在Flutter定义StatefulWidget时，需要控制变量的值来更新UI，我最开始是这样写的：

List _getTabListWidget(){
    List  tabWidgets = [];
    Color c = Color(0xff666666);
    FontWeight weight = FontWeight.normal;
    for(int i = 0;i < widget.tabs.length;i++){
      if(_selectedIndex == i){
        c = Color(0xff606FFF);
        weight = FontWeight.w800;
      }
      tabWidgets.add(Text(widget.tabs[i],
          textAlign:TextAlign.center,
          style: TextStyle(
            color: c,
            fontWeight: weight,
            fontSize: widget.fontSize,
          )
      ));
    }
    return tabWidgets;
  }

然后当用户点击Tab页时执行：预期效果是能够更细Text的颜色，但实际上没执行更新，原因是_selectedIndex没有绑定到Text()上。

setState(() {
     _selectedIndex = index;
});

正确的写法是：

List _getTabListWidget(){
    List  tabWidgets = [];
    for(int i = 0;i < widget.tabs.length;i++){
      tabWidgets.add(Text(widget.tabs[i],
          textAlign:TextAlign.center,
          style: TextStyle(
            color: _selectedIndex==i?Color(0xff606FFF):Color(0xff666666),
            fontWeight: _selectedIndex==i?FontWeight.w800:FontWeight.normal,
            fontSize: widget.fontSize,
          )
      ));
    }
    return tabWidgets;
  }

解决。