Core Apps » Bazaar

package org.fdroid.fdroid.net;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

import org.fdroid.fdroid.ProgressListener;

import java.io.IOException;

/**

 * Given a {@link org.fdroid.fdroid.net.Downloader}, this wrapper will conduct the download operation on a

 * separate thread. All progress/status/error/etc events will be forwarded from that thread to the thread

 * that {@link AsyncDownloader#download()} was invoked on. If you want to respond with UI feedback

 * to these events, it is important that you execute the download method of this class from the UI thread.

 * That way, all forwarded events will be handled on that thread.

 */

@SuppressWarnings("serial")

public class AsyncDownloader extends Handler {

    private static final String TAG = "AsyncDownloadWrapper";

    private static final int MSG_DOWNLOAD_COMPLETE  = 2;

    private static final int MSG_DOWNLOAD_CANCELLED = 3;

    private static final int MSG_ERROR              = 4;

    private static final String MSG_DATA            = "data";

    private final Downloader downloader;

    private final Listener listener;

    private DownloadThread downloadThread = null;

    /**

     * Normally the listener would be provided using a setListener method.

     * However for the purposes of this async downloader, it doesn't make

     * sense to have an async task without any way to notify the outside

     * world about completion. Therefore, we require the listener as a

     * parameter to the constructor.

     */

    public AsyncDownloader(Downloader downloader, Listener listener) {

        this.downloader = downloader;

        this.listener   = listener;

    }

    public void download() {

        downloadThread = new DownloadThread();

        downloadThread.start();

    }

    public void attemptCancel(boolean userRequested) {

        if (downloadThread != null) {

            downloadThread.interrupt();

        }

    }

    /**

     * Receives "messages" from the download thread, and passes them onto the

     * relevant {@link AsyncDownloader.Listener}

     * @param message

     */

    public void handleMessage(Message message) {

        switch (message.arg1) {

        case MSG_DOWNLOAD_COMPLETE:

            listener.onDownloadComplete();

            break;

        case MSG_DOWNLOAD_CANCELLED:

            listener.onDownloadCancelled();

            break;

        case MSG_ERROR:

            listener.onErrorDownloading(message.getData().getString(MSG_DATA));

            break;

        }

    }

    public int getBytesRead() {

        return downloader.getBytesRead();

    }

    public int getTotalBytes() {

        return downloader.getTotalBytes();

    }

    public interface Listener extends ProgressListener {

        void onErrorDownloading(String localisedExceptionDetails);

        void onDownloadComplete();

        void onDownloadCancelled();

    }

    private class DownloadThread extends Thread {

        public void run() {

            try {

                downloader.download();

                sendMessage(MSG_DOWNLOAD_COMPLETE);

            } catch (InterruptedException e) {

                sendMessage(MSG_DOWNLOAD_CANCELLED);

            } catch (IOException e) {

                Log.e(TAG, "I/O exception in download thread", e);

                Bundle data = new Bundle(1);

                data.putString(MSG_DATA, e.getLocalizedMessage());

                Message message = new Message();

                message.arg1 = MSG_ERROR;

                message.setData(data);

                AsyncDownloader.this.sendMessage(message);

            }

        }

        private void sendMessage(int messageType) {

            Message message = new Message();

            message.arg1 = messageType;

            AsyncDownloader.this.sendMessage(message);

        }

    }

}