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This article introduces the relevant knowledge of "how the Flutter initialization process is". Many people will encounter such a dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Flutter initialization timing

Flutter initialization is divided into four parts: FlutterMain initialization, FlutterNativeView initialization, FlutterView initialization and Flutter Bundle initialization.

PlatformViewAndroid::PlatformViewAndroid (): PlatformView (std::make_unique ()), android_surface_ (InitializePlatformSurface ()) {} void PlatformViewAndroid::Attach () {CreateEngine (); / / Eagerly setup the IO thread context. We have already setup the surface. SetupResourceContextOnIOThread (); UpdateThreadPriorities ()

Where:

1. The constructor of PlatformViewAndroid mainly calls the InitializePlatformSurface method, which initializes Surface, in which Surface has the difference of Vulkan, OpenGL and Software.

2. The PlatformViewAndroid::Attach method here mainly calls three methods: CreateEngine, SetupResourceContextOnIOThread and UpdateThreadPriorities.

2.1 CreateEngine is easy to understand. Create an Engine, and here you will recreate an Engine object.

2.2 SetupResourceContextOnIOThread is the context logic in the IO thread to prepare the resource.

2.3 UpdateThreadPriorities sets the thread priority, which sets the GPU thread priority to-2 and UI thread priority to-1.

FlutterView initialization

The initialization of FlutterView is a pure Android layer, so it is relatively simple. If you analyze the constructor of FlutterView.java, you will find that the initialization of the entire FlutterView does two main things besides ensuring the successful creation of FlutterNativeView and some necessary view settings:

1. Register SurfaceHolder snooping, where the surfaceCreated callback will be used as the first frame callback of the Flutter.

two。 Initialize a series of bridging methods that need to be used in Flutter system. For example: localization, navigation, keyevent, system, settings, platform, textinput.

The FlutterView initialization process is mainly shown in the following figure:

Flutter Bundle initialization

Initialization of FlutterBundle starts with a call to FlutterActivityDelegate.runFlutterBundle

Let's take a more in-depth look at the source code:

The onCreate method of FlutterActivity calls its runFlutterBundle method after executing the onCreate method of FlutterActivityDelegate. The runFlutterBundle code is as follows:

Public void runFlutterBundle () {/ / other codes... String appBundlePath = FlutterMain.findAppBundlePath (activity.getApplicationContext ()); if (appBundlePath! = null) {flutterView.runFromBundle (appBundlePath, null, "main", reuseIsolate);}}

Obviously, this runFlutterBundle doesn't do much and calls the FlutterView.runFromBundle method directly. Then walk around and finally call the PlatformViewAndroid::RunBundleAndSnapshot method.

Void PlatformViewAndroid::RunBundleAndSnapshot (JNIEnv* env, std::string bundle_path, std::string snapshot_override, std::string entrypoint, bool reuse_runtime_controller Jobject assetManager) {/ / other codes... Blink::Threads::UI ()-> PostTask ([engine = engine_- > GetWeakPtr (), asset_provider = std::move (asset_provider), bundle_path = std::move (bundle_path), entrypoint = std::move (entrypoint), reuse_runtime_controller = reuse_runtime_controller] {if (engine) engine- > RunBundleWithAssets (std::move (asset_provider), std::move (bundle_path) Std::move (entrypoint), reuse_runtime_controller) });}

PlatformViewAndroid::RunBundleAndSnapshot calls Engine::RunBundleWithAssets in the UI thread, eventually calling Engine::DoRunBundle.

The DoRunBundle method ends up calling only one of the three methods RunFromPrecompiledSnapshot, RunFromKernel, and RunFromScriptSnapshot. All three methods end up calling the SendStartMessage method.

Bool DartController::SendStartMessage (Dart_Handle root_library, const std::string& entrypoint) {/ / other codes... / / Get the closure of main (). Dart_Handle main_closure = Dart_GetClosure (root_library, Dart_NewStringFromCString (entrypoint.c_str (); / / other codes... / / Grab the 'dart:isolate' library. Dart_Handle isolate_lib = Dart_LookupLibrary (ToDart ("dart:isolate")); DART_CHECK_VALID (isolate_lib); / / Send the start message containing the entry point by calling / / _ startMainIsolate in dart:isolate. Const intptr_t kNumIsolateArgs = 2; Dart_Handle isolate_ Args [kNumIsolateArgs]; isolate_args [0] = main_closure; isolate_args [1] = Dart_Null (); Dart_Handle result = Dart_Invoke (isolate_lib, ToDart ("_ startMainIsolate"), kNumIsolateArgs, isolate_args); return LogIfError (result);}

The SendStartMessage method does three main things:

1. Gets the closure of the Flutter entry method, such as the main method.

two。 Get the FlutterLibrary.

3. Send a message to invoke the entry method of Flutter.

This is the end of the content of "what is the initialization process of Flutter". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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