前面我们讲解了Zygote冷启动Application应该设置启动时间的位置是attachBaseContext
Zygote冷启动 启动时间收集

首先看ActivityThtread唤起Activity的方法

 public void handleMessage(Message msg) {
      ···
      case RELAUNCH_ACTIVITY:
          handleRelaunchActivityLocally((IBinder) msg.obj);
      break;
    ···
}

handleRelaunchActivityLocally最终会走到performLaunchActivity

// Activity resources must be initialized with the same loaders as the
                // application context.
                appContext.getResources().addLoaders(
                        app.getResources().getLoaders().toArray(new ResourcesLoader[0]));

                appContext.setOuterContext(activity);
                activity.attach(appContext, this, getInstrumentation(), r.token,
                        r.ident, app, r.intent, r.activityInfo, title, r.parent,
                        r.embeddedID, r.lastNonConfigurationInstances, config,
                        r.referrer, r.voiceInteractor, window, r.configCallback,
                        r.assistToken);

                if (customIntent != null) {
                    activity.mIntent = customIntent;
                }

performLaunchActivity() 中调 OnCreate() 方法前会调用 Activity 的 attach() 方法,这里详细的可以看这里
Window WindowManager WindowManagerService

可以看到Activity里面的attatch方法

final void attach(Context context, ActivityThread aThread,
            Instrumentation instr, IBinder token, int ident,
            Application application, Intent intent, ActivityInfo info,
            CharSequence title, Activity parent, String id,
            NonConfigurationInstances lastNonConfigurationInstances,
            Configuration config, String referrer, IVoiceInteractor voiceInteractor,
            Window window, ActivityConfigCallback activityConfigCallback) {
        //省略部分代码
        ...
 
        mWindow = new PhoneWindow(this, window, activityConfigCallback);
        mWindow.setWindowControllerCallback(this);
        mWindow.setCallback(this);
        mWindow.setOnWindowDismissedCallback(this);
        mWindow.getLayoutInflater().setPrivateFactory(this);
        //省略部分代码
        ...
       
        mWindow.setWindowManager(
                (WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
                mToken, mComponent.flattenToString(),
                (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
        if (mParent != null) {
            mWindow.setContainer(mParent.getWindow());
        }
 
        mWindowManager = mWindow.getWindowManager();
        //省略部分代码
        ...
        
    }

attatch方法中创建了Window唯一实现类PhoneWindow类型的mWindow对象，mWindowManager对象也是从PhoneWindow获取的。那么他是在哪里初始化的呢？