如何在Android中的多个线程中更新Realm？

Question

I am trying to update realm instances of several threads. Instead of explaining everything I created a flowchart as I understand it.

Here it is:

So the problem is when I call notifyAppWidgetViewDataChanged() it doesnt update the realm. I tried adding Realm.OnChangeListener in the Service's onCreate() , but the method is not called when changing the realm from the main thread. I also tried calling getDefaultRealmInstance() from service's onGetViewFactory() instead. Same problem.

Answer 1

Allright, here is my "not-so-memory-efficient" solution:
From the Widget's service I override only one method to create factory instance:

@Override
public RemoteViewsFactory onGetViewFactory(Intent intent) {
    return new WidFactory(getApplicationContext());
}

And then WidFactory class:

class WidFactory implements WidService.RemoteViewsFactory {
    private static int myTasksSize;
    private Context context;
    private Realm realm;
    private RealmResults<Task> myTasks;
    WidFactory(Context context){
        this.context = context;
    }
    @Override
    public void onCreate() {
        realm = Realm.getDefaultInstance();
        myTasks = realm.where(Task.class).findAll();
        myTasksSize = myTasks.size();
        realm.close();
    }
    @Override
    public void onDataSetChanged() {
        realm = Realm.getDefaultInstance();
        realm.refresh();
        myTasks = realm.where(Task.class).findAll();
        myTasksSize = myTasks.size();
        realm.close();
    }

    @Override
    public RemoteViews getViewAt(int position) {
        realm = Realm.getDefaultInstance();
        myTasks = realm.where(Task.class).findAll();
        RemoteViews rv = new RemoteViews(context.getPackageName(), R.layout.widgetrow_layout);
        final Task myTask = myTasks.get(position);
        rv.setTextViewText(R.id.widgetrow_text_id, myTask.getTaskText());
        Intent fillInIntent = new Intent(context, WidShowTaskActivity.class);
        fillInIntent.putExtra("code", myTask.getCode());
        realm.close();
        rv.setOnClickFillInIntent(R.id.widgetrow_text_id, fillInIntent);
        return rv;
    }

    @Override
    public int getCount() {
        return myTasksSize;
    }
    @Override
    public RemoteViews getLoadingView() {
        return null;
    }
    @Override
    public int getViewTypeCount() {
        return 1;
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public boolean hasStableIds() {
        return true;
    }
    @Override
    public void onDestroy() {
        if (!realm.isClosed()){      realm.close();     }
    }
}

The bad thing with this solution is that I open and close realm 3 times: in onCreate() , onDatasetChanged() and in getViewAt() . What is even worse is that generally speaking I only need one realm instance for all widgets, so I wanted to pass the realm in the factories constructor, so all factories use one realm. But 2 problems appeared:
1)i dont know how to "update" the realm instance when started from service; Android doesn't provide any methods.
2)I am not sure how content providers work, but the factory class somehow spreads the work over several threads and Realm doesn't like this. Not at all.
PS Please correct me if I am wrong somewhere I am relatively new to Android and Realm.
And thank you again for your reply :) @G. Blake Meike