iOS接入Flutter填坑记录-代码篇

在上一篇iOS原生接入Flutter添坑记录-接入篇介绍了iOS端接入Flutter的方法，这篇将介绍iOS如何进行耦合，交互。
我只是个不合格的翻译，请看官方介绍.

一.Flutter原生方案

1.1FlutterAppDelegate
这个比较简单，只需在AppDelegate中继承FlutterAppDelegate即可
然后在AppDelegate.h文件中声明一个flutterEngine属性

#import 
#import 

@interface AppDelegate : FlutterAppDelegate
@property (nonatomic,strong) FlutterEngine *flutterEngine;
@end

在AppDelegate.m中

#import  // Only if you have Flutter Plugins
#import "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

FlutterEngine 是用来管理FlutterViewController控制器的，但是FlutterEngine本身是一个比较重的对象，所以官方给出的代码中就是在AppDelegate中初始化一个engine，在其他地方需要使用时再取用，但实际上这里有个坑，这个我们后面1.3页面跳转中会说到。

1.2 FlutterAppLifeCycleProvider 实现协议来完成Flutter耦合
如果你的AppDelegate不幸的已经继承自其他类了，那你就需要使用这个接入方案。简单来说就是自己实现FlutterAppDelegate中实现的协议FlutterAppLifeCycleProvider。
同样的在AppDelegate.h中，声明一个FlutterEngine，同时遵循协议

#import 
#import 
#import  // Only if you have Flutter Plugins

@interface AppDelegate : UIResponder 
@property (strong, nonatomic) UIWindow *window;
@property (nonatomic,strong) FlutterEngine *flutterEngine;
@end

在AppDelegate.m中

@implementation AppDelegate
{
    FlutterPluginAppLifeCycleDelegate *_lifeCycleDelegate;
}

- (instancetype)init {
    if (self = [super init]) {
        _lifeCycleDelegate = [[FlutterPluginAppLifeCycleDelegate alloc] init];
    }
    return self;
}

- (BOOL)application:(UIApplication*)application
didFinishLaunchingWithOptions:(NSDictionary*)launchOptions {
    self.flutterEngine = [[FlutterEngine alloc] initWithName:@"io.flutter" project:nil];
    [self.flutterEngine runWithEntrypoint:nil];
    [GeneratedPluginRegistrant registerWithRegistry:self.flutterEngine]; // Only if you are using Flutter plugins.
    return [_lifeCycleDelegate application:application didFinishLaunchingWithOptions:launchOptions];
}

// Returns the key window's rootViewController, if it's a FlutterViewController.
// Otherwise, returns nil.
- (FlutterViewController*)rootFlutterViewController {
    UIViewController* viewController = [UIApplication sharedApplication].keyWindow.rootViewController;
    if ([viewController isKindOfClass:[FlutterViewController class]]) {
        return (FlutterViewController*)viewController;
    }
    return nil;
}

- (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
    [super touchesBegan:touches withEvent:event];
    
    // Pass status bar taps to key window Flutter rootViewController.
    if (self.rootFlutterViewController != nil) {
        [self.rootFlutterViewController handleStatusBarTouches:event];
    }
}

- (void)applicationDidEnterBackground:(UIApplication*)application {
    [_lifeCycleDelegate applicationDidEnterBackground:application];
}

- (void)applicationWillEnterForeground:(UIApplication*)application {
    [_lifeCycleDelegate applicationWillEnterForeground:application];
}

- (void)applicationWillResignActive:(UIApplication*)application {
    [_lifeCycleDelegate applicationWillResignActive:application];
}

- (void)applicationDidBecomeActive:(UIApplication*)application {
    [_lifeCycleDelegate applicationDidBecomeActive:application];
}

- (void)applicationWillTerminate:(UIApplication*)application {
    [_lifeCycleDelegate applicationWillTerminate:application];
}

- (void)application:(UIApplication*)application
didRegisterUserNotificationSettings:(UIUserNotificationSettings*)notificationSettings {
    [_lifeCycleDelegate application:application
didRegisterUserNotificationSettings:notificationSettings];
}

- (void)application:(UIApplication*)application
didRegisterForRemoteNotificationsWithDeviceToken:(NSData*)deviceToken {
    [_lifeCycleDelegate application:application
didRegisterForRemoteNotificationsWithDeviceToken:deviceToken];
}

