前言

今天主要带大家一起分析下flutter是如何启动、初始化和加载dart代码的。这里有几点需要提前告知：

1. 由于篇幅的问题，关于flutter界面创建、绘制过程将略过；

2. 由于相关的c++代码比较多，而且较为复杂，建议先下载flutter engine的完整开发环境代码，阅读本文更方便；

3. 本文只分析启动过程，参考的项目是基于android studio创建的一个默认flutter项目，以下简称demo。

正文

java层启动过程

熟悉android的朋友都知道，一个APP启动会先执行Application再执行Activity(AndroidManifest.xml中配置的启动Activity)，结合这个，我们先看看Application里做了什么，在分析过程中我们将挑取一些关键的native方法作为c++层入口方法作进一步的分析。

// io.flutter.app.FlutterApplication
public class FlutterApplication extends Application {@Override@CallSuperpublic void onCreate() {super.onCreate();FlutterMain.startInitialization(this);}//这块代码和FlutterActivityDelegate的生命周期方法结合使用private Activity mCurrentActivity = null;public Activity getCurrentActivity() {return mCurrentActivity;}public void setCurrentActivity(Activity mCurrentActivity) {this.mCurrentActivity = mCurrentActivity;}
}// io.flutter.view.FlutterMain中的方法
public static void startInitialization(Context applicationContext, FlutterMain.Settings settings) {if (Looper.myLooper() != Looper.getMainLooper()) {throw new IllegalStateException("startInitialization must be called on the main thread");} else if (sSettings == null) {sSettings = settings;long initStartTimestampMillis = SystemClock.uptimeMillis();initConfig(applicationContext);initAot(applicationContext);initResources(applicationContext);System.loadLibrary("flutter");...}
}复制代码

startInitialization只能执行在主线程中，否则会抛出异常。通过sSettings这个变量可以看出，启动的过程中，这个方法将只执行一遍。initConfig初始化一些变量的配置信息（在AndroidManifest.xml中可以通过meta-data方式配置这些变量值）， System.loadLibrary("flutter")则完成装载flutter库文件，期间会在c++层完成JNI方法的动态注册。initResources方法我们往下看。

private static void initResources(Context applicationContext) {Context context = applicationContext;new ResourceCleaner(context).start();...sResourceExtractor = new ResourceExtractor(context);...sResourceExtractor.start();
}
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ResourceCleaner将清理带有指定标识的缓存文件，ResourceExtractor将完成asset 目录下flutter相关资源的拷贝，这些资源会在后续flutter engine和DartVM等初始化时使用。 然后我们再来看看启动activity都做了些什么

onCreate

//MainActivity.javapublic class MainActivity extends FlutterActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);GeneratedPluginRegistrant.registerWith(this);}
}//FlutterActivity.javaprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);this.eventDelegate.onCreate(savedInstanceState);
}
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先看FlutterActivity中执行onCreate，可以看到这里面并没有当前ContentView的设置，那么其内容界面是在哪里设置的呢，我们可以看到第二句this.eventDelegate.onCreate(savedInstanceState);，最终我们发现Activity中显示的view是在代理类中进行初始化的，下面看下代理类FlutterActivityDelegate的执行,

//FlutterActivityDelegate.javapublic void onCreate(Bundle savedInstanceState) {...String[] args = getArgsFromIntent(this.activity.getIntent());FlutterMain.ensureInitializationComplete(this.activity.getApplicationContext(), args);this.flutterView = this.viewFactory.createFlutterView(this.activity);if (this.flutterView == null) {FlutterNativeView nativeView = this.viewFactory.createFlutterNativeView();this.flutterView = new FlutterView(this.activity, (AttributeSet)null, nativeView);this.flutterView.setLayoutParams(matchParent);this.activity.setContentView(this.flutterView);this.launchView = this.createLaunchView();if (this.launchView != null) {this.addLaunchView();}}...this.runBundle(appBundlePath);...
}
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在这里我们需要注意FlutterMain.ensureInitializationComplete的执行，

//FlutterMain.javapublic static void ensureInitializationComplete(Context applicationContext, String[] args) {...sResourceExtractor.waitForCompletion();...nativeInit(applicationContext, (String[])shellArgs.toArray(new String[0]), appBundlePath, appStoragePath, engineCachesPath);sInitialized = true;...
}//c++关键方法1
private static native void nativeInit(Context var0, String[] var1, String var2, String var3, String var4);
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它将等待解压任务结束，资源处理完毕，然后拼接参数，完成参数初始化后将执行nativeInit方法对c++层初始化。

