Flutter踩坑日记：接入现有iOS项目

之前搞的Flutter版工具链已经弄完了，感兴趣的朋友可以围观下，Android版本dio库（v2.0.14）发送网络请求老是报错，去官方提了issue还没回，于是今天搞一下把Flutter模块接入到已有项目中。

首先Flutter官方已经出了wiki，教大家怎么接入。懒得看官方原文的可以看看这个简易版快速集成，先来看看效果。

一、创建Flutter模块

一般用Flutter或者React Native的团队大部分原因都是因为需要跨平台，所以在已有项目目录的上一级创建Flutter模块，譬如你的工作目录在some/path/MyApp，那么你需要在some/path下执行，这样Flutter可以单独交给一个虚拟团队维护，各自独立。

$ cd some/path/

$ flutter create -t module my_flutter

文件结构如下：

some/path/

  my_flutter/

    lib/main.dart

    .ios/

  MyApp/

      MyApp.xcodeproj

      Podfile

    MyApp/

      AppDelegate.h

      AppDelegate.m (or swift)

二、利用Cocoapods添加依赖

没用过Cocoapods的童鞋可以google搜一下，之前写过很多Cocoapods的文章由于博客主机商跑路都没了，说多了都是泪

1.在Podfile文件加入以下代码：

flutter_application_path = '../my_flutter/'

eval(File.read(File.join(flutter_application_path, '.ios', 'Flutter', 'podhelper.rb')), binding)

注意my_flutter的路径，因为我们是以xcodeproj文件的上一级创建的，所以需要加../，这个和React Native引入依赖路径是一样的，都需要注意这个问题。

2.执行pod install

注：如果报错

[!] InvalidPodfilefile: No such file or directory @ rb_sysopen - ./my_flutter/.ios/Flutter/podhelper.rb.

需要在my_flutter文件夹下执行以下flutter run，把.ios和.android等flutter配置生成出来。

3.禁用bitcode，设置环境变量

找到你的target，Build Settings->Build Options->Enable Bitcode设置为NO，另外在Preprocessor Macros添加FLUTTER_BUILD_MODE=Debug和FLUTTER_BUILD_MODE=Release，如果还有其他环境需要根据情况选择Debug或Release。

4.添加run script

找到你的target，Build Phases -> + -> New Run Script Phase，并且在bash或zsh配置FLUTTER_ROOT，否则打包会出错找不到flutter。涉及多人开发还需要安装路径位置，否则团队小伙伴每个人的路径不一样。

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

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

注：把这个script放到Target Dependencies phasescript的后面。

5.添加assets资源

官网说需要添加Flutter.framework资源，但是这个Cocoapods已经帮忙引入了，所以就不需要了，如果没有被引入进去那就手动引入下。这里只需要添加flutter_assets就行了，记得选Creat folder references引入方式。Flutter 1.0.0版本路径是my_flutter->build->flutter_assets

6.修改AppDelegate

Objective-C:

AppDelegate.h

#import <UIKit/UIKit.h>

#import <Flutter/Flutter.h>

@interface AppDelegate : FlutterAppDelegate

@property (nonatomic,strong) FlutterEngine *flutterEngine;

@end

AppDelegate.m

#import <FlutterPluginRegistrant/GeneratedPluginRegistrant.h> // Only if you have Flutter Plugins

#include "AppDelegate.h"

@implementation AppDelegate

// This override can be omitted if you do not have any Flutter Plugins.

- (BOOL)application:(UIApplication *)application

    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

  self.flutterEngine = [[FlutterEngine alloc] initWithName:@"io.flutter" project:nil];

  [self.flutterEngine runWithEntrypoint:nil];

  [GeneratedPluginRegistrant registerWithRegistry:self.flutterEngine];

  return [super application:application didFinishLaunchingWithOptions:launchOptions];

}

@end

Swift:

AppDelegate.swift

import UIKit

import Flutter

import FlutterPluginRegistrant // Only if you have Flutter Plugins.

@UIApplicationMain

class AppDelegate: FlutterAppDelegate {

  var flutterEngine : FlutterEngine?;

  // Only if you have Flutter plugins.

  override func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

    self.flutterEngine = FlutterEngine(name: "io.flutter", project: nil);

    self.flutterEngine?.run(withEntrypoint: nil);

    GeneratedPluginRegistrant.register(with: self.flutterEngine);

    return super.application(application, didFinishLaunchingWithOptions: launchOptions);

  }

}

到这里，我们的Flutter就算已经引入工程了

三、跳转Flutter页面

Objective-C:

ViewController.m

#import <Flutter/Flutter.h>

#import "AppDelegate.h"

#import "ViewController.h"

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];

    [button addTarget:self

              action:@selector(handleButtonAction)

    forControlEvents:UIControlEventTouchUpInside];

    [button setTitle:@"Press me" forState:UIControlStateNormal];

    [button setBackgroundColor:[UIColor blueColor]];

    button.frame = CGRectMake(80.0, 210.0, 160.0, 40.0);

    [self.view addSubview:button];

}

- (void)handleButtonAction {

    FlutterEngine *flutterEngine = [(AppDelegate *)[[UIApplication sharedApplication] delegate] flutterEngine];

    FlutterViewController *flutterViewController = [[FlutterViewController alloc] initWithEngine:flutterEngine nibName:nil bundle:nil];

    [self presentViewController:flutterViewController animated:false completion:nil];

}

@end

Swift:

ViewController.swift

import UIKit

import Flutter

class ViewController: UIViewController {

  override func viewDidLoad() {

    super.viewDidLoad()

    let button = UIButton(type:UIButtonType.custom)

    button.addTarget(self, action: #selector(handleButtonAction), for: .touchUpInside)

    button.setTitle("Press me", for: UIControlState.normal)

    button.frame = CGRect(x: 80.0, y: 210.0, width: 160.0, height: 40.0)

    button.backgroundColor = UIColor.blue

    self.view.addSubview(button)

  }

  @objc func handleButtonAction() {

    let flutterEngine = (UIApplication.shared.delegate as? AppDelegate)?.flutterEngine;

    let flutterViewController = FlutterViewController(engine: flutterEngine, nibName: nil, bundle: nil)!;

    self.present(flutterViewController, animated: false, completion: nil)

  }

}

剩下的就是写Flutter页面逻辑了以及Flutter模块需要调用Native API（后面专门写一篇文章）。

写完Flutter页面，如果要跳转到指定页面使用Flutter的路由就可以了

Objective-C:

[flutterViewController setInitialRoute:@"route1"];

Swift:

flutterViewController.setInitialRoute("route1")

四、运行

在my_flutter手动flutter run一下，或者直接开启热加载，然后就可以在原有的iOS项目中用Xcoderun起来了。

$ flutter attach --isolate-filter='debug'

Waiting for a connection from Flutter...

Done.

Syncing files to device...      1.1s