FlutterView
- 继承 SurfaceView，它的外部有两个线程即主线程和渲染线程，应用渲染线程中向屏幕上绘图能够防止主线程阻塞，从而进步了程序的反应速度。应用了双缓冲机制。
- 实现 BinaryMesaenger 接口，这个接口定义了 Android 代码和 Flutter 代码间接通信的形式，此接口还有 2 个外部接口。FlutterView 实现了这个接口，领有了和 flutter 通信的的能力
- 实现 TextureRegistry 接口，这个接口次要是创立一个 SurfaceTexture 对象，应用 SurfaceTextureEntry 包装起来，领有惟一的 ID。
- 实现 onAccessibilityChanged 接口，次要用来监听系统 accessibility 状态变动的。
-
创立一大堆 Channel 用于 Android 和 flutter 通信
navigationChannel = new NavigationChannel(dartExecutor); keyEventChannel = new KeyEventChannel(dartExecutor); lifecycleChannel = new LifecycleChannel(dartExecutor); localizationChannel = new LocalizationChannel(dartExecutor); platformChannel = new PlatformChannel(dartExecutor); systemChannel = new SystemChannel(dartExecutor); settingsChannel = new SettingsChannel(dartExecutor); -
创立 FlutterNativeView
// 初始化 mNativeView = new FlutterNativeView(activity.getApplicationContext()); OnAccessibilityChangeListener AccessibilityStateChangeListener -
创立一堆成员变量
mIsSoftwareRenderingEnabled 硬件加速渲染相干的
dartExecutor = mNativeView.getDartExecutor(); flutterRenderer = new FlutterRenderer(mNativeView.getFlutterJNI()); mIsSoftwareRenderingEnabled = mNativeView.getFlutterJNI().nativeGetIsSoftwareRenderingEnabled(); mMetrics = new ViewportMetrics(); mMetrics.devicePixelRatio = context.getResources().getDisplayMetrics().density; setFocusable(true); setFocusableInTouchMode(true); //attach 到以后 Activity mNativeView.attachViewAndActivity(this, activity); mSurfaceCallback = new SurfaceHolder.Callback() { @Override public void surfaceCreated(SurfaceHolder holder) {assertAttached(); mNativeView.getFlutterJNI().onSurfaceCreated(holder.getSurface()); } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {assertAttached(); mNativeView.getFlutterJNI().onSurfaceChanged(width, height); } @Override public void surfaceDestroyed(SurfaceHolder holder) {assertAttached(); mNativeView.getFlutterJNI().onSurfaceDestroyed(); } };
FlutterNativeView
- 创立
if (nativeView == null) {mNativeView = new FlutterNativeView(activity.getApplicationContext());
} else {mNativeView = nativeView;}
public FlutterNativeView(@NonNull Context context, boolean isBackgroundView) {
mContext = context;
mPluginRegistry = new FlutterPluginRegistry(this, context);
mFlutterJNI = new FlutterJNI();
mFlutterJNI.addIsDisplayingFlutterUiListener(flutterUiDisplayListener);
this.dartExecutor = new DartExecutor(mFlutterJNI, context.getAssets());
mFlutterJNI.addEngineLifecycleListener(new EngineLifecycleListenerImpl());
attach(this, isBackgroundView);
assertAttached();}- FlutterPluginRegistry 是 actitiy 和 flutterView 绑定关系操作类，而 FlutterJNI 创立时，将绑定绘制、跨平台通信、生命周期的监听办法。
- mFlutterJNI，Engine 层 c ++ 办法的一个封装类。所有 Flutter JNI 的调用都汇合在这个类中。一个 FlutterJNI 对象是和一个 Platform View 相关联，所以蕴含一个 nativePlatformViewId 来标识
attach(this, isBackgroundView);
private void attach(FlutterNativeView view, boolean isBackgroundView) {mFlutterJNI.attachToNative(isBackgroundView);
dartExecutor.onAttachedToJNI();}
public void attachToNative(boolean isBackgroundView) {ensureRunningOnMainThread();
ensureNotAttachedToNative();
nativePlatformViewId = nativeAttach(this, isBackgroundView);
}总结
- FlutterView 提供了 SurfaceView 来绘制 Flutter 的 UI
- 同时把 Android 的生命周期、点击事件等信息发送给 Flutter。
- FlutterView 并不负责间接和 Flutter Engine 通信，具体的通信性能在 FlutterNativeView
- FlutterNativeView 外部有一个 FlutterJNI，它负责调用 Flutter Engine 的 C ++ 代码。
java 到 c ++ 调用
public void attachToNative(boolean isBackgroundView) {ensureRunningOnMainThread();
ensureNotAttachedToNative();
nativePlatformViewId = nativeAttach(this, isBackgroundView);
}
//nativeAttach 对应
bool RegisterApi(JNIEnv* env) {static const JNINativeMethod flutter_jni_methods[] = {
// Start of methods from FlutterJNI
{
.name = "nativeAttach",
.signature = "(Lio/flutter/embedding/engine/FlutterJNI;Z)J",
.fnPtr = reinterpret_cast<void*>(&AttachJNI),
},
// 对应到 AttachJNI
static jlong AttachJNI(JNIEnv* env,
jclass clazz,
jobject flutterJNI,
jboolean is_background_view) {fml::jni::JavaObjectWeakGlobalRef java_object(env, flutterJNI);
std::shared_ptr<PlatformViewAndroidJNI> jni_facade =
std::make_shared<PlatformViewAndroidJNIImpl>(java_object);
auto shell_holder = std::make_unique<AndroidShellHolder>(FlutterMain::Get().GetSettings(), jni_facade, is_background_view);
if (shell_holder->IsValid()) {return reinterpret_cast<jlong>(shell_holder.release());
} else {return 0;}
}
// 创立 auto shell_holder = std::make_unique<AndroidShellHolder>
// 对应 flutter/shell/platform/android/android_shell_holder.cc
AndroidShellHolder::AndroidShellHolder 创建对象
engine 初始化
AndroidShellHolder::AndroidShellHolder(
flutter::Settings settings,
std::shared_ptr<PlatformViewAndroidJNI> jni_facade,
bool is_background_view)
: settings_(std::move(settings)), jni_facade_(jni_facade) {
static size_t shell_count = 1;
auto thread_label = std::to_string(shell_count++);
FML_CHECK(pthread_key_create(&thread_destruct_key_, ThreadDestructCallback) ==
0);
if (is_background_view) {thread_host_ = {thread_label, ThreadHost::Type::UI};
} else {
thread_host_ = {thread_label, ThreadHost::Type::UI | ThreadHost::Type::GPU |
ThreadHost::Type::IO};
}
// Detach from JNI when the UI and raster threads exit.
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_.raster_thread->GetTaskRunner()->PostTask(jni_exit_task);
}
fml::WeakPtr<PlatformViewAndroid> weak_platform_view;
// 创立 PlatformViewAndroid
// 创立 on_create_platform_view
Shell::CreateCallback<PlatformView> on_create_platform_view =
[is_background_view, &jni_facade, &weak_platform_view](Shell& shell) {
std::unique_ptr<PlatformViewAndroid> platform_view_android;
if (is_background_view) {
platform_view_android = std::make_unique<PlatformViewAndroid>(
shell, // delegate
shell.GetTaskRunners(), // task runners
jni_facade // JNI interop
);
} else {
platform_view_android = std::make_unique<PlatformViewAndroid>(
shell, // delegate
shell.GetTaskRunners(), // task runners
jni_facade, // JNI interop
shell.GetSettings()
.enable_software_rendering // use software rendering
);
}
weak_platform_view = platform_view_android->GetWeakPtr();
return platform_view_android;
};
Shell::CreateCallback<Rasterizer> on_create_rasterizer = [](Shell& shell) {return std::make_unique<Rasterizer>(shell, shell.GetTaskRunners(),
shell.GetIsGpuDisabledSyncSwitch());
};
// 创立四个线程 并把以后线程设置 platform thread
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_.raster_thread->GetTaskRunner();
ui_runner = thread_host_.ui_thread->GetTaskRunner();
io_runner = thread_host_.io_thread->GetTaskRunner();}
flutter::TaskRunners task_runners(thread_label, // label
platform_runner, // platform
gpu_runner, // raster
ui_runner, // ui
io_runner // io
);
//shell 创立
// 不论是 iOS，Android，linux，嵌入式平台，都有对应的 Shell::Create，差别最大的应该是 web 端，web 端的整体架构形式就齐全不同。//Create 的 时候传入 platform view create
shell_ =
Shell::Create(task_runners, // task runners
GetDefaultWindowData(), // window data
settings_, // settings
on_create_platform_view, // platform view create callback
on_create_rasterizer // rasterizer create callback
);
platform_view_ = weak_platform_view;
FML_DCHECK(platform_view_);
is_valid_ = shell_ != nullptr;
if (is_valid_) {task_runners.GetRasterTaskRunner()->PostTask([]() {
// Android describes -8 as "most important display threads, for
// compositing the screen and retrieving input events". Conservatively
// set the raster thread to slightly lower priority than it.
if (::setpriority(PRIO_PROCESS, gettid(), -5) != 0) {
// Defensive fallback. Depending on the OEM, it may not be possible
// to set priority to -5.
if (::setpriority(PRIO_PROCESS, gettid(), -2) != 0) {FML_LOG(ERROR) << "Failed to set GPU task runner priority";
}
}
});
task_runners.GetUITaskRunner()->PostTask([]() {if (::setpriority(PRIO_PROCESS, gettid(), -1) != 0) {FML_LOG(ERROR) << "Failed to set UI task runner priority";
}
});
}
}Shell::Create 中调用 shell = CreateShellOnPlatformThread，而后回调 on_create_platform_view
std::unique_ptr<Shell> Shell::CreateShellOnPlatformThread 中过程
- 创立 shell
auto shell =
std::unique_ptr<Shell>(new Shell(std::move(vm), task_runners, settings));
- 创立 platform view
auto platform_view = on_create_platform_view(*shell.get());
if (!platform_view || !platform_view->GetWeakPtr()) {return nullptr;- 创立 rasterizer
std::promise<std::unique_ptr<Rasterizer>> rasterizer_promise;
auto rasterizer_future = rasterizer_promise.get_future();
std::promise<fml::WeakPtr<SnapshotDelegate>> snapshot_delegate_promise;
auto snapshot_delegate_future = snapshot_delegate_promise.get_future();
fml::TaskRunner::RunNowOrPostTask(task_runners.GetRasterTaskRunner(), [&rasterizer_promise, //
&snapshot_delegate_promise,
on_create_rasterizer, //
shell = shell.get() //]() {TRACE_EVENT0("flutter", "ShellSetupGPUSubsystem");
std::unique_ptr<Rasterizer> rasterizer(on_create_rasterizer(*shell));
snapshot_delegate_promise.set_value(rasterizer->GetSnapshotDelegate());
rasterizer_promise.set_value(std::move(rasterizer));
});- 创立 IO manager
std::promise<std::unique_ptr<ShellIOManager>> io_manager_promise;
auto io_manager_future = io_manager_promise.get_future();
std::promise<fml::WeakPtr<ShellIOManager>> weak_io_manager_promise;
auto weak_io_manager_future = weak_io_manager_promise.get_future();
std::promise<fml::RefPtr<SkiaUnrefQueue>> unref_queue_promise;
auto unref_queue_future = unref_queue_promise.get_future();
auto io_task_runner = shell->GetTaskRunners().GetIOTaskRunner();- 创立 engine
std::promise<std::unique_ptr<Engine>> engine_promise;
auto engine_future = engine_promise.get_future();
fml::TaskRunner::RunNowOrPostTask(shell->GetTaskRunners().GetUITaskRunner(),
fml::MakeCopyable([&engine_promise, //
shell = shell.get(), //
&dispatcher_maker, //
&window_data, //
isolate_snapshot = std::move(isolate_snapshot), //
vsync_waiter = std::move(vsync_waiter), //
&weak_io_manager_future, //
&snapshot_delegate_future, //
&unref_queue_future //
]() mutable {TRACE_EVENT0("flutter", "ShellSetupUISubsystem");
const auto& task_runners = shell->GetTaskRunners();
// The animator is owned by the UI thread but it gets its vsync pulses
// from the platform.
auto animator = std::make_unique<Animator>(*shell, task_runners,
std::move(vsync_waiter));
engine_promise.set_value(std::make_unique<Engine>(
*shell, //
dispatcher_maker, //
*shell->GetDartVM(), //
std::move(isolate_snapshot), //
task_runners, //
window_data, //
shell->GetSettings(), //
std::move(animator), //
weak_io_manager_future.get(), //
unref_queue_future.get(), //
snapshot_delegate_future.get() //));
}));