Persist library dialog state between invocations

app/src/main/java/com/kabouzeid/gramophone/model/CategoryInfo.java

@@ -1,8 +1,11 @@
 package com.kabouzeid.gramophone.model;
 
+import android.os.Parcel;
+import android.os.Parcelable;
+
 import com.kabouzeid.gramophone.R;
 
-public class CategoryInfo {
+public class CategoryInfo implements Parcelable {
     public Category category;
     public boolean visible;
 
@@ -11,6 +14,32 @@ public class CategoryInfo {
         this.visible = visible;
     }
 
+    public CategoryInfo(Parcel source) {
+        category = (Category) source.readSerializable();
+        visible = source.readInt() == 1 ? true : false;
+    }
+
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    public void writeToParcel(Parcel dest, int flags) {
+        dest.writeSerializable(category);
+        dest.writeInt(visible ? 1 : 0);
+    }
+
+    public static final Parcelable.Creator<CategoryInfo> CREATOR = new Parcelable.Creator<CategoryInfo>() {
+        public CategoryInfo createFromParcel(Parcel source) {
+            return new CategoryInfo(source);
+        }
+
+        public CategoryInfo[] newArray(int size) {
+            return new CategoryInfo[size];
+        }
+    };
+
     public enum Category {
         SONGS(R.string.songs),
         ALBUMS(R.string.albums),

app/src/main/java/com/kabouzeid/gramophone/preferences/LibraryPreferenceDialog.java

@@ -22,12 +22,16 @@ public class LibraryPreferenceDialog extends DialogFragment {
         return new LibraryPreferenceDialog();
     }
 
+    private CategoryInfoAdapter adapter;
+
     @NonNull
     @Override
     public Dialog onCreateDialog(Bundle savedInstanceState) {
         View view = getActivity().getLayoutInflater().inflate(R.layout.preference_dialog_library_categories, null);
 
-        CategoryInfoAdapter adapter = new CategoryInfoAdapter(PreferenceUtil.getInstance(getContext()).getLibraryCategoryInfos());
+        adapter = new CategoryInfoAdapter(savedInstanceState != null ?
+                savedInstanceState.getParcelableArrayList(PreferenceUtil.LIBRARY_CATEGORIES) :
+                PreferenceUtil.getInstance(getContext()).getLibraryCategoryInfos());
 
         RecyclerView recyclerView = view.findViewById(R.id.recycler_view);
         recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
@@ -51,6 +55,12 @@ public class LibraryPreferenceDialog extends DialogFragment {
                 .build();
     }
 
+    @Override
+    public void onSaveInstanceState(Bundle outState) {
+        super.onSaveInstanceState(outState);
+        outState.putParcelableArrayList(PreferenceUtil.LIBRARY_CATEGORIES, adapter.getCategoryInfos());
+    }
+
     private void updateCategories(ArrayList<CategoryInfo> categories) {
         if (getSelected(categories) == 0) return;