Android: How to enable/disable option menu item on button click?

On all android versions, easiest way: use this to SHOW a menu action icon as disabled AND make it FUNCTION as disabled as well:

@Override
public boolean onPrepareOptionsMenu(Menu menu) {

    MenuItem item = menu.findItem(R.id.menu_my_item);

    if (myItemShouldBeEnabled) {
        item.setEnabled(true);
        item.getIcon().setAlpha(255);
    } else {
        // disabled
        item.setEnabled(false);
        item.getIcon().setAlpha(130);
    }
}

Anyway, the documentation covers all the things.

Changing menu items at runtime

Once the activity is created, the onCreateOptionsMenu() method is called only once, as described above. The system keeps and re-uses the Menu you define in this method until your activity is destroyed. If you want to change the Options Menu any time after it's first created, you must override the onPrepareOptionsMenu() method. This passes you the Menu object as it currently exists. This is useful if you'd like to remove, add, disable, or enable menu items depending on the current state of your application.

E.g.

@Override
public boolean onPrepareOptionsMenu (Menu menu) {
    if (isFinalized) {
        menu.getItem(1).setEnabled(false);
        // You can also use something like:
        // menu.findItem(R.id.example_foobar).setEnabled(false);
    }
    return true;
}

On Android 3.0 and higher, the options menu is considered to always be open when menu items are presented in the action bar. When an event occurs and you want to perform a menu update, you must call invalidateOptionsMenu() to request that the system call onPrepareOptionsMenu().

How to update the current menu in order to enable or disable the items when an AsyncTask is done.

In my use case I needed to disable my menu while my AsyncTask was loading data, then after loading all the data, I needed to enable all the menu again in order to let the user use it.

This prevented the app to let users click on menu items while data was loading.

First, I declare a state variable , if the variable is 0 the menu is shown, if that variable is 1 the menu is hidden.

private mMenuState = 1; //I initialize it on 1 since I need all elements to be hidden when my activity starts loading.

Then in my onCreateOptionsMenu() I check for this variable , if it's 1 I disable all my items, if not, I just show them all

 @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        getMenuInflater().inflate(R.menu.menu_galeria_pictos, menu);

        if(mMenuState==1){
            for (int i = 0; i < menu.size(); i++) {
                menu.getItem(i).setVisible(false);
            }
        }else{
             for (int i = 0; i < menu.size(); i++) {
                menu.getItem(i).setVisible(true);
            }
        }

        return super.onCreateOptionsMenu(menu);
    }

Now, when my Activity starts, onCreateOptionsMenu() will be called just once, and all my items will be gone because I set up the state for them at the start.

Then I create an AsyncTask Where I set that state variable to 0 in my onPostExecute()

This step is very important!

When you call invalidateOptionsMenu(); it will relaunch onCreateOptionsMenu();

So, after setting up my state to 0, I just redraw all the menu but this time with my variable on 0 , that said, all the menu will be shown after all the asynchronous process is done, and then my user can use the menu.

 public class LoadMyGroups extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            mMenuState = 1; //you can set here the state of the menu too if you dont want to initialize it at global declaration. 

        }

        @Override
        protected Void doInBackground(Void... voids) {
           //Background work

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);

            mMenuState=0; //We change the state and relaunch onCreateOptionsMenu
            invalidateOptionsMenu(); //Relaunch onCreateOptionsMenu

        }
    }

Results

You could save the item as a variable when creating the option menu and then change its properties at will.

private MenuItem securedConnection;
private MenuItem insecuredConnection;

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.connect_menu, menu);
    securedConnection = menu.getItem(0);
    insecuredConnection =  menu.getItem(1);
    return true;
}

public void foo(){
       securedConnection.setEnabled(true);
}