本文主要针对现有iOS项目想接入flutter，怎么接入flutter，如何进行项目管理，以及Native和flutter之间如何调用，如何调试来讲解的。
一、创建Flutter Module
执行下面的命令创建Flutter Moudle
cd some/path/
flutter create --template module my_flutter
some/path/是你要存放工程的目录，然后创建flutter Module，这一步要注意，不要创建成flutter project项目了，执行命令后，控制台会打印：
Creating project my_flutter... androidx: true
my_flutter/test/widget_test.dart (created)
my_flutter/my_flutter.iml (created)
my_flutter/.gitignore (created)
my_flutter/.metadata (created)
my_flutter/pubspec.yaml (created)
my_flutter/README.md (created)
my_flutter/lib/main.dart (created)
my_flutter/my_flutter_android.iml (created)
my_flutter/.idea/libraries/Flutter_for_Android.xml (created)
my_flutter/.idea/libraries/Dart_SDK.xml (created)
my_flutter/.idea/modules.xml (created)
my_flutter/.idea/workspace.xml (created)
Running "flutter pub get" in my_flutter... 1.8s
Wrote 12 files.
All done!
Your module code is in my_flutter/lib/main.dart.
创建完成以后my_flutter文件结构如下：
my_flutter/
├── .ios/
│ ├── Runner.xcworkspace
│ └── Flutter/podhelper.rb
├── lib/
│ └── main.dart
├── test/
└── pubspec.yaml
接下来可以在lib中添加代码逻辑，在pubspec.yaml中，添加依赖的packages和plugins。
二、集成方式
1.使用CocoaPods和Flutter SDK集成
这个方案是针对高于Flutter 1.8.4-pre.21版本的SDK的混编方案，如果使用之前的SDK，请查看Upgrading Flutter added to existing iOS Xcode project和Add Flutter to existing apps
1.1 Podfile 中添加下面配置
flutter_application_path = '../my_flutter'
load File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')
../my_flutter是你flutter Moudle存放的目录，这里my_flutter存放在profile的上一级目录，所以这么写。
1.2 Podfile target 中添加install_all_flutter_pods(flutter_application_path)
target 'MyApp' do
install_all_flutter_pods(flutter_application_path)
end
这里的MyApp就是对应iOS项目的名称，存放到自己项目对应target中就好了。
1.3 pod install
在Podfile所在目录，执行pod install，如果没问题，会在你的项目中增加以下依赖：
Installing Flutter (1.0.0)
Installing FlutterPluginRegistrant (0.0.1)
Installing my_flutter (0.0.1)
在执行pod install以后，如果没有增加上面👆的依赖，那么可能是工程有问题。
问题1.Profile中路径添加错误或者my_flutter是Flutter project，不是Flutter Moudle
提示错误如下：
[!] Invalid `Podfile` file: cannot load such file -- ./my_flutter/.ios/Flutter/podhelper.rb.
# from /Users/Example/Podfile:10
# -------------------------------------------
#
> load File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')
#
# -------------------------------------------
这时候要检查下flutter_application_path是否正确，如果正确，查看下my_flutter是否是Flutter project，可以查看下my_flutter是否包含，.iOS这个文件，注意这是一个隐藏文件，先要在电脑中设置成显示隐藏你文件，再进行查看确认，如果包含则是Moudle，不包含则是project。
问题2.项目签名不对
在my_flutter目录下运行如下命令：
open -a Simulator
flutter build ios
查看能否正确运行，如果提示以下错误，则是证书问题：
It appears that your application still contains the default signing identifier.
Try replacing 'com.example' with your signing id in Xcode:
open ios/Runner.xcworkspace
Encountered error while building for device.
怎么解决这个问题？
方法一：
- 1.找到my_flutter/.ios，打开Runner.xcworkspace文件
- 2.找到Signing & Capabilities，将Signing证书配置正确就可以了(这里要配置Generic iOS Deveice)
方法二：
使用如下命令，忽略签名：
flutter build ios --release --no-codesign
配置成功之后，再次运行flutter build ios，会打印如下信息：
Automatically signing iOS for device deployment using specified development team in Xcode project:
56XB5ELH9A
Running Xcode build...
├─Building Dart code... 78.1s
├─Generating dSYM file... 0.1s
├─Stripping debug symbols... 0.0s
├─Assembling Flutter resources... 0.9s
└─Compiling, linking and signing... 2.9s
Xcode build done. 84.0s
Built
然后再次pod install应该就可以成功了。
1.4 方案优缺点
优点：
- 1.功能配置简单，方便管理。
- 2.使用CocoaPods便于集成。
缺点：
- 1.团队成员都必须配置flutter环境，否则编译不过
- 2.Native代码和Flutter代码存放在一起，会变得复杂。
2.framework方式接入
2.1生成FrameWork
首先切换到my_flutter所在目录，执行下列命令，生成framework
flutter build ios-framework --output=../Flutter/
命令执行成功后，会在my_flutter同一级目录下，产生Flutter的文件，文件结构如下：
Flutter/
├── Debug/
│ ├── Flutter.framework
│ ├── App.framework
│ ├── FlutterPluginRegistrant.framework (only if you have plugins with iOS platform code)
│ └── example_plugin.framework (each plugin is a separate framework)
├── Profile/
│ ├── Flutter.framework
│ ├── App.framework
│ ├── FlutterPluginRegistrant.framework
│ └── example_plugin.framework
└── Release/
├── Flutter.framework
├── App.framework
├── FlutterPluginRegistrant.framework
└── example_plugin.framework
2.2配置frameWork路径
在项目中找到这个路径build settings > Build Phases > Link Binary With Libraries
添加$(PROJECT_DIR)/Flutter/Release/到Framework Search Paths
配置
2.3嵌入frameWork
在项目中找到这个路径General > Frameworks，Libraries and Embedded Content
app.Framework和Flutter.FrameWork添加到项目中，就可以使用了。
问题1.Failed to find assets path for "flutter_assets"
Failed to find assets path for "flutter_assets"
[VERBOSE-2:engine.cc(114)] Engine run configuration was invalid.
如果报上面的错误，则在my_flutter中运行以下命令：
flutter clean
flutter build ios
问题2.dyld: Library not loaded: @rpath/Flutter.framework/Flutter
这个问题是说明嵌入frameWork有问题，可以检查一下，Embed Framework和Link Binary With Libraries。
Embed Framework
2.4 方案优缺点
优点：
- 1.团队成员不依赖flutter环境
缺点：
- 1.打包配置，比较麻烦，都需要手动操作。
3.使用Flutter framework和CocoaPods集成(本地)
3.1生成frameWork
在Flutter v1.13.6之后版本，支持--cocoapods参数，可以使用下面命令。
flutter build ios-framework --cocoapods --output=../Flutter/
生成如下文件结构：
Flutter/
├── Debug/
│ ├── Flutter.podspec
│ ├── App.framework
│ ├── FlutterPluginRegistrant.framework
│ └── example_plugin.framework (each plugin with iOS platform code is a separate framework)
├── Profile/
│ ├── Flutter.podspec
│ ├── App.framework
│ ├── FlutterPluginRegistrant.framework
│ └── example_plugin.framework
└── Release/
├── Flutter.podspec
├── App.framework
├── FlutterPluginRegistrant.framework
└── example_plugin.framework
3.2配置profile文件
pod 'Flutter', :podspec => '../Flutter/{build_mode}/Flutter.podspec'
3.3 方案优缺点
优点：
- 1.团队成员不依赖flutter环境
- 2.可以使用cocoapods集成管理。
缺点：
- 1.Flutter版本有限制
- 2.每次需要自己打frmaework
4.使用Flutter framework和CocoaPods集成(远程)
4.1创建一个CocoaPods私有库
在my_flutter同级目录下，创建CocoaPods私有库
$ pod lib create MyFlutterFramework
终端执行代码：
xingkunkun:FlutterForFW admin$ pod lib create MyFlutterFramework
Cloning `https://github.com/CocoaPods/pod-template.git` into `MyFlutterFramework `.
Configuring MyFlutter template.
------------------------------
To get you started we need to ask a few questions, this should only take a minute.
What platform do you want to use?? [ iOS / macOS ]
> ios
What language do you want to use?? [ Swift / ObjC ]
> objc
Would you like to include a demo application with your library? [ Yes / No ]
> no
Which testing frameworks will you use? [ Specta / Kiwi / None ]
> none
Would you like to do view based testing? [ Yes / No ]
> no
What is your class prefix?
>
Running pod install on your new library.
4.2创建一个Flutter Module
- 1.创建Flutter Module步骤，
flutter create --template module my_flutter
- 2.构建framework
$ flutter build ios --debug
或者
flutter build ios --release --no-codesign（选择不需要证书）
- 3.检查.ios目录下
- 是否有Flutter-->App.framework
- 是否有Flutter-->engine-->Flutter.framework
.ios目录下
Flutter-->App.framework
Flutter-->engine-->Flutter.framework
4.3将CocoaPods私有库集成到Native项目中
在MyFlutterFramework中创建ios_frameworks文件夹，并将App.framework和Flutter.framework拷贝进去。
在MyFlutterFramework的podspec文件中，添加以下配置：
s.static_framework = true
arr = Array.new
arr.push('ios_frameworks/*.framework')
s.ios.vendored_frameworks = arr
之后在MyFlutterFramework的podfile同级目录中执行
$ pod install
在MyApp工程下的podfile文件中添加
platform :ios, '8.0'
target 'MyApp' do
# Comment the next line if you don't want to use dynamic frameworks
use_frameworks!
