30 January 2011

Enabling/disabling menu items on the fly

In one of my applications, I want to disable some menu entries if the database is not valid or is not present at all. To do that, I make use of the onPrepareOptionsMenu() API.

Let's say the user is on the Quiz activity. When the user presses the MENU button, the Quiz item should not be there anymore; and until the application validates the presence of a database, I want the Books item to be unclickable.

So I inflate my menu as usual from the XML file:
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.my_menu, menu);

return true;

private void removeSomeItems(Menu menu){
MenuItem books = menu.findItem(R.id.menu_books);
books.setEnabled(false); // I want this item to be available eventually

menu.removeItem(R.id.menu_quiz); // I want this item to be unavailable for this activity

You have to remember though, that this method is called only ONCE, the very first time the user opens the menu.

The activity does its business as usual. When I am done checking if the database is there already, I want the user to be able to use the Books item. I have a boolean field that I set when the database is validated, and so now I can enable the menu.
public boolean onPrepareOptionsMenu (Menu menu){

MenuItem books = menu.findItem(R.id.menu_books);

return true;

You can change the contents of the menu as often as you want using onPrepareOptionsMenu() because that method is called each and every time the user presses the MENU button.

And that's it!

18 January 2011

Just wondering

You know those postscripts that Google engineers have on their posts in forums? I wonder if they have a sort of "standards body" that came up with it. They all sound like this:
Note: please don't send private questions to me, as I don't have time to provide private support. All such questions should be posted on public
forums, where I and others can see and answer them

I wonder why I wonder about these things.