如何实现延迟加载

Question

我有一个ListView一次加载 10 个项目。 当我到达列表末尾时，我一次添加 10 个元素，因为我试图实现延迟加载 ListView，但我的问题是当我的列表中有 26 个元素时，它会加载前 20 个，但之后显示最后 6 个并显示剩余 4 个的范围错误。有人可以帮我解决这个问题吗？ 这是我迄今为止的尝试-

NotificationListener<ScrollNotification>(
      onNotification: (ScrollNotification notification) {
        if (notification is ScrollEndNotification) {
          if (notification.metrics.extentBefore ==
              notification.metrics.maxScrollExtent) {
             if(listView.length%10 == listView.length%counter) {
                counter+=10;
          } else {
                count.value = gameList.value.length%10;
//error comes when the total value of list is NOT a multiple of 10 (causes range error)
              }
          }
        }

Answer 1

• 替换'listView.length+=10;' 与 'listView.add(NewItemList[i]);'

作为这段代码：

NotificationListener<ScrollNotification>(
  onNotification: (ScrollNotification notification) {
    if (notification is ScrollEndNotification) {
      if (notification.metrics.extentBefore ==
          notification.metrics.maxScrollExtent) {
          for(int i=0;i<NewItemList.length;i++)
           setState(
            {listView.add(NewItemList[i]);}); //here replace
         //error comes when the total value of list is NOT a multiple of 10 (causes range error)
      }
    }

Answer 2

希望这会有所帮助。

      onNotification: (ScrollNotification notification) {
        if (notification is ScrollEndNotification) {
          if (notification.metrics.extentBefore ==
              notification.metrics.maxScrollExtent) {
             if((listView.length - counter) >= 10 ) {
                counter+=10;
          } else {
                counter += listView.length - counter;
         }
          }
        }````