Custom filtering in Android using ArrayAdapter

Question

I'm trying to filter my ListView which is populated with this ArrayAdapter:

package me.alxandr.android.mymir.adapters;  import java.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.HashMap; import java.util.Iterator; import java.util.Set;  import me.alxandr.android.mymir.R; import me.alxandr.android.mymir.model.Manga; import android.content.Context; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ArrayAdapter; import android.widget.Filter; import android.widget.SectionIndexer; import android.widget.TextView;  public class MangaListAdapter extends ArrayAdapter<Manga> implements SectionIndexer {     public ArrayList<Manga> items;     public ArrayList<Manga> filtered;     private Context context;     private HashMap<String, Integer> alphaIndexer;     private String[] sections = new String[0];     private Filter filter;     private boolean enableSections;      public MangaListAdapter(Context context, int textViewResourceId, ArrayList<Manga> items, boolean enableSections)     {         super(context, textViewResourceId, items);         this.filtered = items;         this.items = filtered;         this.context = context;         this.filter = new MangaNameFilter();         this.enableSections = enableSections;          if(enableSections)         {             alphaIndexer = new HashMap<String, Integer>();             for(int i = items.size() - 1; i >= 0; i--)             {                 Manga element = items.get(i);                 String firstChar = element.getName().substring(0, 1).toUpperCase();                 if(firstChar.charAt(0) > 'Z' || firstChar.charAt(0) < 'A')                     firstChar = "@";                  alphaIndexer.put(firstChar, i);             }              Set<String> keys = alphaIndexer.keySet();             Iterator<String> it = keys.iterator();             ArrayList<String> keyList = new ArrayList<String>();             while(it.hasNext())                 keyList.add(it.next());              Collections.sort(keyList);             sections = new String[keyList.size()];             keyList.toArray(sections);         }     }      @Override     public View getView(int position, View convertView, ViewGroup parent)     {         View v = convertView;         if(v == null)         {             LayoutInflater vi = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);             v = vi.inflate(R.layout.mangarow, null);         }          Manga o = items.get(position);         if(o != null)         {             TextView tt = (TextView) v.findViewById(R.id.MangaRow_MangaName);             TextView bt = (TextView) v.findViewById(R.id.MangaRow_MangaExtra);             if(tt != null)                 tt.setText(o.getName());             if(bt != null)                 bt.setText(o.getLastUpdated() + " - " + o.getLatestChapter());              if(enableSections && getSectionForPosition(position) != getSectionForPosition(position + 1))             {                 TextView h = (TextView) v.findViewById(R.id.MangaRow_Header);                 h.setText(sections[getSectionForPosition(position)]);                 h.setVisibility(View.VISIBLE);             }             else             {                 TextView h = (TextView) v.findViewById(R.id.MangaRow_Header);                 h.setVisibility(View.GONE);             }         }          return v;     }      @Override     public void notifyDataSetInvalidated()     {         if(enableSections)         {             for (int i = items.size() - 1; i >= 0; i--)             {                 Manga element = items.get(i);                 String firstChar = element.getName().substring(0, 1).toUpperCase();                 if(firstChar.charAt(0) > 'Z' || firstChar.charAt(0) < 'A')                     firstChar = "@";                 alphaIndexer.put(firstChar, i);             }              Set<String> keys = alphaIndexer.keySet();             Iterator<String> it = keys.iterator();             ArrayList<String> keyList = new ArrayList<String>();             while (it.hasNext())             {                 keyList.add(it.next());             }              Collections.sort(keyList);             sections = new String[keyList.size()];             keyList.toArray(sections);              super.notifyDataSetInvalidated();         }     }      public int getPositionForSection(int section)     {         if(!enableSections) return 0;         String letter = sections[section];          return alphaIndexer.get(letter);     }      public int getSectionForPosition(int position)     {         if(!enableSections) return 0;         int prevIndex = 0;         for(int i = 0; i < sections.length; i++)         {             if(getPositionForSection(i) > position && prevIndex <= position)             {                 prevIndex = i;                 break;             }             prevIndex = i;         }         return prevIndex;     }      public Object[] getSections()     {         return sections;     }      @Override     public Filter getFilter()     {         if(filter == null)             filter = new MangaNameFilter();         return filter;     }      private class MangaNameFilter extends Filter     {          @Override         protected FilterResults performFiltering(CharSequence constraint) {             // NOTE: this function is *always* called from a background thread, and             // not the UI thread.             constraint = constraint.toString().toLowerCase();             FilterResults result = new FilterResults();             if(constraint != null && constraint.toString().length() > 0)             {                 ArrayList<Manga> filt = new ArrayList<Manga>();                 ArrayList<Manga> lItems = new ArrayList<Manga>();                 synchronized (items)                 {                     Collections.copy(lItems, items);                 }                 for(int i = 0, l = lItems.size(); i < l; i++)                 {                     Manga m = lItems.get(i);                     if(m.getName().toLowerCase().contains(constraint))                         filt.add(m);                 }                 result.count = filt.size();                 result.values = filt;             }             else             {                 synchronized(items)                 {                     result.values = items;                     result.count = items.size();                 }             }             return result;         }          @SuppressWarnings("unchecked")         @Override         protected void publishResults(CharSequence constraint, FilterResults results) {             // NOTE: this function is *always* called from the UI thread.             filtered = (ArrayList<Manga>)results.values;             notifyDataSetChanged();         }      } } 

However, when I call filter('test') on the filter nothing happens at all (or the background-thread is run, but the list isn't filtered as far as the user conserns). How can I fix this?

