_gridViewController = ScrollController()
…addListener(() {
print(’${_gridViewController.position}’);
});
}
//Widget build(BuildContext context)
GridView(
controller:_gridViewController,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3,crossAxisSpacing: 3, mainAxisSpacing: 3),
children: List.generate(50, (position) {
return Container(
alignment: Alignment.center,
height: 80,
color: Colors.primaries[position % Colors.primaries.length],
child: Text("$position"),
);
}),
)
3.2 效果图
3.3 ScrollController打印结果
I/flutter (16530): ScrollPositionWithSingleContext#9a250(offset: 72.8, range: 0.0…1746.0, viewport: 444.0, ScrollableState, ClampingScrollPhysics -> RangeMaintainingScrollPhysics, DragScrollActivity#d503a(ScrollDragController#59958), ScrollDirection.reverse)
I/flutter (16530): ScrollPositionWithSingleContext#9a250(offset: 77.2, range: 0.0…1746.0, viewport: 444.0, ScrollableState, ClampingScrollPhysics -> RangeMaintainingScrollPhysics, DragScrollActivity#d503a(ScrollDragController#59958), ScrollDirection.reverse)
I/flutter (16530): ScrollPositionWithSingleContext#9a250(offset: 83.2, range: 0.0…1746.0, viewport: 444.0, ScrollableState, ClampingScrollPhysics -> RangeMaintainingScrollPhysics, DragScrollActivity#d503a(ScrollDragController#59958), ScrollDirection.reverse)
四 快速创建方式：build，custom，count，extent
4.1 GridView.build
构建必须属性
-
itemBuilder是构建子控件 -
itemCount指定数据个数
代码
GridView.builder(
itemCount: 10,
controller:_gridViewController,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3,crossAxisSpacing: 3, mainAxisSpacing: 3),
itemBuilder: (context,index){
return Container(
alignment: Alignment.center,
height: 80,
color: Colors.primaries[index % Colors.primaries.length],
child: Text("$index"),
);
},
)
4.2 GridView.custom
构建必须属性
- childrenDelegate：提供子组件构建的代理，有
SliverChildBuilderDelegate和SliverChildListDelegate可用于快速构建
快速构建代码
SliverChildBuilderDelegate方式
GridView.custom(
controller:_gridViewController,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3,crossAxisSpacing: 3, mainAxisSpacing: 3),
childrenDelegate: SliverChildBuilderDelegate((context,index){
return Container(
alignment: Alignment.center,
height: 80,
color: Colors.primaries[index % Colors.primaries.length],
child: Text("$index"),
);
},childCount: 10) ,
)
SliverChildListDelegate方式
GridView.custom(
controller:_gridViewController,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 3,crossAxisSpacing: 3, mainAxisSpacing: 3),
childrenDelegate: SliverChildListDelegate(List.generate(50, (position) {
return Container(
alignment: Alignment.center,
height: 80,
color: Colors.primaries[position % Colors.primaries.length],
child: Text("$position"),
);})),
)
4.3 GridView.count
构建必须属性
crossAxisCount：交叉轴方向上个数
快速构建代码
GridView.count(
controller:_gridViewController,
crossAxisCount: 3,
children: List.generate(50, (position) {
return Container(
alignment: Alignment.center,
height: 80,
color: Colors.primaries[position % Colors.primaries.length],
child: Text("$position"),
);}),
)
4.4 GridView.extent
构建必须属性
maxCrossAxisExtent：最大的横轴范围
构建代码
GridView.extent(
controller:_gridViewController,
maxCrossAxisExtent:100,
总结
Android架构学习进阶是一条漫长而艰苦的道路，不能靠一时激情，更不是熬几天几夜就能学好的，必须养成平时努力学习的习惯。所以：贵在坚持！
上面分享的字节跳动公司2020年的面试真题解析大全，笔者还把一线互联网企业主流面试技术要点整理成了视频和PDF（实际上比预期多花了不少精力），包含知识脉络 + 诸多细节。详情可以点击我的【Github】
如果你熟练掌握【Github】中列出的知识点，相信将会大大增加你通过前两轮技术面试的几率！这些内容都供大家参考，互相学习。
就先写到这，码字不易，写的很片面不好之处敬请指出，如果觉得有参考价值的朋友也可以关注一下我
就先写到这，码字不易，写的很片面不好之处敬请指出，如果觉得有参考价值的朋友也可以关注一下我
