AddressEntryLoader.java

package net.i2p.android.router.loader;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.Set;
import java.util.TreeSet;

import net.i2p.android.router.util.Util;
import net.i2p.client.naming.NamingService;
import net.i2p.router.RouterContext;

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

public class AddressEntryLoader extends AsyncTaskLoader<List<AddressEntry>> {
    private static final String DEFAULT_NS = "BlockfileNamingService";
    private RouterContext mRContext;
    private String mBook;
    private String mFilter;
    private List<AddressEntry> mData;

    public AddressEntryLoader(Context context, RouterContext rContext,
            String book, String filter) {
        super(context);
        mRContext = rContext;
        mBook = book;
        mFilter = filter;
    }

    @Override
    public List<AddressEntry> loadInBackground() {
        // get the names
        NamingService ns = getNamingService();
        Util.i("NamingService: " + ns.getName());
        // After router shutdown we get nothing... why?
        List<AddressEntry> ret = new ArrayList<AddressEntry>();
        Set<String> names = new TreeSet<String>();
        names.addAll(ns.getNames());
        for (String hostName : names) {
            if (mFilter != null && !hostName.toLowerCase(Locale.US).contains(
                    mFilter.toLowerCase(Locale.US)))
                continue;

            AddressEntry name = new AddressEntry(hostName);
            ret.add(name);
        }
        return ret;
    }

    /** @return the NamingService for the current file name, or the root NamingService */
    private NamingService getNamingService()
    {
        NamingService root = mRContext.namingService();
        NamingService rv = searchNamingService(root, mBook);
        return rv != null ? rv : root;
    }

    /** depth-first search */
    private static NamingService searchNamingService(NamingService ns, String srch)
    {
        String name = ns.getName();
        if (name.equals(srch) || basename(name).equals(srch) || name.equals(DEFAULT_NS))
            return ns;
        List<NamingService> list = ns.getNamingServices();
        if (list != null) {
            for (NamingService nss : list) {
                NamingService rv = searchNamingService(nss, srch);
                if (rv != null)
                    return rv;
            }
        }
        return null;
    }

    private static String basename(String filename) {
        int slash = filename.lastIndexOf('/');
        if (slash >= 0)
            filename = filename.substring(slash + 1);
        return filename;
    }

    @Override
    public void deliverResult(List<AddressEntry> data) {
        if (isReset()) {
            // The Loader has been reset; ignore the result and invalidate the data.
            if (data != null) {
                releaseResources(data);
                return;
            }
        }

        // Hold a reference to the old data so it doesn't get garbage collected.
        // We must protect it until the new data has been delivered.
        List<AddressEntry> oldData = mData;
        mData = data;

        if (isStarted()) {
            // If the Loader is in a started state, have the superclass deliver the
            // results to the client.
            super.deliverResult(data);
        }

        // Invalidate the old data as we don't need it any more.
        if (oldData != null && oldData != data) {
            releaseResources(oldData);
        }
    }

    @Override
    protected void onStartLoading() {
        if (mData != null) {
            // Deliver any previously loaded data immediately.
            deliverResult(mData);
        }

        if (takeContentChanged() || mData == null) {
            // When the observer detects a change, it should call onContentChanged()
            // on the Loader, which will cause the next call to takeContentChanged()
            // to return true. If this is ever the case (or if the current data is
            // null), we force a new load.
            forceLoad();
        }
    }

    @Override
    protected void onStopLoading() {
        // The Loader is in a stopped state, so we should attempt to cancel the 
        // current load (if there is one).
        cancelLoad();

        // Note that we leave the observer as is. Loaders in a stopped state
        // should still monitor the data source for changes so that the Loader
        // will know to force a new load if it is ever started again.
    }

    @Override
    protected void onReset() {
        // Ensure the loader has been stopped.
        onStopLoading();

        // At this point we can release the resources associated with 'mData'.
        if (mData != null) {
            releaseResources(mData);
            mData = null;
        }
    }

    @Override
    public void onCanceled(List<AddressEntry> data) {
        // Attempt to cancel the current asynchronous load.
        super.onCanceled(data);

        // The load has been canceled, so we should release the resources
        // associated with 'data'.
        releaseResources(data);
    }

    private void releaseResources(List<AddressEntry> data) {
        // For a simple List, there is nothing to do. For something like a Cursor, we 
        // would close it in this method. All resources associated with the Loader
        // should be released here.
    }
}