Filtering a cursor the right way?

Question

At the moment I need to filter a Cursor/CursorAdapter to only show rows that match a specific condition in the ListView. I don\'t want to requery the db all the time. I just

Answer 1

I was looking for something similar, in my case I wanted to filter items based on a string comparision. I found this gist https://gist.github.com/ramzes642/5400792, which works fine unless you start playing around with the position of the cursor. So I found satur9nine answer, his one respects the position api but just needs some adjustments for filtering based on cursor, so I merged the two. You can change your code to fit it: https://gist.github.com/rfreitas/ab46edbdc41500b20357

import java.text.Normalizer;

import android.database.Cursor;
import android.database.CursorWrapper;
import android.util.Log;


//by Ricardo derfreitas@gmail.com
//ref: https://gist.github.com/ramzes642/5400792 (the position retrieved is not correct)
//ref: http://stackoverflow.com/a/7343721/689223 (doesn't do string filtering)
//the two code bases were merged to get the best of both worlds
//also added was an option to remove accents from UTF strings
public class FilterCursorWrapper extends CursorWrapper {
    private static final String TAG = FilterCursorWrapper.class.getSimpleName();
    private String filter;
    private int column;
    private int[] filterMap;
    private int mPos = -1;
    private int mCount = 0;

    public FilterCursorWrapper(Cursor cursor,String filter,int column) {
        super(cursor);
        this.filter = deAccent(filter).toLowerCase();
        Log.d(TAG, "filter:"+this.filter);
        this.column = column;
        int count = super.getCount();

        if (!this.filter.isEmpty()) {
            this.filterMap = new int[count];
            int filteredCount = 0;
            for (int i=0;i= count) {
            mPos = count;
            return false;
        }
        // Make sure position isn't before the beginning of the cursor
        if (position < 0) {
            mPos = -1;
            return false;
        }
        final int realPosition = filterMap[position];
        // When moving to an empty position, just pretend we did it
        boolean moved = realPosition == -1 ? true : super.moveToPosition(realPosition);
        if (moved) {
            mPos = position;
        } else {
            mPos = -1;
        }
        Log.d(TAG,"end moveToPosition:"+position);
        return moved;
    }
    @Override
    public final boolean move(int offset) {
        return moveToPosition(mPos + offset);
    }
    @Override
    public final boolean moveToFirst() {
        return moveToPosition(0);
    }
    @Override
    public final boolean moveToLast() {
        return moveToPosition(getCount() - 1);
    }
    @Override
    public final boolean moveToNext() {
        return moveToPosition(mPos + 1);
    }
    @Override
    public final boolean moveToPrevious() {
        return moveToPosition(mPos - 1);
    }
    @Override
    public final boolean isFirst() {
        return mPos == 0 && getCount() != 0;
    }
    @Override
    public final boolean isLast() {
        int cnt = getCount();
        return mPos == (cnt - 1) && cnt != 0;
    }
    @Override
    public final boolean isBeforeFirst() {
        if (getCount() == 0) {
            return true;
        }
        return mPos == -1;
    }
    @Override
    public final boolean isAfterLast() {
        if (getCount() == 0) {
            return true;
        }
        return mPos == getCount();
    }
    @Override
    public int getPosition() {
        return mPos;
    }

    //added by Ricardo
    //ref: http://stackoverflow.com/a/22612054/689223
    //other: http://stackoverflow.com/questions/8523631/remove-accents-from-string
    //other: http://stackoverflow.com/questions/15190656/easy-way-to-remove-utf-8-accents-from-a-string
    public static String deAccent(String str) {
        //return StringUtils.stripAccents(str);//this method from apache.commons respects chinese characters, but it's slower than flattenToAscii
        return flattenToAscii(str);
    }

    //ref: http://stackoverflow.com/a/15191508/689223
    //this is the fastest method using the normalizer found yet, the ones using Regex are too slow
    public static String flattenToAscii(String string) {
        char[] out = new char[string.length()];
        string = Normalizer.normalize(string, Normalizer.Form.NFD);
        int j = 0;
        for (int i = 0, n = string.length(); i < n; ++i) {
            char c = string.charAt(i);
            int type = Character.getType(c);
            if (type != Character.NON_SPACING_MARK){
                out[j] = c;
                j++;
            }
        }
        return new String(out);
    }
}