Flutter通过Container实现时间轴效果
时间轴是前端UI经常用到的效果,先看下效果图:
时间轴的特点
1、在列表中的高度不确定,高度取决于右侧 item 的高度
2、时间轴通常在第一个 item 中的样式和其他 item 中不同。
实现
一、借助 Container 中 decoration 属性,设置左侧的 border,可以实现时间轴高度随着 item 变化效果
Center( child: Container( width: 100, height: 100, decoration: BoxDecoration( // 设置 BoxDecoration 的 border, border 的高度就是 Container 的高度 border: Border(left: BorderSide(color: Colors.red)), color: Color(0x11000000), ), ))
效果 (图中红线是 Container 左侧的 border,可以在这里扩展成 timeline) :
二、重写 BorderDirectional 中 paint 方法
BorderDirectional 中原来的 paint 方法,可以看出,设置不同的属性,会调用不同的绘制方法实现不同的效果,这里重新 paint 方法,实现时间轴的效果
paint 方法中参数
canvas : 这个就是画布了,借助这个 canvas 可以随意实现各种效果
rect : Container 的范围大小
我们的 paint 方法实现,按照 UI 设计图,对应的位置画上圆和线就可以了
@override void paint(Canvas canvas, Rect rect, {TextDirection? textDirection, BoxShape shape = BoxShape.rectangle, BorderRadius? borderRadius}) { if (position != 1) { canvas.drawLine(Offset(rect.left+margin + radius / 2, rect.top), Offset(rect.left +margin+ radius / 2, rect.bottom), _strokePaint()); canvas.drawCircle(Offset(rect.left +margin+ radius / 2, rect.top + radius * 2), radius, _fillPaint()); canvas.drawCircle(Offset(rect.left +margin+ radius / 2, rect.top + radius * 2), radius,_strokePaint()); } else { canvas.drawLine(Offset(rect.left+margin + radius / 2, rect.top + radius * 2), Offset(rect.left+margin + radius / 2, rect.bottom), _strokePaint()); canvas.drawCircle(Offset(rect.left+margin + radius / 2, rect.top + radius * 2), radius, _fillPaint()); canvas.drawCircle(Offset(rect.left +margin+ radius / 2, rect.top + radius * 2), radius, _strokePaint()); canvas.drawCircle(Offset(rect.left +margin+ radius / 2, rect.top + radius * 2), radius / 2, _strokePaint()); } }
最终效果
三、完整代码
class BorderTimeLine extends BorderDirectional { int position; BorderTimeLine(this.position); double radius = 10; double margin= 20; Paint _paint = Paint() ..color = Color(0xFFDDDDDD) ..strokeWidth = 1; @override void paint(Canvas canvas, Rect rect, {TextDirection? textDirection, BoxShape shape = BoxShape.rectangle, BorderRadius? borderRadius}) { if (position != 0) { canvas.drawLine(Offset(rect.left+margin + radius / 2, rect.top), Offset(rect.left +margin+ radius / 2, rect.bottom), _strokePaint()); canvas.drawCircle(Offset(rect.left +margin+ radius / 2, rect.top + radius * 2), radius, _fillPaint()); canvas.drawCircle(Offset(rect.left +margin+ radius / 2, rect.top + radius * 2), radius,_strokePaint()); } else { canvas.drawLine(Offset(rect.left+margin + radius / 2, rect.top + radius * 2), Offset(rect.left+margin + radius / 2, rect.bottom), _strokePaint()); canvas.drawCircle(Offset(rect.left+margin + radius / 2, rect.top + radius * 2), radius, _fillPaint()); canvas.drawCircle(Offset(rect.left +margin+ radius / 2, rect.top + radius * 2), radius, _strokePaint()); canvas.drawCircle(Offset(rect.left +margin+ radius / 2, rect.top + radius * 2), radius / 2, _strokePaint()); } } Paint _fillPaint(){ _paint.color=Colors.white; _paint.style=PaintingStyle.fill; return _paint; } Paint _strokePaint(){ _paint.color=Color(0xFFDDDDDD); _paint.style=PaintingStyle.stroke; return _paint; } }
在 ListView 中的 item 中使用
Widget _buildItem(BuildContext c, int i) { return Container( width: double.infinity, padding: EdgeInsets.symmetric(horizontal: 20), decoration: BoxDecoration(border: BorderTimeLine(i)), child: Padding( padding: const EdgeInsets.symmetric(horizontal: 20), child: Column(crossAxisAlignment: CrossAxisAlignment.start, mainAxisSize: MainAxisSize.min, children: [ Padding(padding: EdgeInsets.symmetric(vertical: 10)), Divider(color: Colors.grey.shade300, thickness: 40), Text("$i" * 6, style: TextStyle(color: Colors.black, fontSize: 16)), Text("abc\n" * Random().nextInt(10)), Padding(padding: EdgeInsets.symmetric(vertical: 10)), ]), )); }
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