Flutter构造方法两种写法

第一种写法(常见写法)

class NavigationIconView {
  NavigationIconView ( Widget icon, Widget title, TickerProvider vsync) {
    this.item = new BottomNavigationBarItem(
      icon: icon,
      title: title,
    );

    this.controller = new AnimationController(
      duration: kThemeAnimationDuration,
      vsync: vsync
    );
  }
}

第二种写法

class NavigationIconView {
  NavigationIconView ({
    Widget icon,
    Widget title,
    TickerProvider vsync,
  }) :
  item = new BottomNavigationBarItem(
      icon: icon,
    title: title,
  ),
  controller = new AnimationController(
      duration: kThemeAnimationDuration,
      vsync: vsync
  );
}

在调用上的区别:
第一种调用

  _navigationViews = <NavigationIconView> [
      new NavigationIconView(new Icon(Icons.assessment), new Text('首页'), this),
      new NavigationIconView(new Icon(Icons.all_inclusive), new Text("想法"), this),
      new NavigationIconView(new Icon(Icons.add_shopping_cart), new Text("市场"), this),
      new NavigationIconView(new Icon(Icons.add_alert), new Text("通知"), this),
      new NavigationIconView(new Icon(Icons.perm_identity), new Text("我的"), this),
    ];

第二种调用

 _navigationViews = <NavigationIconView> [
      new NavigationIconView(
         icon: new Icon(Icons.assessment),
        title: new Text('首页'),
        vsync: this,
    ),
      new NavigationIconView(
        icon: new Icon(Icons.all_inclusive),
        title: new Text("想法"),
        vsync: this,
      ),
      new NavigationIconView(
        icon: new Icon(Icons.add_shopping_cart),
        title: new Text("市场"),
        vsync: this,
      ),
      new NavigationIconView(
        icon: new Icon(Icons.add_alert),
        title: new Text("通知"),
        vsync: this,
      ),
      new NavigationIconView(
        icon: new Icon(Icons.perm_identity),
        title: new Text("我的"),
        vsync: this,
      ),
];

对比可以看出,第二种写法在调用时,代码可读性更好,推荐第二种写法.