然后会创建FlutterView对象，这里面还包含了很多关键对象的创建，这个下文将会分析到。

//FlutterView.java的构造方法
public FlutterView(Context context, AttributeSet attrs, FlutterNativeView nativeView) {super(context, attrs);...if (nativeView == null) {this.mNativeView = new FlutterNativeView(activity.getApplicationContext());} else {this.mNativeView = nativeView;}this.mNativeView.getFlutterJNI();this.mIsSoftwareRenderingEnabled = FlutterJNI.nativeGetIsSoftwareRenderingEnabled();...this.mNativeView.attachViewAndActivity(this, activity);this.mSurfaceCallback = new Callback() {public void surfaceCreated(SurfaceHolder holder) {FlutterView.this.assertAttached();FlutterView.this.mNativeView.getFlutterJNI().onSurfaceCreated(holder.getSurface());}public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {FlutterView.this.assertAttached();FlutterView.this.mNativeView.getFlutterJNI().onSurfaceChanged(width, height);}public void surfaceDestroyed(SurfaceHolder holder) {FlutterView.this.assertAttached();FlutterView.this.mNativeView.getFlutterJNI().onSurfaceDestroyed();}};this.getHolder().addCallback(this.mSurfaceCallback);this.mAccessibilityManager = (AccessibilityManager)this.getContext().getSystemService("accessibility");...this.mFlutterLocalizationChannel = new MethodChannel(this, "flutter/localization", JSONMethodCodec.INSTANCE);...
}
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这个方法中先执行FlutterNativeView对象创建，然后是FlutterJNI对象创建，再通过c++层完成两者的绑定关系。另外activity和flutterView的绑定关系也在这里完成，并会在PlatformViewsController中完成注册方法回调关系。这个方法还包含了界面绘制监听，flutter绘制的关键调用，建立了通讯体系（各类Channel）。在c++层会用到的资源处理对象也是从这里创建的。

//FlutterNativeView.java构造方法public FlutterNativeView(Context context, boolean isBackgroundView) {this.mPluginRegistry = new FlutterPluginRegistry(this, context);this.mFlutterJNI = new FlutterJNI();this.mFlutterJNI.setRenderSurface(new FlutterNativeView.RenderSurfaceImpl());this.mFlutterJNI.setPlatformMessageHandler(new FlutterNativeView.PlatformMessageHandlerImpl());this.mFlutterJNI.addEngineLifecycleListener(new FlutterNativeView.EngineLifecycleListenerImpl());this.attach(this, isBackgroundView);....
}
//c++关键方法2
private native long nativeAttach(FlutterJNI var1, boolean var2);
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FlutterPluginRegistry是actitiy和flutterView绑定关系操作类，而FlutterJNI创建时，将绑定绘制、跨平台通讯、生命周期的监听方法。这里还会涉及到nativeAttach这个c++方法，等一会将会分析到。

继续看runBundle的执行

//FlutterView.javaprivate FlutterNativeView mNativeView;
public void runFromBundle(FlutterRunArguments args) {assertAttached();preRun();mNativeView.runFromBundle(args);...
}//FlutterNativeView.javapublic void runFromBundle(FlutterRunArguments args) {...runFromBundleInternal(new String[] {args.bundlePath, args.defaultPath},args.entrypoint, args.libraryPath);...
}/**
* 这里通过demo，我们需要留意下传入的数据，方便接下来的分析
* bundlePaths:（flutter_assets目录地址）
* entrypoint："main"
* libraryPath：null
*
*/
private void runFromBundleInternal(String[] bundlePaths, String entrypoint,String libraryPath) {....mFlutterJNI.runBundleAndSnapshotFromLibrary(bundlePaths,entrypoint,libraryPath,mContext.getResources().getAssets());....
}
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此时，runFromBundle会先判断资源的绑定，把一些参数通过runBundleAndSnapshotFromLibrary方法中mFlutterJNI对象调用JNI方法来传递指定flutter入口供DartVM执行dart层代码逻辑。

//FlutterJNI.java@UiThread
public void runBundleAndSnapshotFromLibrary(@NonNull String[] prioritizedBundlePaths, @Nullable String entrypointFunctionName, @Nullable String pathToEntrypointFunction, @NonNull AssetManager assetManager) {this.ensureAttachedToNative();this.nativeRunBundleAndSnapshotFromLibrary(this.nativePlatformViewId, prioritizedBundlePaths, entrypointFunctionName, pathToEntrypointFunction, assetManager);
}//最终样例数据：pathToEntrypointFunction = null，entrypointFunctionName="main"
//prioritizedBundlePaths同上面，nativePlatformViewId = 3719055232
private native void nativeRunBundleAndSnapshotFromLibrary(long nativePlatformViewId,@NonNull String[] prioritizedBundlePaths,@Nullable String entrypointFunctionName,@Nullable String pathToEntrypointFunction,@NonNull AssetManager manager
);
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nativeRunBundleAndSnapshotFromLibrary 则是native启动方法的入口，另外这个 nativePlatformViewId 是在FlutterNativeView 创建的时候调用了FlutterJNI的attachToNative方法，其来源是native层shell_holder对象指针，这个对象指针在native启动过程中非常关键。

再看MainActivity中onCreate执行，GeneratedPluginRegistrant.registerWith(this)将执行到如下代码中

//FlutterActivityDelegate.javaprivate FlutterView flutterView;
@Override
public Registrar registrarFor(String pluginKey) {return flutterView.getPluginRegistry().registrarFor(pluginKey);
}//FlutterPluginRegistry.java@Override
public Registrar registrarFor(String pluginKey) {if (mPluginMap.containsKey(pluginKey)) {throw new IllegalStateException("Plugin key " + pluginKey + " is already in use");}mPluginMap.put(pluginKey, null);return new FlutterRegistrar(pluginKey);
}
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registrarFor保存了插件的实例，避免重复注册。

onStart:

以下方法通过生命周期对应的Platform Channel发送生命周期状态给Flutter层来告知当前的APP状态。

this.mFlutterLifecycleChannel.send("AppLifecycleState.inactive");
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onResume:

public void onResume() {Application app = (Application)this.activity.getApplicationContext();FlutterMain.onResume(app);if (app instanceof FlutterApplication) {FlutterApplication flutterApp = (FlutterApplication)app;flutterApp.setCurrentActivity(this.activity);}
}public static void onResume(Context context) {//热更新有关，这里也不分析if (sResourceUpdater != null && sResourceUpdater.getDownloadMode() == DownloadMode.ON_RESUME) {sResourceUpdater.startUpdateDownloadOnce();}
}
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到这里基本完成了java层分析，主要方法调用链可以参考如下

接下来将需要分析的关键JNI方法罗列如下：

• nativeInit
• nativeAttach
• nativeRunBundleAndSnapshotFromLibrary

c/c++层启动过程

nativeInit分析

我们直接找到对应的方法，位于shell/platform/android/flutter_main.cc

void FlutterMain::Init(JNIEnv* env,jclass clazz,jobject context,jobjectArray jargs,jstring bundlePath,jstring appStoragePath,jstring engineCachesPath) {std::vector<std::string> args;args.push_back("flutter");for (auto& arg : fml::jni::StringArrayToVector(env, jargs)) {args.push_back(std::move(arg));}auto command_line = fml::CommandLineFromIterators(args.begin(), args.end());auto settings = SettingsFromCommandLine(command_line);settings.assets_path = fml::jni::JavaStringToString(env, bundlePath);...settings.task_observer_add = [](intptr_t key, fml::closure callback) {fml::MessageLoop::GetCurrent().AddTaskObserver(key, std::move(callback));};settings.task_observer_remove = [](intptr_t key) {fml::MessageLoop::GetCurrent().RemoveTaskObserver(key);};...g_flutter_main.reset(new FlutterMain(std::move(settings)));
}
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这里做了几件事情：

• 解析java传过来的参数
• 创建Setting，保存配置
• 创建FlutterMain，重置其全局对象

nativeAttach分析

static jlong AttachJNI(JNIEnv* env,jclass clazz,jobject flutterJNI,jboolean is_background_view) {fml::jni::JavaObjectWeakGlobalRef java_object(env, flutterJNI);auto shell_holder = std::make_unique<AndroidShellHolder>(FlutterMain::Get().GetSettings(), java_object, is_background_view);if (shell_holder->IsValid()) {return reinterpret_cast<jlong>(shell_holder.release());} else {return 0;}
}//shell/platform/android/android_shell_holder.cc
AndroidShellHolder::AndroidShellHolder(blink::Settings settings,fml::jni::JavaObjectWeakGlobalRef java_object,bool is_background_view): settings_(std::move(settings)), java_object_(java_object) {...auto jni_exit_task([key = thread_destruct_key_]() {FML_CHECK(pthread_setspecific(key, reinterpret_cast<void*>(1)) == 0);});thread_host_.ui_thread->GetTaskRunner()->PostTask(jni_exit_task);if (!is_background_view) {thread_host_.gpu_thread->GetTaskRunner()->PostTask(jni_exit_task);}...fml::MessageLoop::EnsureInitializedForCurrentThread();fml::RefPtr<fml::TaskRunner> gpu_runner;fml::RefPtr<fml::TaskRunner> ui_runner;fml::RefPtr<fml::TaskRunner> io_runner;fml::RefPtr<fml::TaskRunner> platform_runner =fml::MessageLoop::GetCurrent().GetTaskRunner();if (is_background_view) {auto single_task_runner = thread_host_.ui_thread->GetTaskRunner();gpu_runner = single_task_runner;ui_runner = single_task_runner;io_runner = single_task_runner;} else {gpu_runner = thread_host_.gpu_thread->GetTaskRunner();ui_runner = thread_host_.ui_thread->GetTaskRunner();io_runner = thread_host_.io_thread->GetTaskRunner();}blink::TaskRunners task_runners(thread_label,     // labelplatform_runner,  // platformgpu_runner,       // gpuui_runner,        // uiio_runner         // io);shell_ =Shell::Create(task_runners,             // task runnerssettings_,                // settingson_create_platform_view,  // platform view create callbackon_create_rasterizer      // rasterizer create callback);...
}std::unique_ptr<Shell> Shell::Create(blink::TaskRunners task_runners,blink::Settings settings,Shell::CreateCallback<PlatformView> on_create_platform_view,Shell::CreateCallback<Rasterizer> on_create_rasterizer) {PerformInitializationTasks(settings);auto vm = blink::DartVM::ForProcess(settings);FML_CHECK(vm) << "Must be able to initialize the VM.";return Shell::Create(std::move(task_runners),             //std::move(settings),                 //vm->GetIsolateSnapshot(),            //blink::DartSnapshot::Empty(),        //std::move(on_create_platform_view),  //std::move(on_create_rasterizer)      //);
}
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nativeAttach的方法中，调用了AndroidShellHolder对象的创建，包含了JNI生命周期同UI和GPU线程绑定， 视图回调和c++层绘制绑定，启动一些必要的线程。而shell对象的创建中，PerformInitializationTasks包含了一些关键库的初始化，如skia（图形绘制库）、ICU(国际化库)等初始化，shell对象的创建也标志着dart vm的创建。

关键点：AndroidShellHolder对象创建完成后，会将其对象指针值返回给java层保存，用于后续安卓原生层对Flutter层各操作方法的调用。

nativeRunBundleAndSnapshotFromLibrary 分析

在shell/platform/android/io/platform_view_android_jni.cc中，我们很容易找到对应的方法，是采用动态注册的方式：

  {.name = "nativeRunBundleAndSnapshotFromLibrary",.signature = "(J[Ljava/lang/String;Ljava/lang/String;""Ljava/lang/String;Landroid/content/res/AssetManager;)V",.fnPtr =reinterpret_cast<void*>(&shell::RunBundleAndSnapshotFromLibrary),}
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static void RunBundleAndSnapshotFromLibrary(JNIEnv* env,jobject jcaller,jlong shell_holder,jobjectArray jbundlepaths,jstring jEntrypoint,jstring jLibraryUrl,jobject jAssetManager) {auto asset_manager = std::make_shared<blink::AssetManager>();for (const auto& bundlepath :fml::jni::StringArrayToVector(env, jbundlepaths)) {...const auto file_ext_index = bundlepath.rfind(".");if (bundlepath.substr(file_ext_index) == ".zip") {//资源解压asset_manager->PushBack(std::make_unique<blink::ZipAssetStore>(bundlepath, "assets/flutter_assets"));} else {//操作资源地址并存储到容器中asset_manager->PushBack(std::make_unique<blink::DirectoryAssetBundle>(fml::OpenDirectory(bundlepath.c_str(), false, fml::FilePermission::kRead)));...}}auto isolate_configuration = CreateIsolateConfiguration(*asset_manager);...RunConfiguration config(std::move(isolate_configuration),std::move(asset_manager));{auto entrypoint = fml::jni::JavaStringToString(env, jEntrypoint);auto libraryUrl = fml::jni::JavaStringToString(env, jLibraryUrl);if ((entrypoint.size() > 0) && (libraryUrl.size() > 0)) {//设置dart的入口函数，entrypoint为“main”，引用库地址config.SetEntrypointAndLibrary(std::move(entrypoint),std::move(libraryUrl));} else if (entrypoint.size() > 0) {config.SetEntrypoint(std::move(entrypoint));}}ANDROID_SHELL_HOLDER->Launch(std::move(config));
}
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从上面的方法我们可以简单的总结下这个方法做了什么：

• 资源的解压
• 创建AppSnapshotIsolateConfiguration对象
• 执行配置项
• 执行启动方法

android_shell_holder.cc

void AndroidShellHolder::Launch(RunConfiguration config) {//is_valid_ = shell_ != nullptr;正常情况下为trueif (!IsValid()) {return;}shell_->GetTaskRunners().GetUITaskRunner()->PostTask(fml::MakeCopyable([engine = shell_->GetEngine(),  //拿到了引擎的弱引用对象config = std::move(config)     ]() mutable {...//nextif (!engine || engine->Run(std::move(config)) ==shell::Engine::RunStatus::Failure) {...}...}));
}
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Launch方法中拿到engine对象后，调用Run的执行

//engine.cc
Engine::RunStatus Engine::Run(RunConfiguration configuration) {...auto isolate_launch_status =PrepareAndLaunchIsolate(std::move(configuration));....
}shell::Engine::RunStatus Engine::PrepareAndLaunchIsolate(RunConfiguration configuration) {TRACE_EVENT0("flutter", "Engine::PrepareAndLaunchIsolate");UpdateAssetManager(configuration.GetAssetManager());auto isolate_configuration = configuration.TakeIsolateConfiguration();std::shared_ptr<blink::DartIsolate> isolate =runtime_controller_->GetRootIsolate().lock();if (!isolate) {return RunStatus::Failure;}...if (!isolate_configuration->PrepareIsolate(*isolate)) {FML_LOG(ERROR) << "Could not prepare to run the isolate.";return RunStatus::Failure;}if (configuration.GetEntrypointLibrary().empty()) {if (!isolate->Run(configuration.GetEntrypoint())) {FML_LOG(ERROR) << "Could not run the isolate.";return RunStatus::Failure;}} else {if (!isolate->RunFromLibrary(configuration.GetEntrypointLibrary(),configuration.GetEntrypoint())) {FML_LOG(ERROR) << "Could not run the isolate.";return RunStatus::Failure;}}return RunStatus::Success;
}
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在engine的启动过程中，准备和启动isolate,在这个方法中将完成对isolate创建、及状态返回处理。更新资源管理后，PrepareIsolate方法主要检查Isolate的状态，通过属性phase（枚举）来表示不同的状态，然后我们再结合java层传递的数据，可以知道将执行isolate->Run方法。

//dart_api_impl.cc
FML_WARN_UNUSED_RESULT
bool DartIsolate::Run(const std::string& entrypoint_name) {...   auto user_entrypoint_function =Dart_GetField(Dart_RootLibrary(), tonic::ToDart(entrypoint_name.c_str()));if (!InvokeMainEntrypoint(user_entrypoint_function)) {return false;}...
}
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Run方法中也比较简单，继续看下文。

//dart_isolate.cc
FML_WARN_UNUSED_RESULT
static bool InvokeMainEntrypoint(Dart_Handle user_entrypoint_function) {...Dart_Handle start_main_isolate_function =tonic::DartInvokeField(Dart_LookupLibrary(tonic::ToDart("dart:isolate")),"_getStartMainIsolateFunction", {});...if (tonic::LogIfError(tonic::DartInvokeField(Dart_LookupLibrary(tonic::ToDart("dart:ui")), "_runMainZoned",{start_main_isolate_function, user_entrypoint_function}))) {FML_LOG(ERROR) << "Could not invoke the main entrypoint.";return false;}return true;
}
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在InvokeMainEntrypoint方法中 会拿到了Dart_Handle对象，并通过DartInvokeField方法执行Dart_Invoke方法。另外Dart_LookupLibrary中创建的对象是一个Library，这个是下个方法执行步骤的判断依据。

dart_api_impl.cc

DART_EXPORT Dart_Handle Dart_Invoke(Dart_Handle target,Dart_Handle name,int number_of_arguments,Dart_Handle* arguments) {                               DARTSCOPE(Thread::Current());API_TIMELINE_DURATION(T);CHECK_CALLBACK_STATE(T);String& function_name =String::Handle(Z, Api::UnwrapStringHandle(Z, name).raw());if (function_name.IsNull()) {RETURN_TYPE_ERROR(Z, name, String);}if (number_of_arguments < 0) {return Api::NewError("%s expects argument 'number_of_arguments' to be non-negative.",CURRENT_FUNC);}...if (obj.IsType()) {...const Class& cls = Class::Handle(Z, Type::Cast(obj).type_class());...//分析节点1return Api::NewHandle(T, cls.Invoke(function_name, args, arg_names, respect_reflectable,check_is_entrypoint));} else if (obj.IsNull() || obj.IsInstance()) {...Instance& instance = Instance::Handle(Z);...//分析节点2return Api::NewHandle(T, instance.Invoke(function_name, args, arg_names, respect_reflectable,check_is_entrypoint));} else if (obj.IsLibrary()) {...const Library& lib = Library::Cast(obj);...//分析节点3return Api::NewHandle(T, lib.Invoke(function_name, args, arg_names, respect_reflectable,check_is_entrypoint));} ...
}
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在Dart_Invoke方法中，会先进行状态检查 ，然后拿到由java层传递过来的dart 入口函数对应的方法名（也就"main"），注意在这个方法中，不管是错误还是正确都是返回Dart_Handle这个对像。然后再看这个三个分析节点，根据上面的分析，将会执行节点3

//object.cc
RawObject* Library::Invoke(const String& function_name,const Array& args,const Array& arg_names,bool respect_reflectable,bool check_is_entrypoint) const {...Function& function = Function::Handle(zone, LookupStaticFunction(function_name));...return DartEntry::InvokeFunction(function, args, args_descriptor_array);  ...
}
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Invoke方法将会通过方法名拿到内存中Function对象，然后通过dart执行该方法。

这里留意下DartEntry这个类，看源码的注释大意是提取解析dart函数所需的功能的操作对象。是dart函数调用的重要对象之一，接着看看InvokeFunction做了什么。

third_party/dart/runtime/vm/dart_entry.cc

RawObject* DartEntry::InvokeFunction(const Function& function,const Array& arguments,const Array& arguments_descriptor,uword current_sp) {
...
#if defined(TARGET_ARCH_DBC)//具体方法解析调用return Simulator::Current()->Call(code, arguments_descriptor, arguments,thread);
#elif defined(USING_SIMULATOR)//模拟器return bit_copy<RawObject*, int64_t>(Simulator::Current()->Call(reinterpret_cast<intptr_t>(entrypoint), reinterpret_cast<intptr_t>(&code),reinterpret_cast<intptr_t>(&arguments_descriptor),reinterpret_cast<intptr_t>(&arguments),reinterpret_cast<intptr_t>(thread)));...
}
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InvokeFunction 中将先会对Function对象内容是否编译过进行判断（未编译将编译重新调用),拿到当前线程去执行。该方法还会区分生产环境，是否是模拟器等情况对方法进行解析，解析方法执行可以参考Simulator::Current()->Call，在Call的方法内我们可以看到整个方法非常庞大，光方法体就有几千行代码，包含了常量值、字节码等的操作，所以这一篇文章就不展开分析。有兴趣的朋友可以结合虚拟机原理，看看这部分是如何执行的。

总结

至此我们大致看到了整个启动过程，在java层主要是对flutter资源相关的参数进行了赋值、初始化，以及回调方法的注册，资源的拷贝，c++关键方法的调用，建立了通讯体系（各类Channel）。而在c++层，我们发现除去关键对象的创建，还有各类异常的处理（包含各种情况的考量），参数的解析，资源的解析，方法对象的构建等一系列的调用，最后通过dart vm的操作对象对方法进行解析与执行。

作者简介

苏哲，铜板街Android开发工程师，2017年12月加入团队，目前主要负责APP端 Android 日常开发。

本文重点介绍了安卓平台Flutter启动过程的机制，如需获取更多 Flutter 相关的知识，可以扫码关注 “ 铜板街科技 ”公众号 ，并在后台回复 "Flutter" 关键词获取更多精彩内容。