一、引入qr_code_scanner: ^0.7.0出现的问题
1.在flutter项目中的pubspec.yaml引入qr_code_scanner: ^0.7.0后，编译项目，fluter项目中出现的问题如下：
Launching lib/main.dart on 王淑宁的iPhone in debug mode...
Automatically signing iOS for device deployment using specified development team in Xcode project: N7XTE6J8P8
CocoaPods' output:
↳
Preparing
Analyzing dependencies
Inspecting targets to integrate
Using `ARCHS` setting to build architectures of target `Pods-Runner`: (``)
Fetching external sources
-> Fetching podspec for `Flutter` from `Flutter`
-> Fetching podspec for `qr_code_scanner` from `.symlinks/plugins/qr_code_scanner/ios`
Resolving dependencies of `Podfile`
CDN: trunk Relative path: CocoaPods-version.yml exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: all_pods_versions_0_2_a.txt exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.11/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.11/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.10/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.9/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.8/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.7/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.6/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.5/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.3/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.2/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.1/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/5.0.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/4.0.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/3.1.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/3.0.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/2.1.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/2.0.3/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/2.0.2/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/2.0.1/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.9.1/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.9.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.11/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.10/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.9/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.8/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.7/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.6/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.5/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.4/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.3/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.1/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.8.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.7.1/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.7.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.6.1/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.6.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.5.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.4.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.3.2/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.3.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.2.0/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/1.1.18/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/0.1.8/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/0.1.7/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/0.1.6/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/0.1.5/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/0.1.4/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/0.1.3/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/0.1.2/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
CDN: trunk Relative path: Specs/0/2/a/MTBBarcodeScanner/0.1.1/MTBBarcodeScanner.podspec.json exists! Returning local because checking is only performed in repo update
Comparing resolved specification to the sandbox manifest
A Flutter
A MTBBarcodeScanner
A qr_code_scanner
Downloading dependencies
-> Installing Flutter (1.0.0)
-> Installing MTBBarcodeScanner (5.0.11)
> Copying MTBBarcodeScanner from `/Users/ningspeals/Library/Caches/CocoaPods/Pods/Release/MTBBarcodeScanner/5.0.11-f453b` to `Pods/MTBBarcodeScanner`
-> Installing qr_code_scanner (0.2.0)
- Running pre install hooks
[!] The following Swift pods cannot yet be integrated as static libraries:
The Swift pod `qr_code_scanner` depends upon `MTBBarcodeScanner`, which does not define modules. To opt into those targets generating module maps (which is necessary to import them from Swift when building as static libraries), you may set `use_modular_headers!` globally in your Podfile, or specify `:modular_headers => true` for particular dependencies.
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.11.3/lib/cocoapods/installer/xcode/target_validator.rb:151:in `verify_swift_pods_have_module_dependencies'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.11.3/lib/cocoapods/installer/xcode/target_validator.rb:40:in `validate!'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.11.3/lib/cocoapods/installer.rb:597:in `validate_targets'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.11.3/lib/cocoapods/installer.rb:163:in `install!'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.11.3/lib/cocoapods/command/install.rb:52:in `run'
/Library/Ruby/Gems/2.6.0/gems/claide-1.0.3/lib/claide/command.rb:334:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.11.3/lib/cocoapods/command.rb:52:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.11.3/bin/pod:55:in `<top (required)>'
/usr/local/bin/pod:25:in `load'
/usr/local/bin/pod:25:in `<main>'
Error output from CocoaPods:
↳
[!] Automatically assigning platform `iOS` with version `9.0` on target `Runner` because no platform was specified. Please specify a platform for this target in your Podfile. See `https://guides.cocoapods.org/syntax/podfile.html#platform`.
Exception: Error running pod install
Exited (sigterm)
2.用Xcode打开IOS项目，编译项目，出现的问题如图1：
图1
二、解决问题的方法
出现上述问题的原因
1.网络原因，下载GitHub项目需要翻墙，也就是需要VPN代理解决；
打开终端，输入VPN代理命令（eg：export https_proxy=http://127.0.0.1:7890 http_proxy=http://127.0.0.1:7890 all_proxy=socks5://127.0.0.1:7890），cd到相应的iOS目录中，pod update 或 pod install，具体操作步骤如图2：
图2
2.上图中错误有两种原因导致，Xcode中的Podfile文件中没有引入use_frameworks!或者没有引入use_modular_headers!
打开Xcode中的Podfile文件，引入use_frameworks!或use_modular_headers!，具体操作如图3所示（在图中圈出地方引入）：
图3
3.ios 链接库的问题
操作完1.2后，在编译iOS项目，出现ld: library not found for -lXXX，这里的处理方式是：在iOS项目中打开Build Settings -> Other Link Flags 打开以后，发现里面存在对应的库名称，前面还有一个前缀修饰： -lxxx，把和flutter相关的全部都删掉，然后commod + R。
