源碼基于API26
在上一篇中，講到由ActivityThread啟動(dòng)activity了
ActivityThread即我們平時(shí)提到的主線程，上一篇中AMS處理啟動(dòng)activity的task和record信息后通過(guò)binder跨進(jìn)程到應(yīng)用當(dāng)前線程繼續(xù)啟動(dòng)activity
現(xiàn)在看ActivityThread的scheduleLaunchActivity()

@Override
    public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
            ActivityInfo info, Configuration curConfig, Configuration overrideConfig,
            CompatibilityInfo compatInfo, String referrer, IVoiceInteractor voiceInteractor,
            int procState, Bundle state, PersistableBundle persistentState,
            List<ResultInfo> pendingResults, List<ReferrerIntent> pendingNewIntents,
            boolean notResumed, boolean isForward, ProfilerInfo profilerInfo) {
        //更新進(jìn)程狀態(tài)
        updateProcessState(procState, false);
        //創(chuàng)建ActivityClientRecord并賦值
        ActivityClientRecord r = new ActivityClientRecord();
        r.token = token;
        r.ident = ident;
        r.intent = intent;
        r.referrer = referrer;
        r.voiceInteractor = voiceInteractor;
        r.activityInfo = info;
        r.compatInfo = compatInfo;
        r.state = state;
        r.persistentState = persistentState;
        r.pendingResults = pendingResults;
        r.pendingIntents = pendingNewIntents;
        r.startsNotResumed = notResumed;
        r.isForward = isForward;
        r.profilerInfo = profilerInfo;
        r.overrideConfig = overrideConfig;
        updatePendingConfiguration(curConfig);
        //帶著ActivityClientRecord由Handler啟動(dòng)Activity
        sendMessage(H.LAUNCH_ACTIVITY, r);
    }

接著看Handler

public void handleMessage(Message msg) {
        ...
        switch (msg.what) {
            case LAUNCH_ACTIVITY: {
                Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
                //handler傳遞過(guò)來(lái)的ActivityClientRecord
                final ActivityClientRecord r = (ActivityClientRecord) msg.obj;
                //賦值LoadedApk
                r.packageInfo = getPackageInfoNoCheck(
                        r.activityInfo.applicationInfo, r.compatInfo);
                //繼續(xù)啟動(dòng)activity
                handleLaunchActivity(r, null, "LAUNCH_ACTIVITY");
                Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
            } break;

接著handleLaunchActivity()

private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) {
    //跳過(guò)后臺(tái)執(zhí)行g(shù)c
    unscheduleGcIdler();
    mSomeActivitiesChanged = true;
    if (r.profilerInfo != null) {
        mProfiler.setProfiler(r.profilerInfo);
        mProfiler.startProfiling();
    }
    // 確保執(zhí)行最新的配置
    handleConfigurationChanged(null, null);
    if (localLOGV) Slog.v(
        TAG, "Handling launch of " + r);
    // 創(chuàng)建activity之前初始化WindowManagerGlobal,獲取IWindowManger
    WindowManagerGlobal.initialize();
    //啟動(dòng)activity
    Activity a = performLaunchActivity(r, customIntent);
    //activity不為null
    if (a != null) {
        r.createdConfig = new Configuration(mConfiguration);
        reportSizeConfigurations(r);
        Bundle oldState = r.state;
        //恢復(fù)activity
        handleResumeActivity(r.token, false, r.isForward,
                !r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason);
        if (!r.activity.mFinished && r.startsNotResumed) {
            performPauseActivityIfNeeded(r, reason);
            //pre-Honeycomb apps需要保存初始狀態(tài)以便再次創(chuàng)建
            if (r.isPreHoneycomb()) {
                r.state = oldState;
            }
        }
    } else {
        //不管什么原因出錯(cuò)調(diào)用AMS銷毀activity
        try {
            ActivityManager.getService()
                .finishActivity(r.token, Activity.RESULT_CANCELED, null,
                        Activity.DONT_FINISH_TASK_WITH_ACTIVITY);
        } catch (RemoteException ex) {
            throw ex.rethrowFromSystemServer();
        }
    }
}

接著performLaunchActivity()

private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
    //LoadedApk檢驗(yàn)
    ActivityInfo aInfo = r.activityInfo;
    if (r.packageInfo == null) {
        r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
                Context.CONTEXT_INCLUDE_CODE);
    }
    //component檢驗(yàn)
    ComponentName component = r.intent.getComponent();
    if (component == null) {
        component = r.intent.resolveActivity(
            mInitialApplication.getPackageManager());
        r.intent.setComponent(component);
    }
    //原activity不為空可新建component
    if (r.activityInfo.targetActivity != null) {
        component = new ComponentName(r.activityInfo.packageName,
                r.activityInfo.targetActivity);
    }
    //創(chuàng)建contextImpl
    ContextImpl appContext = createBaseContextForActivity(r);
    Activity activity = null;
    try {
        java.lang.ClassLoader cl = appContext.getClassLoader();
        //通過(guò)Instrumentation創(chuàng)建activity實(shí)例
        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 {
        //創(chuàng)建我們親愛(ài)的application
        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) {
            //加載label
            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;
            }
            //context表示為activity
            appContext.setOuterContext(activity);
            //準(zhǔn)備好了嗎我們的activity來(lái)了
            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();
            //設(shè)置主題
            if (theme != 0) {
                activity.setTheme(theme);
            }
            activity.mCalled = false;
            //activity已啟動(dòng)執(zhí)行onCreate()了
            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.stopped = true;
            //沒(méi)有關(guān)閉就要執(zhí)行onStart()了
            if (!r.activity.mFinished) {
                activity.performStart();
                r.stopped = false;
            }
            if (!r.activity.mFinished) {
                //執(zhí)行onRestoreInstanceState()
                if (r.isPersistable()) {
                    if (r.state != null || r.persistentState != null) {
                        mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
                                r.persistentState);
                    }
                } else if (r.state != null) {
                    mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
                }
            }
            //沒(méi)有finish()執(zhí)行onPostCreate()
            if (!r.activity.mFinished) {
                activity.mCalled = false;
                if (r.isPersistable()) {
                    mInstrumentation.callActivityOnPostCreate(activity, r.state,
                            r.persistentState);
                } else {
                    mInstrumentation.callActivityOnPostCreate(activity, r.state);
                }
                if (!activity.mCalled) {
                    throw new SuperNotCalledException(
                        "Activity " + r.intent.getComponent().toShortString() +
                        " did not call through to super.onPostCreate()");
                }
            }
        }
        r.paused = true;
        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;
}

系不系上面這個(gè)方法有點(diǎn)長(zhǎng)了，但是很顯然是我們開(kāi)發(fā)平時(shí)接觸很近的方法了
再看看attach()

//主要是給我們activity賦一大堆值
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*/);
    //window創(chuàng)建并賦值
    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);
    }
    //看見(jiàn)沒(méi)這就是uiThread
    mUiThread = Thread.currentThread();
    //主線程為ActivityThread
    mMainThread = aThread;
    //原來(lái)這貨再這賦值的每一個(gè)activity都有這個(gè)監(jiān)控類
    mInstrumentation = instr;
    mToken = token;
    mIdent = ident;
    mApplication = application;
    mIntent = intent;
    mReferrer = referrer;
    mComponent = intent.getComponent();
    mActivityInfo = info;
    mTitle = title;
    mParent = parent;
    mEmbeddedID = id;
    mLastNonConfigurationInstances = lastNonConfigurationInstances;
    if (voiceInteractor != null) {
        if (lastNonConfigurationInstances != null) {
            mVoiceInteractor = lastNonConfigurationInstances.voiceInteractor;
        } else {
            mVoiceInteractor = new VoiceInteractor(voiceInteractor, this, this,
                    Looper.myLooper());
        }
    }
    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();
    mCurrentConfig = config;
    mWindow.setColorMode(info.colorMode);
}

還要問(wèn)我activity啟動(dòng)了沒(méi)有嗎，我說(shuō)沒(méi)有

scheduleLaunchActivity()、handleLaunchActivity()、performLaunchActivity()
將activity的相關(guān)信息淋漓盡致的展現(xiàn)，沒(méi)事多看看，我還沒(méi)專研細(xì)致的方法呢。