0

我的应用程序上有一个 cupertino bottom_tab_bar，但是每次我点击其中一个图标来更改页面时，调试控制台都会显示：

════════ 手势捕捉到异常═════════════════════════════════════════════════════════ ═════</p>

在 null 上调用了方法“jumpToPage”。

接收方：空

尝试调用：jumpToPage(2)

══════════════════════════════════════════════════ ══════════════════════════════

它不会改变页面。

我的飞镖代码：

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:fluttershare/pages/activity_feed.dart';
import 'package:fluttershare/pages/profile.dart';
import 'package:fluttershare/pages/search.dart';
import 'package:fluttershare/pages/timeline.dart';
import 'package:fluttershare/pages/upload.dart';
import 'package:google_sign_in/google_sign_in.dart';

final GoogleSignIn googleSignIn = GoogleSignIn();

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  bool isAuth = false;
  PageController pageController;
  int pageIndex = 0;

  @override
  void initState() {
    super.initState();
    pageController = PageController();
    // Detects when user signed in
    googleSignIn.onCurrentUserChanged.listen((account) {
      handleSignIn(account);
    }, onError: (err) {
      print('Error signing in: $err');
    });
    // Reauthenticate user when app is opened
    googleSignIn.signInSilently(suppressErrors: false).then((account) {
      handleSignIn(account);
    }).catchError((err) {
      print('Error signing in: $err');
    });
  }

  handleSignIn(GoogleSignInAccount account) {
    if (account != null) {
      print('User signed in!: $account');
      setState(() {
        isAuth = true;
      });
    } else {
      setState(() {
        isAuth = false;
      });
    }
  }

  @override
  void dispose() {
    pageController.dispose();
    super.dispose();
  }

  login() {
    googleSignIn.signIn();
  }

  logout() {
    googleSignIn.signOut();
  }

  onPageChanged(int pageIndex) {
    setState(() {
      this.pageIndex = pageIndex;
    });
  }

  onTap(int pageIndex) {
    pageController.jumpToPage(
      pageIndex,
    );
  }

  Scaffold buildAuthScreen() {
    return Scaffold(
      body: PageView(
        children: <Widget>[
          Timeline(),
          ActivityFeed(),
          Upload(),
          Search(),
          Profile(),
        ],
        controller: pageController,
        onPageChanged: onPageChanged,
        physics: NeverScrollableScrollPhysics(),
      ),
      bottomNavigationBar: CupertinoTabBar(
          currentIndex: pageIndex,
          onTap: onTap,
          activeColor: Theme.of(context).primaryColor,
          items: [
            BottomNavigationBarItem(icon: Icon(Icons.whatshot)),
            BottomNavigationBarItem(icon: Icon(Icons.notifications_active)),
            BottomNavigationBarItem(
              icon: Icon(
                Icons.photo_camera,
                size: 35.0,
              ),
            ),
            BottomNavigationBarItem(icon: Icon(Icons.search)),
            BottomNavigationBarItem(icon: Icon(Icons.account_circle)),
          ]),
    );
    // return RaisedButton(
    //   child: Text('Logout'),
    //   onPressed: logout,
    // );
  }

  Scaffold buildUnAuthScreen() {
    return Scaffold(
      body: Container(
        decoration: BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.topRight,
            end: Alignment.bottomLeft,
            colors: [
              Theme.of(context).accentColor,
              Theme.of(context).primaryColor,
            ],
          ),
        ),
        alignment: Alignment.center,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            Text(
              'FlutterShare',
              style: TextStyle(
                fontFamily: "Signatra",
                fontSize: 90.0,
                color: Colors.white,
              ),
            ),
            GestureDetector(
              onTap: login,
              child: Container(
                width: 260.0,
                height: 60.0,
                decoration: BoxDecoration(
                  image: DecorationImage(
                    image: AssetImage(
                      'assets/images/google_signin_button.png',
                    ),
                    fit: BoxFit.cover,
                  ),
                ),
              ),
            )
          ],
        ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return isAuth ? buildAuthScreen() : buildUnAuthScreen();
  }
}

Flutter 版本：已经是最新的。Flutter 已经在频道测试版上更新 Flutter 1.14.6 • 频道测试版 • https://github.com/flutter/flutter.git 框架 • 修订版 fabeb2a16f（4 周前） • 2020-01-28 07:56:51 -0800 引擎 • 修订版 c4229bfbba 工具 • Dart 2.8.0（内部版本 2.8.0-dev.5.0 fc3af737c7）

4

1 回答 1

0

首先，我建议不要为了onTap()保持良好实践而命名方法。

在您的情况下，在您的情况下，当您在Widget的属性pageIndex中调用方法时，您没有指定或提供值。这应该是正确的方法，也应该解决问题onTapCupertinoTabBar

      bottomNavigationBar: CupertinoTabBar(
          currentIndex: pageIndex,
          onTap: onTap(pageIndex),
    //rest of your code

由于您没有提供 a pageIndex，因此它将值作为 null 并尝试jumpToPage在 null 值上调用该方法。

于 2020-02-28T12:53:39.317 回答