怎么动态修改适配器中的背景色

SimpleAdapter adapter = new SimpleAdapter(this, items, R.layout.scontent,
             new String[] {"ls_content","ls_name","ls_time","ls_back"},
             new int[] {R.id.ls_content,R.id.ls_name, R.id.ls_time,R.id.layout});
     adapter.notifyDataSetChanged();
其中 R.id.layout 这种表现出来的是值text是"ls_back"
我想改成 R.id.layout.background但是报错，，请问怎么改啊