AbstractAsyncSqliteLoader.java

/**
 * Copyright (C) 2013 Johannes Schnatterer
 *
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This file is part of nusic.
 *
 * nusic is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * nusic is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with nusic.  If not, see <http://www.gnu.org/licenses/>.
 */
package info.schnatterer.nusic.android.loaders;

import info.schnatterer.nusic.data.model.Entity;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import android.content.Context;
import android.support.v4.content.AsyncTaskLoader;

public abstract class AbstractAsyncSqliteLoader<RESULT, ENTITY extends Entity>
        extends AsyncTaskLoader<AsyncResult<RESULT>> {
    private static final Logger LOG = LoggerFactory
            .getLogger(AbstractAsyncSqliteLoader.class);

    private AsyncResult<RESULT> data;

    /**
     * Uses a specific context.
     * 
     * @param context
     */
    public AbstractAsyncSqliteLoader(Context context) {
        super(context);
    }

    public abstract RESULT doLoadInBackground() throws Exception;

    @Override
    public void deliverResult(AsyncResult<RESULT> data) {
        if (isReset()) {
            // a query came in while the loader is stopped
            return;
        }

        this.data = data;

        super.deliverResult(data);
    }

    @Override
    public AsyncResult<RESULT> loadInBackground() {
        AsyncResult<RESULT> result = new AsyncResult<RESULT>();

        RESULT dataList = null;

        try {
            dataList = doLoadInBackground();

        } catch (Exception e) {
            LOG.error(e.getMessage(), e);
            result.setException(e);
        }

        result.setData(dataList);

        return result;
    }

    @Override
    protected void onStartLoading() {
        if (data != null) {
            deliverResult(data);
        }

        if (takeContentChanged() || data == null) {
            forceLoad();
        }
    }

    @Override
    protected void onStopLoading() {
        cancelLoad();
    }

    @Override
    protected void onReset() {
        super.onReset();

        onStopLoading();

        data = null;
    }

    @Override
    public void onCanceled(AsyncResult<RESULT> data) {
        // Attempt to cancel the current asynchronous load.
        super.onCanceled(data);
        // Allow garbage collection
        data = null;
    }
}