目录
- 前言
- 启动插件
- Flutter代码
- Android代码
- IOS代码
- 启动模块
- 使用
- android端
- ios端
前言
因为在移动端中启动Flutter页面会有短暂空白,虽然官方提供了引擎预热机制,但是需要提前将所有页面都进行预热,这样开发成本较高,在研究了闲鱼的FlutterBoost插件后,我看看能不能自己实现一个简单的快速启动框架。
这篇文章用到的知识点都在《flutter混合开发:native与flutter交互》中详细讲解了,大家可以先读一下这篇文章再来看本文。本文不再赘述这些内容,直接上干货。
启动插件
创建一个Flutter Plugin项目,并添加git,然后编写三端代码:
Flutter代码
首先是flutter端的代码
1)RouteManager
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_boot/BasePage.dart';class RouteManager{factory RouteManager() => _getInstance();static RouteManager get instance => _getInstance();static RouteManager _instance;RouteManager._internal(){}static RouteManager _getInstance(){if(_instance == null){_instance = new RouteManager._internal();}return _instance;}Map<String, BasePage> routes = Map();void registerRoute(String route, BasePage page){routes[route] = page;}RouteFactory getRouteFactory(){return getRoute;}MaterialPageRoute getRoute(RouteSettings settings){if(routes.containsKey(settings.name)){return MaterialPageRoute(builder: (BuildContext context) {return routes[settings.name];}, settings: settings);}else{return MaterialPageRoute(builder: (BuildContext context) {return PageNotFount();});}}BasePage getPage(String name){if(routes.containsKey(name)) {return routes[name];}else{return PageNotFount();}}
}class PageNotFount extends BasePage{State<StatefulWidget> createState() {return _PageNotFount();}}class _PageNotFount extends BaseState<PageNotFount>{Widget buildImpl(BuildContext context) {return Scaffold(body: Center(child: Text("page not found"),),);}
}
它的作用就是管理路由,是一个单例,用一个map来维护路由映射。其中三个函数比较重要:
- registerRoute:注册路由。一般在启动时调用。
- getRouteFactory:返回RouteFactory。将它赋值给MaterialApp的onGenerateRoute字段
- getPage:通过route名称返回页面widget。
这里getRouteFactory和getPage共用一个路由map,所以不论是页面内切换还是页面切换都保持统一。
2)BaseApp
import 'dart:convert';import 'package:flutter/cupertino.dart';
import 'package:flutter/services.dart';
import 'package:flutter_boot/RouteManager.dart';abstract class BaseApp extends StatefulWidget{State<StatefulWidget> createState() {registerRoutes();return _BaseApp(build);}Widget build(BuildContext context, Widget page);void registerRoutes();}class _BaseApp extends State<BaseApp>{Function buildImpl;static const bootChannel = const BasicMessageChannel<String>("startPage", StringCodec());Widget curPage = RouteManager.instance.getPage("");_BaseApp(this.buildImpl){bootChannel.setMessageHandler((message) async {setState(() {var json = jsonDecode(message);var route = json["route"];var page = RouteManager.instance.getPage(route);page.args = json["params"];curPage = page;});return "";});}Widget build(BuildContext context) {return buildImpl.call(context, curPage);}}
是一个抽象类,真正的flutter app需要继承它。主要是封装了一个BasicMessageChannel用来与android/ios交互,并根据收到的消息处理页面内的切换,实现快速启动。
继承它的子类需要实现registerRoutes函数,在这里使用RouteManager的registerRoute将每个页面注册一下即可。
3)BasePage
import 'package:flutter/material.dart';abstract class BasePage extends StatefulWidget{dynamic args;
}abstract class BaseState<T extends BasePage> extends State<T>{dynamic args;Widget build(BuildContext context) {if(ModalRoute.of(context).settings.arguments == null){args = widget.args;}else{args = ModalRoute.of(context).settings.arguments;}return buildImpl(context);}Widget buildImpl(BuildContext context);
}
同样是抽象类,每个flutter页面都需要继承它,它主要是处理两种启动方式传过来的参数,统一到args中,这样子类就可以直接使用而不需要考虑是如何启动的。
Android代码
接下来是plugin中的android的代码
1)BootEngine
package com.bennu.flutter_bootimport android.app.Application
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.embedding.engine.FlutterEngineCache
import io.flutter.embedding.engine.dart.DartExecutor
import io.flutter.plugin.common.BasicMessageChannel
import io.flutter.plugin.common.StringCodecobject BootEngine {public var flutterBoot : BasicMessageChannel<String>? = nullfun init(context: Application){var flutterEngine = FlutterEngine(context)flutterEngine.dartExecutor.executeDartEntrypoint(DartExecutor.DartEntrypoint.createDefault())FlutterEngineCache.getInstance().put("main", flutterEngine)flutterBoot = BasicMessageChannel<String>(flutterEngine.dartExecutor.binaryMessenger, "startPage", StringCodec.INSTANCE)}
}
这个是单例,初始化并预热FlutterEngine,同时创建BasicMessageChannel用于后续交互。需要在Application的onCreate中调用它的init函数来初始化。
2)FlutterBootActivity
package com.bennu.flutter_bootimport android.content.ComponentName
import android.content.Context
import android.content.Intent
import android.os.Bundle
import android.os.PersistableBundle
import io.flutter.embedding.android.FlutterActivity
import org.json.JSONObjectclass FlutterBootActivity : FlutterActivity() {companion object{const val ROUTE_KEY = "flutter.route.key"fun build(context: Context, routeName : String, params : Map<String, String>?) : Intent{var intent = withCachedEngine("main").build(context)intent.component = ComponentName(context, FlutterBootActivity::class.java)var json = JSONObject()json.put("route", routeName)var paramsObj = JSONObject()params?.let {for(entry in it){paramsObj.put(entry.key, entry.value)}}json.put("params", paramsObj)intent.putExtra(ROUTE_KEY, json.toString())return intent}}override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)}override fun onCreate(savedInstanceState: Bundle?, persistentState: PersistableBundle?) {super.onCreate(savedInstanceState, persistentState)}override fun onResume() {super.onResume()var route = intent.getStringExtra(ROUTE_KEY)BootEngine.flutterBoot?.send(route)}override fun onDestroy() {super.onDestroy()}
}
继承FlutterActivity,提供一个build(context: Context, routeName : String, params : Map<String, String>?)函数来启动,传递路由名称和参数。在onResume的时候通过BasicMessageChannel将这两个数据send给flutter处理。
IOS代码
ios与android类似
1)FlutterBootEngine
FlutterBootEngine.h
#ifndef FlutterBootEngine_h
#define FlutterBootEngine_h#import <Foundation/Foundation.h>
#import <Flutter/Flutter.h>@interface FlutterBootEngine : NSObject+ (nonnull instancetype)sharedInstance;- (FlutterBasicMessageChannel *)channel;
- (FlutterEngine *)engine;
- (void)initEngine;
@end#endif /* FlutterBootEngine_h */
FlutterBootEngine.m
#import "FlutterBootEngine.h"
#import <Flutter/Flutter.h>@implementation FlutterBootEnginestatic FlutterBootEngine * instance = nil;FlutterEngine * engine = nil;
FlutterBasicMessageChannel * channel = nil;+(nonnull FlutterBootEngine *)sharedInstance{if(instance == nil){instance = [self.class new];}return instance;
}+(id)allocWithZone:(struct _NSZone *)zone{if(instance == nil){instance = [[super allocWithZone:zone]init];}return instance;
}- (id)copyWithZone:(NSZone *)zone{return instance;
}- (FlutterEngine *)engine{return engine;
}- (FlutterBasicMessageChannel *)channel{return channel;
}- (void)initEngine{engine = [[FlutterEngine alloc]initWithName:@"flutter engine"];channel = [FlutterBasicMessageChannel messageChannelWithName:@"startPage" binaryMessenger:engine.binaryMessenger codec:[FlutterStringCodec sharedInstance]];[engine run];
}@end
这是也是一个单例,初始化并启动FlutterEngine,并创建一个FlutterBasicMessageChannel与flutter交互。
需要在ios项目的AppDelegate初始化时调用它的initEngine函数。
2)FlutterBootViewController
FlutterBootViewController.h
#ifndef FlutterBootViewController_h
#define FlutterBootViewController_h#import <Flutter/FlutterViewController.h>@interface FlutterBootViewController : FlutterViewController- (nonnull instancetype)initWithRoute:(nonnull NSString*)routeparams:(nullable NSDictionary*)params;@end#endif /* FlutterBootViewController_h */
FlutterBootViewController.m
#import "FlutterBootViewController.h"
#import "FlutterBootEngine.h"@implementation FlutterBootViewControllerNSString * mRoute = nil;
NSDictionary * mParams = nil;- (nonnull instancetype)initWithRoute:(nonnull NSString *)route params:(nullable NSDictionary *)params{self = [super initWithEngine:FlutterBootEngine.sharedInstance.engine nibName:nil bundle:nil];mRoute = route;mParams = params;return self;
}//viewDidAppear时机有点晚,会先显示一下上一个页面才更新到新页面,所以换成viewWillAppear
- (void)viewWillAppear:(BOOL)animated{[super viewWillAppear:animated];if(mParams == nil){mParams = [[NSDictionary alloc]init];}NSDictionary * dict = @{@"route" : mRoute, @"params" : mParams};NSData * jsonData = [NSJSONSerialization dataWithJSONObject:dict options:0 error:NULL];NSString * str = [[NSString alloc]initWithData:jsonData encoding:NSUTF8StringEncoding];NSLog(@"%@", str);[FlutterBootEngine.sharedInstance.channel sendMessage:str];
}@end
同样新增一个使用路由名和参数的构造函数,然后在viewWillAppear时通知flutter。
注意这里如果改成viewDidAppear时机有点晚,会先显示一下上一个页面才更新到新页面,所以换成viewWillAppear。
3)FlutterBoot.h
#ifndef FlutterBoot_h
#define FlutterBoot_h#import "FlutterBootEngine.h"
#import "FlutterBootViewController.h"#endif /* FlutterBoot_h */
这个是swift的桥接文件,通过它swift就可以使用我们上面定义的类。
这样我们的plugin就开发完成了,可以发布到pub上。我这里是push到git仓库中,通过git的方式依赖使用。
启动模块
创建一个flutter module,然后引入我们的plugin,在pubspec.yaml中:
dependencies:flutter:sdk: flutter...flutter_boot:git: https://gitee.com/chzphoenix/flutter-boot.git
然后我们开发两个页面用于测试。
1)FirstPage.dart
import 'package:flutter/material.dart';
import 'package:flutter_boot/BasePage.dart';class FirstPage extends BasePage{State<StatefulWidget> createState() {return _FirstPage();}
}class _FirstPage extends BaseState<FirstPage>{void _goClick() {Navigator.of(context).pushNamed("second", arguments: {"key":"123"});}Widget buildImpl(BuildContext context) {return Scaffold(appBar: AppBar(title: Text("Flutter Demo Home Page"),),body: Center(child: ...,),floatingActionButton: FloatingActionButton(onPressed: _goClick,tooltip: 'Increment',child: Icon(Icons.add),), // This trailing comma makes auto-formatting nicer for build methods.);}
}
继承BasePage和BaseState即可,点击按钮可以跳转到页面2
2)SecondPage.dart
