
     @Override
     public int hashCode() {
-        int result = id != null ? id.hashCode() : 0;
+        int result = (int) (id ^ (id >>> 32));
         result = 31 * result + (remoteId != null ? remoteId.hashCode() : 0);
-        result = 31 * result + (accountId != null ? accountId.hashCode() : 0);
-        result = 31 * result + (status != null ? status.hashCode() : 0);
-        result = 31 * result + (title != null ? title.hashCode() : 0);
+        result = 31 * result + (int) (accountId ^ (accountId >>> 32));
+        result = 31 * result + status.hashCode();
+        result = 31 * result + title.hashCode();
         result = 31 * result + (modified != null ? modified.hashCode() : 0);
-        result = 31 * result + (content != null ? content.hashCode() : 0);
-        result = 31 * result + (favorite != null ? favorite.hashCode() : 0);
+        result = 31 * result + content.hashCode();
+        result = 31 * result + (favorite ? 1 : 0);
         result = 31 * result + (categoryId != null ? categoryId.hashCode() : 0);
         result = 31 * result + (eTag != null ? eTag.hashCode() : 0);
         result = 31 * result + excerpt.hashCode();
-        result = 31 * result + (scrollY != null ? scrollY.hashCode() : 0);
+        result = 31 * result + scrollY;
         return result;
     }
 
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/NoteWithCategory.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/NoteWithCategory.java
index ee3a212d..187839bc 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/NoteWithCategory.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/NoteWithCategory.java
@@ -14,7 +14,8 @@ import it.niedermann.owncloud.notes.shared.model.Item;
 public class NoteWithCategory implements Serializable, Item {
     @Embedded
     private Note note;
-    private String category;
+    @NonNull
+    private String category = "";
 
     public NoteWithCategory() {
         // Default constructor
@@ -22,55 +23,62 @@ public class NoteWithCategory implements Serializable, Item {
 
     @Ignore
     public NoteWithCategory(@NonNull Note note) {
-        this(note, null);
+        this.note = note;
     }
 
     @Ignore
-    public NoteWithCategory(@NonNull Note note, @Nullable String category) {
+    public NoteWithCategory(@NonNull Note note, @NonNull String category) {
         this.note = note;
         this.category = category;
     }
 
+    @NonNull
     public Note getNote() {
         return note;
     }
 
-    public void setNote(Note note) {
+    public void setNote(@NonNull Note note) {
         this.note = note;
     }
 
-    public Long getId() {
+    public long getId() {
         return note.getId();
     }
 
+    @Nullable
     public Long getRemoteId() {
         return note.getRemoteId();
     }
 
-    public Long getAccountId() {
+    public long getAccountId() {
         return note.getAccountId();
     }
 
+    @NonNull
     public DBStatus getStatus() {
         return note.getStatus();
     }
 
+    @NonNull
     public String getTitle() {
         return note.getTitle();
     }
 
+    @Nullable
     public Calendar getModified() {
         return note.getModified();
     }
 
+    @NonNull
     public String getContent() {
         return note.getContent();
     }
 
-    public Boolean getFavorite() {
+    public boolean getFavorite() {
         return note.getFavorite();
     }
 
+    @Nullable
     public String getETag() {
         return note.getETag();
     }
@@ -80,15 +88,16 @@ public class NoteWithCategory implements Serializable, Item {
         return note.getExcerpt();
     }
 
-    public Integer getScrollY() {
+    public int getScrollY() {
         return note.getScrollY();
     }
 
+    @NonNull
     public String getCategory() {
         return category;
     }
 
-    public void setCategory(String category) {
+    public void setCategory(@NonNull String category) {
         this.category = category;
     }
 
@@ -100,13 +109,13 @@ public class NoteWithCategory implements Serializable, Item {
         NoteWithCategory that = (NoteWithCategory) o;
 
         if (note != null ? !note.equals(that.note) : that.note != null) return false;
-        return category != null ? category.equals(that.category) : that.category == null;
+        return category.equals(that.category);
     }
 
     @Override
     public int hashCode() {
         int result = note != null ? note.hashCode() : 0;
-        result = 31 * result + (category != null ? category.hashCode() : 0);
+        result = 31 * result + category.hashCode();
         return result;
     }
 
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/NotesListWidgetData.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/NotesListWidgetData.java
index 8ec12007..a7d95172 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/NotesListWidgetData.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/NotesListWidgetData.java
@@ -3,7 +3,6 @@ package it.niedermann.owncloud.notes.persistence.entity;
 import androidx.annotation.IntRange;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.room.ColumnInfo;
 import androidx.room.Entity;
 import androidx.room.ForeignKey;
 import androidx.room.Ignore;
@@ -42,6 +41,7 @@ public class NotesListWidgetData extends AbstractWidgetData {
 
