DownloadBoundServiceSync.java

package vandy.mooc.model.services;

import vandy.mooc.common.DownloadUtils;
import vandy.mooc.common.LifecycleLoggingService;
import vandy.mooc.model.aidl.DownloadCall;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.IBinder;
import android.os.RemoteException;

/**
 * This class handles downloads using synchronous AIDL
 * interactions. The component that binds to this service should
 * receive an IBinder. This IBinder should be an instance of
 * DownloadCall, which extends IBinder. The component can then
 * interact with this service by making normal calls on the
 * DownloadCall object. Specifically, the component can ask this
 * service to download an image by calling downloadImage() on the
 * DownloadCall object, which will run synchronously in this service
 * until it finishes downloading and returns the file name of the
 * downloaded file as a String.
 *  
 * AIDL is an example of the Broker Pattern, in which all interprocess
 * communication details are hidden behind the AIDL interfaces.
 */
public class DownloadBoundServiceSync 
       extends LifecycleLoggingService {
    /**
     * Make an explicit Intent that will start this service when
     * passed to bindService().
     *
     * @param context		
     *        The context of the calling component.
     */
    public static Intent makeIntent(Context context) {
        // Create an explicit Intent and return it to the caller.
        return new Intent(context,
                          DownloadBoundServiceSync.class);		
    }

    /**
     * An implementation of the AIDL Interface DownloadCall.  We
     * extend the Stub class, which implements DownloadCall, so that
     * Android can properly handle calls across process boundaries.
     * 
     * This implementation plays the role of Invoker in the Broker
     * Pattern
     */
    DownloadCall.Stub mDownloadCallImpl =
        new DownloadCall.Stub() {
            /**
             * Download the image at the given Uri and return a
             * pathname to the file on the Android file system.
             * 
             * Use the methods defined in DownloadUtils for code
             * brevity.
             */
            @Override
            public Uri downloadImage(Uri uri) throws RemoteException {
                // Download the file using the appropriate helper
                // method in DownloadUtils and then return the
                // pathname back to the client.
                return DownloadUtils.downloadFile
                    (DownloadBoundServiceSync.this,
                     uri);
            }
	};
	
    /**
     * Called when a component calls bindService() with the proper
     * intent.  Return the concrete implementation of DownloadCall
     * cast as an IBinder.
     */
    @Override
    public IBinder onBind(Intent intent) {
        return mDownloadCallImpl;
    }
}