core/java/android/widget/CursorFilter.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.widget;

import android.database.Cursor;

/**
 * <p>The CursorFilter delegates most of the work to the CursorAdapter.
 * Subclasses should override these delegate methods to run the queries
 * and convert the results into String that can be used by auto-completion
 * widgets.</p>
 */
class CursorFilter extends Filter {
    
    CursorFilterClient mClient;
    
    interface CursorFilterClient {
        CharSequence convertToString(Cursor cursor);
        Cursor runQueryOnBackgroundThread(CharSequence constraint);
        Cursor getCursor();
        void changeCursor(Cursor cursor);
    }

    CursorFilter(CursorFilterClient client) {
        mClient = client;
    }
    
    @Override
    public CharSequence convertResultToString(Object resultValue) {
        return mClient.convertToString((Cursor) resultValue);
    }

    @Override
    protected FilterResults performFiltering(CharSequence constraint) {
        Cursor cursor = mClient.runQueryOnBackgroundThread(constraint);

        FilterResults results = new FilterResults();
        if (cursor != null) {
            results.count = cursor.getCount();
            results.values = cursor;
        } else {
            results.count = 0;
            results.values = null;
        }
        return results;
    }

    @Override
    protected void publishResults(CharSequence constraint, FilterResults results) {
        Cursor oldCursor = mClient.getCursor();
        
        if (results.values != null && results.values != oldCursor) {
            mClient.changeCursor((Cursor) results.values);
        }
    }
}