Flutter混合开发iOS集成填坑

Flutter因为优秀的跨平台开发效率受到很多开发者的青睐。对于大多数开发者来说，可能会优先考虑采用混合开发方案。Flutter也给出了混合开发的解决方案：Add Flutter to existing apps。这篇文档中已经给出了详细的解决方案，本文就不再赘述。本文主要介绍我在集成过程中踩过的坑和解决办法。

1. 编译过程中环境变量找不到

• FLUTTER_ROOT
  在~/.bash_profile中增加以下几行代码

export FLUTTER_ROOT=${Your_Flutter_Install_Path}
export PATH=$FLUTTER_ROOT/bin:$PATH

然后执行source ~/.bash_profile

• DART_SDK
  在~/.bash_profile中增加以下几行代码

export DART_SDK=${FLUTTER_ROOT}/bin/cache/dart-sdk
export PATH=${DART_SDK}/bin:$PATH

然后执行source ~/.bash_profile

• FLUTTER_APPLICATION_PATH
  在Run Script Phase之前加入这个变量的定义，完整的Script文件如下：

export FLUTTER_APPLICATION_PATH=${Your_Flutter_Application_Path}
"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" build
"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" embed

2. 内存泄漏
   Flutter内存泄漏问题由来已久，手把手教你解决 Flutter engine 内存泄漏这篇文章介绍了如何解决内存泄漏问题，可能是我的使用方法不对，按照这篇文章的方法每次进入FlutterViewController之后还是发现会多一个Isolate，意味着还是会有内存泄漏。最后我将FlutterViewController封装成了一个单例解决了这个问题。但是这样解决会存在另外一个问题：FlutterViewController有多个route的时候，第二次进入的route不会刷新，解决方案在下面。

3. 多个flutter route界面不刷新
   这个问题我参考了这个issue，但是发现写完以后并不能运行。然后查看了我的Flutter安装包，发现安装包这个目录下integration_tests并没有ios_add2app这个工程，查看GitHub上的Flutter代码发现master分支上是有这个工程的，所以决定升级Flutter，考虑到稳定性，只将Flutter升级到了beta版本。升级命令如下：

flutter channel beta
flutter upgrade

升级之后可以参考integration_tests目录下的ios_add2app这个工程来修改代码了。

最新的stable版本已经支持了这个功能

4. Failed to find assets path for "flutter_assets"
   重新切换以下flutter channel即可

flutter channel master
flutter channel beta

5. 上传App Store报错
   错误信息如下：

ERROR ITMS-90087: “Unsupported Architectures. The executable for YourApp.app/Frameworks/Flutter.framework contains unsupported architecture ‘[x86_64]’”

ERROR ITMS-90209: “Invalid Segment Alignment. The app binary at ‘YourApp.app/Frameworks/Flutter.framework/Flutter’ does not have proper segment alignment. Try rebuilding the app with the latest Xcode version.”

ERROR ITMS-90125: “The binary is invalid. The encryption info in the LC_ENCRYPTION_INFO load command is either missing or invalid, or the binary is already encrypted. This binary does not seem to have been built with Apple’s linker.”

WARNING ITMS-90080: “The executable ‘Payload/YourApp.app/Frameworks/Flutter.framework’ is not a Position Independent Executable. Please ensure that your build settings are configured to create PIE executables. For more information refer to Technical Q&A QA 1788 - Building a Position Independent Executable in the iOS Developer Library.”

解决方案：
在Xcode Build Phase的Run Script Phase最下面新增一行：

"$FLUTTER_ROOT/packages/flutter_tools/bin/xcode_backend.sh" thin

6. 'Flutter/Flutter.h' file not found
   在Flutter工程目录下执行flutter run，之后在iOS工程执行pod install，重新编译iOS主工程

7. 新增image不显示
   在Flutter工程下执行

flutter packages upgrade
flutter run

之后在iOS工程执行pod install，重新编译iOS主工程