How can you implement multi-selection and Contextual ActionMode in ActionBarSherlock?

So here's what I did.

Edit:Over a year passed since I found out the previous answer had alot of useless code (woops) and the CAB thing can be achieved with much less effort and a cleaner code, so I took some time and updated it

The LibraryFragment ListView should be defined with choice mode "none"

<ListView    android:id="@android:id/list"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:choiceMode="none"/>

The list item should have an ?attr/activatedBackgroundIndicator foreground in order to automatically draw highlighted semitransparent overlay on list.setItemChecked(pos, true)

list_item_library.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:foreground="?attr/activatedBackgroundIndicator"    android:paddingBottom="5dp"    android:paddingTop="5dp" >....

The ListFragment

import android.support.v4.app.DialogFragment;import com.actionbarsherlock.app.SherlockListFragment;import com.actionbarsherlock.view.ActionMode;import com.actionbarsherlock.view.Menu;public final class LibraryFragment        extends SherlockListFragment{    private MyListAdapter adapter;    private ListView list;    // if ActoinMode is null - assume we are in normal mode    private ActionMode actionMode;    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,            Bundle savedInstanceState)    {        View v = inflater.inflate(R.layout.fragment_library, null);        this.list = (ListView) v.findViewById(android.R.id.list);        this.initListView();        return v;    }    @Override    public void onPause()    {        super.onPause();        if (this.actionMode != null) {            this.actionMode.finish();        }    }    @Override    public void onResume() {        super.onResume();        updateData();    }    // update ListView    protected void updateData()    {        if (adapter == null) {            return;        }        adapter.clear();        // my kinda stuff :)        File[] items = scan();        if (items != null) {            adapter.updateData(items);            if (actionMode != null) {                actionMode.invalidate();            }        }        // if empty - finish action mode.        if (actionMode != null && (files == null || files.length == 0)) {            actionMode.finish();        }    }    private void initListView()    {        this.adapter = new MyAdapter(getActivity());        this.list.setAdapter(adapter);        this.list.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener()        {            @Override            public boolean onItemLongClick(AdapterView<?> arg0,                    View arg1, int arg2, long arg3)            {                if (actionMode != null) {                    // if already in action mode - do nothing                    return false;                }                // set checked selected item and enter multi selection mode                list.setChoiceMode(AbsListView.CHOICE_MODE_MULTIPLE);                list.setItemChecked(arg2, true);                getSherlockActivity().startActionMode(                        new ActionModeCallback());                return true;            }        });        this.list.setOnItemClickListener(new AdapterView.OnItemClickListener()        {            @Override            public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,                    long arg3)            {                if (actionMode != null) {                    // the items are auomatically "checked" becaise we've set AbsListView.CHOICE_MODE_MULTIPLE before                    // starting action mode, so the only thing we have to care about is invalidating the actionmode                    actionMode.invalidate(); //invalidate title and menus.                } else {                    // do whatever you should on item click                }            }        });    }    // all our ActionMode stuff here :)    private final class ActionModeCallback            implements ActionMode.Callback    {        // " selected" string resource to update ActionBar text        private String selected = getActivity().getString(                R.string.library_selected);        @Override        public boolean onCreateActionMode(ActionMode mode, Menu menu)        {            actionMode = mode;            return true;        }        @Override        public boolean onPrepareActionMode(ActionMode mode, Menu menu)        {            // remove previous items            menu.clear();            final int checked = list.getCheckedItemCount();            // update title with number of checked items            mode.setTitle(checked + this.selected);            switch (checked) {            case 0:                // if nothing checked - exit action mode                mode.finish();                return true;            case 1:                // all items - rename + delete                getSherlockActivity().getSupportMenuInflater().inflate(                        R.menu.library_context, menu);                return true;            default:                getSherlockActivity().getSupportMenuInflater().inflate(                        R.menu.library_context, menu);                // remove rename option - because we have more than one selected                menu.removeItem(R.id.library_context_rename);                return true;            }        }        @Override        public boolean onActionItemClicked(ActionMode mode,                com.actionbarsherlock.view.MenuItem item)        {            SparseBooleanArray checked;            switch (item.getItemId()) {            case R.id.library_context_rename:                // the rename action is present only when only one item is selected.                 // so when the first checked item found, show the dialog and break                checked = list.getCheckedItemPositions();                for (int i = 0; i < checked.size(); i++) {                    final int index = checked.keyAt(i);                    if (checked.get(index)) {                        final DialogFragment d = RenameDialog.instantiate(adapter.getItem(index).getFile(), LibraryFragment.this);                        d.show(getActivity().getSupportFragmentManager(), "dialog");                        break;                    }                }                return true;            case R.id.library_context_delete:                // delete every checked item                checked = list.getCheckedItemPositions();                for (int i = 0; i < checked.size(); i++) {                    final int index = checked.keyAt(i);                    if (checked.get(index)) {                        adapter.getItem(index).getFile().delete();                    }                }                updateData();                return true;            default:                return false;            }        }        @Override        public void onDestroyActionMode(ActionMode mode)        {            list.clearChoices();            //workaround for some items not being unchecked.            //see http://stackoverflow.com/a/10542628/1366471            for (int i = 0; i < list.getChildCount(); i++) {                (list.getChildAt(i).getBackground()).setState(new int[] { 0 });            }            list.setChoiceMode(AbsListView.CHOICE_MODE_NONE);            actionMode = null;        }    }

your solution is the best and easiest solution for this thread. But there is a tiny issue in the getView() - refer back to my comments above.

int version = android.os.Build.VERSION.SDK_INT;     if(version < 11){    if (checkedItems.contains(Integer.valueOf(position))) {        convertView.getBackground().setState(                new int[] { android.R.attr.state_checked });    } else {        convertView.getBackground().setState(                new int[] { -android.R.attr.state_checked });    }}else{    if (checkedItems.contains(Integer.valueOf(position))) {        convertView.setActivated(true);    } else {        convertView.setActivated(false);            }}

This will give you full support from API8 to API18