我没有关于语法的错误，但应用程序不起作用

Question

我正在尝试制作一个标签栏并在每个标签中包含一些页面。我没有收到错误，模拟器运行应用程序，但是，它只显示标签栏及其动画，而不是我需要的其他页面。

当我在页面的按钮上设置 Widget buildPages 时出现了一些错误，因此我将 _MyAppState 类下的小部件代码关联起来。

我不确定代码的哪一部分错位了，或者是否有任何额外的功能，例如 var index;

import 'package:curved_navigation_bar/curved_navigation_bar.dart';
import 'package:flutter/material.dart';
import 'package:gg/tabBarScreens/Following.dart';
import 'package:gg/tabBarScreens/Liked%20Albums.dart';
import 'package:gg/tabBarScreens/profileTabBar.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  //State class
  @override
  _MyAppState createState() => _MyAppState();
}


class _MyAppState extends State<MyApp> {
  int page = 0;
  
  Widget buildPages(){
    var index;
    switch (index){
      case 2:
        return profileTabBar();
      case 1:
        return likedAlbums();
      case 0:
      default: 0;
      return Following();
    }
  }

  GlobalKey<CurvedNavigationBarState> _bottomNavigationKey = GlobalKey();

  @override
  Widget build(BuildContext context) {
    return MaterialApp( home: Scaffold(
        bottomNavigationBar: CurvedNavigationBar(
          key: _bottomNavigationKey,
          items: <Widget>[
            Icon(Icons.add, size: 30),
            Icon(Icons.list, size: 30),
            Icon(Icons.compare_arrows, size: 30),
          ],
          onTap: (index) {
            setState(() {
              page = index;
            });
          },
        ),
        body: buildPages(),


    ),

    );
  }
}

Answer 1

在您的 buildPages 函数中删除“var index”并在 switch statement 中将您的 variable_expression 替换为页面

  Widget buildPages() {
    switch (page) {
      case 2:
        return profileTabBar();
      case 1:
        return likedAlbums();
      case 0:
        return Following();
      default:
        return Following();
    }
  }

一个基本工作示例的完整代码，您甚至可以粘贴 here 并查看它的实际效果

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  //State class
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  int page = 0;

  Widget buildPages() {
    switch (page) {
      case 2:
        return Container(color: Colors.red);
      case 1:
        return Container(color: Colors.blue);
      case 0:
        return Container(color: Colors.green);

      default:
        return Container(color: Colors.green);
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        bottomNavigationBar: BottomNavigationBar(
          items: <BottomNavigationBarItem>[
            BottomNavigationBarItem(
              label: "",
              icon: Icon(Icons.add, size: 30),
            ),
            BottomNavigationBarItem(
              label: "",
              icon: Icon(Icons.list, size: 30),
            ),
            BottomNavigationBarItem(
              label: "",
              icon: Icon(Icons.compare_arrows, size: 30),
            ),
          ],
          onTap: (index) {
            setState(() {
              page = index;
            });
          },
        ),
        body: buildPages(),
      ),
    );
  }
}

点击第三个标签

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