Android:Activity、Service启动过程(Android 10源码)

本文源码均取自Android 10

文章目录

    • Activity启动过程
    • Service启动过程

Activity启动过程

当我们使用startActivity() 启动另一个Activity后,主要会调用以下的一些函数。

MyActivity.startActivity() 
Activity.startActivity() 
Activity.startActivityForResult 
Instrumentation.execStartActivty 
ActivityManagerNative.getDefault().startActivityAsUser() 

以上步骤的调用可参考Android Activity启动流程分析
使用Binder机制最终启动Activity的核心源码在(SDK)android.app.ActivityThread.java中的performLaunchActivity()方法。
系统源码路径:frameworks/base/core/java/android/app/ActivityThread.java
主要步骤:

  • step 1: 创建LoadedApk对象;
  • step 2: 创建ContextImpl对象;
  • step 3: 创建Activity对象;
  • step 4: 创建Application对象;
  • step 5: 将Application/ContextImpl都attach到Activity对象;
  • step 6: 执行回调onCreate;

ActivityThread.java

/**  Core implementation of activity launch. */
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
        ActivityInfo aInfo = r.activityInfo;
        if (r.packageInfo == null) {
        // 1、 创建LoadedApk对象----------------------------
            r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
                    Context.CONTEXT_INCLUDE_CODE);
        }
        // component初始化过程
        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);
        }

		// 2、 创建ContextImpl对象---------------
        ContextImpl appContext = createBaseContextForActivity(r);
        Activity activity = null;
        try {
            java.lang.ClassLoader cl = appContext.getClassLoader();
            // 3、创建Activity对象-----------------
            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 {
        // 4、创建Application对象
            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) {
                // 更新配置信息
                    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);
                // 5、将Application/ContextImpl都attach到Activity对象-------------------
                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;
                }
                r.lastNonConfigurationInstances = null;
                checkAndBlockForNetworkAccess();
                activity.mStartedActivity = false;
                int theme = r.activityInfo.getThemeResource();
                if (theme != 0) {
                    activity.setTheme(theme);
                }

                activity.mCalled = false;
                // 6、执行回调onCreate
                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);

            // updatePendingActivityConfiguration() reads from mActivities to update
            // ActivityClientRecord which runs in a different thread. Protect modifications to
            // mActivities to avoid race.
            synchronized (mResourcesManager) {
                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;
    }

举一反三

Service启动过程

Service核心启动源码与上面类似,这里贴出源码体会一下:
ActivityThread.java

@UnsupportedAppUsage
   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();

   // 1、 LoadedApk
       LoadedApk packageInfo = getPackageInfoNoCheck(
               data.info.applicationInfo, data.compatInfo);
       Service service = null;
       try {
           java.lang.ClassLoader cl = packageInfo.getClassLoader();
           // 2、 创建Service
           service = packageInfo.getAppFactory()
                   .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);

   		// 3、创建ContextImpl
           ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
           context.setOuterContext(service);

   		// 3、创建 Application
           Application app = packageInfo.makeApplication(false, mInstrumentation);
           // 4、绑定ContextImpl  &  Application
           service.attach(context, this, data.info.name, data.token, app,
                   ActivityManager.getService());
            // 5、回调onCreate()
           service.onCreate();
           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);
           }
       }
   }

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