     @IntRange(from = 0, to = 2)
     private int mode;
+    @Nullable
     private Long categoryId;
 
     @Nullable
@@ -53,14 +53,33 @@ public class NotesListWidgetData extends AbstractWidgetData {
         this.categoryId = categoryId;
     }
 
-    public void setMode(int mode) {
+    public void setMode(@IntRange(from = 0, to = 2) int mode) {
         this.mode = mode;
     }
 
+    @IntRange(from = 0, to = 2)
     public int getMode() {
         return mode;
     }
 
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof NotesListWidgetData)) return false;
+
+        NotesListWidgetData that = (NotesListWidgetData) o;
+
+        if (mode != that.mode) return false;
+        return categoryId != null ? categoryId.equals(that.categoryId) : that.categoryId == null;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = mode;
+        result = 31 * result + (categoryId != null ? categoryId.hashCode() : 0);
+        return result;
+    }
+
     @NonNull
     @Override
     public String toString() {
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/SingleNoteWidgetData.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/SingleNoteWidgetData.java
index d7fad48c..3e726242 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/SingleNoteWidgetData.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/entity/SingleNoteWidgetData.java
@@ -1,6 +1,5 @@
 package it.niedermann.owncloud.notes.persistence.entity;
 
-import androidx.room.ColumnInfo;
 import androidx.room.Entity;
 import androidx.room.ForeignKey;
 import androidx.room.Ignore;
@@ -32,7 +31,7 @@ public class SingleNoteWidgetData extends AbstractWidgetData {
     private long noteId;
 
     public SingleNoteWidgetData() {
-
+        // Default constructor
     }
 
     @Ignore
@@ -48,4 +47,19 @@ public class SingleNoteWidgetData extends AbstractWidgetData {
     public void setNoteId(long noteId) {
         this.noteId = noteId;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof SingleNoteWidgetData)) return false;
+
+        SingleNoteWidgetData that = (SingleNoteWidgetData) o;
+
+        return noteId == that.noteId;
+    }
+
+    @Override
+    public int hashCode() {
+        return (int) (noteId ^ (noteId >>> 32));
+    }
 }
\ No newline at end of file
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_19_20.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_19_20.java
index bff6f181..9f749d86 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_19_20.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_19_20.java
@@ -37,9 +37,9 @@ public class Migration_19_20 extends Migration {
         db.execSQL("DROP INDEX NOTES_CATEGORY_idx");
         db.execSQL("DROP INDEX NOTES_MODIFIED_idx");
 
-        db.execSQL("CREATE TABLE `Account` (`id` INTEGER PRIMARY KEY AUTOINCREMENT, `url` TEXT, `userName` TEXT, `accountName` TEXT, `eTag` TEXT, `modified` INTEGER, `apiVersion` TEXT, `color` INTEGER DEFAULT -16743735, `textColor` INTEGER DEFAULT -16777216, `capabilitiesETag` TEXT)");
-        db.execSQL("CREATE TABLE `Category` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `accountId` INTEGER NOT NULL, `title` TEXT, `sortingMethod` INTEGER, FOREIGN KEY(`accountId`) REFERENCES `Account`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE )");
-        db.execSQL("CREATE TABLE `Note` (`id` INTEGER PRIMARY KEY AUTOINCREMENT, `remoteId` INTEGER, `accountId` INTEGER, `status` TEXT, `title` TEXT, `modified` INTEGER DEFAULT 0, `content` TEXT, `favorite` INTEGER DEFAULT 0, `categoryId` INTEGER, `eTag` TEXT, `excerpt` TEXT NOT NULL DEFAULT '', `scrollY` INTEGER DEFAULT 0, FOREIGN KEY(`accountId`) REFERENCES `Account`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`categoryId`) REFERENCES `Category`(`id`) ON UPDATE NO ACTION ON DELETE NO ACTION )");
+        db.execSQL("CREATE TABLE `Account` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `url` TEXT NOT NULL DEFAULT '', `userName` TEXT NOT NULL DEFAULT '', `accountName` TEXT NOT NULL DEFAULT '', `eTag` TEXT, `modified` INTEGER, `apiVersion` TEXT, `color` INTEGER NOT NULL DEFAULT -16743735, `textColor` INTEGER NOT NULL DEFAULT -16777216, `capabilitiesETag` TEXT)");
+        db.execSQL("CREATE TABLE `Category` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `accountId` INTEGER NOT NULL, `title` TEXT NOT NULL DEFAULT '', `sortingMethod` INTEGER, FOREIGN KEY(`accountId`) REFERENCES `Account`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE )");
+        db.execSQL("CREATE TABLE `Note` (`id` INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, `remoteId` INTEGER, `accountId` INTEGER NOT NULL, `status` TEXT NOT NULL, `title` TEXT NOT NULL DEFAULT '', `modified` INTEGER, `content` TEXT NOT NULL DEFAULT '', `favorite` INTEGER NOT NULL DEFAULT 0, `categoryId` INTEGER, `eTag` TEXT, `excerpt` TEXT NOT NULL DEFAULT '', `scrollY` INTEGER NOT NULL DEFAULT 0, FOREIGN KEY(`accountId`) REFERENCES `Account`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`categoryId`) REFERENCES `Category`(`id`) ON UPDATE NO ACTION ON DELETE NO ACTION )");
         db.execSQL("CREATE TABLE `NotesListWidgetData` (`mode` INTEGER NOT NULL, `categoryId` INTEGER, `id` INTEGER NOT NULL, `accountId` INTEGER NOT NULL, `themeMode` INTEGER NOT NULL, PRIMARY KEY(`id`), FOREIGN KEY(`accountId`) REFERENCES `Account`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`categoryId`) REFERENCES `Category`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE )");
         db.execSQL("CREATE TABLE `SingleNoteWidgetData` (`noteId` INTEGER NOT NULL, `id` INTEGER NOT NULL, `accountId` INTEGER NOT NULL, `themeMode` INTEGER NOT NULL, PRIMARY KEY(`id`), FOREIGN KEY(`accountId`) REFERENCES `Account`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE , FOREIGN KEY(`noteId`) REFERENCES `Note`(`id`) ON UPDATE NO ACTION ON DELETE CASCADE )");
 
