安卓应用提示Error:(18, 79) 错误: 找不到符号 符号: 变量 layout 位置: 类 id

打算简单实现一个listview，但是layout部分一直提示cannot，不符合能在网上找到的各个情况，头秃

private String data[]={"aa","bb","cc","dd","aa","bb","cc","dd","aa","bb","cc","dd","aa","bb","cc","dd",};
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ListView listView=(ListView)findViewById(R.id.listview);
    ArrayAdapter<String>adapter=new ArrayAdapter<String>(this,android.R.id.layout. simple_list_item_1,data);
    listView.setAdapter(adapter);
}