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_boot/BasePage.dart';class SecondPage extends BasePage{State<StatefulWidget> createState() {return _SecondPage();}}class _SecondPage extends BaseState<SecondPage>{Widget buildImpl(BuildContext context) {return Scaffold(appBar: AppBar(title: Text("test"),),body:Text("test:${args["key"]}"));}
}
这个页面获取传递过来的参数key,并展示。
3)main.dart
import 'package:flutter/material.dart';
import 'package:flutter_boot/BaseApp.dart';
import 'package:flutter_boot/RouteManager.dart';import 'FirstPage.dart';
import 'SecondPage.dart';void main() => runApp(MyApp());class MyApp extends BaseApp {Widget build(BuildContext context, Widget page) {return MaterialApp(title: 'Flutter Demo',theme: ThemeData(primarySwatch: Colors.blue,),home: page,onGenerateRoute: RouteManager.instance.getRouteFactory(),);}void registerRoutes() {RouteManager.instance.registerRoute("main", FirstPage());RouteManager.instance.registerRoute("second", SecondPage());}
}
入口继承BaseApp,并实现registerRoutes,注册这两个页面。
注意这里的onGenerateRoute使用RouteManager.instance.getRouteFactory(),这样一次注册就可以了,不必自己去实现。
使用
module开发完后,就可以在andorid/ios上使用了。
android端
在android上比较简单,在android项目中引入刚才的module即可,然后需要在android的主module(一般是app)的build.gradle中引入module和plugin,如下:
dependencies {implementation fileTree(dir: "libs", include: ["*.jar"])...implementation project(path: ':flutter') //moduleprovided rootProject.findProject(":flutter_boot") //plugin
}
注意plugin的名称是之前在module中的pubspec.yaml定义的。
然后就可以在android中使用了,首先要初始化,如下:
import android.app.Application
import com.bennu.flutter_boot.BootEnginepublic class App : Application() {override fun onCreate() {super.onCreate()BootEngine.init(this)...}
}
然后合适的时候启动flutter页面即可,启动代码如下:
button.setOnClickListener {startActivity(FlutterBootActivity.build(this, "main", null))
}
button2.setOnClickListener {var params = HashMap<String, String>()params.put("key", "123")startActivity(FlutterBootActivity.build(this, "second", params))
}
一个启动无参的页面1,一个启动有参的页面2。
测试可以发现无论打开哪个页面都非常快,几乎没有加载时间。这样就实现了快速启动。
ios端
ios端稍微复杂一些,需要先了解一下ios如何加入flutter,见《flutter混合开发:在已有ios项目中引入flutter》
我选用的是framework的方式引入,所以在flutter module项目下通过命令编译打包framework
flutter build ios-framework --xcframework --no-universal --output=./Flutter/
然后引入到ios项目中,与上一篇文章不同的是,因为这个module中加入了plugin,所以framework产物是四个:
- App.xcframework
- flutter_boot.xcframework (这个就是我们的plugin中的ios部分)
- Flutter.xcframework
- FlutterPluginRegistrant.xcframework
这四个都需要引入到ios项目中。
然后AppDelegate需要继承FlutterAppDelegate(如果无法继承,则需要处理每个生命周期,见https://flutter.cn/docs/development/add-to-app/ios/add-flutter-screen?tab=engine-swift-tab) 。
然后在AppDelegate中初始化,如下:
import UIKit
import Flutter
import flutter_boot@UIApplicationMain
class AppDelegate: FlutterAppDelegate {override func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {FlutterBootEngine.sharedInstance().initEngine()return true}override func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)}
}
然后在合适的地方启动flutter页面即可,如下:
@objc func showMain() {let flutterViewController =FlutterBootViewController(route: "main", params: nil)present(flutterViewController, animated: true, completion: nil)}@objc func showSecond() {let params : Dictionary<String, String> = ["key" : "123"]let flutterViewController =FlutterBootViewController(route: "second", params: params)present(flutterViewController, animated: true, completion: nil)}
同样分别打开两个页面,可以看到启动几乎没有加载时间,同时参数也正确传递。