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/shared/model/CategorySortingMethod.java b/app/src/main/java/it/niedermann/owncloud/notes/shared/model/CategorySortingMethod.java
index 35ab8b66..6191bb9e 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/shared/model/CategorySortingMethod.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/shared/model/CategorySortingMethod.java
@@ -4,7 +4,7 @@ public enum CategorySortingMethod {
     SORT_MODIFIED_DESC("MODIFIED DESC"),
     SORT_LEXICOGRAPHICAL_ASC("TITLE COLLATE NOCASE ASC");
 
-    private String sorder;  // sorting method OrderBy for SQL
+    private final String sorder;  // sorting method OrderBy for SQL
 
     /***
      * Constructor
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/shared/model/ServerResponse.java b/app/src/main/java/it/niedermann/owncloud/notes/shared/model/ServerResponse.java
index 2e0ca30d..fbf94237 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/shared/model/ServerResponse.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/shared/model/ServerResponse.java
@@ -76,7 +76,7 @@ public class ServerResponse {
         String content = "";
         Calendar modified = null;
         boolean favorite = false;
-        String category = null;
+        String category = "";
         String etag = null;
         if (!json.isNull(NotesClient.JSON_ID)) {
             id = json.getLong(NotesClient.JSON_ID);
@@ -88,7 +88,7 @@ public class ServerResponse {
             content = json.getString(NotesClient.JSON_CONTENT);
         }
         if (!json.isNull(NotesClient.JSON_MODIFIED)) {
-            modified = GregorianCalendar.getInstance();
+            modified = Calendar.getInstance();
             modified.setTimeInMillis(json.getLong(NotesClient.JSON_MODIFIED) * 1000);
         }
         if (!json.isNull(NotesClient.JSON_FAVORITE)) {
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/widget/AbstractWidgetData.java b/app/src/main/java/it/niedermann/owncloud/notes/widget/AbstractWidgetData.java
index 9873d100..f561f638 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/widget/AbstractWidgetData.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/widget/AbstractWidgetData.java
@@ -12,7 +12,7 @@ public abstract class AbstractWidgetData {
     private int themeMode;
 
     protected AbstractWidgetData() {
-
+        // Default constructor
     }
 
     protected AbstractWidgetData(int id, long accountId, @IntRange(from = 0, to = 2) int themeMode) {
@@ -45,4 +45,24 @@ public abstract class AbstractWidgetData {
     public void setThemeMode(@IntRange(from = 0, to = 2) int themeMode) {
         this.themeMode = themeMode;
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof AbstractWidgetData)) return false;
+
+        AbstractWidgetData that = (AbstractWidgetData) o;
+
+        if (id != that.id) return false;
+        if (accountId != that.accountId) return false;
+        return themeMode == that.themeMode;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = id;
+        result = 31 * result + (int) (accountId ^ (accountId >>> 32));
+        result = 31 * result + themeMode;
+        return result;
+    }
 }