问android - setItemChecked不工作

EN

        alertDialogBuilder.setMultiChoiceItems(R.array.list_array, list_values, new DialogInterface.OnMultiChoiceClickListener() {
        public void onClick(DialogInterface dialog, int item, boolean isChecked) {
            Toast.makeText(getContext(), "You have selected " + list[item], Toast.LENGTH_SHORT).show();
        }
    });
    alertDialogBuilder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int id) {
            SparseBooleanArray checkedItems = ((AlertDialog) dialog).getListView().getCheckedItemPositions();
            int size = checkedItems.size();
            Toast.makeText(getContext(), "Save " + size, Toast.LENGTH_SHORT).show();
        }
    });
    alertDialog = alertDialogBuilder.create();
    if (isAlreadyOpened) {
        alertDialog.getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
        alertDialog.getListView().setItemChecked(4, true);
    }