flutter-登录token本地存储(shared_preferences)、路由拦截

App一般都会遇到这样的需求：没有登录则跳转登录页面，登录了则跳转至指定页面。

思路：

1.登录之后存储token。

2.路由拦截，没有登录则跳转至登录页面，登录了则跳转至指定页面。

步骤：

一：首先在pubspec.yaml中添加shared_preferences依赖库

shared_preferences: ^2.0.17

整个pubspec.yaml如下所示：

name: flutter_doctor_app
description: A new Flutter application.

# The following line prevents the package from being accidentally published to
# pub.dev using `pub publish`. This is preferred for private packages.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1

environment:
  sdk: ">=2.19.2 <3.0.0"

dependencies:
  flutter:
    sdk: flutter


  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS