在Android啓動的過程當中，會掃描系統中特定的目錄，以便對保存在裏面的應用程序進行安裝，例如/system/app,/data/app。這個主要是靠PackageManagerService來實現，PackageManagerService在安裝一個應用程序的過程當中主要作兩件事，一、解析這個應用程序的配置文件AndroidManifest.xml 以便獲取安裝信息，二、爲這個應用程序分配Linux用戶ID和Linux用戶組ID，以便他能夠運行在系統中得到權限java
Android系統中最後一步是啓動一個HOME程序，用來顯示系統中已經安裝的應用程序，Android提供原聲的程序是Launcher,應用程序在啓動中，會請求PackageManagerService提供安裝的應用程序信息，再將程序信息封裝成一個快捷圖標在屏幕中，這樣用戶就能夠根據圖標來啓動對應的程序，
android
PackageManagerService在安裝一個應用程序的時候，對AndroidManifest.xml進行解析，獲取到組件信息，Android系統的每個應用程序都有一個Linux用戶ID，這些ID是有PackageManagerService負責分配的，PackageManagerService在安裝一個應用程序的時候，若是發現沒有其餘應用程序共享一個Linux用戶ID，那麼就會爲它分配惟一的Linux用戶ID，這樣能夠得到所需的權限，有了用戶ID以外還有若干個Linux用戶組ID，以便得到更多的資源，Linux用戶組ID也是PackageManagerService來負責分配的，shell
在PackageManagerService.java中app
public static final IPackageManager main(Context context, boolean factoryTest,
boolean onlyCore) {
PackageManagerService m = new PackageManagerService(context, factoryTest, onlyCore);
ServiceManager.addService("package", m);
return m;
}
首先將PackageManagerService啓動起來，而後註冊到ServiceManager中，這樣系統經過ServiceManager來獲取安裝服務。ide
public PackageManagerService(Context context, boolean factoryTest, boolean onlyCore) {
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_START,
SystemClock.uptimeMillis());
if (mSdkVersion <= 0) {
Slog.w(TAG, "**** ro.build.version.sdk not set!");
}
mContext = context;
mFactoryTest = factoryTest;
mOnlyCore = onlyCore;
mNoDexOpt = "eng".equals(SystemProperties.get("ro.build.type"));
mMetrics = new DisplayMetrics();
mSettings = new Settings();
mSettings.addSharedUserLPw("android.uid.system",
Process.SYSTEM_UID, ApplicationInfo.FLAG_SYSTEM);
mSettings.addSharedUserLPw("android.uid.phone",
MULTIPLE_APPLICATION_UIDS
? RADIO_UID : FIRST_APPLICATION_UID,
ApplicationInfo.FLAG_SYSTEM);
mSettings.addSharedUserLPw("android.uid.log",
MULTIPLE_APPLICATION_UIDS
? LOG_UID : FIRST_APPLICATION_UID,
ApplicationInfo.FLAG_SYSTEM);
mSettings.addSharedUserLPw("android.uid.nfc",
MULTIPLE_APPLICATION_UIDS
? NFC_UID : FIRST_APPLICATION_UID,
ApplicationInfo.FLAG_SYSTEM);
String separateProcesses = SystemProperties.get("debug.separate_processes");
if (separateProcesses != null && separateProcesses.length() > 0) {
if ("*".equals(separateProcesses)) {
mDefParseFlags = PackageParser.PARSE_IGNORE_PROCESSES;
mSeparateProcesses = null;
Slog.w(TAG, "Running with debug.separate_processes: * (ALL)");
} else {
mDefParseFlags = 0;
mSeparateProcesses = separateProcesses.split(",");
Slog.w(TAG, "Running with debug.separate_processes: "
+ separateProcesses);
}
} else {
mDefParseFlags = 0;
mSeparateProcesses = null;
}
mInstaller = new Installer();
WindowManager wm = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
Display d = wm.getDefaultDisplay();
d.getMetrics(mMetrics);
synchronized (mInstallLock) {
// writer
synchronized (mPackages) {
mHandlerThread.start();
mHandler = new PackageHandler(mHandlerThread.getLooper());
File dataDir = Environment.getDataDirectory();//得到系統的數據目錄/data
mAppDataDir = new File(dataDir, "data");
mUserAppDataDir = new File(dataDir, "user");
mDrmAppPrivateInstallDir = new File(dataDir, "app-private");//得到的是/data/app-private目錄，主要是受DRM保護的私有應用程序，/data/app下面是本身安裝的應用程序。
mUserManager = new UserManager(mInstaller, mUserAppDataDir);
readPermissions();
mRestoredSettings = mSettings.readLPw();//恢復上一次應用程序的安裝信息，接下來就掃描和安裝保存在特定目錄的應用程序
long startTime = SystemClock.uptimeMillis();
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,
startTime);
// Set flag to monitor and not change apk file paths when
// scanning install directories.
int scanMode = SCAN_MONITOR | SCAN_NO_PATHS | SCAN_DEFER_DEX;
if (mNoDexOpt) {
Slog.w(TAG, "Running ENG build: no pre-dexopt!");
scanMode |= SCAN_NO_DEX;
}
final HashSet<String> libFiles = new HashSet<String>();
mFrameworkDir = new File(Environment.getRootDirectory(), "framework");//得到的是/system/framework目錄
mDalvikCacheDir = new File(dataDir, "dalvik-cache");
boolean didDexOpt = false;
/**
* Out of paranoia, ensure that everything in the boot class
* path has been dexed.
*/
String bootClassPath = System.getProperty("java.boot.class.path");
if (bootClassPath != null) {
String[] paths = splitString(bootClassPath, ':');
for (int i=0; i<paths.length; i++) {
try {
if (dalvik.system.DexFile.isDexOptNeeded(paths[i])) {
libFiles.add(paths[i]);
mInstaller.dexopt(paths[i], Process.SYSTEM_UID, true);
didDexOpt = true;
}
} catch (FileNotFoundException e) {
Slog.w(TAG, "Boot class path not found: " + paths[i]);
} catch (IOException e) {
Slog.w(TAG, "Cannot dexopt " + paths[i] + "; is it an APK or JAR? "
+ e.getMessage());
}
}
} else {
Slog.w(TAG, "No BOOTCLASSPATH found!");
}
/**
* Also ensure all external libraries have had dexopt run on them.
*/
if (mSharedLibraries.size() > 0) {
Iterator<String> libs = mSharedLibraries.values().iterator();
while (libs.hasNext()) {
String lib = libs.next();
try {
if (dalvik.system.DexFile.isDexOptNeeded(lib)) {
libFiles.add(lib);
mInstaller.dexopt(lib, Process.SYSTEM_UID, true);
didDexOpt = true;
}
} catch (FileNotFoundException e) {
Slog.w(TAG, "Library not found: " + lib);
} catch (IOException e) {
Slog.w(TAG, "Cannot dexopt " + lib + "; is it an APK or JAR? "
+ e.getMessage());
}
}
}
// Gross hack for now: we know this file doesn't contain any
// code, so don't dexopt it to avoid the resulting log spew.
libFiles.add(mFrameworkDir.getPath() + "/framework-res.apk");
/**
* And there are a number of commands implemented in Java, which
* we currently need to do the dexopt on so that they can be
* run from a non-root shell.
*/
String[] frameworkFiles = mFrameworkDir.list();
if (frameworkFiles != null) {
for (int i=0; i<frameworkFiles.length; i++) {
File libPath = new File(mFrameworkDir, frameworkFiles[i]);
String path = libPath.getPath();
// Skip the file if we alrady did it.
if (libFiles.contains(path)) {
continue;
}
// Skip the file if it is not a type we want to dexopt.
if (!path.endsWith(".apk") && !path.endsWith(".jar")) {
continue;
}
try {
if (dalvik.system.DexFile.isDexOptNeeded(path)) {
mInstaller.dexopt(path, Process.SYSTEM_UID, true);
didDexOpt = true;
}
} catch (FileNotFoundException e) {
Slog.w(TAG, "Jar not found: " + path);
} catch (IOException e) {
Slog.w(TAG, "Exception reading jar: " + path, e);
}
}
}
if (didDexOpt) {
// If we had to do a dexopt of one of the previous
// things, then something on the system has changed.
// Consider this significant, and wipe away all other
// existing dexopt files to ensure we don't leave any
// dangling around.
String[] files = mDalvikCacheDir.list();
if (files != null) {
for (int i=0; i<files.length; i++) {
String fn = files[i];
if (fn.startsWith("data@app@")
|| fn.startsWith("data@app-private@")) {
Slog.i(TAG, "Pruning dalvik file: " + fn);
(new File(mDalvikCacheDir, fn)).delete();
}
}
}
}
// Find base frameworks (resource packages without code).
mFrameworkInstallObserver = new AppDirObserver(
mFrameworkDir.getPath(), OBSERVER_EVENTS, true);
mFrameworkInstallObserver.startWatching();
scanDirLI(mFrameworkDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR,
scanMode | SCAN_NO_DEX, 0);
// Collect all system packages.
mSystemAppDir = new File(Environment.getRootDirectory(), "app");//得到的是/system/app目錄
mSystemInstallObserver = new AppDirObserver(
mSystemAppDir.getPath(), OBSERVER_EVENTS, true);
mSystemInstallObserver.startWatching();
scanDirLI(mSystemAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);
// Collect all vendor packages.
mVendorAppDir = new File("/vendor/app");//得到的是/vendor/app裏面主要是設備廠家提供的應用程序。
mVendorInstallObserver = new AppDirObserver(
mVendorAppDir.getPath(), OBSERVER_EVENTS, true);
mVendorInstallObserver.startWatching();
scanDirLI(mVendorAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);//scanDieLI用來安裝裏面的應用程序。
if (DEBUG_UPGRADE) Log.v(TAG, "Running installd update commands");
mInstaller.moveFiles();
// Prune any system packages that no longer exist.
if (!mOnlyCore) {
Iterator<PackageSetting> psit = mSettings.mPackages.values().iterator();
while (psit.hasNext()) {
PackageSetting ps = psit.next();
if ((ps.pkgFlags&ApplicationInfo.FLAG_SYSTEM) != 0
&& !mPackages.containsKey(ps.name)
&& !mSettings.mDisabledSysPackages.containsKey(ps.name)) {
psit.remove();
String msg = "System package " + ps.name
+ " no longer exists; wiping its data";
reportSettingsProblem(Log.WARN, msg);
mInstaller.remove(ps.name, 0);
mUserManager.removePackageForAllUsers(ps.name);
}
}
}
mAppInstallDir = new File(dataDir, "app");
//look for any incomplete package installations
ArrayList<PackageSetting> deletePkgsList = mSettings.getListOfIncompleteInstallPackagesLPr();
//clean up list
for(int i = 0; i < deletePkgsList.size(); i++) {
//clean up here
cleanupInstallFailedPackage(deletePkgsList.get(i));
}
//delete tmp files
deleteTempPackageFiles();
if (!mOnlyCore) {
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
SystemClock.uptimeMillis());
mAppInstallObserver = new AppDirObserver(
mAppInstallDir.getPath(), OBSERVER_EVENTS, false);
mAppInstallObserver.startWatching();
scanDirLI(mAppInstallDir, 0, scanMode, 0);
mDrmAppInstallObserver = new AppDirObserver(
mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false);
mDrmAppInstallObserver.startWatching();
scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,
scanMode, 0);
} else {
mAppInstallObserver = null;
mDrmAppInstallObserver = null;
}
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SCAN_END,
SystemClock.uptimeMillis());
Slog.i(TAG, "Time to scan packages: "
+ ((SystemClock.uptimeMillis()-startTime)/1000f)
+ " seconds");
// If the platform SDK has changed since the last time we booted,
// we need to re-grant app permission to catch any new ones that
// appear. This is really a hack, and means that apps can in some
// cases get permissions that the user didn't initially explicitly
// allow... it would be nice to have some better way to handle
// this situation.
final boolean regrantPermissions = mSettings.mInternalSdkPlatform
!= mSdkVersion;
if (regrantPermissions) Slog.i(TAG, "Platform changed from "
+ mSettings.mInternalSdkPlatform + " to " + mSdkVersion
+ "; regranting permissions for internal storage");
mSettings.mInternalSdkPlatform = mSdkVersion;
updatePermissionsLPw(null, null, true, regrantPermissions, regrantPermissions);
// can downgrade to reader
mSettings.writeLPr();
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_READY,
SystemClock.uptimeMillis());
// Now after opening every single application zip, make sure they
// are all flushed. Not really needed, but keeps things nice and
// tidy.
Runtime.getRuntime().gc();
mRequiredVerifierPackage = getRequiredVerifierLPr();
} // synchronized (mPackages)
} // synchronized (mInstallLock)
未完善，oop