Activity何时被创建的？

在ActivityThread中的performLaunchActivity

Activity activity = null;
    try {
        java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
        activity = mInstrumentation.newActivity(
                cl, component.getClassName(), r.intent);
        ...
    } catch (Exception e) {
       ...
    }

activity的生命周期由谁控制？
Instrumentation

if (r.isPersistable()) {
                mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
            } else {
                mInstrumentation.callActivityOnCreate(activity, r.state);
            }

Instrumentation还负责检查启动activity的结果checkStartActivityResult类似

case ActivityManager.START_INTENT_NOT_RESOLVED:
case ActivityManager.START_CLASS_NOT_FOUND:
    if (intent instanceof Intent && ((Intent)intent).getComponent() != null)
        throw new ActivityNotFoundException(
                "Unable to find explicit activity class "
                + ((Intent)intent).getComponent().toShortString()
                + "; have you declared this activity in your AndroidManifest.xml?");
    throw new ActivityNotFoundException(
            "No Activity found to handle " + intent);
case ActivityManager.START_PERMISSION_DENIED:
    throw new SecurityException("Not allowed to start activity "
            + intent);
case ActivityManager.START_FORWARD_AND_REQUEST_CONFLICT:
    throw new AndroidRuntimeException(
            "FORWARD_RESULT_FLAG used while also requesting a result");
case ActivityManager.START_NOT_ACTIVITY:
    throw new IllegalArgumentException(
            "PendingIntent is not an activity");

Window的创建时机为，在Activity调用attach时

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) {
    attachBaseContext(context);

    mFragments.attachHost(null /*parent*/);

    mWindow = new PhoneWindow(this, window, activityConfigCallback);
    mWindow.setWindowControllerCallback(this);
    mWindow.setCallback(this);
    mWindow.setOnWindowDismissedCallback(this);
    mWindow.getLayoutInflater().setPrivateFactory(this);
    if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
        mWindow.setSoftInputMode(info.softInputMode);
    }
    if (info.uiOptions != 0) {
        mWindow.setUiOptions(info.uiOptions);
    }
    mUiThread = Thread.currentThread();

并且在PhoneWindow内部初始化了mLayoutInflate并且传入的context为当前activity.this，因此在view获取的context都为activity

public PhoneWindow(Context context) {
    super(context);
    mLayoutInflater = LayoutInflater.from(context);
}

Application是在什么时候创建的

也是在ActivityThread的performLaunchActivity中，在创建activity之后会检测当前app是否为null，决定是否创建application

public Application makeApplication(boolean forceDefaultAppClass,
        Instrumentation instrumentation) {
    if (mApplication != null) {
        return mApplication;
    }

    Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "makeApplication");

    Application app = null;

    String appClass = mApplicationInfo.className;
    if (forceDefaultAppClass || (appClass == null)) {
        appClass = "android.app.Application";
    }

    try {
        java.lang.ClassLoader cl = getClassLoader();
        if (!mPackageName.equals("android")) {
            Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER,
                    "initializeJavaContextClassLoader");
            initializeJavaContextClassLoader();
            Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
        }
        ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this);
        app = mActivityThread.mInstrumentation.newApplication(
                cl, appClass, appContext);
        appContext.setOuterContext(app);
    } catch (Exception e) {
        ...
    }
    return app;
}

与Activity相同，Application最终的创建的也是由classLoader去loadclass创建对象

cl.loadClass(className).newInstance();