嘿，我试图在flatlist中显示来自API的数据，但我不断收到以下错误消息：“不变违规：元素类型无效：预期为内置字符串（对于内置组件）或类/函数复合组件，但未定义。...检查“ UsersScreen”的渲染方法

我不确定代码的哪一部分会导致此错误

import { API,graphqlOperation } from 'aws-amplify'
import { Text,View,flatlist } from 'react-native'


const listUsers = `query listUsers {
  listUsers {
      username


  }
}`;

class UsersScreen extends Component {

  listQuery = async () => {
    console.log('listing Users');
    const allUsers = await API.graphql(graphqlOperation(listUsers));
    alert(JSON.stringify(allUsers));
  };
 render() {
  return(
    <flatlist 
    data={listUsers} 
    renderItem={({ item }) => (
      <View>
        <Text>{item.username}</Text>
      </View>
    )}
    />

  )
  }
}

export default UsersScreen;