Answer 1

This fixed my problem. I'm not certain it's the best solution, but it works. My project's open-source, so feel free to use any of the code here should it prove usefull :-).

package me.alxandr.android.mymir.adapters;  import java.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.HashMap; import java.util.Iterator; import java.util.Set;  import me.alxandr.android.mymir.R; import me.alxandr.android.mymir.model.Manga; import android.content.Context; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ArrayAdapter; import android.widget.Filter; import android.widget.SectionIndexer; import android.widget.TextView;  public class MangaListAdapter extends ArrayAdapter<Manga> implements SectionIndexer {     public ArrayList<Manga> items;     public ArrayList<Manga> filtered;     private Context context;     private HashMap<String, Integer> alphaIndexer;     private String[] sections = new String[0];     private Filter filter;     private boolean enableSections;      public Manga getByPosition(int position)     {         return items.get(position);     }      public MangaListAdapter(Context context, int textViewResourceId, ArrayList<Manga> items, boolean enableSections)     {         super(context, textViewResourceId, items);         this.filtered = items;         this.items = ArrayList<Manga> items.clone();         this.context = context;         this.filter = new MangaNameFilter();         this.enableSections = enableSections;          if(enableSections)         {             alphaIndexer = new HashMap<String, Integer>();             for(int i = items.size() - 1; i >= 0; i--)             {                 Manga element = items.get(i);                 String firstChar = element.getName().substring(0, 1).toUpperCase();                 if(firstChar.charAt(0) > 'Z' || firstChar.charAt(0) < 'A')                     firstChar = "@";                  alphaIndexer.put(firstChar, i);             }              Set<String> keys = alphaIndexer.keySet();             Iterator<String> it = keys.iterator();             ArrayList<String> keyList = new ArrayList<String>();             while(it.hasNext())                 keyList.add(it.next());              Collections.sort(keyList);             sections = new String[keyList.size()];             keyList.toArray(sections);         }     }      @Override     public View getView(int position, View convertView, ViewGroup parent)     {         View v = convertView;         if(v == null)         {             LayoutInflater vi = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);             v = vi.inflate(R.layout.mangarow, null);         }          Manga o = filtered.get(position);         if(o != null)         {             TextView tt = (TextView) v.findViewById(R.id.MangaRow_MangaName);             TextView bt = (TextView) v.findViewById(R.id.MangaRow_MangaExtra);             if(tt != null)                 tt.setText(o.getName());             if(bt != null)                 bt.setText(o.getLastUpdated() + " - " + o.getLatestChapter());              if(enableSections && getSectionForPosition(position) != getSectionForPosition(position + 1))             {                 TextView h = (TextView) v.findViewById(R.id.MangaRow_Header);                 h.setText(sections[getSectionForPosition(position)]);                 h.setVisibility(View.VISIBLE);             }             else             {                 TextView h = (TextView) v.findViewById(R.id.MangaRow_Header);                 h.setVisibility(View.GONE);             }         }          return v;     }      @Override     public void notifyDataSetInvalidated()     {         if(enableSections)         {             for (int i = items.size() - 1; i >= 0; i--)             {                 Manga element = items.get(i);                 String firstChar = element.getName().substring(0, 1).toUpperCase();                 if(firstChar.charAt(0) > 'Z' || firstChar.charAt(0) < 'A')                     firstChar = "@";                 alphaIndexer.put(firstChar, i);             }              Set<String> keys = alphaIndexer.keySet();             Iterator<String> it = keys.iterator();             ArrayList<String> keyList = new ArrayList<String>();             while (it.hasNext())             {                 keyList.add(it.next());             }              Collections.sort(keyList);             sections = new String[keyList.size()];             keyList.toArray(sections);              super.notifyDataSetInvalidated();         }     }      public int getPositionForSection(int section)     {         if(!enableSections) return 0;         String letter = sections[section];          return alphaIndexer.get(letter);     }      public int getSectionForPosition(int position)     {         if(!enableSections) return 0;         int prevIndex = 0;         for(int i = 0; i < sections.length; i++)         {             if(getPositionForSection(i) > position && prevIndex <= position)             {                 prevIndex = i;                 break;             }             prevIndex = i;         }         return prevIndex;     }      public Object[] getSections()     {         return sections;     }      @Override     public Filter getFilter()     {         if(filter == null)             filter = new MangaNameFilter();         return filter;     }      private class MangaNameFilter extends Filter     {          @Override         protected FilterResults performFiltering(CharSequence constraint) {             // NOTE: this function is *always* called from a background thread, and             // not the UI thread.             constraint = constraint.toString().toLowerCase();             FilterResults result = new FilterResults();             if(constraint != null && constraint.toString().length() > 0)             {                 ArrayList<Manga> filt = new ArrayList<Manga>();                 ArrayList<Manga> lItems = new ArrayList<Manga>();                 synchronized (this)                 {                     lItems.addAll(items);                 }                 for(int i = 0, l = lItems.size(); i < l; i++)                 {                     Manga m = lItems.get(i);                     if(m.getName().toLowerCase().contains(constraint))                         filt.add(m);                 }                 result.count = filt.size();                 result.values = filt;             }             else             {                 synchronized(this)                 {                     result.values = items;                     result.count = items.size();                 }             }             return result;         }          @SuppressWarnings("unchecked")         @Override         protected void publishResults(CharSequence constraint, FilterResults results) {             // NOTE: this function is *always* called from the UI thread.             filtered = (ArrayList<Manga>)results.values;             notifyDataSetChanged();             clear();             for(int i = 0, l = filtered.size(); i < l; i++)                 add(filtered.get(i));             notifyDataSetInvalidated();         }      } }