Flutter笔记-There are multiple heroes that share the same tag within a subtree

在使用FloatingActionButton时报错了

floatingActionButton: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          FloatingActionButton(
            onPressed: () => _addItem(),
            child: Icon(Icons.add),
          ),
          SizedBox(
            width: 60,
          ),
          FloatingActionButton(
            onPressed: () => _removeItem(),
            child: Icon(Icons.remove),
          ),
        ],
      ),

报错内容：

════════ Exception caught by scheduler library ═════════════════════════════════
The following assertion was thrown during a scheduler callback:
There are multiple heroes that share the same tag within a subtree.

Within each subtree for which heroes are to be animated (i.e. a PageRoute subtree), each Hero must have a unique non-null tag.
In this case, multiple heroes had the following tag: 
Here is the subtree for one of the offending heroes: Hero
    tag: 
    state: _HeroState#2520e

主要问题是在使用多个FloatingActionButton时heroTag需是唯一的。

解决方案：

floatingActionButton: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          FloatingActionButton(
            heroTag: 'first',
            onPressed: () => _addItem(),
            child: Icon(Icons.add),
          ),
          SizedBox(
            width: 60,
          ),
          FloatingActionButton(
            heroTag: 'second',
            onPressed: () => _removeItem(),
            child: Icon(Icons.remove),
          ),