<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <item android:id="@+id/action_share"
        android:title="@string/share"
        app:showAsAction="always"
        app:actionProviderClass="android.support.v7.widget.ShareActionProvider"/>

    <item android:id="@+id/about"
        android:title="@string/about"
        app:showAsAction="never"/>

</menu>

// Locate MenuItem with ShareActionProvider
        MenuItem item = menu.findItem(R.id.action_share);
        // Fetch and store ShareActionProvider
        mShareActionProvider = (ShareActionProvider) MenuItemCompat.getActionProvider(item);

        return true;
    }

    private void setShareIntent() {

        Intent myShareIntent = new Intent(Intent.ACTION_SEND);
        myShareIntent.setType("text/plain");
        myShareIntent.putExtra(Intent.EXTRA_TEXT, "some text");
        mShareActionProvider.setShareIntent(myShareIntent);
        startActivity(myShareIntent);

    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle item selection
        switch (item.getItemId()) {
            case R.id.action_share:
                setShareIntent();
                break;
      ....