安卓-如何从子AlertDialog更新父AlertDialog

AlertDialog.Builder parentBuilder = new AlertDialog.Builder(MainActivity.this);
parentBuilder.setTitle("父AlertDialog");
parentBuilder.setMessage("点击按钮以显示子AlertDialog");
parentBuilder.setPositiveButton("显示子AlertDialog", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        // 在这里显示子AlertDialog
        showDialogChild();
    }
});
AlertDialog parentDialog = parentBuilder.create();
parentDialog.show();

private void showDialogChild() {
    AlertDialog.Builder childBuilder = new AlertDialog.Builder(MainActivity.this);
    childBuilder.setTitle("子AlertDialog");
    childBuilder.setMessage("点击按钮以更新父AlertDialog");
    childBuilder.setPositiveButton("更新父AlertDialog", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            // 在这里更新父AlertDialog
            updateParentDialog();
        }
    });
    AlertDialog childDialog = childBuilder.create();
    childDialog.show();
}

private void updateParentDialog() {
    AlertDialog parentDialog = (AlertDialog) MainActivity.this.findViewById(R.id.parent_dialog);
    if (parentDialog != null) {
        parentDialog.setMessage("父AlertDialog已被更新");
    }
}