centerTitle

[ghost]

  Row (
    mainAxisAlignment: mainAxisAlignment,
    crossAxisAlignment: crossAxisAlignment,
    children: <Widget>[
      leading ??
          const BackButton(
            onPressed: null,
          ),
      titleWidget,
      actions ?? Container(),
    ],
  );

改成

  Stack(
    alignment: Alignment.center,
    children: [
      Row (
        mainAxisAlignment: mainAxisAlignment,
        crossAxisAlignment: crossAxisAlignment,
        children: <Widget>[
          leading ??
              const BackButton(
                onPressed: null,
              ),
          const Spacer(),
          actions ?? Container(),
        ],
      ),
      titleWidget,
    ],
  );

才能让title居中,不然 两边不一样(指有leading没actions)就不是居中的了

[zmtzawqlp]

1，leading,action可以放Containter 2. 组件只是个简单例子。要复制一份是很简单。