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从handleLaunchActivity方法内部，又调用了performLaunchActivity方法，

我们看下，上面有段注释： Core implementation of activity launch

一：performLaunchActivity

/**  Core implementation of activity launch. */    private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {        ActivityInfo aInfo = r.activityInfo;        if (r.packageInfo == null) {            r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,                    Context.CONTEXT_INCLUDE_CODE);        }        ComponentName component = r.intent.getComponent();        if (component == null) {            component = r.intent.resolveActivity(                mInitialApplication.getPackageManager());            r.intent.setComponent(component);        }        if (r.activityInfo.targetActivity != null) {            component = new ComponentName(r.activityInfo.packageName,                    r.activityInfo.targetActivity);        }        ContextImpl appContext = createBaseContextForActivity(r);        Activity activity = null;        try {            java.lang.ClassLoader cl = appContext.getClassLoader();            activity = mInstrumentation.newActivity(                    cl, component.getClassName(), r.intent);            StrictMode.incrementExpectedActivityCount(activity.getClass());            r.intent.setExtrasClassLoader(cl);            r.intent.prepareToEnterProcess();            if (r.state != null) {                r.state.setClassLoader(cl);            }        } catch (Exception e) {            if (!mInstrumentation.onException(activity, e)) {                throw new RuntimeException(                    "Unable to instantiate activity " + component                    + ": " + e.toString(), e);            }        }        try {            Application app = r.packageInfo.makeApplication(false, mInstrumentation);            if (localLOGV) Slog.v(TAG, "Performing launch of " + r);            if (localLOGV) Slog.v(                    TAG, r + ": app=" + app                    + ", appName=" + app.getPackageName()                    + ", pkg=" + r.packageInfo.getPackageName()                    + ", comp=" + r.intent.getComponent().toShortString()                    + ", dir=" + r.packageInfo.getAppDir());            if (activity != null) {                CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());                Configuration config = new Configuration(mCompatConfiguration);                if (r.overrideConfig != null) {                    config.updateFrom(r.overrideConfig);                }                if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "                        + r.activityInfo.name + " with config " + config);                Window window = null;                if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {                    window = r.mPendingRemoveWindow;                    r.mPendingRemoveWindow = null;                    r.mPendingRemoveWindowManager = null;                }                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);                if (customIntent != null) {                    activity.mIntent = customIntent;                }                r.lastNonConfigurationInstances = null;                checkAndBlockForNetworkAccess();                activity.mStartedActivity = false;                int theme = r.activityInfo.getThemeResource();                if (theme != 0) {                    activity.setTheme(theme);                }                activity.mCalled = false;                if (r.isPersistable()) {                    mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);                } else {                    mInstrumentation.callActivityOnCreate(activity, r.state);                }                if (!activity.mCalled) {                    throw new SuperNotCalledException(                        "Activity " + r.intent.getComponent().toShortString() +                        " did not call through to super.onCreate()");                }                r.activity = activity;            }            r.setState(ON_CREATE);            mActivities.put(r.token, r);        } catch (SuperNotCalledException e) {            throw e;        } catch (Exception e) {            if (!mInstrumentation.onException(activity, e)) {                throw new RuntimeException(                    "Unable to start activity " + component                    + ": " + e.toString(), e);            }        }        return activity;    }

这个方法的内部可以看到  new了一个activity,同时调用了其attach方法

activity = mInstrumentation.newActivity(                    cl, component.getClassName(), r.intent);

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);

接着Instrumentation调用了一个很重要的方法

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

二 activity的oncreate

/**     * Perform calling of an activity's {@link Activity#onCreate}     * method.  The default implementation simply calls through to that method.     *     * @param activity The activity being created.     * @param icicle The previously frozen state (or null) to pass through to onCreate().     */    public void callActivityOnCreate(Activity activity, Bundle icicle) {        prePerformCreate(activity);        activity.performCreate(icicle);        postPerformCreate(activity);    }

final void performCreate(Bundle icicle) {        performCreate(icicle, null);    }

final void performCreate(Bundle icicle, PersistableBundle persistentState) {        mCanEnterPictureInPicture = true;        restoreHasCurrentPermissionRequest(icicle);        if (persistentState != null) {            onCreate(icicle, persistentState);        } else {            onCreate(icicle);        }        writeEventLog(LOG_AM_ON_CREATE_CALLED, "performCreate");        mActivityTransitionState.readState(icicle);        mVisibleFromClient = !mWindow.getWindowStyle().getBoolean(                com.android.internal.R.styleable.Window_windowNoDisplay, false);        mFragments.dispatchActivityCreated();        mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());    }

终于走到onCreate了，不容易啊。。

/**     * Called when the activity is starting.  This is where most initialization     * should go: calling {@link #setContentView(int)} to inflate the     * activity's UI, using {@link #findViewById} to programmatically interact     * with widgets in the UI, calling     * {@link #managedQuery(android.net.Uri , String[], String, String[], String)} to retrieve     * cursors for data being displayed, etc.     *     * 
You can call {@link #finish} from within this function, in     * which case onDestroy() will be immediately called after {@link #onCreate} without any of the     * rest of the activity lifecycle ({@link #onStart}, {@link #onResume}, {@link #onPause}, etc)     * executing.     *     * 
Derived classes must call through to the super class's     * implementation of this method.  If they do not, an exception will be     * thrown.
     *     * @param savedInstanceState If the activity is being re-initialized after     *     previously being shut down then this Bundle contains the data it most     *     recently supplied in {@link #onSaveInstanceState}.  Note: Otherwise it is null.     *     * @see #onStart     * @see #onSaveInstanceState     * @see #onRestoreInstanceState     * @see #onPostCreate     */    @MainThread    @CallSuper    protected void onCreate(@Nullable Bundle savedInstanceState) {        if (DEBUG_LIFECYCLE) Slog.v(TAG, "onCreate " + this + ": " + savedInstanceState);        if (mLastNonConfigurationInstances != null) {            mFragments.restoreLoaderNonConfig(mLastNonConfigurationInstances.loaders);        }        if (mActivityInfo.parentActivityName != null) {            if (mActionBar == null) {                mEnableDefaultActionBarUp = true;            } else {                mActionBar.setDefaultDisplayHomeAsUpEnabled(true);            }        }        if (savedInstanceState != null) {            mAutoFillResetNeeded = savedInstanceState.getBoolean(AUTOFILL_RESET_NEEDED, false);            mLastAutofillId = savedInstanceState.getInt(LAST_AUTOFILL_ID,                    View.LAST_APP_AUTOFILL_ID);            if (mAutoFillResetNeeded) {                getAutofillManager().onCreate(savedInstanceState);            }            Parcelable p = savedInstanceState.getParcelable(FRAGMENTS_TAG);            mFragments.restoreAllState(p, mLastNonConfigurationInstances != null                    ? mLastNonConfigurationInstances.fragments : null);        }        mFragments.dispatchCreate();        getApplication().dispatchActivityCreated(this, savedInstanceState);        if (mVoiceInteractor != null) {            mVoiceInteractor.attachActivity(this);        }        mRestoredFromBundle = savedInstanceState != null;        mCalled = true;    }

至此，executeCallbacks 执行完了，

下面是executeLifecycleState，下文将继续探索。

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