Dagger2在SystemUI中的应用，深入浅出Android性能调优_systemui dagger

作者：喵喵爱编程 | 2024-07-15 18:00:18

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systemui dagger

只要保证这个注解标记的 Component 在 App 进程中为单例的，并且得到正确的实现(被正确的标记到类构造器或 Module 中的 @Provides 标记的方法)，那么它对应生成的类实例就是单例的。

SystemUI中的dagger2使用

AppComponentFactory

SystemUI的application标签定义了一个appComponentFactory属性

AppComponentFactory用于控制manifest清单文件里的组件的初始化

developer.android.com/reference/a…

在manifest清单文件里的组件构建对象时会调用这些方法

SystemUIFactory

src/com/android/systemui/SystemUIAppComponentFactory.java

public Application instantiateApplicationCompat(
@NonNull ClassLoader cl, @NonNull String className)
throws InstantiationException, IllegalAccessException, ClassNotFoundException {
Application app = super.instantiateApplicationCompat(cl, className);
if (app instanceof ContextInitializer) {
((ContextInitializer) app).setContextAvailableCallback(
context -> {
SystemUIFactory.createFromConfig(context);
SystemUIFactory.getInstance().getSysUIComponent().inject(
SystemUIAppComponentFactory.this);
}
);
}

return app;
}

在SystemUIApplication onCreate时回调 ContextAvailableCallback, 构建SystemUIFactory，并对它进行初始化

src/com/android/systemui/SystemUIFactory.java

public static void createFromConfig(Context context, boolean fromTest) {
if (mFactory != null) {
return;
}

final String clsName = context.getString(R.string.config_systemUIFactoryComponent);
if (clsName == null || clsName.length() == 0) {
throw new RuntimeException(“No SystemUIFactory component configured”);
}

try {
Class<?> cls = null;
cls = context.getClassLoader().loadClass(clsName);
// 创建SystemUIFactory实例
mFactory = (SystemUIFactory) cls.newInstance();
// 初始化SystemUIFactory
mFactory.init(context, fromTest);
} catch (Throwable t) {
Log.w(TAG, "Error creating SystemUIFactory component: " + clsName, t);
throw new RuntimeException(t);
}
}

public void init(Context context, boolean fromTest)
throws ExecutionException, InterruptedException {
…
// 获取dagger组件
mRootComponent = buildGlobalRootComponent(context);
…

// 获取systemui的dagger组件
// And finally, retrieve whatever SysUI needs from WMShell and build SysUI.
SysUIComponent.Builder builder = mRootComponent.getSysUIComponent();
mSysUIComponent = builder.build();
…

// 构建Dependency实例并初始化
// Every other part of our codebase currently relies on Dependency, so we
// really need to ensure the Dependency gets initialized early on.
Dependency dependency = mSysUIComponent.createDependency();
dependency.start();
}

protected GlobalRootComponent buildGlobalRootComponent(Context context) {
return DaggerGlobalRootComponent.builder()
.context(context)
.build();
}

Dependency组件使用@Lazy标签懒加载：首先构建LazyDependencyCreator放入mProviders，然后在真正使用dependency时调用createDependency进行创建

src/com/android/systemui/Dependency.java

private final ArrayMap<Object, Object> mDependencies = new ArrayMap<>();
private final ArrayMap<Object, LazyDependencyCreator> mProviders = new ArrayMap<>();

@Inject Lazy mActivityStarter;
@Inject Lazy mBroadcastDispatcher;
@Inject Lazy mAsyncSensorManager;
@Inject Lazy mBluetoothController;

protected void start() {
// 构建LazyDependencyCreator放入mProviders
mProviders.put(TIME_TICK_HANDLER, mTimeTickHandler::get);
mProviders.put(BG_LOOPER, mBgLooper::get);
mProviders.put(MAIN_LOOPER, mMainLooper::get);
mProviders.put(MAIN_HANDLER, mMainHandler::get);
mProviders.put(MAIN_EXECUTOR, mMainExecutor::get);
mProviders.put(BACKGROUND_EXECUTOR, mBackgroundExecutor::get);
mProviders.put(ActivityStarter.class, mActivityStarter::get);
mProviders.put(BroadcastDispatcher.class, mBroadcastDispatcher::get);
…

// 获取dependency
private synchronized T getDependencyInner(Object key) {
@SuppressWarnings(“unchecked”)
T obj = (T) mDependencies.get(key);
if (obj == null) {
// 若未创建则创建
obj = createDependency(key);
mDependencies.put(key, obj);
…
}
return obj;
}

public T createDependency(Object cls) {
Preconditions.checkArgument(cls instanceof DependencyKey<?> || cls instanceof Class<?>);

@SuppressWarnings(“unchecked”)
LazyDependencyCreator provider = mProviders.get(cls);
if (provider == null) {
throw new IllegalArgumentException("Unsupported dependency " + cls