Question

尝试使用 sticky header 环绕 GridView.builder 小部件，因为当用户向下滚动屏幕时，我希望有一个标题跟随，但得到“NoSuchMethodError: The getter 'position' was called on null. Receiver: null 尝试调用: position 另见: https://flutter.dev/docs/testing/errors". 我使用这个相同的小部件来包裹一个 Column 小部件。我尝试用 Container、Column 和其他小部件包裹 GridView。我只会得到其他错误。这个错误是什么意思？

return _stickyHeader.render(
        headerChild: Text(''),
        content: GridView.builder(
          shrinkWrap: true,
          physics: ScrollPhysics(),
          gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
            crossAxisCount: 2,
            crossAxisSpacing: 5.0,
            mainAxisSpacing: 5.0,
          ),
          itemCount: state.avatarUrlList.length,
          itemBuilder: (BuildContext context, int index) {
            if (index == state.currentSelectedAvatarIndex) {
              return Center(
                child: InkWell(
                  onTap: () => _onAvatarImageClicked(
                      state.avatarUrlList[index], index),
                  child: Container(
                    decoration: BoxDecoration(
                      shape: BoxShape.circle,
                      border: Border.all(
                        color: Colors.red,
                        width: 4.0,
                      ),
                    ),
                    child: CircleAvatar(
                      radius: 60,
                      backgroundColor: Colors.transparent,
                      backgroundImage:
                      NetworkImage(state.avatarUrlList[index]),
                    ),
                  ),
                ),
              );
            } else {
              return Center(
                child: InkWell(
                  onTap: () => _onAvatarImageClicked(
                      state.avatarUrlList[index], index),
                  child: CircleAvatar(
                    radius: 60,
                    backgroundColor: Colors.transparent,
                    backgroundImage:
                    NetworkImage(state.avatarUrlList[index]),
                  ),
                ),
              );
            }
          },
        ),
      );
    }




Widget render({Widget headerChild, Widget content}) {
return StickyHeader(
  header: Container(
    decoration: BoxDecoration(
      color: ThemeConstants.ceruleanCrayola,
      borderRadius: BorderRadius.circular(15),
    ),
    height: 50.0,
    padding: EdgeInsets.symmetric(horizontal: 16.0),
    margin: EdgeInsets.symmetric(horizontal: 20.0),
    alignment: Alignment.centerLeft,
    child: headerChild,
  ),
  content: content,
);

}

Answer 1

基于https://pub.dev/packages/sticky_headers

<块引用>

您可以在任何可滚动内容中放置 StickyHeader 或 StickyHeaderBuilder，例如：ListView、GridView、CustomScrollView、SingleChildScrollView 或类似内容。

您可能需要尝试将 StickyHeader 设置为 SingleChildScrollView 以进行基本操作。

当粘性标头用于环绕 GirdView.builder 小部件时，颤动“NoSuchMethodError：getter 'position' was called on null”

1 个答案: