cm-14.1 Android系统启动过程分析（四）-Launcher 启动过程
16lz
2022-05-12
声明
- 前阶段在项目中涉及到了Android系统定制任务，Android系统定制前提要知道Android系统是如何启动的。
- 本文参考了一些书籍的若干章节，比如《Android进阶解密-第2章-Android系统启动》、《深入理解Android虚拟机-第8/9/10章-init进程详解/Dalvik VM的进程系统/Dalvik VM运作流程详解》、《深入理解Android系统-第6/7/8章-init启动进程详解/Zygote进程详解/System进程详解》等。
- 本文使用的代码是LineageOS的cm-14.1，对应Android 7.1.2，可以参考我的另一篇博客：如何下载Nexus5的LineageOS14.1(cm-14.1)系统源码并编译、刷机。
- 很多代码注释待详细写
0 写在前面的
等本章结束，Android系统的启动基本就结束了，因为对于用户来说可以看到显示屏上的Launcher界面就代表系统已经启动完成了。Launcher在启动过程中会请求 PackageManagerService 返回系统中已经安装的应用程序的信息，并将这些信息封装成一个快捷图标列表显示在系统屏幕上，这样用户可以通过点击这些快捷图标来启动相应的应用程序。
Launcher 就是 Android 系统的桌面，它的作用主要有以下两点：
- 用于启动应用程序。
- 用于显示和管理应用程序的快捷图标或者其他桌面组件。
0 Launcher启动过程
SystemServer 进程在启动的过程中会启动PackageManagerService, PackageManagerService 启动后会将系统中的预置的应用程序安装（其中就包含Launcher应用），然后系统服务 AMS 会将 Launcher 启动起来。
...... SystemServer AMS ActivityStackSupervisor ActivityStack startOtherServices systemReady resumeFocusedStack resumeTopActivity... resumeTopActivityInnerLocked resumeHomeStackTask startHomeActivityLocked ...... SystemServer AMS ActivityStackSupervisor ActivityStack启动Launcher的入口为AMS的systemReady方法，它在SystemServer的startOtherServices 方告中被调用。其在源码目录：~/LineageOS/frameworks/base/services/java/com/android/server/SystemServer.java
// We now tell the activity manager it is okay to run third party // code. It will call back into us once it has gotten to the state // where third party code can really run (but before it has actually // started launching the initial applications), for us to complete our // initialization. mActivityManagerService.systemReady(new Runnable() { @Override public void run() { Slog.i(TAG, "Making services ready"); mSystemServiceManager.startBootPhase( SystemService.PHASE_ACTIVITY_MANAGER_READY); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "PhaseActivityManagerReady"); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartObservingNativeCrashes"); try { mActivityManagerService.startObservingNativeCrashes(); } catch (Throwable e) { reportWtf("observing native crashes", e); } Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); if (!mOnlyCore) { Slog.i(TAG, "WebViewFactory preparation"); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "WebViewFactoryPreparation"); mWebViewUpdateService.prepareWebViewInSystemServer(); Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); } Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartSystemUI"); try { startSystemUi(context); } catch (Throwable e) { reportWtf("starting System UI", e); } Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "MakeNetworkScoreReady"); try { if (networkScoreF != null) networkScoreF.systemReady(); } catch (Throwable e) { reportWtf("making Network Score Service ready", e); } Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "MakeNetworkManagementServiceReady"); try { if (networkManagementF != null) networkManagementF.systemReady(); } catch (Throwable e) { reportWtf("making Network Managment Service ready", e); } Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "MakeNetworkStatsServiceReady"); try { if (networkStatsF != null) networkStatsF.systemReady(); } catch (Throwable e) { reportWtf("making Network Stats Service ready", e); } Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "MakeNetworkPolicyServiceReady"); try { if (networkPolicyF != null) networkPolicyF.systemReady(); } catch (Throwable e) { reportWtf("making Network Policy Service ready", e); } Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "MakeConnectivityServiceReady"); try { if (connectivityF != null) connectivityF.systemReady(); } catch (Throwable e) { reportWtf("making Connectivity Service ready", e); } Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); Watchdog.getInstance().start(); // It is now okay to let the various system services start their // third party code... Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "PhaseThirdPartyAppsCanStart"); mSystemServiceManager.startBootPhase( SystemService.PHASE_THIRD_PARTY_APPS_CAN_START); try { if (locationF != null) locationF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying Location Service running", e); } try { if (countryDetectorF != null) countryDetectorF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying CountryDetectorService running", e); } try { if (networkTimeUpdaterF != null) networkTimeUpdaterF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying NetworkTimeService running", e); } try { if (commonTimeMgmtServiceF != null) { commonTimeMgmtServiceF.systemRunning(); } } catch (Throwable e) { reportWtf("Notifying CommonTimeManagementService running", e); } try { if (atlasF != null) atlasF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying AssetAtlasService running", e); } try { // TODO(BT) Pass parameter to input manager if (inputManagerF != null) inputManagerF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying InputManagerService running", e); } try { if (telephonyRegistryF != null) telephonyRegistryF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying TelephonyRegistry running", e); } try { if (mediaRouterF != null) mediaRouterF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying MediaRouterService running", e); } try { if (mmsServiceF != null) mmsServiceF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying MmsService running", e); } try { if (networkScoreF != null) networkScoreF.systemRunning(); } catch (Throwable e) { reportWtf("Notifying NetworkScoreService running", e); } Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER); } }); }下面来查看 AMS systernReady 方法做了什么：
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