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Building The Android Options Menu

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Handling the menu that an activity pops up when the user presses the Menu
button normally requires two stages: 1) put all the items into the menu 2)
respond to a menu selection and invoke the appropriate action.

I came up with a way of combining most of the work of the two into one
stage. I build a table that maps menu items into Runnable objects that
perform the corresponding action:

    java.util.Map<android.view.MenuItem, Runnable> OptionsMenu;

Then my onCreateOptionsMenu method builds the menu and attaches the actions
in a single sequence, something like this:

    @Override
    public boolean onCreateOptionsMenu
      (
        android.view.Menu TheMenu
      )
      {
        OptionsMenu = new java.util.HashMap<android.view.MenuItem, Runnable>();
        OptionsMenu.put
          (
            TheMenu.add(R.string.show_calc_help),
            new Runnable()
              {
                public void run()
                  {
                    startActivity
                      (
                        new android.content.Intent
                          (
                            android.content.Intent.ACTION_VIEW,
                            android.net.Uri.fromParts
                              (
                                "file",
                                "/android_asset/help/index.html",
                                null
                              )
                          ).setClass(Main.this, Help.class)
                      );
                  } /*run*/
              } /*Runnable*/
          );
        OptionsMenu.put
          (
            TheMenu.add(... another string ...),
            new Runnable()
              {
                public void run()
                  {
                    ... another action ...
                  } /*run*/
              } /*Runnable*/
          );
        ... more OptionsMenu.put calls for more items ...
        return
            true;
      } /*onCreateOptionsMenu*/

And the actual handler for item selections can be this simple generic
routine:

    @Override
    public boolean onOptionsItemSelected
      (
        android.view.MenuItem TheItem
      )
      {
        boolean Handled = false;
        final Runnable Action = OptionsMenu.get(TheItem);
        if (Action != null)
          {
            Action.run();
            Handled = true;
          } /*if*/
        return
            Handled;
      } /*onOptionsItemSelected*/

For a full example of this technique in operation (and a similar one for
handling results from sub-activities), see
<https://github.com/ldo/ti5x_android/blob/master/src/Main.java>.

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Thread

Building The Android Options Menu Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-05-13 22:52 +1200

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