如何將Navigator或Void函式作為引數傳遞給ListTileWidget-Flutter

我正在從我的主頁呼叫小部件，并將所需的資料作為引數發送。像這樣：

     AppDrawerListTile(
                      title: 'Logout',     // title of the List Tile.
                      icon: Icons.logout, // icon for the list tile.
                      action: () {       // onTap action for ListTile - which is not working
                        Navigator.push(context, MaterialPageRoute(builder: (context) => LoginPage()));
                      }),

這是自定義公共串列，我在其中獲取引數并將其提供給 ListTile。

class AppDrawerListTile extends StatelessWidget {
  final String title;
  final IconData icon;
  final Function action;
  const AppDrawerListTile({
    Key? key,
    required this.title,
    required this.icon,
    required this.action,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ListTile(
      minVerticalPadding: 0,
      title: title.text.make().p0(),
      dense: true,
      // visualDensity: const VisualDensity(horizontal: -2, vertical: -3),
      // leading: Image(image: AssetImage('assets/images/mmsc_logo.png')),
      leading: Icon(icon),
      minLeadingWidth: 5,
      onTap: () => action, // Here I want the passed navigator function to work.
    );
  }
}

除了 onTap 操作方法外，一切都在這里作業，我不明白，我應該將變數宣告為 Function 還是其他？

uj5u.com熱心網友回復：

您只需在小部件中創建一個型別并將其用作建構式引數。

例如：

//here declare the type
typedef TypeNameYouWant = void Function();

class AppDrawerListTile extends StatelessWidget {
  final String title;
  final IconData icon;
  final TypeNameYouWant action; //here use the type declared
  const AppDrawerListTile({
    Key? key,
    required this.title,
    required this.icon,
    required this.action,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
        return ListTile(
          minVerticalPadding: 0,
          title: title.text.make().p0(),
          dense: true,
      // visualDensity: const VisualDensity(horizontal: -2, vertical: -3),
      // leading: Image(image: AssetImage('assets/images/mmsc_logo.png')),
      leading: Icon(icon),
      minLeadingWidth: 5,
      onTap: () => action(), // Here you use your action param like a fn
    );
  }
}

uj5u.com熱心網友回復：

使用 VoidCallback 代替函式

final VoidCallback action;

uj5u.com熱心網友回復：

只需在課堂( )上添加，代碼應該是actionAppDrawerListTile

onTap: () => action(),

完整代碼

class AppDrawerListTile extends StatelessWidget {
  final String title;
  final IconData icon;
  final Function action;
  const AppDrawerListTile({
    Key? key,
    required this.title,
    required this.icon,
    required this.action,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ListTile(
      minVerticalPadding: 0,
      title: title.text.make().p0(),
      dense: true,
      // visualDensity: const VisualDensity(horizontal: -2, vertical: -3),
      // leading: Image(image: AssetImage('assets/images/mmsc_logo.png')),
      leading: Icon(icon),
      minLeadingWidth: 5,
      onTap: () => action(), // Here I want the passed navigator function to work.
    );
  }
}

為什么？

如果沒有()標志，則表示onTap呼叫匿名函式，該函式回傳action并且不呼叫action.

() => action // returns action

// similar to
(){
 return action;
}

如果添加()符號，則表示onTap呼叫匿名函式，匿名函式呼叫action函式。

() => action() // calls action

// similar to
(){
  action();
}

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