我們在前面已經知道activity和service的啟動流程涉枫，activity和service本質上也是一個Context對象文捶，在其啟動過程中會創(chuàng)建一個與之關聯(lián)的Context對象

1：Activity的Context創(chuàng)建流程

當我們在啟動activity的過程是調用的方法都是startActivity,我們知道這是一個跨進程的過程，涉及到binder調用框沟，在AMS端Activity是以ActivityRecord形式存在的晋修，被TaskRecord以棧的形式管理，在啟動activity的過程中會根據(jù)intent和flag信息為其找到合適的Stack和Task,我們都知道主線程俺孙，ActivityThread便是Android應用程序的主線程辣卒，它是有應用程序進程創(chuàng)建過程中由zyote進程反射調用的，在Activity啟動過程中會調用handleLaunchActivity來啟動一個activity, 在其內部會調用performLaunchActivity來完成Activity的啟動

1.1:handleLaunchActivity

 // Initialize before creating the activity
        if (!ThreadedRenderer.sRendererDisabled) {
            GraphicsEnvironment.earlyInitEGL();
        }
        WindowManagerGlobal.initialize();
        final Activity a = performLaunchActivity(r, customIntent);
        if (a != null) {
            r.createdConfig = new Configuration(mConfiguration);
            reportSizeConfigurations(r);
            if (!r.activity.mFinished && pendingActions != null) {
                pendingActions.setOldState(r.state);
                pendingActions.setRestoreInstanceState(true);
                pendingActions.setCallOnPostCreate(true);
            }
        } else {
            // If there was an error, for any reason, tell the activity manager to stop us.
            try {
                ActivityManager.getService()
                        .finishActivity(r.token, Activity.RESULT_CANCELED, null,
                                Activity.DONT_FINISH_TASK_WITH_ACTIVITY);
            } catch (RemoteException ex) {
                throw ex.rethrowFromSystemServer();
            }
        }

1.2:performLaunchActivity的具體實現(xiàn)

 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();-------->intent中有沒有指定組件名稱
        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);------->為activity創(chuàng)建ContextImpl對象
        Activity activity = null;
        try {
            java.lang.ClassLoader cl = appContext.getClassLoader();
            activity = mInstrumentation.newActivity(--------->通過classLoader創(chuàng)建一個Activity對象
                    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 (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);----->將創(chuàng)建的activity對象和ContextImpl對象關聯(lián)起來
                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);

1.3:Activity的attch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) {
        attachBaseContext(context);------>關聯(lián)ContextImpl對象
        mFragments.attachHost(null /*parent*/);
        mWindow = new PhoneWindow(this, window, activityConfigCallback);---->創(chuàng)建PhoneWindow對象
        mWindow.setWindowControllerCallback(this);
        mWindow.setCallback(this);--------------------->將this也就是activity和PhoneWindow關聯(lián)起來
        mWindow.setOnWindowDismissedCallback(this);
        mWindow.getLayoutInflater().setPrivateFactory(this);
       ...................................................
    }

1.4:attachBaseContext的實現(xiàn)

    protected void attachBaseContext(Context newBase) {
        super.attachBaseContext(newBase);
        if (newBase != null) {
            newBase.setAutofillClient(this);
        }
    }

1.5:attachBaseContext

@Override
protected void attachBaseContext(Context newBase) {
    super.attachBaseContext(newBase);
}
protected void attachBaseContext(Context base) {
    if (mBase != null) {
        throw new IllegalStateException("Base context already set");
    }
    mBase = base;--------------->mBase的數(shù)據(jù)類型是Context
}

由于Activity是繼承ContextThemeWrapper睛榄，ContextThemeWrapper是ContextWrapper的子類荣茫，這樣便將上面的ContextImpl和Activity的成員變量mBase關聯(lián)起來了

2.Service的Context創(chuàng)建過程

service的context創(chuàng)建流程和activity的context創(chuàng)建流程大致上是一致的

        public final void scheduleCreateService(IBinder token,
                ServiceInfo info, CompatibilityInfo compatInfo, int processState) {
            updateProcessState(processState, false);
            CreateServiceData s = new CreateServiceData();
            s.token = token;
            s.info = info;
            s.compatInfo = compatInfo;
            sendMessage(H.CREATE_SERVICE, s);
        }

最終的方法是handleCreateService

private void handleCreateService(CreateServiceData data) {
        // If we are getting ready to gc after going to the background, well
        // we are back active so skip it.
        unscheduleGcIdler();
        LoadedApk packageInfo = getPackageInfoNoCheck(
                data.info.applicationInfo, data.compatInfo);
        Service service = null;
        try {
            java.lang.ClassLoader cl = packageInfo.getClassLoader();
            service = packageInfo.getAppFactory()----------->創(chuàng)建一個service對象
                    .instantiateService(cl, data.info.name, data.intent);
        } catch (Exception e) {
            if (!mInstrumentation.onException(service, e)) {
                throw new RuntimeException(
                    "Unable to instantiate service " + data.info.name
                    + ": " + e.toString(), e);
            }
        }
        try {
            if (localLOGV) Slog.v(TAG, "Creating service " + data.info.name);
            ContextImpl context = ContextImpl.createAppContext(this, packageInfo);----->創(chuàng)建一個ContextImpl對象
            context.setOuterContext(service);------>將service對象和ContextImpl對象關聯(lián)起來
            Application app = packageInfo.makeApplication(false, mInstrumentation);
            service.attach(context, this, data.info.name, data.token, app,
                    ActivityManager.getService());-------------------->調用attach方法
            service.onCreate();----------------------------------------->回調其生命周期
            mServices.put(data.token, service);
            try {
                ActivityManager.getService().serviceDoneExecuting(
                        data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
            } catch (RemoteException e) {
                throw e.rethrowFromSystemServer();
            }
        } catch (Exception e) {
            if (!mInstrumentation.onException(service, e)) {
                throw new RuntimeException(
                    "Unable to create service " + data.info.name
                    + ": " + e.toString(), e);
            }
        }
    }

2.1service的attach方法實現(xiàn)

    public final void attach(
            Context context,
            ActivityThread thread, String className, IBinder token,
            Application application, Object activityManager) {
        attachBaseContext(context);----------------->關聯(lián)ContextImpl對象
        mThread = thread;           // NOTE:  unused - remove?
        mClassName = className;
        mToken = token;
        mApplication = application;
        mActivityManager = (IActivityManager)activityManager;
        mStartCompatibility = getApplicationInfo().targetSdkVersion
                < Build.VERSION_CODES.ECLAIR;
    }

這樣service的context對象便關聯(lián)和創(chuàng)建