自定义状态栏通知以进行后台下载

Question

I am new to android development and I try to create a background download feature for my app. I followed this http://developer.android.com/guide/topics/ui/notifiers/notifications.html#CustomExpandedView to create my custom notification.

The downloading is performed, I checked the downloaded file in the sdcard. Also,the status bar icon and title are changed properly.

The problem is that the custom layout I provide for the notification does not appear (expand under the bar). Here is the related code parts inside private AsyncTask class:

    @Override
    protected void onPreExecute() {
        // create and configure the notification
        notification = new Notification(R.drawable.download, "Downloading map..", System.currentTimeMillis());
        notification.flags = notification.flags | Notification.FLAG_ONGOING_EVENT;

        //create a custom layout for the notification
        myContentView = new RemoteViews(appContext.getPackageName(), R.layout.download_progress);
        myContentView.setImageViewResource(R.id.status_icon, R.drawable.ic_menu_save);
        myContentView.setTextViewText(R.id.status_text, "download in progress");
        myContentView.setProgressBar(R.id.status_progress, 100, 0, false);
        notification.contentView = myContentView;
        notification.contentView.apply(appContext, dl.getListView());

        //instantiate the pending intent
        Intent myIntent = new Intent(appContext, DownloadList.class);
        myIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        int requestID = (int) System.currentTimeMillis();
        PendingIntent myPendingIntent = PendingIntent.getActivity(appContext, requestID, myIntent, 0);
        notification.contentIntent = myPendingIntent;

        //add the Notification object to the notification manager
        notificationManager = (NotificationManager) appContext.getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.notify(NOTIF_ID, notification);
    }

    @Override
    protected void onProgressUpdate(Integer... progress) {
        //update progress bar
        notification.contentView.setProgressBar(R.id.status_progress, 100, progress[0], false);
        notificationManager.notify(NOTIF_ID, notification);
    }

}

Note that my DownloadList class extends ListActivity.

Do I need to do something more that just "notification.contentView = myContentView;" in order to inflate the layout?

Answer 1

Hmm... Well I compared your code to my code that already works... and I don't see many differences... But, it is possible that one of these minor differences is important.

final Notification notification = new Notification(R.drawable.icon, "Downloading", System.currentTimeMillis());
notification.flags = notification.flags | Notification.FLAG_ONGOING_EVENT;

notification.contentView = new RemoteViews(getApplicationContext().getPackageName(), R.layout.download_progress);

notification.contentView.setImageViewResource(R.id.status_icon, R.drawable.ic_status);
notification.contentView.setTextViewText(R.id.status_text, "Downloading in progress");
notification.contentView.setProgressBar(R.id.status_progress, 100, progress, false);
Intent notificationIntent = new Intent(MainPage.mainActivity, MainPage.class);
PendingIntent contentIntent = PendingIntent.getActivity(MainPage.mainActivity, 0, notificationIntent, 0);
notification.contentIntent = contentIntent;

//getApplicationContext();
final NotificationManager notificationManager = (NotificationManager) getApplicationContext().getSystemService(
                Context.NOTIFICATION_SERVICE);
notificationManager.notify(NOTIFICATION_MESSAGE, notification);

First, I looked at your old code and noticed that the NOTIF_ID = 1 I'm not so sure that is a good idea because what if someone else has an ID of one. Of course I could be mistaken about that, but I just pounded in a number like 792489743 and I expect no one else would have the same number. Just a precaution I suppose.

Second, I didn't get to see if the resources were correct? What does the stack trace say? I suppose that it would've just quit out on it if there was a problem there though.

Third, I put my in its own task as Service kinda as follows

public class DownloadService extends IntentService {
    //initializing code and stuff
    private class DownloadTask extends AsyncTask<String, Void, Boolean> {

and I did it in the doInBackground This way if the user kills the app or what not it wouldn't kill the download.

Lastly, I've never used apply I don't personally see how it would hurt, but I haven't seen an example that uses it either.

Hope this helps some!

Answer 2

It was an emulator problem after all.....

It lagged when I "dragged down" the notification! I killed some CPU extensive processes on my PC resulting to a faster emulator.

Lesson learned. Leave the heavy multitasking to pros or to another PC.