Android应用程序安装过程源代码分析（3）

Step 7.PackageManagerService.main

这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：[cpp] view plain copy

classPackageManagerServiceextendsIPackageManager.Stub{
......
publicstaticfinalIPackageManagermain(Contextcontext,booleanfactoryTest){
PackageManagerServicem=newPackageManagerService(context,factoryTest);
ServiceManager.addService("package",m);
returnm;
}
......
}

这个函数创建了一个PackageManagerService服务实例，然后把这个服务添加到ServiceManager中去，ServiceManager是Android系统Binder进程间通信机制的守护进程，负责管理系统中的Binder对象，具体可以参考浅谈Service Manager成为Android进程间通信（IPC）机制Binder守护进程之路一文。在创建这个PackageManagerService服务实例时，会在PackageManagerService类的构造函数中开始执行安装应用程序的过程：[java] view plain copy

classPackageManagerServiceextendsIPackageManager.Stub{
......
publicPackageManagerService(Contextcontext,booleanfactoryTest){
......
synchronized(mInstallLock){
synchronized(mPackages){
......
FiledataDir=Environment.getDataDirectory();
mAppDataDir=newFile(dataDir,"data");
mSecureAppDataDir=newFile(dataDir,"secure/data");
mDrmAppPrivateInstallDir=newFile(dataDir,"app-private");
......
mFrameworkDir=newFile(Environment.getRootDirectory(),"framework");
mDalvikCacheDir=newFile(dataDir,"dalvik-cache");
......
//Findbaseframeworks(resourcepackageswithoutcode).
mFrameworkInstallObserver=newAppDirObserver(
mFrameworkDir.getPath(),OBSERVER_EVENTS,true);
mFrameworkInstallObserver.startWatching();
scanDirLI(mFrameworkDir,PackageParser.PARSE_IS_SYSTEM
|PackageParser.PARSE_IS_SYSTEM_DIR,
scanMode|SCAN_NO_DEX,0);
//Collectallsystempackages.
mSystemAppDir=newFile(Environment.getRootDirectory(),"app");
mSystemInstallObserver=newAppDirObserver(
mSystemAppDir.getPath(),OBSERVER_EVENTS,true);
mSystemInstallObserver.startWatching();
scanDirLI(mSystemAppDir,PackageParser.PARSE_IS_SYSTEM
|PackageParser.PARSE_IS_SYSTEM_DIR,scanMode,0);
//Collectallvendorpackages.
mVendorAppDir=newFile("/vendor/app");
mVendorInstallObserver=newAppDirObserver(
mVendorAppDir.getPath(),OBSERVER_EVENTS,true);
mVendorInstallObserver.startWatching();
scanDirLI(mVendorAppDir,PackageParser.PARSE_IS_SYSTEM
|PackageParser.PARSE_IS_SYSTEM_DIR,scanMode,0);
mAppInstallObserver=newAppDirObserver(
mAppInstallDir.getPath(),OBSERVER_EVENTS,false);
mAppInstallObserver.startWatching();
scanDirLI(mAppInstallDir,0,scanMode,0);
mDrmAppInstallObserver=newAppDirObserver(
mDrmAppPrivateInstallDir.getPath(),OBSERVER_EVENTS,false);
mDrmAppInstallObserver.startWatching();
scanDirLI(mDrmAppPrivateInstallDir,PackageParser.PARSE_FORWARD_LOCK,
scanMode,0);
......
}
}
}
......
}

这里会调用scanDirLI函数来扫描移动设备上的下面这五个目录中的Apk文件
/system/framework /system/app /vendor/app /data/app /data/app-private Step 8.PackageManagerService.scanDirLI
这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：[java] view plain copy

classPackageManagerServiceextendsIPackageManager.Stub{
......
privatevoidscanDirLI(Filedir,intflags,intscanMode,longcurrentTime){
String[]files=dir.list();
......
inti;
for(i=0;i<files.length;i++){
Filefile=newFile(dir,files[i]);
if(!isPackageFilename(files[i])){
//Ignoreentrieswhicharenotapk's
continue;
}
PackageParser.Packagepkg=scanPackageLI(file,
flags|PackageParser.PARSE_MUST_BE_APK,scanMode,currentTime);
//Don'tmessaroundwithappsinsystempartition.
if(pkg==null&&(flags&PackageParser.PARSE_IS_SYSTEM)==0&&
mLastScanError==PackageManager.INSTALL_FAILED_INVALID_APK){
//Deletetheapk
Slog.w(TAG,"Cleaningupfailedinstallof"+file);
file.delete();
}
}
}
......
}

对于目录中的每一个文件，如果是以后Apk作为后缀名，那么就调用scanPackageLI函数来对它进行解析和安装。 Step 9.PackageManagerService.scanPackageLI
这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：[java] view plain copy

classPackageManagerServiceextendsIPackageManager.Stub{
......
privatePackageParser.PackagescanPackageLI(FilescanFile,
intparseFlags,intscanMode,longcurrentTime){
......
StringscanPath=scanFile.getPath();
parseFlags|=mDefParseFlags;
PackageParserpp=newPackageParser(scanPath);
......
finalPackageParser.Packagepkg=pp.parsePackage(scanFile,
scanPath,mMetrics,parseFlags);
......
returnscanPackageLI(pkg,parseFlags,scanMode|SCAN_UPDATE_SIGNATURE,currentTime);
}
......
}

这个函数首先会为这个Apk文件创建一个PackageParser实例，接着调用这个实例的parsePackage函数来对这个Apk文件进行解析。这个函数最后还会调用另外一个版本的scanPackageLI函数把来解析后得到的应用程序信息保存在PackageManagerService中。

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