Fix filter fragment crash

app/src/main/java/com/hippo/ehviewer/EhDB.java

@@ -595,9 +595,20 @@ public class EhDB {
         return sDaoSession.getFilterDao().queryBuilder().list();
     }
 
-    public static synchronized void addFilter(Filter filter) {
-        filter.setId(null);
-        filter.setId(sDaoSession.getFilterDao().insert(filter));
+    public static synchronized boolean addFilter(Filter filter) {
+        Filter existFilter;
+        try {
+            existFilter = sDaoSession.getFilterDao().queryBuilder().where(FilterDao.Properties.Text.eq(filter.text), FilterDao.Properties.Mode.eq(filter.mode)).unique();
+        } catch (Exception e) {
+            existFilter = null;
+        }
+        if (existFilter == null) {
+            filter.setId(null);
+            filter.setId(sDaoSession.getFilterDao().insert(filter));
+            return true;
+        } else {
+            return false;
+        }
     }
 
     public static synchronized void deleteFilter(Filter filter) {

app/src/main/java/com/hippo/ehviewer/client/EhFilter.java

@@ -88,10 +88,10 @@ public final class EhFilter {
         return mTagNamespaceFilterList;
     }
 
-    public synchronized void addFilter(Filter filter) {
+    public synchronized boolean addFilter(Filter filter) {
         // enable filter by default before it is added to database
         filter.enable = true;
-        EhDB.addFilter(filter);
+        if (!EhDB.addFilter(filter)) return false;
 
         switch (filter.mode) {
             case MODE_TITLE:
@@ -113,6 +113,7 @@ public final class EhFilter {
                 Log.d(TAG, "Unknown mode: " + filter.mode);
                 break;
         }
+        return true;
     }
 
     public synchronized void triggerFilter(Filter filter) {

app/src/main/java/com/hippo/ehviewer/ui/fragment/FilterFragment.java

@@ -219,7 +219,12 @@ public class FilterFragment extends BaseFragment {
             Filter filter = new Filter();
             filter.mode = mode;
             filter.text = text;
-            mFilterList.add(filter);
+            if (!mFilterList.add(filter)) {
+                mInputLayout.setError(getString(R.string.label_text_exist));
+                return;
+            } else {
+                mInputLayout.setError(null);
+            }
 
             if (null != mAdapter) {
                 mAdapter.notifyDataSetChanged();
@@ -314,7 +319,12 @@ public class FilterFragment extends BaseFragment {
 
         @Override
         public long getItemId(int position) {
-            return null != mFilterList ? mFilterList.get(position).text.hashCode() : 0;
+            if (mFilterList == null) {
+                return 0;
+            } else {
+                Filter filter = mFilterList.get(position);
+                return filter.text.hashCode() >> filter.mode;
+            }
         }
     }
 
@@ -436,8 +446,8 @@ public class FilterFragment extends BaseFragment {
             throw new IndexOutOfBoundsException();
         }
 
-        public void add(Filter filter) {
-            mEhFilter.addFilter(filter);
+        public boolean add(Filter filter) {
+            return mEhFilter.addFilter(filter);
         }
 
         public void delete(Filter filter) {