Updating Action Bar Menu Item due to AsyncTask result without delay

问题

I developed an Application which offers a detail view Activity (An activity which is called when clicking on a list item to display further information). This details Activity shall display a "favorite" start in the Action Bar (it is yellow if the item is a favorite, transparent if not - for this purpose I have to different image resources)

If i click the menu item, the item is added / removed form the user's favorites:

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId() == android.R.id.home) {
        ...
    } else if (item.getItemId() == R.id.action_no_favorite) {
        ...
        new FavoriteTask(DetailsActivity.this).execute(user, item);
        mMenu.findItem(R.id.action_favorite).setVisible(true);
        mMenu.findItem(R.id.action_no_favorite).setVisible(false);
    } else if (item.getItemId() == R.id.action_favorite) {
        ...
        new NoFavoriteTask(DetailsActivity.this).execute(user, item);
        mMenu.findItem(R.id.action_favorite).setVisible(false);
        mMenu.findItem(R.id.action_no_favorite).setVisible(true);
    }
    return super.onOptionsItemSelected(item);
}

This works without any problem.

But if the user opens the detail view, the Action Bar menu item needs to be updated immediately, depending on if this item is already a favorite or not. I solved this issue by overriding onCreateOptionsMenu:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.details_activity_actions, menu);
    this.mMenu = menu;
    ...
    new FetchFavortieStatusTask().execute(user, item);
    return super.onCreateOptionsMenu(menu);
}

FavoriteStatusTask delivers a simple response (if the item is a favorite or not) and works like a charm. In onPostExecute, I update the menu item:

    @Override
    public void onPostExecute(String result) {
        super.onPostExecute(result);
        if (mMenu != null) {
            if (result.equals("no favorite")) {
                ...
                mMenu.findItem(R.id.action_favorite).setVisible(false);
                mMenu.findItem(R.id.action_no_favorite).setVisible(true);
            } else {
                ...
                mMenu.findItem(R.id.action_favorite).setVisible(true);
                mMenu.findItem(R.id.action_no_favorite).setVisible(false);
            }
        }
    }

The problem that occurs: If I open a list item to get the detail view, the icon is changed after a delay of ~3 seconds or immediately if I touch the screen. The delay is definetly not caused by the AsyncTask, the result is delivered way faster. If I execute FetchFavortieStatusTask() in the end of the Activity's onCreate method, it works as expected most of the time (but still, sometimes I do have this delay). Moving the AsyncTask to onPrepareOptionsMenu doesn't change anything.

回答1:

ci_'s comment is a good hint but I had to adapt the solution in a bit different way (based on this answer: Is supportInvalidateOptionsMenu() working?)

I call the AsyncTask in onCreate() now and in its onPostExecute method I only set a member variable mIsFavorite to true or false and then execute supportInvalidateOptionsMenu() which calles onPrepareOptionsMenu a second time (but not onCreateOptionsMenu!). This means that I have to update the menu items in onPrepareOptionsMenu, based on the value of mIsFavorite.

来源：https://stackoverflow.com/questions/29239804/updating-action-bar-menu-item-due-to-asynctask-result-without-delay