- (void)application:(UIApplication*)application
didReceiveRemoteNotification:(NSDictionary*)userInfo
fetchCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler {
    [_lifeCycleDelegate application:application
       didReceiveRemoteNotification:userInfo
             fetchCompletionHandler:completionHandler];
}

- (BOOL)application:(UIApplication*)application
            openURL:(NSURL*)url
            options:(NSDictionary*)options {
    return [_lifeCycleDelegate application:application openURL:url options:options];
}

- (BOOL)application:(UIApplication*)application handleOpenURL:(NSURL*)url {
    return [_lifeCycleDelegate application:application handleOpenURL:url];
}

- (BOOL)application:(UIApplication*)application
            openURL:(NSURL*)url
  sourceApplication:(NSString*)sourceApplication
         annotation:(id)annotation {
    return [_lifeCycleDelegate application:application
                                   openURL:url
                         sourceApplication:sourceApplication
                                annotation:annotation];
}

- (void)application:(UIApplication*)application
performActionForShortcutItem:(UIApplicationShortcutItem*)shortcutItem
  completionHandler:(void (^)(BOOL succeeded))completionHandler NS_AVAILABLE_IOS(9_0) {
    [_lifeCycleDelegate application:application
       performActionForShortcutItem:shortcutItem
                  completionHandler:completionHandler];
}

- (void)application:(UIApplication*)application
handleEventsForBackgroundURLSession:(nonnull NSString*)identifier
  completionHandler:(nonnull void (^)(void))completionHandler {
    [_lifeCycleDelegate application:application
handleEventsForBackgroundURLSession:identifier
                  completionHandler:completionHandler];
}

- (void)application:(UIApplication*)application
performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler {
    [_lifeCycleDelegate application:application performFetchWithCompletionHandler:completionHandler];
}

- (void)addApplicationLifeCycleDelegate:(NSObject*)delegate {
    [_lifeCycleDelegate addDelegate:delegate];
}
@end

并不是所有的协议都需要实现，各位可以根据自己工程都实际需要来实现协议方法即可

1.3 原生跳转Flutter 页面

#import 
#import "AppDelegate.h"
#import "ViewController.h"

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad]; 
}

// 点击事件
- (void)handleButtonAction {
    AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
    FlutterViewController *flutterCon = [[FlutterViewController alloc] initWithEngine:appDelegate.flutterEngine nibName:nil bundle:nil]; 
    [self.navigationController pushViewController:flutterCon animated:YES];
}
@end

上面的这段代码会可以将main.dart文件创建的视图绘制在flutterViewController中。
但是如果需要跳转到不同的页面该怎么办。

    // 设置跳转的页面，实际上这个方法并不会生效
    [flutterViewController setInitialRoute:@"route1"];

官方给的方式经过在下实践发现并不会生效，然后在Flutter的 issue#27216中找到了答案，虽然官方推荐在App中避免重复创建FlutterEngine来节省资源，但是目前Fluter对此方法并没有做出很好对支持，解决办法在issue#27216中也有提到，就是在每个ViewController中创建自己对Engine来进行管理。代码修正如下

- (void)handleButtonAction {
    AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
    FlutterViewController *flutterCon = [[FlutterViewController alloc] initWithEngine:appDelegate.flutterEngine nibName:nil bundle:nil];
    [GeneratedPluginRegistrant registerWithRegistry:flutterCon];
    [flutterCon setInitialRoute:@"route1"];
    [self.navigationController pushViewController:flutterCon animated:YES];
}

1.4 在main.dart中
在main.dart中我们只需稍作修改即可实现跳转不同对页面

import 'dart:ui';
import 'package:flutter/material.dart';

// window.defaulteRouteName 即为 setInitialRoute：传来对参数，只需要根据此参数来创建不同对widget即可
void main() => runApp(_widgetForRoute(window.defaultRouteName));

Widget _widgetForRoute(String route) {
  switch (route) {
    case 'route1':
      return SomeWidget(...);
    case 'route2':
      return SomeOtherWidget(...);
    default:
      return Center(
        child: Text('Unknown route: $route', textDirection: TextDirection.ltr),
      );
  }
}

至此已基本实现了iOS与Flutter的对接，但是flutter与native之间的页面跳转都由于FlutterEngine的存在遗留里一系列的问题，这方面闲鱼技术团队闲鱼开源 FlutterBoost：实现 Flutter 混合开发和京东团队京东技术中台的 Flutter 实践之路都有比较深入的探究，在下暂且当个搬运工将闲鱼的FlutterBoost作为方案二搬运过来供各位借鉴一下。

二. FlutterBoost 闲鱼开源方案

FlutterBoost是闲鱼技术给出的原生接入Flutter的路由方案，总体思路是，引用原文“Native容器Container通过消息驱动Flutter页面容器Container，从而达到Native Container与Flutter Container的同步目的”。

图片来源见水印

下面通过代码来进一步理解这个过程。同样的也可以分为三步。
1.创建原生Router，暂且称为FLBRouter

#import 
#import 

NS_ASSUME_NONNULL_BEGIN
// 遵循协议FLBPlatform
@interface FLBRouter : NSObject

@property (nonatomic, strong) UINavigationController *navigationController;

+ (instancetype)sharedRouter;

@end

#import "FLBRouter.h"
#import 

@implementation FLBRouter

+ (instancetype)sharedRouter {
    static FLBRouter *_shareRouter;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _shareRouter = [FLBRouter new];
    });
    return _shareRouter;
}

// 实现协议方法
- (void)close:(nonnull NSString *)uid result:(nonnull NSDictionary *)result exts:(nonnull NSDictionary *)exts completion:(nonnull void (^)(BOOL))completion {
    FLBFlutterViewContainer *vc = (id)self.navigationController.presentedViewController;
    if([vc isKindOfClass:FLBFlutterViewContainer.class] && [vc.uniqueIDString isEqual: uid]){
        [vc dismissViewControllerAnimated:YES completion:^{}];
    }else{
        [self.navigationController popViewControllerAnimated:YES];
    }
}

- (void)open:(nonnull NSString *)url urlParams:(nonnull NSDictionary *)urlParams exts:(nonnull NSDictionary *)exts completion:(nonnull void (^)(BOOL))completion {
    if([urlParams[@"present"] boolValue]){
        FLBFlutterViewContainer *vc = FLBFlutterViewContainer.new;
        [vc setName:url params:urlParams];
        [self.navigationController presentViewController:vc animated:YES completion:^{}];
    }else{
        FLBFlutterViewContainer *vc = FLBFlutterViewContainer.new;
        [vc setName:url params:urlParams];
        [self.navigationController pushViewController:vc animated:YES];
    }
}

@end

2.在AppDelelgate中，直接继承FLBFlutterAppDelegate

#import 
#import 

@interface AppDelegate : FLBFlutterAppDelegate 

@end

#import "AppDelegate.h"
#import "ViewController.h"
#import "FLBRouter.h"
#import 

@interface AppDelegate ()

@end

@implementation AppDelegate

// This override can be omitted if you do not have any Flutter Plugins.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
    self.window.backgroundColor = [UIColor whiteColor];
    
    UINavigationController *navigationCon = [[UINavigationController alloc] initWithRootViewController:[ViewController new]];
    self.window.rootViewController = navigationCon;
    [self.window makeKeyAndVisible];
    
    FLBRouter *router = [FLBRouter sharedRouter];
    // 这个navigationCon可以看做原生的Contianer
    router.navigationController = navigationCon;
    [FlutterBoostPlugin.sharedInstance startFlutterWithPlatform:router
                                                        onStart:^(id engine) {
                                                            
                                                        }];
    return YES;
}
// 这里省略了其他生命周期
...

@end

页面添加跳转方法

- (void)onClickAction {
    [FLBRouter.sharedRouter open:@"first"
                       urlParams:@{@"present" : @(YES)}
                            exts:@{@"animated" : @(YES)}
                      completion:^(BOOL finished) {
                          
                      }];
}

至此原生iOS端就可以进行跳转了，下面看Flutter怎样同步。

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State {
  @override
  void initState() {
    super.initState();

    FlutterBoost.singleton.registerPageBuilders({ 
      /// 根据不同的信息来创建不同的Wdiget
      'first': (pageName, params, _) => _firstRouteWidgte(),

      ///可以在native层通过 getContainerParams 来传递参数
      'flutterPage': (pageName, params, _) {
        print("flutterPage params:$params"); 
        return FlutterRouteWidget();
      },
    });
  }

  Widget _firstRouteWidgte() {
    return Text('FirstPage');
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        title: 'Flutter Boost example',
        builder: FlutterBoost.init(postPush: _onRoutePushed),
        home: Container());
  }

  void _onRoutePushed(
      String pageName, String uniqueId, Map params, Route route, Future _) {
  }
}

完成！

iOS接入Flutter填坑记录-代码篇

一.Flutter原生方案

二. FlutterBoost 闲鱼开源方案

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