Flutter.io(dart) - 如何创建左侧填充覆盖？

Question

在Flutter中,容器有填充:

padding: const EdgeInsets.only(
  left: MyMeasurements.globalLeftPadding,
  right: 20.0,
),

我希望能够覆盖"左".

如果我这样做,我会收到运行时错误:

class MySectionHeader extends StatelessWidget {
    final double left;

MySectionHeader({
  this.left,
});

// down to the widget body
padding: const EdgeInsets.only(
  left: left ?? MyMeasurements.globalLeftPadding,
  right: 20.0,
),

// and in the container that has the override...
new MySectionHeader(
  left: 12.0,
),

这也会出现运行时错误:

padding: const EdgeInsets.only(
  left: left ?? 14.0,
  right: 20.0,
),

// and in the container that has the override...
new MySectionHeader(
  left: 12.0,
),

建议？

Answer 1

您不能同时使用const构造函数和动态内容。这样做new EdgeInsets.only(，而不是