# Pods for MyApp
pod 'MyFlutterFramework', :path => '../MyFlutterFramework'
end
之后在MyApp的podfile同级目录中执行
$ pod install
这时在MyApp中，就可以找到App.framework和Flutter.framework
4.4将MyFlutterFramework和my_flutter推送到远程仓库
- 1.MyFlutterFramework和my_flutter推送到远程仓库
- 2.修改MyApp工程下的podfile，将
pod 'MyFlutterFramework'依赖修改为MyFlutterFramework远程连接。
platform :ios, '8.0'
target 'MyApp' do
# Comment the next line if you don't want to use dynamic frameworks
use_frameworks!
# Pods for MyApp
pod 'MyFlutterFramework', :git=>'https://gitlab.com/MyFlutterFramework.git'
end
- 如果MyFlutterFramework中的ios_frameworks不详推送到远程仓库，可以在gitignore文件中添加一下
# 忽略ios_frameworks中文件
ios_frameworks
4.5 方案优缺点
优点：
- 1.团队成员不依赖flutter环境
- 2.可以使用cocoapods集成管理。
- 3.可以使用远程仓库共享和管理项目代码
缺点：
- 1.每次重新构建，需要移动framework位置，比较繁琐，可以使用脚本解决。
三、Flutter与Native交互
Flutter 官方提供了一种 Platform Channel 的方案，用于 Dart 和平台之间相互通信。
核心原理：
- Flutter应用通过Platform Channel将传递的数据编码成消息的形式，跨线程发送到该应用所在的宿主(Android或iOS)；
- 宿主接收到Platform Channel的消息后，调用相应平台的API，也就是原生编程语言来执行相应方法；
- 执行完成后将结果数据通过同样方式原路返回给应用程序的Flutter部分。
Flutter提供了三种不同的Channel：
- BasicMessageChannel（主要是传递字符串和一些半结构体的数据）
- MethodChannel（用于传递方法调用）
- EventChannel（数据流的通信）
下面是使用Platform Channel进行通信的示例：
示例代码
1.Native app主动与Flutter交互
交互主要分为三步：
- 1.flutter注册MethodChannel
- 2.flutter MethodChannel监听native消息
- 3.native通过MethodChannel发送消息
Dart代码
class HomePage extends StatefulWidget {
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
String title = 'Flutter to Native';
Color backGroundColor = Colors.red;
// 注册一个通知
static const MethodChannel methodChannel = const MethodChannel('com.pages.your/native_get');
_HomePageState(){
//Native调用Dart方法
methodChannel.setMethodCallHandler((MethodCall call){
if(call.method == "NativeToFlutter"){
setState(() {
title = call.arguments;
backGroundColor = Colors.yellow;
});
}
return Future<dynamic>.value();
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: backGroundColor,
body: Center(
child: GestureDetector(
behavior: HitTestBehavior.opaque,
child: new Text(title),
onTap: (){
_iOSPushToVC();
},
),
),
);
}
}
Native代码
#import "ViewController.h"
#import <Flutter/Flutter.h>
#define SCREEN_WIDTH ([[UIScreen mainScreen] bounds].size.width)
@interface ViewController ()
@property (nonatomic, strong) FlutterMethodChannel *messageChannel;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
[button addTarget:self action:@selector(pressOn) forControlEvents:UIControlEventTouchUpInside];
[button setTitle:@"加载Flutter" forState:UIControlStateNormal];
[button setBackgroundColor:[UIColor blueColor]];
button.frame = CGRectMake((SCREEN_WIDTH-100)/2, 100, 100, 60);
[self.view addSubview:button];
}
- (void)pressOn
{
FlutterViewController *flutterViewController =[FlutterViewController new];
//设置路由参数
[flutterViewController setInitialRoute:@"route"];
NSString *channelName = @"com.pages.your/native_get";// 要与main.dart中一致
_messageChannel = [FlutterMethodChannel methodChannelWithName:channelName binaryMessenger:flutterViewController];
[self nativeToFlutter];
[self presentViewController:flutterViewController animated:false completion:nil];
}
- (void)nativeToFlutter
{
sleep(5);
[_messageChannel invokeMethod:@"NativeToFlutter" arguments:@"NativeToFlutter"];
}
@end
2.Flutter主动与Native app交互
交互主要分为以下几步：
- 1.Native创建MethodChannel。
- 2.Native添加HandleBlcok。
- 3.Flutter发送消息。
Dart代码
class HomePage extends StatefulWidget {
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
String title = 'Flutter to Native';
Color backGroundColor = Colors.red;
// 注册一个通知
static const MethodChannel methodChannel = const MethodChannel('com.pages.your/native_get');
//Dart调用Native方法，并接收返回值。
_iOSPushToVC() async {
title = await methodChannel.invokeMethod('FlutterToNative');
setState(() {
backGroundColor = Colors.green;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: backGroundColor,
body: Center(
child: GestureDetector(
behavior: HitTestBehavior.opaque,
child: new Text(title),
onTap: (){
_iOSPushToVC();
},
),
),
);
}
}
Native代码
#import "ViewController.h"
#import <Flutter/Flutter.h>
#define SCREEN_WIDTH ([[UIScreen mainScreen] bounds].size.width)
@interface ViewController ()
@property (nonatomic, strong) FlutterMethodChannel *messageChannel;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
[button addTarget:self action:@selector(pressOn) forControlEvents:UIControlEventTouchUpInside];
[button setTitle:@"加载Flutter" forState:UIControlStateNormal];
[button setBackgroundColor:[UIColor blueColor]];
button.frame = CGRectMake((SCREEN_WIDTH-100)/2, 100, 100, 60);
[self.view addSubview:button];
}
- (void)pressOn
{
FlutterViewController *flutterViewController =[FlutterViewController new];
//设置路由参数
[flutterViewController setInitialRoute:@"route"];
NSString *channelName = @"com.pages.your/native_get";// 要与main.dart中一致
_messageChannel = [FlutterMethodChannel methodChannelWithName:channelName binaryMessenger:flutterViewController];
__weak typeof(self) weakSelf = self;
[_messageChannel setMethodCallHandler:^(FlutterMethodCall * _Nonnull call, FlutterResult _Nonnull result)
{
__strong typeof(self) strongSelf = weakSelf;
if ([call.method isEqualToString:@"FlutterToNative"]) {
if (result) {
result(@"NativeBack");
}
}
}];
[self presentViewController:flutterViewController animated:false completion:nil];
}
@end
四、app调试
混合开发的时候，需要在XCode调试代码，在调试的过程中，怎么调试Dart代码呢？或者能不能使用热加载？
1.调试Dart代码
在混合开发过程中,在iOS项目中，我们如何调试dart代码呢？
- 1.关闭我们的app
- 2.点击Android Studio工具栏上的Flutter Attach按钮
- 点击之后会提示Waiting for a connection from Flutter on iPhone 11 Pro...
- 3.启动我们的app
- 启动app之后，会提示Syncing files to device iPhone 11 Pro...
接下来就可以像调试普通Flutter项目一样来调试混合开发模式下的Dart代码了。
2.热加载
- 1.关闭我们的app
- 2.在terminal中运行 flutter attach命令。
$ flutter attach
Waiting for a connection from Flutter on iPhone 11 Pro Max...
注意，这里如果提示有多个设备，如下所示：
More than one device connected; please specify a device with the '-d <deviceId>' flag, or use '-d all' to act on all devices.
我的 iPhone • 00008030-000445611146802E • ios • iOS 13.3
iPhone 11 Pro Max • 67FCC5B2-DA5D-4EF0-8DE1-53E8F8C4CBA9 • ios • com.apple.CoreSimulator.SimRuntime.iOS-13-2 (simulator)
可以使用以下命令：
flutter attach -d 67FCC5B2-DA5D-4EF0-8DE1-53E8F8C4CBA9 //67FCC5B2-DA5D-4EF0-8DE1-53E8F8C4CBA9是设备对应的id
- 3.启动app，启动之后会有如下提示,就代表成功了。
Syncing files to device iPhone 11 Pro Max...
4,196ms (!)
🔥 To hot reload changes while running, press "r". To hot restart (and rebuild state), press "R".
An Observatory debugger and profiler on iPhone 11 Pro Max is available at: http://127.0.0.1:62889/T9DjblAu03w=/
For a more detailed help message, press "h". To detach, press "d"; to quit, press "q".
接下来就可以在terminal调试了：
r : 热加载；
R : 热重启；
h : 获取帮助；
d : 断开连接；
q : 退出；
参考资料：
Integrate a Flutter module into your iOS project
Upgrading Flutter added to existing iOS Xcode project
Add Flutter to existing apps
flutter集成进iOS工程
闲鱼flutter-boot介绍
优雅的 Flutter 组件化 混编方案
Flutter和原生iOS交互
Flutter混合开发(二)：iOS项目集成Flutter模块详细指南
深入理解Flutter Platform Channel
Flutter混合开发二-FlutterBoost使用介绍
如何用 Flutter 实现混合开发？
深入理解Flutter的Platform Channel机制
